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\0^j MAKING SOMETHING ^ OUT OF NOTHING Legal limits on asbestos exposure are becoming increasingly less. But how are valid air samplings made when the values measured are near zero? By Jeffrey A. Boggs t is critical that decisions to re Jopen removal sites to the un protected public are supported by statistically valid test data. Today a method for estimating lowlevel airborne asbestos fiber concen trations with statistical confidence, both prior to and following abatement projects, has been developed. This "Poisson" distribution method has been tested and found the best statis tical model for determining both unexposed membrane filters (back ground levels) and sample membrane filters (exposed levels) of asbestos. The "limits of reliable detection" for the USPHS/NIOSH methods P&CAM 239 or 7400 are the limit of quatitaMve detection (LOD) and the limit ofquantitative detection (LOQ). Standard calculating procedures utilizing known variables--such as microscope field area, filter effective collecting area and sample air volume--provide guidelines for deter mining detection limits. The protocol has been simplified for laboratory analysis of low-level airborne fiber concentrations by the presently preferred NIOSH methods. Additional formulae, which determine the re quired air volume (Q) to "reliably detect'' the filter surface fiber concen tration standards (S) help laboratories and hygienists specify appropriate sampling strategies, a priori. Thus, the proposed standard methodology offers two significant contributions for determining lowlevel airborne asbestos fiber concen- MAY/JUNE 1988 ASBESTOS ABATEMENT 23 HWBUI0001317 nations: 1) provides point estimates based on the calculated, known "limit of detection'' for any volume of air sampled, and 2) permits statistically valid "re-entry" decisions. OSHA first regulated occupational exposures to asbestos (See Figure 2) in 1971 when it adopted a 12 f/ce limit. In June 1972, OSHA pro mulgated the present standard which is found at 29 CFR 1910.1001. This standard established an 8-hour TWA permissible exposure limit (PEL) of 5 f/cc (with a ceiling limit of 10 fee), and mandated further reduction in the PEL to 2 fee effective July, 1976. In 1975, OSHA again proposed to lower the PEL from 2.0 fee to 0.5 fee and the ceiling limit from 10 fee to 5 fee. This notice of proposed rulemaking was based on then-available evidence which OSHA believed had "accumulated to warrant the des ignation of asbestos as a human carcinogen.'' In 1982, the State of Maryland Figure 1 % f O i 2345678 FIBERS/MM2 REAL-TIME ASBESTOS FAM-1 Laser Fiber Counter No special training required High correlation to PCM Immediate notification of methods potentially hazardous Sensitive to .0001 fibers/cc exposures Completely portable Digital readout infibers/cc Selectable sample/result Differentiates between fibrous and nonfibrous particles times as short as one minute Optional battery pack The FAM-1 can be used in schools, factories, and other public buildings to determine airborne asbestos concentra tions prior to, during, and after removal operations. For complete information, call or write to: / cMIE- MIE, Inc.* 213 Burlington Road Bedford. Massachusetts 01730 (617) 275-5444 Telex: 92-3339 (Formerly a division of GCAl 24 ASBESTOS ABATEMENT MAY/JUNE 1988 promulgated asbestos regulations that required final air testing on any large project. Areas could not be opened to the public until airborne concentra tions were less than 0.1 fee. In November 1983, OSHA published an Emergency Temporary Standard (ETS) which mandated an immediate reduction in the PEL to 0.5 fee. In June 1985, the EPA published "Guidance For Controlling AsbestosContaining Materials in Buildings". This text is generally regarded as the latest information on asbestos hazard evaluation. Appendix M of the docu ment recommends that if any phasecontrast microscope samples exceed 0.01 fee, the abatement site should be recleaned. The Veterans Administration has specified that authorization for removal of barriers of small area asbestos removals will be authorized if the air sample is 0.005 fee. These current re-occupancy stan dards would suggest very low and zero fiber counts in post-abatement environments. The problem, there fore, is how to handle "zero" or "near zero" data values. In industrial hygiene work, zero value levels are generally undetectable. These levels do occur, however, and there is no HWBUI0001318 When you go into bidding with a 60% reduction m labor and material costs, you've got one big competitive edge! And an opportunity for greater profits. The HEPA VAC automated vacuum system reduces bag handling from 5 or more workers to 2. Cuts bag use by 75%. Why? Because wet or dry asbestos is moved, not by muscle, but by a vacuum hose up to 1000 ft. long at the rate of 9-18 tons/hi Certified HEPA air filtration assures system will meet or exceed OSHA and EPA safety regs. From pick up to bagging, fibers are captured in a fully enclosed, negative pressure system. The HEPA VAC never leaves the site, working continuously until the job is done. And John Deere diesel engine, quality construction and proven design means the job gets done faster and more safely than the oldfashioned manual way A faster job A safer job. Abetter <ob-A less expensive (ob. Bring on the competit.an! 