Document 2XLveGegn8jQmJ7VDJY5yrrr

A/C Pipe Producers Association Board of Directors T0 International Affairs Committee PLAINTIFF'S EXHIBIT CAP-558 Sternal Correspondence January 24, 1984 Presentation on A/C Pipe ACTIO;'! REQUIRED: Review for information IInotos-ai is a papar presented by Dr* Brian Commi;::.; at the Associations Nationals Di Tagejneria Sanitaria Congress on Materials for Pipes. For the most pact it is a cocap it elation of Coro mins' technical report, BTR-1, Asbestos Fibres in Drin'dng Viator, previously routed. If you have any questions, please do not hesitate to call. JFT.Y/ajb Enclosure cc; A. uahr. Esq. copies to: Board of Directors International Aflairs Committee Ii. Ambler O', Eomr-t L. Cojndo J. Couture L. Taylor It. Borner A. Junes C3. Zavisno Hlol-.i L. Bolbeau P. Hart R. Hobbs U. Jalan JI. Hudson M. Bel court 13. Giboin B. Dubois E. van dec Res!- w/j r-r.cl. E. Coscj v//o end. J. Se'imsus E. Cairns F. Uansour J. Glanvilie A. SaouU'j V. Pattabni C. Barton S. Al-Tarhait C. Saerg-Xuio 0122012391 Cirrono CAPCO JEN 0026065 ASUKSTOS FIBRES IN DRINKING WATER WITH SPECIAI. RF.KKItlCNCK TO ASUKSTOS-riKMENl i'IJ'F. USAGE n.T.Commins, DSc. ,MSc.,i'hD. ,CChcm. ,I'fl.SC. i Independent Consultant, and Specialist .in Water and Air contamination {'Pippins', Altwood Close, Maidenhead, Berkshire, Si.6 England) . AiiSTi'iACT The paper describes the potential sources ol` asbestos in drinlciriy water, the sampli.no and analysis of asbestos in drinking water ant! the levels found. The use of asbestos-cement pipes is discussed in relation to the usually .small amounts of fibre they release; some of the advantages of ashestos-cc.wunt pi over other types of piping materials are highlighted. An analysis of the results of extensive animal experimentation and a serje; of human epidemiological studies lias allowed some firm conclusions to he reached regarding the health implications of ingested asbestos .in drinking water. The animal ingestion studies are wholly negative, and no firm .vidor.tnof adverse.health effects appears to exist as a result of the evaluation of studies of human populations exposed to asbestos in drinking water. In '.he ease of the higher levels in drinking water, eg., that arising from natural cor.Lamination-or from effluent discharges to water sources, it can bo concluded that any health effects would appear to be sensibly /,oro or at the most, vor> small indeed. Additionally, for the lower levels in water, eg., those duo fo the use of asbestos-cement pipes, the health risk of ingested asbestos would seem to be sensibly zero or at the most exceedingly low; although there may bo no greater health risk for extremely aggressive water, the levels of asbestos fibres in drinking water could bo increased in some cases. A considerable amount of money and effort bas been spent in evaluating whether ingested asbestos in drinking watei- is a problem. For all practical purposes, the controversy regarding the subject would seem to have ended and one could conclude that the issue now appears to be a non-problem. A (1) CAPCO JEN 0026066 1. INTRODUCTION For many thousands of years asbestos fibres vill have been present in some waters used for drinking purposes because a relatively common source of the fibres is naturally occurring asbestos mineral deposits, some of which come in contact with water supplies(l). However, only in the last two decades or so has it become possible to detect and to identify satisfactorily asbestos in water, and in the early 1970's asbestos fibres were found in the source of water supply for the City of Duluth, Minnesota, USA(2); this source(Lake Superior) was found to be contaminated by a mining discharge which contained asbestos,and concern arose. The measurement unit used to express the levels in water was millions of fibres per litre of water. The use of this particular measurement unit (one which is simply for the convenience of the analyst making the measurement), alarmed people, although we now know that even a million chrysotile fibres per litre is only typically,0*005 F9 Per litre(3)f a level which is much lower than the concentration `one normally considers as a trace substance, concentration in drinking water. In addition, there has been concern regarding occupational exposure to asbestos via inhalation and the effects on the human lung, and it was natural to consider whether ingested asbestos was also a problem. In the 1970's there was a good deal of over reaction to environmental issues generally, including the finding of asbestos in drinking water. Most asbestos fibres in drinking water are extremely small. For the commonest type of fibre, chrysotile asbestos, they are typically 0*03 to Olpn in diiuneter and 0-5 to 2^un lonp.(l). The mass of a single fibril of chrysotile asbestos can be of the order ogl0"*7g.. but typically for fibrils or bundles of fibrils, the mass range 10"i to 10"*^ g., will apply.