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FILE NAME Packings and Gaskets PAG DATE 2014 DOC PAG062 DOCUMENT DESCRIPTION Journal Article - Airborne Asbestos Associated with Gasket and Packing Replacement YRTPH No. of Pages 15 Model 5G Regulatory Toxicology and Pharmacology xxx 2014 XXX Contents lists available at ScienceDirect Regulatory Toxicology and Pharmacology journal homepage www.elsevier.com/locate/yrtph 3 Airborne asbestos exposures associated with gasket and packing 4 replacement A simulation study and analysis Q1 Amy K. Madl Dana M. Hollins Kathryn D. Devlin Ellen P. Donovan Pamela J. Dopart 8 Paul K. Scott Angela L. Perez 9 10 11 12 Q2 a Cardno ChemRisk 20 Stanwix Street Suite 505 Pittsburgh PA 15222 United States Cardno ChemRisk 101 2nd Street Suite 700 San Francisco CA 94105 United States Cardno ChemRisk 4840 Pearl East Circle Suite 300 West Boulder CO 80301 United States Cardno ChemRisk 130 Vantis Suite 170 Aliso Viejo CA 92656 United States ARTICLE INFO Article history Received 27 November 2013 Available online xxxx Keywords Asbestos Gasket Packing Equipment Exposure Task Tool Valve ABSTRACT Exposures to airborne asbestos during the removal and installation of internal gaskets and packing asso- 31 ciated with a valve overhaul were characterized and compared to published data according to different 32 variables e.g. product equipment task tool setting duration Personal breathing zone and area sam- 33 ples were collected during twelve events simulating gasket and packing replacement clean and cloth- 34 ing handling These samples were analyzed using PCM and TEM methods and equivalent PCME 35 airborne asbestos concentrations were calculated A analysis was performed to compare these data 36 with airborne asbestos concentrations measured in other studies involving gaskets and packing 37 Short mechanic and assistant airborne asbestos concentrations during valve work averaged 38 0.013 cc and 0.008 cc PCME respectively Area samples averaged 0.008 cc 0.016 cc and 0.003 / cc PCME for center bystander and remote background respectively Assuming a tradesman conserva- 40 tively performs 1-3 gasket and packing replacements daily an average h TWA was estimated to be 41 0.002-0.0c1c0 PCME Combining these results in a analysis of the published exposure data 42 showed that the majority of airborne asbestos exposures during work with gaskets and packing fall 43 within a consistent and low range Significant differences in airborne concentrations were observed 44 between power versus manual tools and removal versus installation tasks Airborne asbestos concentra- 45 tions resulting from gasket and packing work during a valve overhaul are consistent with historical 46 exposure data on replacement of containing gasket and packing materials involving multiple 47 variables and in nearly all plausible scenarios result in average airborne asbestos concentrations below 48 contemporaneous occupational exposure limits for asbestos 49 '2014 Published by Elsevier Inc. 50 51 52 1. Introduction containing gaskets and packing materials were used in industrial and maritime settings such as refineries chemical plants naval ships and energy plants Cheng and McDermott 1991 Lundell 1973 Spence and Rocchi 1996 Naval specifications required that asbestos containing gaskets be used on many ships United States Navy 1924 1953 In the past the asbestos content of gaskets typically ranged from 40 to 90 with binders and fillers making up the rest of the material Madl et al 2007 In most cases chrysotile asbestos was the only asbestos fiber used in these * Corresponding author Fax +1 949 616 3899 mail address any madl@cardo.cmadl@coardo.mcom A.K Madl http dx.doi.org dx.doi.org 10.1016 y~-lph2014 04 007 0273-2300 2014 Published by Elsevier Inc materials although crocidolite asbestos was sometimes used 64 within very specialized acidic or corrosive environments 65 Relatively few studies in the 1970s and 1980s evaluated expo- 66 sures related to gasket and packing work especially when com- 67 pared to the many evaluations of asbestos insulation due to a 68 perception that asbestos exposures during such work would be 69 negligible or relatively small Lindell 1973 Selikoff 1970 Stud- 70 ies both published and unpublished which evaluated airborne 71 asbestos exposures due to handling gaskets and packing were gen- 72 erally conducted at worksites or simulated in a controlled environ- 73 ment Later studies tried to limit background asbestos levels e.g. 74 the extensive use of asbestos insulation on pipes and machinery 75 by simulating the work activity in controlled environments e.g. 76 laboratory test facilities The first comprehensive study which 77 characterized potential worker exposures to airborne asbestos 78 packing replacement A simulation study and 28 April 2014 2 AK Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx Pages No. of Model 5G 15; 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 during the removal and installation of containing gaskets was conducted by the U.S. Navy in 1978 Lukonen et al 1978 This worksite study was performed in a shipyard setting and although unclear how background airborne concentrations resulting from other containing materials being used at the shipyard may have influenced the results the vast majority of airborne asbestos exposures were below contemporaneous occupational exposure limits Liukonen et al 1978 A review published by Madl et al 2007 was the first to summarize all of the published data as well as selected unpublished data on airborne asbestos concentrations associated with the han- dling of containing gaskets and packing materials Madl et al 2007 In that study eight simulation studies or series of simulation studies and four worksite studies of industrial and maritime settings which involved collection of more than 300 air samples were analyzed Boelter et al 2002 Cheng and McDermott 1991 Liukonen et al 1978 Longo et al 2002 Mangold et al 2006 McKinnery and Moore 1992. Millette and Mount 1993 Spence and Rocchi 1996 Spencer 1998a The replacement of gaskets and packing using hand tools showed with few exceptions short average exposures less than the current min OSHA Excursion Limit of 1.0 cc and all of the term average exposures were less than the current h TWA PEL of 0.1 cc It was concluded that the use of hand tools and operated power tools to remove or install gaskets or packing should not under conditions normally encountered have pro- duced airborne concentrations in excess of contemporaneous reg- ulatory levels Madl et al 2007 While several published studies have evaluated asbestos expo- sures to workers removing and installing gaskets and packing none have characterized exposures to a worker performing valve repair work limited to the replacement of internal gaskets and packing materials e.g. as would be performed during a valve overhaul Therefore it was of interest to evaluate airborne asbestos concentrations generated during replacement of gaskets and packing internal to the valve and how these concentrations might contribute to asbestos exposures experienced by a worker or bystander The primary objective of this work was to 1 characterize exposures to airborne asbestos during the removal and installation of containing packing and gaskets contained within vintage valves 2 measure short- and term exposures during packing and gasket replacement and characterize the fiber type size distribution e.g. 5 and 20 ...mlength and morphology of airborne asbestos fibers generated during these work activities 3 compare short and term measurements to the occupational exposure limits OELS set forth by the Occupational Safety and Health Administration OSHA min Excursion Limit EL and h Time Weighted Average Permissible Exposure Limit PEL 4 conduct a statistical comparison of the airborne asbestos concentrations measured in this study to the body of available data from similar studies in the published literature and 5 use the combined dataset i.e. data from this simulation study and the published literature to perform additional statistical comparisons according to different variables e.g. product type tool task or equipment and explore any other trends that may be discerned when considering the full body of data available to date 135 136 138 139 140 2. Methods 2.1 Valve simulation study 2.1.1 Equipment test site and study conditions Ten vintage Edward valves manufactured prior to the 1980s an era in which some packing and gaskets contained asbestos were selected for this study Two in 2.54 cm valves and eight in 7.62 cm valves were used all of the valves were globe valves with the exception of one gate valve Each valve was blasted with abrasive material prior to testing to remove possible external debris or contamination The service life of each valve was unknown however it was understood by the investigators that the valves were historically used on maritime vessels It was not determined until after the testing through bulk sample analysis whether each valve housed containing packing and gasket material Complete valve overhauls were performed inside an enclosed room by two retired mechanics with 50 combined years of training and experience in the U.S. Navy servicing and repairing equip- ment Further description of the study room is described in the Supplementary Information SI Prior to conducting the study permission from a medical institutional review board IRB was requested and obtained Copernicus Group IRB Research Triangle Park NC USA 2.1.2 Exposure scenarios Airborne asbestos concentrations were measured during activi- ties conducted during twelve sampling events Ten of these events characterized exposures during valve overhaul work which included the removal and installation of containing packing and gaskets contained within ten vintage valves Event 1 3-11 one characterized exposures associated with valve overhaul clean work Event 2 and one characterized exposures during the handling of coveralls worn during the study Event 12 The packing replacement process was similar for all ten valves Event 1 3-11 On nine of the ten valves Event 1 3-4 6-11 the gasket was also removed and on three of those occasions Event 3 4 and 6 a new gasket was fabricated In general the mechanics took approximately 15-40 min to replace the packing material and approximately 10-30 min to replace the gasket thus resulting in a total duration of approximately 30-60 min for a complete valve overhaul The process of packing and gasket removal and installation and cleanup are described in further detail in the SI Clothes handling i.e. shaking and folding of coveralls worn during valve overhaul work was also studied In total six coveralls worn by the worker and the assistant one pair each per day were collected and sealed separately in plastic bags At the conclusion of the study coveralls worn by the mechanic and assistant and collected each day of the testing new coveralls were worn each day were shaken folded and turned inside out for approximately 1-3 min by a volunteer simulating the handling of these potentially contaminated work clothes Event 12 