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Call or write today for more information about the HEPA-AIRE 2000 or for the name of your local Abatement Technologies distributor. HEPA-AIRE 2000-the state-of-the-art in asbestos air filtration products. Now available in 3 models... H2000A-2 speed full feature electric H2000C - 2 speed contractors electric H2000P-variable speed air driven model i T'ANCED PRODUCTS fop the ASBESTOS REMOVAL INDUSTF- m HWBUI0001320 BATEMENT Ecmmcxms 3305 Breckinridge Blvd. Suite 118 Duluth, GA 30136 404-925-2781 FAX 1-404-381-7454 HWBUI0001321 1 o 12 F/CC single accepted way to handle them. One method is to obtain from the analytical laboratory the least amount of the contaminant which the analy tical method can detect. This value is then used to determine the least detectable concentration in the amount of air sampled, and then substituted for all zero values. By resolving the proper distributional model, one can then apply the ap propriate probability function, and thereby the detection power, to the analytical methods. Methods and Results We have accumulated data over the past several years (See Figure 1) for fiber counts on unexposed filters as a routine quality control measure for background fiber surface concentra tions. The observed frequency distri bution of these fiber concentrations, shown as fibers per square millimeter, was obtained from phase-contrast microscope counts using the NIOSH analytical methods P&CAM 239. Some 100 separate factory lot num bers of 37mm-diameter, celluloseester membrane filters have been analyzed with a microscope optical system using a Patterson-Globe graticule that has a calibrated field area of .0062 square millimeters. 28 ASBESTOS ABATEMENT MAY/JUNE 1988 1 HWBUI0001322 f A striking feature of the data is the large frequency of zero concentra tions, 33 percent of the total. Addi tionally, the clumping of 0-2 fibers/mm2 results in the observed relative frequency of nearly 60 percent. These results indicate that back ground fibers concentrations might be adequately described by the Poisson distribution. The Poisson distribu tional model also seems appropriate based on the low mean value of 2.3 fibers/mm2 with a high coefficient of variation of 87 percent. The purpose of fitting a Poisson distribution to numbers of rare events is to test whether the events occur independ ently with respect to each other. If they do, they will follow the Poisson distribution. We have tested this observed dis tribution as well as the observed fre quency distribution of re-occupancy sample fiber concentrations against the expected Poisson frequencies and evaluated the comparison by the ChiSquare test for goodness of fit. The plot of cumulative, relative observed and expected frequencies of fibers concentrations (17mm2) from unex posed filters shows good agreement throughout the range of measured values (See Figure 3). The shape of the Poisson expected frequency curve is completely defined by the mean of the observed values. The Chi-Square test value was less than the Chi-Square critical value at 10 percent with four degrees of freedom and by interpolation was ac tually less than the critical value at 30 percent. This significant agreement, therefore, supports our hypothesis that the observed fiber concentrations of unexposed filters are Poisson distributed. Having adequately described the Poisson distribution of background fiber concentrations, we have ran domly selected 100 re-occupancy samples and plotted the observed fre quency distribution for fiber concen trations in fiber/mm2 (See Figure 4). Not too surprisingly, as predicted from these presumed clean air en vironments, there is a relatively high frequency of low, 0-3 fibers/mm2, concentrations accounting for more than 20 percent of the distribution with more than 50 percent being less OBSERVED FREQUENCY: POISSON DISTRIBUTION: REOCCUPANCY FIBER SURFACE CONCENTRATIONS FIBERS/MM2 Figure 5 than 8 fibers/mm2. The observed mean for this data set was 8.8 fibers/mm2 with a coefficient