(l). The demand for asbestos products has increased dramatically this century and over 3000 uses have been identifi`'d(4). The following countries are particularly noted for their production of asbestos: Russia, Canada, South Africa, Zimbabwe, China, Italy, brazil, USA and Australia(5). Because of 4 die widespread use of asbestos and products containing it, ineviatably some contamination of the environment has arisen; the problem of environmental contamination was greater in the past because of the existence of fewer control measures being used then. 2. i'OfSNTIAL SOURCES OF ASBESTOS IN Dl'INICfNG WATER Asbestos fibres ore often found in water; the fibres can be introduced into source waters by the dissolution of natural asbestos containing minerals, from industrial effluents and atmospheric, fallout(3,6,7)* Sedimentation, resuspension, migration and chemical reactions affect the movement,abundance and fate of asbestos in water; some of these mechanisms will affect the asbestos fibres in distribution systems conveying potable water. The use of asbestos-cement water pipes will in come cases also contribute to the level of asbestos in distributed water(l) 2.1 Natural and Effluent source's cf asbestos in drinking water. A major source of asbestos in drinking water supplies in some countries is natural contamination arising through vatex' making contact with asbestos mineral doposits(b). Although jt is di.fficult to assess how widespread natural asbestos contnmjnation is, adr-stos deposits are fairly common in a number of parts of Hie world and one might anticipate that such natural con(arnination is fairly widespread. Concentrations as high as 2000 million (2) CAPCO JEN 0026067 fibres per litre have been rccorded(8), ami levels of several hundreds of millions of fibres per litre are not unusual; the more widespread natural contamination level is probably relatively low however. Effluent discharges to water bodies used for potable supply can also be the cause of a significant level in drinking water(3,7)- Concentrations of up to several hundreds of millions of fibres per litre of drinking water 'have been reported where effluents have contaminated water sources(3); nowadays the control of such effluents is generally carefully maintained and levels of more than 10 niillion fibres per litre would be unusual. In addition asbestos fibres leaching from asbestos waste dumps adjacent to water sources may cause some contamination(1). 2.2 Airborne sources, asbestos-cement tanks, asbestos-cement roofs,etc. Airborne sources of .asbestos arising from the weathering etc., of asbestos products may contaminate surface water supplies.' However, because in general the levels of asbestos in air are lov(9-13), and since the volume of water which could be possibly contaminated is normally vast, the extent of the contamination is almost certainly generally very low indeed. Asbestos-cement storage tanks are clearly potential sources of contamination; relatively,high levels of asbestos may occur where water is allowed to make contact with the cement surface and the water is not drawn off regularly, as might occur in some situations. Asbestos-cement roofing tiles can apparently be a particularly significant source of asbestos fibres where roof run-off water is collected for potable purposes. Levels of over 500 Million fibres per litre of water have been recorded in some situations(llt) . 2.3 Asbestos-cement pipes Although some literature reports have suggested(15,16,1?) that significant levels of asbestos can arise when these pipes are used, the general concensus of opinion is that the degree of fibre contamination to the water is relatively. low(l,12,15,16), except perhaps in some circumstances where the water is particularly aggressive(13,1^); this is discussed in section `j. 3. SAMPLING AND ANALYSIS OP ASBESTOS IN VATEH 3.1 Sampling The difficulties of sampling are often underestimated. Glass or polyethylene collection bottles (one litre capacity)can be used^*). Before use they must be ultrasonic.illy cleaned; washing carefully with double-distilled water is important too(20,22,23). Where possible, each sample should be collected in duplicate because of the fact that sometimes very discrepant results arc obtained. Discrepancies can be caused by chance inclusions of a fibre bundle in one sample and not others, or by chance contamination occuri'ing in one bottle; even an invisible tiny bundle of fibres can produce a result, of several million fibres per litre(l). Samples should be 'collected at normal flow rates to provide a representative result; samples collected at hydrants may be totally um'cprescntative of the water quality in a distribution syst-cm(l). (3) CAPCO JEN 0026068 3-2 Sample* preparation prior to analysis Once collected, samples should be stored in the dark; they should be analysed within a week or so of collection. Immediately prior to analysis the samples should be ultrasonically agitated(20). The next stage consists of using a variety of possible techniques to allow electron microscope specimens to be prepared from the sample of water; low temperature ashing or ozone treatment may be necessary(20). These procedures and those which are involved in the electron microscopical analysis are highly specialized. Considerable experience is needed to get good results and one analysis may take many hours to comjjlete; the cost can be several hundred US dollars per analysis. 