Document mm5abgQGmgXB8BzZLn1vb4QxZ

/bm.cffcif. Uyt. Vol. 12, pp. I4I-I4J. Perganm Rrea 1969. Primted in Great Britain \ " ' . ... - A DUST SURVEY CARRIED OUT IN BUILDINGS INCORPORATING ASBESTOS-BASED MATERIALS IN THEIR CONSTRUCTION . J. C. Byrom, A. A. Hodgson and S. Holmes Asbestosis Research Council, Rochdale, Lancs. Abstract--An assessment has been made of the amount of asbestos dust in the respirable size ranee present in typical situations where the .principal types of asbestos-based building . materials hive been used. More than 60 buildings of various types have been included in . the survey.;In over 90 per cent of the loquioas aamplod, the asbestos dust concentrations.. present in the atmosphere of the completed buildings doootexcced one-tenth of the level, regarded at acceptable for occupational exposure.; More .than 40 percent of the coocaotralions are of the same order as the level in bmldio^^herepovasbestos,h*s beea uved. i ,*w. : . .... INTRODUCTIONS It has been linown for many yearsthatprolonged^exposure to high concentration of asbestos dus^could result in a progressive fibrosis ofthe lungs known as asbestosis. It appears that ijl commercial types of asbestos arc involved, but it has been shown within the asbestos industry that improvements in.working conditions have been., accompanied by a\reduclion in the incidence of.the disease and it has recently been possible for a Conkmittee of the British . Occupational Hygiene Society to draw up Hygiene Standardsfir Ckrysotile Asbestos Dust (1968) based on occupational exposure data. It has also been recognised that asbestosis can lead to lung cancer, but where dust control has been established, the asbestosis has been reduced to such a low level that the risk of canceri^no greater than urtbe general population. (Knox et ai, 1968). In recent years the health problems within the industry have been complicated by . the discovery that certain\ asbestos exposure appears to be associated with the occur-. :; rence of a very rare forn^of cancer known as mesothelioma, although it must.be emphasised that it has not been possible to establish a connection with asbestos in all cases of this disease. The association seemed to be strongest with croddolite (blue) asbestos, the other types (chrysotile and amosite) beipg implicated to a much lesser extent, amosite perhaps not pt alL This new hazard has been widely publicised, because it has been suggested that minimal exposure, not necessarily occupational, was sufficient'to lead to the 'disease. (Wagner, Sleggs and Marchand, 1960; NEWHOUSEand Thompson, 1965a Responsible medical opinion, however, now believes that there is a dose-response relationship, not yet determined, but probably different from that for asbestosis. \\ The above situation has led to speculation regarding possible health risks attending many uses of asbestos and it has even been suggested that there is danger to the. occupants of buildings incorpbratingysbestos in their construction. Although there is. ' no evidence whatever to support this suggestion, the Asbestosis Research Council . \ 141 V - : ~r'. * a?t *..* *>* > ' - ~*rS 1 *' '* *1 T * ..:! ' j.; ;' r 5 I! !?' ' li a I i T. .1 i i* .Nfr. 142 J. C. Byrom, A- A. Hodgson and S. Holmes. decided to carry out a dust survey, believed to be the first of its kind in the environments concerned. DETAILS OF SURVEY The survey comprised dust tests in 73 different locations in over 60 buildings known to incorporate asbestos or asbestos products in their construction. The buildings sampled included hospitals, schools, factories, offices, .shops, places of assembly and residences. The asbestos products encountered embraced insulation boards, asbestos-cement sheeting, sprayed asbestos and other building materials, incorporating either chrysotile or amosite asbestos. METHOD OF SAMPLING AND ASSESSMENT The membrane filter method of sampling and evaluation (Holmes, 1965) was used throughout the survey, the results being expressed in terms of fibres-'em* air. White Millipore gridded membrane filters (type DAWG 025) were used. They were held in 1 in. dia. Gelman open sampling heads and.Austcn-Dymax diaphragm pumps were used to draw the sample air through them. The flow rate was measured with a suitable Rotameter flow meter. The sampling heads were washed thoroughly and other sampling apparatus was al^o cleaned carefully. Using dean tweezers, the membrane filters were charged into the sampling heads in a `clean' room or cabinet They were then covered immediately with either a dust cap or adhesive tape for transport to the sampling site. The volume of air sampled was approximately 1201. for all tests, equivalent to about 401. through each cm* area of filter in the 1 in. dia. Gelman heads. This gave a satisfactory deposit of dust on most samples. Pumping rates ofaround 21/min were employed, the sampling period therefore being approximately 1 hr. The samples were fixed in the environment under test by carefully