of variation of 76 percent. These sam ple concentrations are measured from filtered volumes of 1000-1500 liters and have not been corrected for background fiber concentrations. With such a high coefficient of varia tion and a relatively low total fiber concentration, we felt this observed frequency distribution might also be Poisson distributed. Again, we have plotted (See Figure 5) the observed and expected cumu lative frequencies of the fiber concen trations in fibers/mm2. We wished to evaluate the low-level concentration MAY/JUNE 1988 ASBESTOS ABATEMENT 29 HWBUI0001323 portion of the curve--comparable to the previously shown background fiber concentration distribution--sep arately from the higher concentration portion from 9 to 23 fibers/mm2. For the purpose of Chi-Square testing for fit of the two curves we therefore chose to have just one degree of freedom. Under these testing conditions the Chi-Square measured value was less than the critical value at 50 percent. Thus we now have two separate tests of significant agreement with the Poisson distributional model using both unexposed and exposed filter fiber concentrations. These results provide the proper statistical frame work from which we can evaluate the limits of qualitative detection (LOD) as well as the limits of quantitative detection (L)Q). Limits of Detection We have chosen the 95th percen tile of the observed, Poisson distributed, unexposed filter fiber concentration for the limit of LIMITS OF QUALITATIVE DETECTION (L.O.D.) UNEXPOSED FILTER CONCENTRATIONS (FIBERS/SQ. MM) MEAN STD. DEV. + 3 S.D. POISSON A.MA 2.3 2.0 -- 6.0* N.I.O.S.H. 2.5 1.5 7.0" Table 1 (a) ESTIMATED L.O.D. METHOD 7400 (b) PROPOSED L.O.D. FUNCTIONAL RELATIONSHIP FOR FIBER COUNT L.O.D.: L.O.D. - (MICROSCOPE AREA) (FIBERS/SQ. MM) (100 FIELDS) EXAMPLE: L.O.D. * (.006 SQ. MM) ( ) (100) L.O.D. a 3.6 FIBERS IN 100 FIELDS Table 2 f ASBESTOS LIABILITY INSURANCE $1,000,000 Limit Occurrence Non-Cancelable Domestic Carrier "A" Rated A Not-For-Profit Association 'N, 1. Gross Asbestos Removal 2. % Liab. Ins. 3. $lns. Cost Average Actual 1987 A.A.A. Member $1,460,000 2.9% $42,000 Typical Comparable Competitor $1,460,000 13% $190,000 SAYINGS =$148,000 How Much Could You Save 1,460,000 ?% ?$ =??? Asbestos Abatement Association 101 S. Stratford Rd., Winston-Salem, N.C. 27104 919-722-9895 30 ASBESTOS ABATEMENT MAY/JUNE 1988 HWBUI0001324 a CUBEMASTER A latch-on unit for either end of Enviromaster to expand changing area. Locker facilities can be included. A ENVIROMASTER A compact unit offering similar facilities to the Enviromajor. Easily dismantled for transportation then assembled on site in 6 minutes. VENTMASTER AIRMOVER Compact 2-part fan/filter system which creates negative pressure and captures airborne contamination. Suitable for airflow requirements up to 1000 CFM. Roving prefilter available for maximum versatility TORCHCROSS AIRMOVER A single unit fan/filter with the same function as Ventmaster but for airflows up to 3000 CFM. Shown with roving prefilter. A SMOKE GENERATOR Indicates airflow conditions within the work area and provides a simple visual check to prove effective tent sealing. REGENCY ENVIROMASTER INC. P.O. Box 3541, West Chester. Pennsylvania 19382. Telephone: (215) 344 0637. Toll Free 1-800 USA ENV1 PRESSURE MONITORING Monitor... displays negative pressure with safe/unsafe indication and alarm. Printer... provides continuous trace of monitored pressure. Power Switching Unit... automatically switches on standby fan/filter unit if pressure becomes unsafe. HWBUI0001325 qualitative detection, LOD. From our data set (See Table 1), in fact, the 95-99 percentile occured at the sur face concentration of 6 fibers/mm2. "DETECTION POWER" (PROBABILITY) FOR Such clumping is a result of the limited classes available from the LIMIT OF QUANTITATIVE DETECTION (L.O.Q.) counting of either whole or half fibers only. The comparison of our data set with the results obtained by the POISSON DISTRIBUTED CUMULATIVE PROBABILITY OF COUNTING L.O.D. AT THE 95 PERCENT DETECTION POWER: NIOSH Division of Physical Science and Engineering shows good agree ment. There is no significant dif ference between the means of the two data sets. However, the proposed (H-O . Pr(<L.O.D.) - t - --^rf-- E.G. " 1! LOD of 6 fibers/mm2 is based on the tested Poisson model. The normally distributed mean plus three standard Pr (<.L.O.D.) - 1 - .05 - L.O.Q. L.O.D. - 4 FIBERS IN 100 FIELDS deviations (or 99th percentile) has been given by NIOSH as the esti L.O.Q. 7.8 FIBERS IN 100 FIELDS mated LOD for Method 7400. The fiber count LOD in fiber/100 Table 3 fields (See Table 2) is a function of the microscope field area for counting (mm2) and the 95th