3.3 Elcctrorunicroscopical analysis The details of tiie analysis have been described elsewhere(1,3,20). Transmission electron microscopical analysis rather than scanning electron microscopical analysis is required; in addition cither electron diffraction analysis and/or X-ray energy dispersive analysis is essential. 3.4 Statistical evaluation of the results Standardized procedures are now available for interpreting the results; proper statistical evaluation is ari essential requirement for analysis. The analytical results are not precise as in normal chemical analysis; typically the 95% confidenec limits for a sample result containing one million fibres per litre water may be as wide as 0*4 to 2*2 million fibres per litre(l). 4. CONCENTRATIONS OF ASBESTOS FIBRES IN WATER. A number of the earlier studies involved the use of rather unreliable sampling methods and ;>oor sample preparation techniques, as well as inadequate identification and quantification for asoestos fibres. The results reported here have been selected on the basis of reliable data; any analyses by optical microscopy and by scanning electron microscopy have been rejected. Although some publications have reported concentrations expressed in mass terms, ie., yin or tig per litre, most results are provided as a number concentration, ie., as millions of fibres per litre of water. The results given here are given as millions of fibres per litre but it is important to recognize that the mass concentrations are generally very low. For example: typically, one million fibres per litre chrysofcile is only 0*005 pg per litre, and typically one million fibres per litre amphi.bole asbestos is 0*2 jig per litre(3). The conversion factor depends on the precise fibre dimensions and the density of the mineral fibre. Outside USA and Canada very few analytical results are available. In the USA(3) a survey of over 1500 samples, representing 365 cities gave results as follows: 24*6% of samples contained less than one million fibres per litre; 9"5%ine to 10million fibres per litre,and 11*2% greater than 30 mi-llion fibres 'per litre. In Canada(359 samples), 75% of supplies contained less than one million fibres per litre, 20% one to 10 million fibres per litre and 5% greater than 10 million fibres per litre(20). A few samples from Sweden, Netherlands,UK, Germany and Switzerland suggest results around one million fibres per litz'e(l). For various studios carried out in US/, and Canada, it lias been possible to (4) CAPCO JEN 0026069 conclude that natural asbestos contamination can produce levels as high as over 2000 million fibres per litre and effluent discharges over 600 million fibres per litre(l). Contamination from the use of asbestos-cement pipes is rarely significant and in many studies it is consistently lower than that produced by natural or effluent discharge sources of asbestos(l). In some cases levels of asbestos from the use of asbestos-cement pipes has been suggested to be above 100 million fibres per litre(3)j careful examination of the results however shows no proven evidence for the pipes causing this level of contamination(l). More typically, the contamination of water supplies by asbestos-cement pipes is at the most a few million fibres per litre and this is usually where the water has been classified as highly aggressive(l). 5. ASBESTOS CEMENT PIPES AND THEIR USE FOR CONVEYiNCi'.'POTABLS UATER. 5.1 Asbestos-cement pipe usage. The type of asbestos pipe used in different parts of the world may vary somewhat. Although most contain nowadays about 15% of asbestos, some utilize only chrysotile asbestos but others also incorporate some amosite and/or crocidolite'(l). Some pipes contain added silica mixed with the cement base material(l). In some countries, autoclaved pipes are used and in certain parts of the world, lined or coated p.ipes(eg. bitumen) are popular. Asbestoscement pipes sfcarted[to be manufactured and used around 1916. Italy seemed to be the first country to make and use them(l2,l8). It has been estimated that some 2-J- million kilometres of pipe have been installed (ie., approximately sixty times round the world). Estimates of usage, where data is available (expressed as thousands of kilometres of pipe laid) are: USA(536), Japan(336), UK(257), Italy(125), Indonesiu(99), India(97), Australia(90), South Africa(86), Nigeria(70)1 Germany(54), Greece(44), Argentina(4l), Netherlands(36), Malaysia(27) , Cliile(l7), New Zcaland(i6), Austria (15), I3elgium(l4) Svitzerland(12), Derimark(lO), Sweden(G), Kuwait(6). (l). 