applying a 0-025 % solution of polymethyl methacrylate in chloroform to the filter whilst air was drawn through it for a few seconds at the' end of the sampling time. The samples were then mounted in a dust-free room or cabinet by the following technique. Several drops of filtered glycerol triacetate were placed on a clean 3 X 1 in. microscope slide (0-8-10 mm thick). The filter was removed by means of clean tweezers from the sampling head and placed on the glycerol triacetate, dust side uppermost A further drop or two was then added on top of the filter. The filter was then covered with a clean cover slip (1 in. dia.. No. 11) and left for about 30 rain to clear. The cleared samples were observed in transmitted light under phase contrast conditions at a magnification of approximately 500 X. As the density of the asbestos deposit was nearly always very low, it was necessary' to count a relatively large area of the sample, 100-200 random fields of view or, if.the dust was evenly distributed, se\ eral complete filter grids. A Patterson Globe and Circle eyepiece graticule was used to ascertain the size of the fibres. The optical system was exactly as that used for the occupational survey on which the recommendations given in the Bruish Occupa tional Hygiene Society Report (1968) were based, and the fibres counted were in the ;ame size range, 5 and 100 n in length with a length'dia. ratio of at least 3:1. Tie fibre concentration is given by the following expression: A dust survey in buildings incorporating asbestos-baYed materials where D'N d*nu ' D =i Diameter of dust deposit on.filter./ d = Diameter, of each field of view:- \ . v = Volume of air sample (cm1). IV = No. of fibres counted. n -- No. of fields observed. If gridded filters are used the fibre concentration is' AAltD. where ' A' => Area of each grid unit ^.< ; :'.k'n " No. of units observed. .; o 143 same time as thefilters on which'test samplesnweret.to .be CoUt^ctodJTHey were'taken , to the site of the test and fixedalong-with;tte;sample membranes in-an id ' manner. They were mounted and counted.at the same time, as the samples and if\tbe background count was found to be significantv it .was subtracted from the rele sample fibre coutU. ' ?' - .s '. v-r. v . *. ' RESULTS AND iCO^CLUSTONS .-M- \\ classified by type of asbestos product, and'in Table;2.by type of building. In'.tfae; , British Occupational Hygiene Society Report, the asbestosiconcentration regarded: Table 1. Awards oust concentrations acco*oing to matejoau used Concentration (fibre/cm5) 0-0-005 >0005-0010 : >0010-0020 . >0020-0030' ; .>0030-0040 >0040-0050 >0050-0080 Type of Material Asbestos Insulation cement Sprayed board sheeting asbeitos Others* 17 8 6 2 2 2 2 2 3 2 I 0 0 0 7 5 2 3 0 o, 1- 8 0 0 0 0 0. 0 Total (No.) (%) 34 16 10 6 :2 2 :3 . : 46 1 22` 14 8. 3.-'- 3V 4L . ' Includes fully compressed flat sheets, partition board and low density rigid panels.  ft- i .. I i; j. fF t- A dust survey, in buildings incorporating asbestos-based materials *- 145 as presenting a negligible hazard for a life-time's occupational exposure is 0-4 fibre/cm1; this leads to a non-occupationai limit of 0-04 fibre/cm*, as such' limits are often set at one-tenth the value adopted for occupational exposure. It will be seen that 93 per cent of the results fall within this limit and in the remaining 7 per cent (5 locations) where the level was in the range > 0-40-0-080 fibre,'em', work was in some cases still in progress and in the others there was evidence of failure to clean up properly after completion. In order to obtain an estimate of the general environmental level of asbestos dust, a number of tests were taken in buildings which did not incorporate asbestos in their construction. The figures fell within the range 0-0-004 fibre'em1, which is similar to 46 per cent of the cases shown in Tables 1 and 2, where the dust levels were in the range 0-0-005 fibre cm*. Furthermore, most of the buildings sampled were built within the last two or three years and the dust levels are likely to decline further with age. It is intended that this will be checked by further tests at a later date. In our present state of knowledge, the dust concentrations found in completed buildings incorporating asbestos-based products in their construction are not con sidered likely to constitute a hazard to the health of the occupants. Acknowledgements--The authors wish to record their,thanksto Messrs. J. B. Alexander, L Harness and R. Picot, who were responsible for the field work! . ' - . REFERENCES British Occupational Hygiene Society (1968) Hygiene Standards for Chrysotiie Asbestos Dust Pcrgamon Press, Oxford. Holmes. S. (1965) Ann. H. Y. Acad. Sci. 132,288. Knox, J. F. K.. Holmes, S., Doll, R. S. and Hell. I. D. (1968) Br. J. ind. Med. 25,293. N'ewhouse, M. L. and Thompson, H. (1965) Br. J. ind. Med. 22, 261. Wagner, J. C, Sleggs, C. A. and Marchand, P. (1960) Br. J. ind. Med. 17, 260. v- ( i V i \ \ \ \ \ \ '\ \ \