fractile value for the distribution of background fiber surface concentrations for unexposed FUNCTIONAL RELATIONSHIP FOR AVERAGE SURFACE FIBER CONCENTRATIONS, S: filters, or the LOD in fibers/mm2. For example, for our laboratory us ing a microscope with a count field area of 0.006 mm2, the fiber count LOD is four fibers in 100 fields. There L.O.Q. (FIBERS AT 95% POWER) (MICROSCOPE FIELD AREA) (100 FIELDS) are two conclusions which can result from the comparison of the fib^r count LOD to a measured fiber count that exceeds the fiber count LOD: With regard to quality control, any EXAMPLE: filter lot from which representative C -- _________ 7.8 FIBERS IN 100 HELDS filters have a measured fiber count greater than four fibers in 100 fields (LOD) should be discarded. Also, four (.006 SQ. MM) (100) = 13.0 FIBERS/SQ. MM fibers in a 100-field count is the minimum total count that must be ob tained from any exposed filter sam Table 4 ple before concluding the exposed filter has a significantly greater sur face concentration of fibers than an unexposed filter. (This may not ProCounsel ASBESTOS ABATEMENT PERSONNEL PLACEMENT NATIONWIDE always be the case as shown earlier.) We now have the tools necessary for estimating a sufficient surface fiber concentration to yield a specified GENERAL SUPERINTENDENTS PROJECT MANAGERS WORKING FOREMEN GENERAL MANAGERS SAMPLING TECHNICIANS . COORDINATORS SALES MANAGERS ESTIMATORS SALES HYGIENIST power of counting at least the fiber count LOD of fibers in 100 fields, for a given set of measurement condi Placements are made with CONTRACTORS, CONSULTANTS. MANUFACTURERS, and DISTRIBUTORS, Fees paid by employer All information kept in strictest confidence We respect your needs tor (he right geographical location, (he right compensation and the right challenge Contact SHANNON SMITH Toll Free 1S00-545-5900 or 214-939G635 (24 hour ans. srvc,) tions (See Thble 3). First, we assume a distribution of many 100-field fiber counts is adequately described by the Poisson distribution. Next, we can solve for the 95th cumulative proba bility on counting less than or equal 32 ASBESTOS ABATEMENT MAY/JUNE 1988 HWBUI0001326  HWBUI0001327 for a .006 mm2 field area. The value of S for Method 7400, where the microscope field area equals 0.00785 mm2, was computed to be 12 fibers/mm2. Having computed the values for LOD and LOQ concentrations, look again at the cumulative observed and expected frequency distribution for re-occupancy sample fiber surface concentrations (See Figure 5). The vertical arrows indicate the LOD and LOQ fiber concentrations of 6 and 13 fibers/mm2, respectively. As can be seen, we have observed sample con centrations less than or equal to LOD at a frequency of 45 percent and less than or equal to LOQ at at frequency of 72 percent. It appears, therefore, we have chosen the appropriate dis tributional model and confidence limits under the condition of low-level airborne concentrations. The relationship for the required air volume Q, in liters, to detect a given concentration level, such as a re- LIMITS OF QUANTIFIABLE DETECTION (L.O.Q.) FROM K (l.o.q.) VOLUME (LITERS) 100 500 1000 2000 5000 FIBERS/CC 0.111 <0.022 <0.011 <0.006 <0.002 Table 6 occupancy standard, is computed by the effective collection area of the filter used, times the fiber surface concentration LOQ equals S, divided by a given concentration we wish to detect (See Thbie 5). In this example, we are using P&CAM 239, i.e., a 37mm-diameter filter and S equals 13 fibers/mm2, where we must be able to detect the typical re-occupancy limit of 0.01 fibers/cc. The computed required voume of air, Q, is 1112 liters. Those familiar with the EPA guid ance for the limit of reliable quantifi cation of 0.01 fibers/cc using P&CAM 239 method will recognize that this Q of 1112 liters is somewhat lower than GET SPECIALIZED & PERSONALIZED ASBESTOS ABATEMENT We'll help you with... 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Anthony Brown at (312) 480-3570 Rose-Tillmann, Inc. 630 Dundee Road, Suite 200 Northbrook, IL 60062 36 ASBESTOS ABATEMENT MAY/JUNE 1988 HWBUI0001328 Asbestos AbatementThe Solution EUROCLEAN has developed a unique, patented system for the safe, efficient removal of asbestos and the safe, efficient clean-up of asbestos removal equipment. The main component of the system is a combination cyclone and cleaning filter. The cyclone separates out the heavier dust particles into a replaceable, removable plastic bag. The FlipStrip Filter The FlipStrip filter, a five stage cleaning filter, is an easily removable cartridge that traps the finer dust particles. Air enters through the core of the tubular FlipStrip filter and sets hanging strips in motion that