2.1.3 Sampling and analytical methods Collection and analysis of air samples Airborne asbestos were col- lected onto mixed cellulose ester membranes as described else- where as well as further described in the SI Madl et al 2009 During an entire valve job personal samples from the mechanic's and assistant's lapel bystander and remote area samples and ambient samples for airborne asbestos were collected Consecutive min samples term samples and samples spanning the duration of one complete study day were collected on the right and left lapels of both the mechanic and the assistant After each event once the work activities had ceased the room was venti- lated for 30 min and background samples were taken prior to the start of the next testing event All air samples were collected and analyzed for asbestos by phase contrast microscopy PCM and transmission electron microscopy TEM according to NIOSH Methods 7400 and 7402 which defines fibers 5 ...min length and 0.25...min diameter and having at least a 3 aspect ratio NationalInstitute for Occupational Safety and Health NIOSH simulation replacement 1994 the ISO Using methodology 10312 1995 asbestos fibers A study and 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 ~ No. of Pages 15 Model 5G A.K. Madl et al / Regulatory Toxicology and Pharmacology xxx 2014 xxx 3 205 were classified according to fiber size and morphology as described 206 in the Sl 207 During each overhaul samples of all packing and gasket mate- 208 rial removed and installed were collected for bulk sample analysis 209 of asbestos content Bulk samples were also taken of the debris 210 found on the workbench for two events Events 10 and 11 and 211 of the material removed from the bonnet area of one valve Event 212 9 The bulk materials were analyzed by EMS Laboratories using 213 polarized light microscopy PLM according to NIOSH Method 214 9002 National Institute for Occupational Safety and Health 215 NIOSH 1994 Sulfur hexafluoride SF was used as a tracer gas 216 to estimate the air exchange rate within the study room see SI The air exchange in the room passive ventilation was found to 218 be approximately 2-3 air changes per hour ACH 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 249 250 251 252 253 254 2.1.4 Data analysis of valve simulation study results Descriptive statistics were performed on PCM TEM and equivalent measurements of airborne fiber concentrations collected during gasket and packing replacement on valves as well as during clothes handling Results below the analytical sensitivity limit were assigned a value equal to half the sensitivity limit Description of the analytical sensitivity limits and the calculation of the PCM equivalent PCME concentration is described in the Sl Results were analyzed by sample location e.g. worker assistant center bystander and remote area and task Eight TWA asbestos exposures during gasket and packing replacement on valves and flanges were calculated In order to determine the average worst frequency and duration of gasket and packing work and assure potential exposures are not underestimated the testimony of over 60 workers who had filed lawsuits against gasket and packing manufacturers were reviewed and the frequency and duration information for several tasks such as gasket removal fabrication installation and replacement and packing removal installation and replacement was extracted and qualitatively reviewed further detail provided in the SI For the purposes of our h TWA calculation we assumed that under worse case conditions a worker whose primary job duties involve the greatest opportunity for routine field gasket and packing work e.g. machinist mechanic pipefitter boilermaker would perform this type of work 1-3 times per day for a duration of 30-60 min each time on average over a given year Thus personal h TWAS were calculated for 1-3 gasket and packing replace- ments as follows * 480 min where C is the average airborne concentration cc for the left and right lapel collected for each of the sampling segments and t is the duration 30-60 min of the task Therefore it was assumed that gasket and packing work could comprise 30 min to h of an h workday 255 256 257 258 259 260 261 262 263 264 265 266 267 2.2 analysis of gasket and packing exposure studies 2.2.1 Literature review and compilation of combined dataset In order to provide a statistical comparison of the samples col- lected in this simulation study to airborne asbestos concentrations measured in other studies involving gaskets and packing the available published data were compiled and analyzed as a whole A literature search was conducted using several database search engines e.g. TOXNET PUBMED to identify potentially relevant publications in the reviewed literature in particular those published since Madl et al in 2007 Madl et al 2007 Description of the studies included and excluded in the analysis is described in the SI After the relevant studies were identified each individual study was reviewed in detail to obtain information regarding the tasks performed number and types of products and tools used task and sample duration and asbestos content A total of 11 studies were identified for the combined data analysis Boelter et al 2002 2011 Cheng and McDermott 1991 Liukonen et al 1978 Longo et al 2002 Mangold et al 2006 McKinnery and Moore 1992 Millette and Mount 1993 Spence and Rocchi 1996 Spencer 1998a One published study provided only summary level information such as mean values or ranges Boelter et al 2011 and therefore could not be incorporated into the combined analysis described below However the reported average concentrations were included in comparisons of average airborne asbes- tos concentrations across all of the studies Specific variables were recorded for each study including the reported airborne asbestos concentration based on PCM and if available TEM results sampling time sampling location including whether the samples were collected in a chamber task performed including a description of any tools that were used containing material that was handled including information about percent asbestos or fiber type if available type of equipment being handled sampling information i.e. flow rate total air volume analytical methods used and a description of any engineering controls that may have been in place during the sampling Analyses were performed using half the limit of detection for all samples that reported detectable quantities unless otherwise noted 2.2.2 Statistical analyses of combined dataset Statistical comparisons of airborne asbestos concentrations were performed for several different factors including sample duration material equipment task and study Fig ) For the material variable differences in asbestos concentration between gaskets includes plate gasket and spiral wound gasket packing and packing were evaluated For the equipment variable asbestos concentration differences based on the type of equipment and specific material being serviced were evaluated and included gasket and packing work on boiler headers flanges valves pumps valves and flanges work was conducted on both types of equipment simultaneously ventilation duct heaters and unknown equipment was unknown or not specified but the task would have required the use of a specific type of equipment as in the case of gasket removal Samples where the type of equipment was not specified or applicable meaning that the task was not necessarily associated with a specific type of equipment as in the case of fabricating gaskets were not included in the equip- ment analysis Worker task descriptions were coded in the combined database as gasket removal gasket fabrication gasket installation gasket replacement packing removal packing installation packing replacement combined packing work this code usually referred to replacement of gaskets and packing within a single sampling period and clean this code involved clean fol- lowing gasket and packing work Similarly the studies frequently provided information regarding the tools that were used in the course of installing or replacing a gasket or packing material Tools were grouped based on whether they were hand manual or power tools Power tools that were likely only to be found in a machine shop e.g. machine puncher were also grouped separately For the tool analysis gasket and packing materials were pooled since few tools were specified for work involving packing materials The analysis was limited to personal samples collected on the worker handling the gaskets and packing although general summary statistics for personal samples collected on bystanders or assistants were also calculated Worker samples were grouped according to analytical method PCM or TEM and the underlying sample distributions were tested using ProUCL 4.0 software FPA saree replacemnt A simulation study and 269 270 271 272 273 275 276 277 278 279 280 282 289 304 305 306 307 308 309 311 312 313 314 315 316 317 318 319 320 321 324 4 A.K Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx Sample Duration min min < 60 min > 60 min Material Gaskets, Packing Gaskets & Packing Equipment Valve Valves & Flanges Pump Boiler Header Ventilation Duct Heater \. J \ a Task Fabrication Installation Replacement Removal Combined Gasket & Packing Work a y, ~ : Tool Group > . ~ Study { Group 1 Power wire brush power shears and miscellaneous hand tools unknown or no tool listed \ y, f Group 2 Ball peen hammer circular cutter hand brush hand punch hand wire brush multiple gasket formation with hand tools multiple including shop replacement using multiple hand tools scraper and hand wire brush scraper and power wire brush f ' Group 3 Machine punching scraper .. , Fig 1. Hierarchy of variables evaluated in the analysis of airborne fiber concentrations during work with gasket and packing materials 333 1975 Probability plots were also used to evaluate the sample dis- samples several simulation studies evaluated a worker's daily 373 334 tribution Based on the probability plots which indicated that the exposure by collecting breathing zone samples while the worker 374 sample distributions appeared to be lognormal data were log repeatedly performed specific tasks over the course of an h work- 375 336 transformed prior to performing any statistical analyses All analy- day Not all of these studies reported the number of repetitions of 376 337 ses were conducted with SYSTAT statistical software Chicago IL the task during the sampling period however many of the studies 377 338 Several statistical analyses were conducted using the full dataset reported that the worker performed four to eight repetitions of the 378 339 All comparisons were performed initially using PCM data Three activity of interest over the course of the day Boeltci et al 2002 379 340 published studies McKinnery and Moore 1992 Millette and Mangold et al 2006 Spencer 1998b Thusin these cases it is pos- 380 341 Mount 1993 Spence and Rocchi 1996 underlying data from sible that there were portions of the total sampling time where the 342 Longo et al 2002 and our simulation study also reported TEM workers