5*2 Asbestos-cement pipe and fibres released to water There has been considerable confusion regarding the quantity of fibres being released to water and recently a review of the situation has been published(1). Most studies have indicated either zero or a rather low level of fibre release(i,12). Some anomalous results have arisen because (a) the disaggregation of fibre bundles of natural asbestos can occur in distribution systems which leads to an increase in fibre number concentration, (b) samples for analysis were collected at water hydrants, or after water disturbance (caused by system flushing), leading to highly unrepresentative and atypical deposits being sampled,(c) highly aggressive water passing through asbestoscement pipes for a short period of time , quite atypical of the general water quality, (d) asbestos-cement pipes being inst.al3.ed and used contrary to the manufacturers standard recommendations, (e) inadequate statistical design or analysis in the investigation of fibre release under field testing conditions (1,12). It should be noted that even where the water conveyed through asbestoscement pipes is highly ciggressive, the release of fibres in some cases may be very low because of natural protection by manganese or iron in water supplies or natural organic substances in some situations(l,12,19). Although some idea of the quantity of fibres released can be predicted from a knowledge of certain water quality parameters such as alkalinity,pH, hardness, there is at present no wholly satisfactory means of prediction for a wide range of circumstances (5) CAPCO JEN 0026070 and conditions(1). The Langelier Index and the Aggressiveness Index have been useful in a number of situations(12). Where the water is highly aggressive it is recommended that advice be .sought from the manufacturers regarding the use of asbestos-cement pipes(21); proper considerations can avoid operational difficulties at a later point in time(21). One might anticipate that there will be better control of the quality of distributed water in the future which will minimize not only fibre release from asbestos-cement but also general corrosion problems in distribution systems, including also the plumbing in buildings, etc 5.3 Advantages of asbestos-cement pipes i.11 relation to some other piping materials Apax-t from the relatively low cost and ease of manufacture in different parts of the world, asbestos-cement pipes have some other advantages. They can be laid without too much difficulty, and with care any exposure to the workers laying the pipes can be controlled to very low and acceptable levels. Asbestos-cement does not corrode in the way iron piping can. It is essential to coat iron pipes with bitumen or other similar type of material to prevent serious corrosion. Some asbestos-cement pipes are coated but this practice only applies to a few areas or situations in some countries; autoclaved pipes have proved to be very satisfactory in many countries and can be used where waters are aggressive. The practice of coating of any type of pipe is currently being investigated by a t/S. National Academy of Sciences Conmiitee(12) among the reasons for reviewing such coatings are the possible health implications of certain organic materials dissolving into water supplies(12). One particular feature of asbestos-cement'is that the products used to manufacture it are natural materials. These materials often come in contact. with various water supplies in nature and the vater contains some of these natural dissolved materials. Asbestos fibres are similarly of natural origin; this important characteristic of asbestos-cement piping does not apply to other piping material such as pvc or polyethylene, etc- In health terms it is often the organic substances which are of greatest concern in water supplies and asbestos pipes do not provide organic contamination. Finally,asbestos-cement piping is really the only material which happens to have been the subject of extensive health testing. This is because both toxicological(animal experimentation) and cpidemiologyChuman studies) have been carried out in relation to ingested asbestos in drinking water, and any health effects would seem to be sensibly zero(see section 6). No other material have been so tested and given essential!)' a clean bill of health. 