agglomerate the microscopic dust particles into larger particles that work down to the bottom of the cartridge. After four more stages of filtration, the air leaving the filter is virtually clean -- the outside of the filter remains clean at all times and the filter can be handled safely. The five stage filtration process of the FlipStrip filter also enhances filter capacity and efficiency. lTER Plastic Bag Intended and designed for heavy industrial use, the EUROCLEAN system easily outperforms statutory requirements and meets maximum permissible hygienic levels. Since the FlipStrip filter and the cyclone are internal components, they remain completely clean and dust-free on the outside. This means that the FlipStrip filter and the plastic bag can be changed at any time without risk of contamination and without the need to wear protective garments. In addition, the FlipStrip filter outlasts conventional micro filters by a factor of ten times. Euroclean 907 West Irving Park Road, Itasca, Illinois 60143 800-323-3553 (In IL 312-773-2111) iSK? HWBUI0001329 the 1500 liter specification where 10 fibers must be counted in 100 fields. Our result, however, permits the "detection limit" of 0.01 free to be used when 1112 liters have been sampled and fewer than eight fibers are counted in 100 fields. Conclusions We have shown how to compute the required volume Q to detect a given airborne fiber concentration. However, analytical laboratories do not usually control the volume sampled for individual analysis. As such, we have algebraically solved for the detection nit based on the volume of air sampled given as a con stant K. This computation uses the same features as the relationship for Q, i.e., the effective filter area times the LOQ, surface fiber concentration as known. However, this method solves for the concentration of air borne fibers/cc as a function of the volume sampled. Here, we show for our own laboratory, that K equals 11.12 MAGNITUDE OF ERRORS ENCOUNTERED WITH LOW FIBER CONCENTRATIONS: CONDITIONS: 37 MM DIA. FILTER .006 SQ MM FIELD AREA 960 LITERS 2 FIBERS IN 100 FIELDS BY CALCULATION: FIBERS/CC (2/100 FIBERS) (855 SQ. MM) (.006 SQ. MM) (960 LITERS) (1000 CC/L) = .003 FROM K (L.O.Q.) FIBERS/CC = 11.12 FIBERS/CC 960 A i. ie* 3 to 251PM with adjustable flowmeter removable telescoping arm compact and rugged Also 25mm and 37mm filter cassettes Model VM-3 call or write FREE LITERATURE Simplex Air Sampler Division 779 Fifth Avenue Brooklyn, n.y. 11232-1695 Tollfree 800-221-0822 (718) 768-3333 Table 7 = .012 fibers/cc divided by the dimension less value of the volume sampled. Somewhat obviously, if we divided K by the required volume Q to detect the previously shown re-occupancy limit, we solve for 0.01 fibers/cc. Once analytical laboratories have derived a constant LOQ, they can derive the analytical detection limit based on the volume of air sampled when the fiber count LOQ is not ex ceeded. The results shown here (See Table 6) for volumes varying from 100 to 5000 liters give corresponding detection limits of 0.12 to 0.002 fibers/cc. We show here (See Table 7) in the two computations the type of error that results from calculating the air borne asbestos fiber concentration when the LOQ fiber count is not known. This is not a worst-case situa tion but rather, unfortunately, a con dition that arises quite often for samples submitted for re-occupancy. In the upper calculation there were two fibers in 100 fields measured, a value even lower than the LOD, for a sample volume of 960 liters. This is essentially an 8-hour TWA at 2 liters/min. Were the laboratory to release the result of 0.003 fibers/cc, the area would be improperly cleared for re-entry of the unprotected public when the limit of detection is actually 0.012 fibersec. This, again, is a moderate problem u n compared to a fiber count of zero whose detection limit is still 0.012 fibers'cc--but without this LOQ relationship the analytical laboratory has no quantita tive estimate for the airborne fiber concentration. The value is not truly zero but rather the concentration was undetectable. (About the Author: Jeffrey Boggs is an analytical consultant with Aerosoi Monitoring & Analysis, Inc., Hunt Valley, Md. Also amtnbutmg to this article were M.J. Cirri and B E. Lippy of the same laboratory, and N.A. Leidel of the federal Centerfor Disease Control, Atlanta, Ga. 38 ASBESTOS ABATEMENT MAY/JUNE 1988 HWBUI0001330 s MO SUPPLIES... NO WORK. ITS THAT SIMPLE! When removing asbestos, lack of sup plies is more than just an inconvience. It's crucial to the safety of your crew. Being short one Respirator means you have one less worker to do the job! 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