were not handling containing components 382 _ 343 data and therefore a separate analyses were repeated using these GLM ANOVAs were performed to evaluate whether there were 383 344 TEM results significant differences based on type of equipment task tool 384 345 Although samples involving work with asbestos containing material or the individual study These analyses were conducted 385 346 materials were excluded there were some samples that were col- separately for PCM and TEM sampling results A value of less 386 347 lected during work that involved asbestos and asbestos mate- than 0.05 was considered to be significant rials simultaneously This occurred in both Spence and Rocchi To evaluate consistency across analytical methods PCM results 388 Spence and Rocchi 1996 and our simulation study The samples were plotted against TEM results for studies that reported both 389 encompassing work with both asbestos and asbestos measurements Comparisons between PCM and TEM were con- 390 materials from the simulation study were included in the analysis ducted separately for two sample duration categories 60 and 391 and the reported concentration was adjusted to account for the 6m0in using a multiple linear regression model of TEM concen- 392 portion of the sampling time that was spent handling only trations versus PCM concentrations with the categorical variable 354 containing components where possible This adjustment representing the individual studies study and PCM by study 394 was not possible for samples of longer duration however these The purpose of this multiple linear regression model is to deter- 395 samples were included in the analysis if any of the materials used mine if there are any significant differences in the slope or y inter- 396 during the sample time were containing For consistency cept for linear regression models of TEM versus PCM by study 397 three samples from Spence and Rocchu 1996 whose sampling time spanned work with both asbestos and asbestos contain- 3. Results 398 360 ing gaskets were also included in the analysis Spence and Rocchi 1996 For purposes of comparison samples were initially categorized by sample duration as follows 60 min 60-240 min and 240 min These groupings were established based on professional judgment and knowledge of the nature and duration of the various tasks and to ensure that each group contained a sufficient number of samples to facilitate statistical analysis A single factor general- ized linear model GLM analysis of variance ANOVA however 369 indicated that there was not a significant difference between sam- ples in the 60-240 min and 240 min sample groups so all subse- quent analyses were performed separately for two groups long 60 min and 60 min It should be noted that for the term 3.1 Simulation study 399 A total of 228 airborne asbestos samples were collected over the 400 course of the day study including 78 worker samples 40 assis- 401 tant samples 57 area samples 18 clearance samples six back- 402 ground samples nine ambient samples and 20 field blanks Of 403 these samples a total of 58 worker samples 26 assistant samples 404 and 52 area samples were used in the analysis since they were col- 405 lected during activities involving containing components 406 In addition a total of 59 bulk samples were collected on the asso- 407 ciated packing and gasket material as well as on miscellaneous 408 dust created during valve work 409 424 426 427 428 429 430 431 AK Madl et al./Regulatory al./Regulatory Toxicology and Pharmacology xxx 2014 xxx 5 Ten of the 12 events involved gasket and packing work on valves and each of these ten events involved work on a single valve Nine of the ten events involved removing or replacing at least one containing component packing removed and or installed gasket removed and installed During the one event that did not involve any containing components Event 5 the stem and bonnet of the valve were frozen and the mechanic was unable to remove the packing rings or the gasket No asbestos was detected in the pieces of packing material removed from this valve and thus results from this event were not included in the analysis The asbestos bulk content of the packing material removed from the valves was ND- chrysotile 1 valve and 40-70 chrysotile 3 valves no asbestos was detected in the packing material removed from the remaining six valves The bulk content of the packing material installed in the valves ranged from 25 to 70 chrysotile asbestos The asbestos bulk content of the gasket material removed from the valves was ND- chrysotile 4 valves % chrysotile 1 valve and 50-55 chrysotile 2 valves no asbestos was detected in the gasket material removed from the remaining two valves The bulk content of the gasket material installed in the valves ranged from 45 to 65 chrysotile asbestos No amphibole fibers were detected in any of the gasket or packing materials or installed into the valves Average worker airborne asbestos concentrations as measured by PCME during packing and gasket work were higher than assistant airborne asbestos concentrations during the same tasks Average short airborne asbestos concentrations for the worker performing gasket and packing work 16-36 min sample duration were 0.059 0.014 and 0.013 cc as measured by PCM TEM and PCME respectively whereas average short concentrations for the assistant were 0.056 cc PCM 0.006 cc TEM and 0.008 cc PCME Table ) Cleanup activities following packing and gasket work when both the packing material and gaskets removed and installed were positive for asbestos showed average airborne asbestos concentrations of 0.049 0.005 and 0.006 cc as measured by PCM TEM and PCME respectively During clothes handling the average airborne asbestos concentrations measured on the volunteer handling the clothes were 0.107 cc PCM 0.005 cc TEM and 0.005 cc PCME As mentioned above PCME was only calculated for samples in which asbestos fibers were detected by TEM Asbestos fibers were not detected by TEM in approximately 40 of the short worker samples and approximately 55 of the short assistant samples 432 433 434 435 436 437 438 439 440 441 442 443 444 445 447 448 449 450 451 452 453 Table 1 Q3 Airborne asbestos fiber concentrations for worker and assistant 30 min during the replacement of gaskets and packing in valves Task # of events Asbestos fiber concentrations cc PCM TEM n ND NR Avg SD MIN MAX n ND Avg SD PCMF MIN MAX n Avg SD MIN MAX Worker Packing work Removal Installation Replacement Summary - packing 1 20 0 0.047 - 0047 0.047 2 0 0 0.020 - 0.020 0.0202 0.0202 0.013 - 0013 0013 618 12 0 0.073 0.038 0.041 0.137 12 4 0 0.019 0.026 0.002 0.068 8 0.020 0024 0.003 0061 618 20 0 0.078 - 0.078 00782 00782 2 0 0.002 - 0.002 0.002 0 - - - - 618 16 0 0.071 0.034 0.041 0.137 16 6 0 0.017 0.023 0.002 0.068 10 0.019 0.022 0.003 0.061 Gasket work Removal 020N Installation 020N Replacement 020N Summary - gasket 020N Combined packing work Packing and gasket removal 1 Packing and gasket installation 1 Packing installation gasket removal 1 Summary - combined gasket 3 packing Summary - all valve work 13 0 40 40 40 TOTO - - - - - + 0 0047 0.010 0.040 0.054 4 1 TOTO - - - - - - TOTO 0.047 0.010 0.040 0.054 4 1 - - - - - - > - - - 0 0008 0.001 0008 0009 3 0.006 0.000 005 0006 - - - - - - - 1 - - 0 0.008 0.001 0.008 0.009 3 0.006 0.000 0.005 0.006 2 200N - - - - 2 0 0.007 - 0.007 0.007 - - - - - 20 200N 0.012 - 0.012 0.012 2 0 0 0.026 - 0.026 0.026 2 0.004 ~ 0.004 0.004 0.004 20 200N 0.036 - 0.036 0.036 2 1 0 0.002 - 0.002 0.002 1 004 - 0004 0.004 60 200N 0.024 0.017 0.012 0.036 6 2 0 0.012 0.012 0.002 0.026 3 0.004 0.000 0.004 0.004 26 0 2 0.059 0.033 0.012 0.137 26 9 0 0.014 0.018 0.002 0.068 16 0.013 0.018 0.003 0.061 Misc activities Cleaning Clothes handling 21 40 0 0.049 0.034 0.025 0.073 4 2 0 0.005 0.002 0.004 0.006 2 0006 0.005 0.002 0010 21 20 0 0.107 - 107 0.107 2 1 0 0.005 - 0005 0.005 1 0005 - 0.005 0.005 Assistant Packing work Removal Installation Replacement Summary - packing 1697 0 - - - - - - - - ~ - ~ - - - - - - 1697 12 0 0.060 023 0.039 0.096 12 7 0 0.008 0010 0002 0.026 5 0012 0.012 0.002 0.028 1697 20 0 0.072 - 0.072 0.072 2 2 0 0.002 - 0.002 0.002 0 - - - - 1697 14 0 0.062 0.021 0.039 0.096 14 0 0.007 0.009 0.002 0.026 5 0.012 0.012 0.002 0.028 Gasket work Removal ONONO Installation ONONO Replacement ONONO Summary - gasket ONONO Summary - all assistant samples = ONONO 0- - - - - - - - - - - - - - - - - - 40 0 0 0.036 0.001 0.035 0.037 4 1 - - - - ~ - - 0 0.003 0.002 0.002 0.004 3 0.002 0.001 0.001 0.002 - - - - - - - - - - 40 0 0.036 0.001 0.035 0.037 4 1 0 0.003 0.002 0.002 0.004 3 0.002 0.001 0.001 0.002 18 0 0.056 0.022 0.035 0.096 18 10 0 0.006 0.008 0.002 0.026 8 0.008 0.011 0.001 0.028 PCM phase contrast microscopy TEM transmission electron microscopy PCME PCM concentration multiplied by the ratio of asbestos fibers to total fibers measured by TEM n number of samples ND number of samples in which asbestos was not detected NR number of samples not readable Avg average SD standard deviation ~ not applicable * Based on samples in which asbestos fibers were detected by TEM a Short samples ranged from 16-36 min in length b Event 5 was excluded from the analysis because no asbestos in the packing material removed and the gasket was not replace due to a frozen valve stem and bonnet simulation study and 28 April 2014 No. ofPages 15 Model 5G 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 6 A.K Madl et al Regulatory Toxicology and Pharmacology xxx 2014 XXX Because some of the packing material and gaskets removed from the valves did not contain asbestos the time handling asbestos components was subtracted from the total sample duration for the short 16-36 min samples When adjusted for time handling asbestos components the average airborne asbestos concentrations as measured by PCM TEM and PCME for the worker were 0.121 0.027 and 0.027 cc respectively Table 2 Samples collected for longer durations 31-84 min over the course of the complete valve overhaul could not be adjusted for time handling asbestos materials and showed average airborne asbestos concentrations as measured by PCM TEM and PCME of 0.069 0.013 and 0.015 cc respectively Table 3 Average area asbestos concentrations were lower than those observed for the personal lapel worker and assistant samples Table 4 Asbestos was not detected in approximately 70 center 30 bystander and 45 remote background of the area samples as determined by TEM In addition average airborne asbestos concentrations as measured by PCME at the center 0.008 cc and bystander 0.005 cc locations were approximately half to thirds less than those measured for the worker 0.015 cc Airborne asbestos concentrations found at the remote background locations were even lower than those found at the bystander locations No asbestos fibers were detected in any of the ambient or field blank samples as measured by TEM Of the total asbestos fibers detected in samples collected from the lapel of the worker fiber size and morphology analysis of the airborne asbestos fibers showed that approximately 40 of fibers existed in a cluster or matrix whereas the remaining proportion of fibers existed as free fibers or bundles Table 5 Based on the abovementioned designation of a respirable fiber i.e. 0.7 ...mor < ...mdiameter approximately 42-65 of fibers counted were respirable If either designation of respirability is applied fiber 0.7 ...mor < ...mdiameter or particle 10 ...mbetween 24 and 65 of fibers counted were respirable Estimated h TWA asbestos exposures were calculated for the worker using short PCME data taking into account the duration in which containing products gaskets or packing material were handled Table 2 Based on the assumption that under worse case conditions a worker whose primary job duties involve the greatest opportunity for routine field gaskets and packing work e.g. machinist mechanic pipefitter boilermaker would perform 1-3 times per day for a duration of 30-60 min each time on average Additionally based on the average worker exposure during all valve work involving gasket and packing replacement of 0.027 cc PCME Table 2 the resulting average h TWAs was estimated to be 0.002-0.010 cc 0.5-3 h of gasket and packing in a workday Based on the results of the valve simulation study a mechanic performing similar work 1- 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 Table 2 Comparison of worker and assistant average asbestos concentrations 30 min with and without adjustment for time handling asbestos components Task # of events Average asbestos fiber concentrations cc total sample duration PCM TEM PCME Average asbestos fiber concentrations cc adjusted for time handling asbestos components PCM TEM PCME Worker Packing work Removal Installation Replacement Summary ~ packing work 1 0.047 0.020 0.013 0.047 6 0.073 0.019 0.020 0.183 1 0.078 0002 - 0.133 8 0.071 0.017 0.019 0.160 0.020 046 0.003 0.037 0013 0.047 ~ 0.041 Gasket work Removal ONON Installation ONON Replacement ONON Summary - gasket work ONON Combined gasket and packing work Packing and gasket removal 1 Packing and gasket installation 1 installation Packing Summary - Summary gasket removal 1 gasket packing combined combined and work 3 Summary - all valve work 13 - 0047 - 0.047 - 0.012 0.036 0.024 0.059 ~ 0.008 - 0.008 0.007 0.026 0.002 0.012 0.014 - 0006 - 0.006 . - 0.004 0.004 0.004 0.013 - 0063 - 0.063 - 0.012 0.036 0.024 0.121 - 0.011 - 0.011 0.007 0.026 0.002 0.012 0.027 - 0.007 - 0.007 - 0004 0004 0.004 0.027 Misc Activities Cleaning Clothes Handling 2 0.049 0.005 006 0.049 21 0.107 0.005 0.005 0.107 0005 0.005 0.006 0.005 Assistant Packing work Removal Installation Replacement Summary - packing work Gasket work Removal Installation Replacement - work Summary gasket Summary - all samples 1190 - - - - 1190 0.060 0.008 0.012 0.142 1190 0.072 0.002 - 0.113 1190 0.062 0.007 0.012 0.138 02020 - - - - 02020 0036 0.003 0.002 0.047 02020 - - ~ - 02020 0.036 0.003 0.002 0.047 9 0.056 0.006 0.008 0.118 - 0.018 0003 0.016 ~ 0.004 ~ 0.004 0.013 - 0.027 - 0.027 - 0.002 ~ 0.002 0.019 PCM phase contrast microscopy TEM transmission electron microscopy PCME PCM concentration multiplied by the ratio of asbestos fibers to total fibers measured by TEM - not applicable * Based on samples in which asbestos fibers were detected by TEM a Short samples ranged from 16--36 min in length b Event 5 was excluded from the analysis because no asbestos in the packing material removed and the gasket was not replace due to a frozen valve stem and bonnet Tasks affected by adjusting task time when asbestos components were handled Please cite this article A.K Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx 7 Table 3 Airborne asbestos fiber concentrations for worker 60 min according to task valve size and event during the replacement of gaskets and packing in valves valve event # of events Task Packing replacement 1 Packing installation 4 Packing and gasket installation 2 Packing replacement gasket 1 removal Packing and gasket replacement 1 Valve size in 27 in 27 Asbestos fiber concentrations cc PCM TEM n ND NR Avg SD MIN MAX n ND NR Avg SD PCME MIN MAX n Avg SD j MIN MAX 20 0 0.081 - 0.081 0.081 21 0 0.007 - 0.007 0.007 1 0.006 - 0.006 0.006 80 0 0.084 0.032 0.055 0.126 84 84 0 0.021 0.023 0.002 0.049 4 0.033 0.007 0.028 0037 0 0 0056 0.008 0.050 0.062 40 0 0006 0.002 0.004 0.007 4 0.006 0.004 0.004 0.009 20 0 0.021 - 0.021 0.021 20 0 0.005 - 0.005 0.005 2 0.005 - 0.005 0.005 - 2 - - - - 20 0 0.006 - 0.006 0.006 - - - - - 40 02 0.073 0.011 0.065 0.081 43 0 0.005 0.003 0.003 0.007 1 0.006 - 0.006 0.006 14 02 0.067 0.036 0.021 0.126 14 2 0 0015 0.018 0.002 0.049 10 0016 0015 0.004 0.037 Event 1 1 3 1 4 1 6 1 7 1 8 1 9 1 10 1 11 1 Summary - all term samples 9 20 20 20 20 20 20 20 20 20 18 0 0.021 - 0.021 0.021 20 2 - ~ - - 20 0 0.050 - 0.050 050 20 0 0.062 - 0.062 0.062 20 0 0.065 - 0.065 0.065 22 0 0.081 - 0.081 0.081 2 0 0.089 - 0.089 0.089 20 0 0.126 - 0.126 0.126 20 0 0.055 M 0.055 0.055 22 2 0.069 0.031 0.021 0.126 18 5 0 0.005 0.005 0.005 2 0.005 - 0.005 0005 0 0.006 - 0.006 0.006 - - - - - 0 0.004 - 0.004 0004 2 0.004 - 0.004 0.004 0 0.007 - 0.007 0.007 2 0.009 - 0.009 0009 0009 0 0.003 - 0.003 0.003 0 - - - - 0 0,007 - 0.007 0.007 1 0.006 - 0006 0.006 0 0.049 - 0.049 0.049 2 0.037 - 0037 0037 0.037 0 0.031 - 031 0031 2 0.028 - 0028 0.028 0 0.002 - 0.002 0.002 0 - - = - 0 0.013 0.016 0.002 0.049 11 0.015 0.014 0.004 0.037 PCM phase contrast microscopy TEM transmission electron microscopy PCME PCM concentration multiplied by the ratio of asbestos fibers to total fibers measured by TEM n number of samples ND number of samples in which asbestos was not detected NR number of samples not readable Avg average SD standard deviation - not applicable Based on samples in which asbestos fibers were detected by TEM a term samples ranged from 31-84 min in length b Event 5 was excluded from the analysis since no asbestos was found in the pieces of packing material removed and the stem and bonnet of the valve were frozen 502 503 504 505 506 507 508 509 511 512 513 514 515 516 517 518 519 520 521 522 524 525 526 527 528 529 530 531 532 533 3 times over the course of a workday would have an a h TWA approximately fiftieth to tenth below the current OSHA PEL of 0.1 cc 3.2 analysis of gasket and packing exposure studies A total of 395 PCM sample results for workers were available for analysis in the combined dataset Initial statistical comparisons indicated that sample time had a significant impact on airborne asbestos concentration p < 0.001 and further analyses were conducted within two sample duration categories min n = 265 and 60 min n = 127 no sample duration was provided for three samples from McKinnery and Moore 1992 and as such these data were excluded from the analysis A total of 89 TEM sample results were available from five studies and the simulation study for analysis in the combined dataset Longo et al 2002 McKinnery and Moore 1992 Millette and Mount 1993 Spence and Rocchi 1996 Similar to the PCM results sample time hada significant impact on airborne asbestos concen- trations wherein the 60 min samples n 75 were significantly greater than the 60 min samples n 14 at a p 0.0001 based on a two sample Student t test Other than for a comparison between studies the number of samples for the 60 min category was too few for further pairwise comparisons Additionally a Student t test was conducted to compare the average worker personal data to the associated bystander bystander or assistant data for the entire PCM combined dataset without accounting for duration study or task Overall there was no significant difference between worker and bystander airborne fiber concentrations p = 0.926 The influence of study duration 60 and 60 min and task on bystander versus worker exposures were evaluated for the following variables in a two factor GLM ANOVA paired approach Each personal and bystander sample was paired based on events where possible to avoid diluting differences between samples collected during two different events where exposures may have differed e.g. removal versus installation The bystander comparison using paired t tests and repeated measures GLM showed a significant overall difference between worker and bystander samples p = 0.004 a significant difference by study and no significant difference by task Because we evaluated the data on a paired sample basis sampling duration was not an issue because each pair of personal and bystander samples had similar durations In the comparison by study the longo longo et al 2002 worker samples differed significantly than bystander samples p < 0.0001 while the simulation study worker samples and those reported in Spencer 1998 were not significantly different than bystander samples p > 0.094 A lack of statistical difference between worker and bystander measurements in the simulation and Spencer studies is likely attributed to the overall low intensity of exposure e.g. near the limits of detection in contrast to that reported by Longo et al 2002 For personal samples measured by PCM a more detailed analysis was performed to assess differences in fiber concentration in the breathing zone during the use of gaskets and packing associated with specific equipment tasks and tools Fig ) 3.2.1 Comparison of airborne asbestos concentrations by study An initial comparison was performed in order to determine if the airborne asbestos concentrations by PCM for each sample tion category were consistent across studies Only four of the studies one of which was our simulation study had samples in both the 60 and min sample duration categories Cheng and McDermott 1991 Liukonen et al 1978 Spencer 1998b The seven studies with samples 60 min were ranked into three general categories from highest to lowest based on the relative mean airborne asbestos concentrations ranking category one included the Longo studies ranking category two included Millette and Mount 1993 McKinnery and Moore 1992 and 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 556 557 558 559 560 561 562 563 564 565 28Apri20l14 8 A.K. Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx Table 4 Q4 Airborne asbestos fiber concentrations for area locations during the replacement of gaskets and packing in valves Valve event # of events Asbestos fiber concentrations cc PCM TEM PCME Center Valve size in - in Event 4 6 7 8 9 10 11 Summary - center n ND NR Avg SD MIN MAX n ND NR Avg SD MIN MAX n Avg SD MIN MAX 2 20 0 0.062 0.013 0.053 0.071 22 22 0 0.003 0.000 0.002 0.003 0 - - - - 5 50 0 0.059 0.014 0.039 0.076 53 53 0 0.006 0.007 0.001 0.015 2 0.008 0.001 0.007 0.009 1 0 0 0.039 - 0.039 0.039 1 0 0.001 - 0.001 0.001 0 - - - - 1 0 0 0.065 - 0.065 0.065 1 0 0001 - 0.001 0.001 0 - - ~ - 1 0 O 0.071 - 0.071 071 1 0 0002 - 0.002 0.002 0 - ~ - - 1 10 0 0.053 - 0.053 0.053 1 O 0.003 - 0.003 0.003 0 - - - ~ 1 10 0 0.064 - 0064 0.064 10 0 0.015 - 0.015 0.015 1 0007 - 0.007 0.007 1 10 0 0.076 - 0.076 0.076 10 0 0.012 - 0.012 0.012 1 0.009 - 0.009 0.009 1 10 0 0.051 - 0.051 0.051 1 0 0.002 - 0.002 0.002 0 - - - - 7 70 0 0.060 0.013 0.039 0.076 75 0 0.005 0.006 0.001 0.015 2 0.008 0.001 0.007 0.009 Bystander Valve size in in Event 40 0 0.046 0021 0.024 0.064 44 0 0.001 0.000 0.001 0.001 0 - - ~ - 7 14 4 0.050 0.016 0.031 0.077 14 2 0 0.006 0.005 0.001 0019 8 0.005 0.005 0002 0016 1 3 4 19 19 8 9 10 11 Summary ~ bystander 1 20 2200 - - - - 20 0 0.004 0.002 0.003 0.006 ~ - - - ~ 1 20 2200 - - - ~- 20 . 0 0.004 0.003 0.002 0.006 - - = - - 1 20 2200 0.036 0.002 0.034 0.037 2 1 0 0.003 0.003 0.001 0.005 1 0.004 - 0.004 0004 1 20 2200 0045 0.008 0039 0.051 1 0 0.004 0.004 0.001 0.007 1 0.004 - 0.004 0.004 1 20 0 0.028 0.006 0.024 0.032 22 0 0.001 0.000 0.001 0.001 0 - - - - 1 20 oo004 0.064 0001 0.063 0.064 22 0 0.001 0.000 0.001 0.001 0 - - - - 1 20 oo004 0075 0.003 0.073 0.077 20 0 0010 0012 0.002 0019 2 0.009 0010 0.002 0016 1 20 oo004 0056 0.007 0.051 0.061 20 0 0.009 0.001 0009 0010 2 0006 0001 0.005 0007 1 20 oo004 0.040 0.012 0.031 0.049 20 0 0.004 0.003 0.002 0.006 2 0.002 0.001 0.002 0.003 9 18 0 oo004 0.049 0.017 0.024 0.077 18 6 0 0.005 0.005 0.001 0.019 8 0.005 0.005 0.002 0.016 Remote background Valve size in in 2 40 0 0.038 0.007 0.032 0.048 44 0 0001 0.000 0.001 0.001 0 - - - - 7 14 4 0.050 0.017 0.026 0.082 14 4 0 0.003 0.003 0.001 0.010 7 0.003 0.002 0.001 0.006 Event 1 1 3 1 4 1 6 1 7 1 8 1 9 1 10 1 11 1 Summary ~ remote background 9 20 22 - - - - 20 0 0.002 0.000 0.002 0.003 - - - - - 20 22 - - - - 2 0 0001 0.001 0.001 0.002 - - - - = 20 0 0038 0.007 0.032 0.043 2 0 0.001 0.000 0.001 0001 1 0001 - 0001 0.001 20 0 0.051 0.014 0.041 0.061 2 0 0.003 0003 0.001 0.005 1 0.004 - 0004 0.004 20 0 0.033 0.001 0.032 0.033 22 22 0 0.001 0.000 0.001 0.001 0 - - - - 20 0 0043 0.007 0.038 0.048 2 2 0 0.001 0.000 0.001 0.001 0 - - - - 20 0 0.070 0.017 0.058 0.082 20 0 0.007 0.005 0.003 0.010 2 0.005 0.001 0.004 0.006 20 0 0.039 0.019 0.026 0.052 20 0 0.005 0.002 0.004 0.006 2 0.003 0.002 0.002 0.004 20 0 0.054 0.017 0.041 0.066 2 0 0002 0.001 0.001 0002 1 0001 - 0001 0.001 18 0 4 0.047 0.016 0.026 0.082 18 8 0 0.003 0.002 0.001 0.010 7 0.003 0.002 0.001 0.006 Activity # of events Asbestos fiber concentrations cc PCM TEM PCME Misc activities Cleaning Bystander 1 Remote background 1 Clothes handling Center 1 Bystander 1 Remote background 1 Ambient Day 1 - Day 2 ~ Day 3 11 Summary - ambient 11 samples n ND NR Avg SD = MIN MAX n ND Avg SD MIN MAX Avg SD MIN MAX 20 0 0.060 0.014 0.050 0.070 22 1 0 0.004 0.002 0.003 0.005 0.003 - 0.003 0.003 20 0 0.085 0.036 0.060 0111 22 0 0.002 0.000 0.002 0.002 0 - - = - 10 0 0.204 - 0.204 0.204 10 0 0.010 - 0.010 0010 0008 - 008 0008 20 0 0.099 0.008 0093 0.104 22 0 0.003 0.000 0.003 0.003 0 - ~ oH - 20 0 0.096 0.003 0.094 0.097 22 0 0.003 0.000 0.002 0.003 0 - = - 30 0 0.0024 0.0020 0.0004 0.0043 3 3 0 00008 0.0003 0.0005 0.0011 10 - - 1 30 0 0.0018 0.0009 0.0008 0.0026 3 3 0 0.0003 0.0001 0.0002 0.0004 0 - - - - 30 0 0.0014 0.0005 0.0010 0.0020 3 3 0 0.0003 0.0001 0.0002 0.0005 0 - - - ! 90 0 0.0019 0.0012 0.0004 0.0043 9 9 0 0.0005 0.0003 0.0002 0.0011 0 - ~ - I continued on next page simulation study and AK Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx 9 Table 4 continued Activity # of events Asbestos fiber concentrations cc PCM TEM n_n ND NR Avg SD MIN MAX n ND NR Avg SD MIN PCME MAX Avg SD MIN MAX Background - 60 0 0.0159 0.0032 00113 00198 65 65 0 0.0010 0.0005 0.0006 0.0016 1 0.0004 - 0.0004 0.0004 Clearance - 180 180 2 0.0174 0.0056 0.0088 0.0268 18 18 0 0.0016 0.0001 0.0014 0.0018 0 - - - - PCM phase contrast microscopy TEM transmission electron microscopy PCME PCM concentration multiplied by the ratio of asbestos fibers to total fibers measured by TEM n number of samples ND number of samples in which asbestos was not detected NR number of samples not readable Avg average SD standard deviation not applicable Area samples ranged from 17 to 91 min in length Based on samples in which asbestos fibers were detected by TEM b Event 5 was excluded since no asbestos was found in the pieces of packing material removed and the stem and bonnet of the valve were frozen Events 2 cleaning and 12 clothes handling are presented separately L Center samples were collected beginning with Event 4. Thus no center sample was collected for Events 1-3 including cleaning Event 2 Table 5 Fiber size and Morphology of the Airborne Asbestos Fibers in the Worker's Breathing Zone Fiber structure classification n Percent of total fibers Percent of total fibers % classified as respirable with dimensions of % Respirable fiber Respirable particle 0.7 ...mwidth 3 ...mwidth 10 ...mwidth Total fibers Free bundle Fiber clusters Matrix disperse 196 - 115 59 22 11 58 30 5-20 ...m length 1200 29 1200 1200 20 ...m length 1600 1600 1600 1600 5-20 ...m length - 43 0 3 20 ...m length - 12 0 0 5-20 ... length - 2 15 20 ...m length - 0 4 567 Cheng and McDermott 1991 and ranking category three included Laukonen et al 1978 Spencer 1998 - involving removal and installation of gaskets and packing material and the simula- 570 tion study dataset An additional comparison indicated that there were some significant differences within the Longo data with the first test results being significantly different than the second and third test results average airborne asbestos concentrations were 574 3.89 16.2 and 22.4 cc respectively the second and third test results were not found to differ significantly from each other Com- bining the three Longo test results into a single group resulted in several slight changes to values but did not change the overall significance of any pairwise comparisons therefore the three data sets underlying Longo et al 2002 were kept as separate groups in this analysis Longo et al 2002 The average airborne asbestos concentrations for ranking category one which included the Longo studies was 12.4 range 1.6-29.8 cc and was 44 times higher than ranking category two average 0.28 cc range 0.019-1.4 cc and 62 times higher than ranking category three average 0.20 cc range 0.005-5 cc Comparisons using TEM data yielded similar results although the number of studies with TEM data was considerably less The studies 60 min were grouped into three ranking categories from highest air concentrations ranking highest to lowest asbestos air concentrations ranking category one included the three datasets in Longo et al 2002 ranking cat- egory two included Millette and Mount 1993 and McKinnery and Moore 1992 and ranking category three included our simulation 593 study An additional comparison revealed that there were some significant differences within the Longo TEM data with the first test being significantly less than the third average airborne asbes- 596 597 598 tos concentrations were 82 and 1169 cc respectively p = 0.011 cc the second averagaveragee aiairborne rborne asbestosasbestos concentration cc third differ concentration concentration significantly of of 470 and third tests were not found to differ significantly Average air- 599 borne asbestos concentrations for the remaining studies with 600 TEM data were considerably lower in the ranking category two cc for Millette Mount 1993 601 group 25 25 and 6.4 Millette and 1993 and 602 McKinnery McKinnery and Moore 1992 respectively and in ranking cate- 603 gory three 0.022 cc for our simulation study For the 6s0 amples using PCM there were also differences in mean asbestos concentrations among the individual studies p < 0.0001 Similar to the 60 min sample duration data- sets the studies with the 60 min sample data can be divided into three ranking groups based on significant differences in their average asbestos concentrations The first ranking group was com- prised of the simulation study results two of the underlying reports of the Mangold publication and Spence and Rocchi 1996 among these studies the average asbestos concentrations ranged from 0.027 to 0.058 cc Mangold 1982b 1983 Spence and Rocchi 1996 The second group included Boelter et al 2002 and Liukonen et al 1978 with average concentrations of 0.019 and 0.041 cc respectively Boelter et al 2002 Imkonen et al 1978 The third group was comprised of Cheng and McDermott 1991 ten of the Mangold reports and the two Spen- 10000 _ | 1000 j + | 100 | cccc / 10 Concetraions ! Concetraions S Concetraions TEM ... TEM ; 1 001 : 0001 0.0001 0.001 ' a" ay! *, 5 . ", = A DDD ae DDD ran se as o . oe +f ee . r ane 3" 2 0 Longo 2002 52 Longo 2002 53 A Madl 2009 " McKinnery 1992 Millette @ Spence and Mount 1993 and Rocchi 1996 , : : : 0.01 01 1 10 100 PCM Concentrations cc . Fig 2. Comparison across studies of the airborne fiber concentrations by phase contrast microscopy PCM in fibers per cubic centimeter cc and by transmission electron microscopy TEM in cc 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 ofPages 15 Model 5G 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 10 AK Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx cer reports with average airborne asbestos concentrations ranging from 0.0042 to 0.0092 cc Cheng and McDermott 1991 Mangold 1982a Mangold 1989a Mangold and Gay 1991 Spencer 1998a As with the short sample data mean asbestos concentration of each ranking group was significantly different from one another but mean asbestos concentrations of the studies within each ranking group did not differ significantly Only two studies had TEM results in the 60 min category our simulation study mean 0.01 cc n 7 and Spence and Rocchi 1996 mean 0.001 cc = 7 the simulation study was significantly greater than Spence and Rocchi ( 1996 using a Student t test with p = 0.0005 3.2.2 Comparison of PCM and TEM results by study A comparison of the results from gasket and packing studies that report both PCM and TEM data generally show that as PCM concentration increases TEM concentration also increases Fig 2 Differences however were noted among the individual studies in the magnitude of increase of TEM concentrations com- pared with PCM concentrations Spence and Rocchi 1996 and our simulation study show average PCM ratios of less than one average ratio 0.04 range 0.005-0.19 and average ratio 0.25 range 0.02-2.11 respectively Spence and Rocchi 1996 while Millette and Mount 1993 demonstrated an average ratio of 2.9 range 2.2-3.3 Millette and Mount 1993 The ratios reported by Longo et al 2002 and McKinnery and Moore 1992 were markedly higher average ratio 37 range 5.2-77 and average ratio 31 range 0.5-354 respectively Longo et al 2002 McKinnery and Moore 1992 3.2.3 Evaluation of equipment A total of 165 PCM samples 60 min sample duration were available in ten equipment categories flange pump valve and flange valve www pertaining to the handling of packing gaskets or both packing and gaskets ventilation duct heater boiler header and not specified - pertaining to the handling of gaskets or packing Results are presented in Fig 3 and show concentrations measured during the use of gaskets and packing associated with 30 25 cc f 20 Concentration Concentration Concentration Concentration 15 Concentration Concentration Concentration Concentration 10 4.8 I S 22.4 | Sampling duration < 60 minutes 0* 17 Flange 23,11 23,11 014 Valve 23 Valve and [| Flange |n | 0.11 - Pump 2 Gaskets 043 www : Ventilation Duct Heaters | n 009 wo. Boiler Header 27 011 0.28 www Not i Valve | Specified 23 | 19 + 0.26 ee Not Specified 38 0.02 Valve = 2 i Packing i Gaskets Packing 0.20 - Sampling duration 60 minutes 637 638 639 640 641 642 643 644 645 646 647 648 cc 0.15 : / : Concentration : Concentration : Concentration 10 < Concentration Concentration Concentration Concentration : Concentration 0.05 * 0.00 ... 0.025 Flange 59 0.047 . ie ~ Valve and Flange 12 Not Specified 11 Gaskets 0050 a Boiler Header 2 0024 Valve n Packing 0.04 Valve n Gaskets Packing Fig 3. Airborne asbestos concentrations during work with gasket and packing materials by equipment type Legend average airborne fiber concentrations cc by phase contrast microscopy during personal gasket and packing tasks performed on the indicated equipment for sampling durations less than 60 min or greater than or equal to 60 min The flange category 60 min was the only category that contained data from the Longo 2002 study as well as from other studies Thus for the 60 min flange category the data was analyzed including white and excluding black bar the Longo data Sample numbers n including and excluding data from Longo 2002 respectively are provided for the flange category The 60 min valve and flange category only contained data from Longo 2002 white bar wise statistical comparisons were performed to identify significant differences p < 0.05 No comparisons were performed in categories with 3 samples Statistical significance for samples 60 min in duiation is as follows gasket work on valves and flanges is significantly greater than gasket work on all other equipment includes Longo 2002 data p < 0 0007 flange gasket work is significantly greater than gasket work on boiler headers valves or when the specific equipment was unspecified and packing work on unspecified equipment p < 0008 0008 when data from Longo 2002 is excluded packing work on valves and not specified equipment and gasket work on ventilation duct heaters is significantly greater than flange gasket work p 002 002 Results for samples 60 min is as follows gasket work on flanges gasket work on unspecified equipment packing work on valves and combined packing and gasket work on valves are significantly greater than gasket work on valves and flanges p < 0.007 No data were available for samples 60 min in duration for gasket work associated with pumps ventilation duct heaters or valves Error bars represent standard error simulation study and 11 A.K Madl et al./Regulatory Toxicology and Pharmacology xxx 2014 xxx existed for the available TEM samples 60 min and based 721 655 the various types of equipment For gasket and packing samples gories asbestos concentrations during combined 722 656 60 min in duration many of the samples in thefrtowmo tchaetegLoornigeos o ganspkaeitrawnidsepcaockmipnagriwsoornk on valves was higher than gasket work on 723 724 657 with the highest asbestos concentrations were differ from the unknown equipment p = 0.0004 658 simulation tests which were previously shown to 660 673 674 675 676 677 679 680 682 683 684 685 686 687 688 689 690 691 692 693 694 697 709 711 712 713 714 715 716 717 718 719 720 rest of the published studies by a factor of 5-100 Specifically valve and flange gasket samples had a significantly higher average concentration than all other categories p < 0.0007 The samples in the valve and flange gasket category were all derived from the longo et al 2002 study and were collected over a 10min period during gasket removal with a power wire brush Longo et al 2002 Average concentrations during flange gasket work the second highest category were significantly higher than the average concentrations for gasket work on boiler headers valves and unknown equipment as well as packing work on unknown equipment p < 0.0008 While the majority of the samples in the flange group involved gasket removal using handheld tools there were also a few samples collected during gasket installation as well as one sample collected during gasket removal with a power sander With the Longo data excluded the valve and flange category was removed as there were no other data representing work with combined types of equipment In addition the flange category had a much lower average airborne asbestos concentration 0.17 cc compared to 4.8 cc once the Longo data had been excluded Fig 3 Two categories including gasket work on pumps and combined gasket and packing work on valves had inadequate sample size for statistical comparison TEM data were available for comparisons by equipment type for seven of the ten equipment categories evaluated for PCM data for sample durations 60 min and 6m0in flange valve and flange valve - pertaining to the handling of packing gaskets or both packing and gaskets and not specified - pertaining to the handling of gaskets or packing Results from pairwise comparisons for sampling durations 60 min indicated similar trends as were observed in the PCM data with valves and flange and flange categories consisting of data only from the Longo et al 2002 study having significantly greater average airborne asbestos concentrations than the other equipment categories p < 0.0001 all comparisons but not from each other In general the average airborne asbestos con- centrations associated with work with equipment as measured by TEM decreased in the following order including data from Longo et al 2002 valves and flanges gaskets > flanges gaskets > not specified gaskets > valves gaskets > not specified pack- ing valve packing > valve packing and gasket combined When data from Longo et al 2002 was both included and excluded combined packing and gasket work and packing work associated with valves was significantly less than gasket work on valves and gasket work when the equipment was not specified p 0/.003 and packing samples when the equipment was not specified p < 0.003 The samples in which the equipment was not specified were largely from the McKinnery and Moore 1992 study in which all fibers greater than 0.5 ...m in length were counted by TEM McKinnery and Moore 1992 A similar comparison was performed on PCM samples 6m0in n 98 across six equipment categories flange valve and flange valve pertaining to the handling of packing or combined gaskets and packing boiler header and equipment not specified Although asbestos concentration for the category of boiler header average is included in Fig 3 there were too few samples to include this cat- in the statistical analysis Average airborne asbestos concen- egory trations for samples collected 6m0in among the gasket packing and combined gasket and packing samples were considerably lower compared to 60 min samples The valve and flange equipment category for gasket samples was significantly less than all other categories p 0/.007 with an average value of 0.0046 cc compared to a range of average concentrations of 0.025-0.047 / cc for the other four categories Fig ) Only two equipment cate- 3.2.4 Evaluation of task A total of nine tasks were considered in this evaluation gasket and packing installation removal and replacement gasket fabrication combined gasket and packing work and clean The combined gasket and packing category only contained two samples which precluded its inclusion in the analysis For samples 60 min the average asbestos concentrations measured during gasket removal were greater than average concentrations during all other related activities as well as packing installation p < 0.018 Fig 4 Sixteen of the 72 shorter samples in the gasket removal task category were from the Longo tests When these samples were excluded the average airborne asbestos concentration for the removal task decreased to % of the original calculated average when the Longo data were included average excluding Longo 0.17 cc range 0.015-1.4 cc n = 56 In addition average asbestos concentrations during packing removal were greater than gasket installation and gasket replacement when Longo data were included Concentrations during packing removal were also greater than during fabrication -installation replacement and -removal and greater than packing installation when the data from Longo were excluded p < 0.016 Average concentrations across all studies for gasket and packing work 60 min with the exception of Longo et al 2002 are well below the cur- rent OSHA Excursion Limit of 1 cc TEM data were available for eight task categories among the 60 min samples gasket removal -fabrication -installation packing removal installation -replacement combined gasket and packing work and clean Less than three samples were available for gasket installation so this task was not included in the statistical analysis In general the average airborne asbestos concentration associated with specific tasks as measured by TEM decreased in the following order gasket removal > gasket fabrica- tion > packing removal > clean > packing installation > combined packing and gasket work > packing replacement Sixteen of the 25 gasket removal samples originated from the Longo et al 2002 study When the Longo data was included gasket removal tasks had significantly greater average airborne asbestos fiber concentrations than all other activities p < 0.003 When these sam- ples were removed from the analysis the tasks of packing removal and gasket fabrication were no longer significantly less than gasket removal p > ) Moreover gasket fabrication tasks were significantly greater than packing installation packing replacement and combined packing and gasket tasks including and excluding Longo data p < 0.047 In addition the average asbestos concentration for the task of packing removal was signif- icantly higher than packing installation packing replacement and combined packing and gasket tasks including Longo data < 0.001 in addition to clean tasks when the Longo data was excluded p < 0.028 For samples 60 min by PCM n = 123 gasket removal tasks were statistically greater than gasket replacement tasks average airborne asbestos concentrations was 0.03 cc compared to 0.01 cc respectively p 0.0001 Fig 4 Moreover combined gasket and packing work was also significantly greater than gasket replacement p = 0.0085 Although it had the highest average asbestos concentration the packing installation category only contained one sample which precluded its inclusion in the analysis The average airborne fiber concentrations for sampling duration 60 min across all tasks were less than the current OSHA PEL Similar to the equipment analysis only two task categories existed min and based on pairwise 725 726 727 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 784 785 htp:/dx.oirg/10.6/j asbestos exposures and simulation study YRTPH 3031 0 28 April 2014 12 on A.K. Madl et al./Regulatory al./Regulatory Toxicology andand Pharmacology xxx 2014 xxx No. ofPages Model 5G Sampling duration < 60 minutes 29 cc f 3 Concentration Concentration Concentration Concentration Concentration 2 Concentration Concentration . 0.28 17 oo- ; eerste som seomattonane. : : Fabrication Installation Removal , Replacement 94 n 72,56 + 27 Gaskets 038 Clean up 4 013 ; met * Installation n 28 . H 0.44 Removal n 26 Packing s enna . Replacement n weenie Combined n Packing Gaskets 0.20 cc 015 Concentration Concentration 10 - Concetraion Concentration 05 - 0.00 + 0.030 0.030 = Fabrication 28 0.022 =: Installation i n3 } 0029 = Removal 63 Gaskets 010 a Replacement 16 011 Sampling duration > 60 m.rutes . Installation n 0.014 i Replacement ft 8 ' Packing : : 0.039 0.039 | Combined 5 Packing Gasket removal asbestos concentrations during work with gasket and packing materials by task Legend average airborne fiber concentrations cc by phase contrast Fig 4. Airborne tasks associated with gaskets and packing for samples samples less than 60 min or greater than or equal to 60 min in duration For the one microscopy during specific personal the 2002 study gasket removal the data are plotted including white bar and excluding black bar the Longo results Sample category that contained data from Longo removal respectively combined signifies combined gasket and packing work wise numbers n including and excluding data from Longo 2002 are provided for gasket removal in with 3 samples Statistical significance for statistical comparisons were performed to identify significant differences p < 0.05 No comparisons compartishoanns were peirnfstoarlmleadtion caantdeggoarisekset replacement includes Longo 2002 data samples 60 min is as follows gasket removal and packing removal is significantly greater gasket data from 2002 is excluded packing p002 p002 gasket removal is also significantly greater than gasket fabrication and packing installation p < 002 When Longo 2002 data < 0.003 gasket tasks are significantly greater than gasket fabrication -installation -removal and -replacement as well as packing installation excludes Longo p and than gasket installation p = 0.03 Statistical significance significance for samples 60 min is as follows gasket removal and combined gasket fabrication is significantly greater available for samples 60 min in duration for cleanup and packing removal tasks packing work are significantly greater than gasket replacement p < 0.009 No data were Error bars represent standard error 786 787 788 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 comparison asbestos concentrations during combined gasket and packing work was higher than gasket removal p = 0.0004 3.2.5 Evaluation of tool A total of 15 tool categories were considered Fig ) As previ- ously mentioned no significant differences were observed between packing and gasket samples and only a few of the tool groups included samples associated with work on packing material as such packing and gasket samples were pooled for the eval- uation by tool Similar to the study categorization when all sample durations are combined tools fall into three general groups from highest to lowest airborne asbestos concentrations including the Longo data group one included power wire brushing and the use a of scraper and hand wire brush group two included hand punch- ing and shearing power shearing and the use of miscellaneous hand tools machine punching the use of multiple tools including shop and not specified tools while group three consisted of all other tool categories For the 6m0in data no samples were available for hand brush and multiple tools including shop although two additional tool categories were added ball peen A hammer and scraper and power wire brush total of five tool cat- egories had inadequate sample size n < 3 for inclusion in either the 60 min or 6m0in pairwise analysis For the 60 min sample duration category average airborne asbestos concentrations for scraper and hand wire brushing including the Longo data were significantly greater than all other tool categories with the excep- tion of power wire brush which also included data from Longo et al 2002 p < 0.002 Fig 5 Similarly power wire brushing including the Longo data was significantly greater than all tools except miscellaneous tools including shop tools and power shears and miscellaneous hand tools p < 0.007 When the Longo data were excluded from the tool comparison scraping and hand wire brushing and power wire brushing were no longer greater than any of the other tool categories Fig 5 However average concentrations during work with power shears and miscellaneous hand tools were greater than concentration during machine punching when data from Longo were included p < 0.031 as well as scraping when data from Longo were excluded p < 0.04 For the 6m0in data there were no significant pairwise differences between the tool categories For the TEM results in the 60 min sample duration category the average airborne asbestos concentrations across the available tool categories including the Longo data decreased in the > following order power wire brushing scraper and hand wire order brushing power shears and miscellaneous hand tools > hand brush > tool not specified > circular cutter > replacement using multiple hand tools Four of the seven power wire brush samples and all of the scraper and hand wire brush samples originated from the Longo studies When the data from Longo et al 2002 were included the average airborne asbestos concentrations dur- packing replacAesimmuelatniotn study and + 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 831 832 833 834 of Page1s5Model 5G A.K Madl et al Regulatory Toxicology and Pharmacology xxx 2014 xxx 13 12 10 . 7.1 Sampling duration < 60 minutes 6.8 BB: cc cc ( Concentration 6 Concentration Concentration Concentration Concentration 4. Concentration Concentration Concentration 2 0.04 005 0 -~ a cance Replacement using multiple | hand * Circular cutter + tools n 0.10 0.10 Scraper 18 0.40 011 el Hand | Hand , Hand - punch brush 10 n : i : Manual 11 ee 12 17 ee oe 0.29 33 026 017 a * [ Multiple Power shears gasket formation * hand Hand brush file t 13 ' with | tools 1 : & Scraper hand brush 16,4 Power wire misc hand brush tools > 13,9 34 | Machine punching | 31 } Multiple including shop n : n 12 Power 0.24 Not specified . 100 Other 5. Airborne asbestos concentrations during work with gasket and packing materials materials by tool type Legend average airborne fiber concentrations by phase contrast Fig manual and tools associated with gasket and packing removal fabrication and installation tasks Samples were grouped by microscopy during the use of specific power data from Longo 2002 scraper & hand wire brush durations of less than 60 min and greater than or equal to 60 min For the samples 60 min the two categories that contain and wire brush are presented including white bars and excluding black bars the Longo data Sample numbers including and excluding data from Longo 2002 are power differences between the tool categories both including and provided for these two categories wise statistical comparisons were performed to identify significant & excluding data from Longo 2002 p < 0.05 No comparisons were performed performed in categories with 3 samples Statistical significance for samples 60 min as follows scraper hand wire brush is significantly greater than all other categories except power wire brush including Longo 2002 data p < 0002 0002 power wire brush is significantly greater & hand wire brush miscellaneous including shop and power shears & miscellaneous hand tools including Longo 2002 data than all other categories except scraper than machine punch including and excluding Longo 2002 data p < 0003 and also greater than p < 0.007 Power shears & miscellaneous hand tools is significantly greater differences between tool categories p < 0.05 Tool when data from Longo 2002 is excluded p = 004 004 For the samples 60 min there were no significant pairwise scraper for which all some of the samples were taken in a machine shop setting are noted with an asterisk * Samples were predominantly collected during gasket wcaotregkorhioeswever tool cateogrories for which some of the samples were taken during packing work or combined packing and gasket work are noted with a positive sign + Error Q5 bars represent standard error 835 836 838 839 840 841 842 843 844 845 846 847 848 849 850 852 853 854 856 857 858 859 860 861 862 863 864 865 866 ing power wire brushing was significantly greater than all tool categories except scraper and hand wire brushing and hand brush p < 0.018 Similarly average concentrations during the use of a scraper and hand wire brush were significantly greater than the reported concentrations during the use of all other tools except power wire brushing p < 0.027 Work with power shears and miscellaneous hand tools as well as hand brush resulted in average asbestos concentrations significantly greater than those measured during work with a circular cutter and when no tool was listed p = 0.032 Removal of the Longo data resulted in elimination of the category of scraper and hand wire brush In addition average concentrations during power wire brushing were only greater than one category circular cutter p < 0.028 Average airborne concentrations during the use of power shearing and miscellaneous hand tools and the use of a hand brush were significantly greater than average concentrations during work with a circular cutter and when the specific tool was unspecified p < 0.034 Three categories were available for comparative analysis among the 6m0in data circular cutter replacement using multiple hand held tools and tool not specified but no significant differences were measured between these categories 4. Discussion Results of the simulation study showed that exposures associated with replacement of gasket and packing materials internal valves are consistent with the body of exposure data collected over the last 30 years representing a wide range of variables including equipment task tool and duration The creation of a combined dataset not only allowed us to test for consistency between the simulation study and previously published data but also enabled statistical comparisons across multiple variables The average airborne asbestos concentrations measured in this simulation study for both a mechanic performing a valve overhaul as well as a bystander working in the vicinity of such activity were below both the current and all previous U.S. occupational asbestos standards This study found that short exposures 30 min of a mechanic to airborne asbestos during packing and gasket replace- ment on valve as measured by PCME were 0.027 cc range 0.004-0.047 cc whereas h TWA exposure averaged 0.002-0.0c1c0 based on the assumption that 1-3 gasket or packing replacements could be performed within a workday over the course of a year Similarly in the analysis of the combined gasket and packing data by PCM 30 min the overall average of all samples was 0.24 cc 95th percentile 0.78 cc and only six of 155 samples 30 min excluding the Longo data exceeded the current OSHA excursion limit It is noteworthy that all six samples exceeding the current Excursion Limit represented activities involving power or machine equipment in an industrial setting where background fiber sources can confound measurements Cheng and McDermott 1991 Lukonen et al 1978 For longer samples 6m0in in the combined dataset 95 were below the current OSHA PEL h TWA of 0.1 cc average 0.026 cc 95th percentile 0.087 cc 95 UCL 0.031 cc Airborne asbestos concentrations for six of 127 samples exceeded the current OSHA PEL ranging from 0.11 to 0.24 cc Similarly noted for the short samples at least four of the six samples 6m0in were either collected in industrial locations e.g. shipyard maritime vessel plant where background asbestos concentrations likely confounded results or in a machine shop setting Liukonen et al 1978 Mangold et al 2006 Spence and Rocchi 1996 In support of the results from the combined analysis a recent study conducted by Boelter et al ( 2011 gathered over 10 years worth of asbestos fiber release exposure assessment data representing more than 700 samples associated with removal and or replacement of gaskets and packing and used three methods to estimate the geometric mean and geometric standard deviation of the maximum likelihood estimation nonparametric Kaplan- gasket and packing replacA seimumlateionnstutdy and 868 869 870 871 872 873 874 875 876 877 878 879 880 882 883 884 885 886 887 889 890 892 893 894 895 896 897 898 899 900 901 28 April 2014 2014 xxx A.K Madl et al Regulatory Toxicology and Pharmacology 2014 xxx 14 902 903 904 905 907 908 909 910 911 912 914 915 916 918 919 920 921 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 939 940 941 942 943 944 945 946 958 959 960 962 963 965 966 967 Meier and lognormal statistics Boelter et al concluded that all three sets of statistics suggest that the mean and median exposures were less than 25 of 0.1 cc h TWA sample or 1.0 cc min samples Boelter et al 2011 After accounting for sample duration there were certain data- sets that appeared to influence the low and high end of the data distribution which in turn influenced the statistical significance of certain variables e.g. equipment task tool type The upper range of the complete worker dataset represented data from the Longo studies whereas the valve simulation study presented herein reflected data at the low end of the distribution Statistical compar- isons showed that the Longo data was greater than the 99th percen- tile which provided compelling evidence that the Longo data was an outlier compared to all other samples in the dataset Pairwise comparisons demonstrated that exposure data categorized by equipment task or tool were no longer statistically significant for categories highly represented by the Longo data once it was excluded For example gasket removal activities with sample times 60 min were no longer significantly different from fabrication installation or replacement once the Longo data were excluded A similar outlier analysis was performed on the valve simulation study data at the low end of the data distribution Excluding the 20 worker samples from the valve simulation study that were 60 min showed minimal impact % on the 1st and 5th percen- tiles of the combined dataset and only two of the 20 samples were less than the 25th percentile of the overall dataset which supported the conclusion that the simulation study data was not an outlier at the low end of the overall data distribution in the same way that the Longo et al 2002 data were for the upper end of the distribution Explanation for the Longo dataset being inconsistent or an outlier with other published studies on gaskets and packing has been described by others Boelter 2003 In short the aggressive use of a power wire brush unrealistic number of gaskets removed within a short time period low sample volume fiber density outside the recommended range work performed by a tradesman fiber size classification outside regulatory guidelines and high back- ground levels likely contribute to the measurements being outlier to the combined published data The fiber and asbestos concentrations measured during work with gaskets and packing associated with various equipment tasks and tools were fairly consistent aside from the studies by longo et al 2002 with pairwise comparisons showing some significant differences between the tasks by material equipment by material and between the various tool categories The use of power tools was associated with higher airborne asbestos concentrations compared to hand tools 60 min with the average air- borne asbestos concentrations associated with the use of hand tools being all below 0.2 cc with the exception of the use of a hand punch or shear Longo data excluded In support of this Boelter et al 2011 reported detectable total and asbestos fiber average concentrations of 0.269 cc and 0.200 cc respectively for power tools and 0.060 cc for the use of a hand held wire brush Boelter et al 2011 While comparisons of TEM results by task equipment and tool show generally similar relative trends with PCM results inappropriate sample preparation methods and varying fiber counting classification criteria for over half of the TEM results prevent any meaningful comparisons between studies Our simulation study as well as studies by Millerre and Mount 1993 and Spence and Rocchi 1996 used NIOSH 7402 for TEM analysis however Spence and Rocchi 1996 did not provide details of the counting criteria used in their study Millette and Mount 1993 Spence and Rocchi 1996 Per the requirements of NIOSH 7402 all studies with the exception of Longo et al 2002 presumably utilized the direct preparation of MCE or polycarbonate filters prior to counting McKinnery and Moore ( 1992 report using a modified version Bes of the AHERA method with the modifications including low sam- ple volumes and high loadings such that the number of grid openings counted were reduced from 200 to approximately five McKimery and Moore 1992 The EPA AHERA method specifies that all fibers 0.5 ...min length are counted while NIOSH class~-- fies fibers 5...min length 0.25 min diameter and having at least a 3 aspect ratio TEM results by Longo were based on the indirect sample preparation method ASTM D5755-95 and included fibers of all widths in addition to those > ...min length It has been demonstrated by other researchers that this indirect method yields higher counts than samples prepared by the direct method in some reports as high as 1700 times greater than fibers seen using the direct method Boelier 2003 CDC Centers for Disease Control and Prevention 2008 Chatfiel 2000 The indi- rect method involves sonication as well as resuspension of fibers in liquid which can alter the physical form and ultimately the number of fibers counted It is also noteworthy that the ASTM method is for settled dust and states this test method does not describe procedures or techniques required to evaluate the safety or habitability of building with containing materials or compliance with federal state or local regulations or statues American Society for Testing Materials ASTM 1995 Therefore the TEM results derived from samples prepared by indirect meth- ods or analyzed with alternative counting criteria are not informative in terms of comparison to any occupational exposure limits or instructive for implications of health risk In summary the simulation study results and analysis of the available published exposure data associated with work involving containing gaskets and packing material and consider- ing the range of variables product equipment task tool duration that could influence potential exposures have shown that trades- men performing such work in nearly all plausible scenarios are exposed to airborne asbestos concentrations below historical and current occupational exposure limits for asbestos Of note when considering the number of air samples described in the Boelter et 2011 study in addition to the data considered in this analysis over a 1000 industrial hygiene samples of gasket and packing work during varying work practices and workplace conditions have been characterized in the published literature during the last 30 years This analysis shows that with few exceptions airborne asbestos exposures during work with containing gaskets and packing fall within a relatively narrow and low range Summary of the historical exposure data on gasket and packing materials according to different variables product equipment task tool and duration should provide useful information to exposure and health risk assessors in conducting quantitative historical exposure assessments for a variety of industrial settings Acknowledgments The authors affiliations are as shown on the cover page Six of the seven authors are currently employed by Cardno ChemRisk a consulting firm who provides scientific advice to the government corporations law firms and various professional organizations The authors have sole responsibility for the writing and content of the paper Funding for the preparation of this article and the underlying research was provided by Invensys and John Crane Inc. which have been involved in litigation involving gaskets and packing These two funding sources and their counsel did not provide editorial comments or review the paper before submission to the journal Two of the authors A.K.M. and D.M.H. have served as expert witnesses regarding historical expo- sures of various tradesmen to asbestos A.K.M. has testified on matters related to gasket and packing materials on behalf of John Crane Inc. and Invensys simulation study and 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 990 991 992 993 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 Pages 15 Model 5G 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 AK Madl et al./Regulatory al./Regulatory al./Regulatory Toxicology and Pharmacology xxx 2014 xxx 15 Appendix A. 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Evaluation of airborne asbestos fiber levels during removal and installation of valve gaskets and packing Am Ind Hyg Assoc J. 53 531-532 Millette J.R. Mount M.D. 1993 A study determining asbestos fiber release during the removal of valve packing Appl Occup Environ Hyg 8 790-793 National Institute for Occupational Safety and Health NIOSH 1994. NIOSH Method 9002 Asbestos bulk by polarized light microscopy PLM NIOSH Manual of Analytical Methods DHHS Publication No 94-113 National Institute for Occupational Safety and Health Washington DC Selikoff J. 1970. Partnership for prevention - the insulation industry hygiene research program IMS Ind Med Surg 39 162-166 Spence S.K. Rocchi P.S. 1996. Exposure to asbestos fibres during gasket removal Ann Occup Hyg 40 583-588 Spencer JW 1998a Exposure Assessment An Contribution of Airborne Asbestos Fibers from Evaluation of the Fabrication the , Actual of Gaskets Environmental Profiles Inc Baltimore MD Spencer J.W. 1998b Exposure Assessment An Evaluation of the Actual Contribution of Airborne Asbestos Fibers from the Removal and Installation of Gaskets and Packing Material Environmental Profiles IncCompres d Baltimore MD United States Navy 1924. Packing Sheet Asbestos Compressed 33P13 Department of Specifications Washington DC United States Navy 1953. Military Specification 17472 Asbestos Sheet Compressed Packing Material Bureau of Ships Navy Department Washington DC 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 Airborne asbestos exposures associated with gasket and htp:/dx.doi.org/10.1016/j.yrtph.2014.04.07 htp:/dx.doi.org/10.1016/j.yrtph.2014.04.07