6. ASBESTOS EXPOSURE AND HEALTH IMPLICATIONS 6.1 General Considerations It has been known for a long time that occupationally inhaled asbestos dust can have a serious effect on the lungs of people exposed to high concentrations (24-26). In some studies an apparent excess of gastro-intestinal cancer has been reported in asbestos workers(l); this association has however not been definitely proven and the explanation that such cancers might arise as a result of indirectly ingesting asbestos; via the inhalation route is not universally acceptable(l). In fact if gastro-intestinal tumours were to arise in occupational circumstances, they would seem to be more likely to occur by systemic migration of asbestos deposited first in the lung(l); other (6) CAPCO JEN 0026071 occupational carcinogens, smoking or dietary habits, may in any case also account for gastro-intestinal t"mours being found. Food and certain beverages are a source of ingested asbestos, although Uttte quantitative data is available(l). For the general public, ambient air and dust can also provide a limited source of some ingested asbestos(l). Occupational situations especially in the past have given rise to much higher exposures of asbestos capable of being ingested. 6.2 Animal experimentation One of the most important recent findings is that despite numer.ous animal feeding studies, the accumulated evidence would indicate that ingested asbestos is not carcinogenic. The animal experiments(l) included at least a dozen studies and a total of almostl0,000 animals, in which.some were fed very high doses of asbestos eg., up to 300mg per rat per day. In one study the rats' were fed lOJa asbestos in their diet and yet no carcinogenic effects ware detectable. The available evidence for a significant proportion of asbestos passing through the gastro-intestinal mucosa is weak and this has been checked in a number of species, including primates; one fibre in 10,000 or even one in 100,000 has been suggested(27). All the known relevant animal feeding studies were reviewed at the EPA Workshop on Ingested Asbestos held in Cincinnati in October 1982(28). The general views expressed at that meeting were that ingested asbestos had been shown to be essentially non-carcinogenic to animals. 6.3 Human Epidemiological Studies There have been several long term epidemiological studies carried out in the USA and Canada; in some of these studies, the levels of asbestos in drinking water were very high(l). Critical examination of the findings has not revealed any firm evidence for adverse health effects in human populations drinking water containing asbestos fibres(l). However, it has to be admitted that because of certain confounding variables, the sensitivity of the methods used was somewhat limited. Any effect of ingested asbestos from drinking water* if one exists at all, would ajipear to be relatively small, otherwise it should have been consistently observed in the studies where the levels of asbestos in the water were high. In a few studies, some statistically significant associations between certain specific cancer sites out of many examined have been observed(l); they have not been consistently detected in other studies and vould appear to be chance findings. These views are consistent with those presented at the US EPA Workshop on ingested asbestos held in October 1932(23). G.h Appraisal of animal and epidemiological studies in relation to health implications for humans ingesting asbestos in drinking water. %< The doses of asbestos used in the negative animal experiments were so high that when equated to human exposure, they represent 200,000 to almost a million tines the quantity present in the most contaminated drinking waters on record(l). In o:ie such experiment, where the dose was equivalent to 1% of the animal's diet, when equated to man would correspond to 15*6g`of asbestos per day; this calculates to a huge safety factor, approaching 10^ in comparison with the typical daily human exposure of not more than 0-02 iig chrysotile in drinking water(1). (7) CAPCO JEN 0026072 It has been estimated that possibly one fibre in every 10,000 could enter and may get through the gastro-intestinal mucosa(27); in the case of human beings ingesting typical drinking water containing up to 2 million fibres per litre, the total quantity capable of migrating to elsewhere in the body would be only 0'05 jig in a lifetime. Talcing account of (a) the negative animal ingestion studies, (b) the apparent rare event of a fibre penetrating the gastro-intestinal tract mucosa and also (c) the lack of firm evidence for adverse health effects from epidemiological studies, combine to suggest that the level of a carcinogenic effect in the normal population even where the water being drunk contains many hundreds of millions of fibres per litre, would seem to be sensibly zero or at the most very small indeed. For the more typical low level exposure to asbestos in drinking water, ie., from a low degree of cotamination, including that which may result from the use of asbestos-cement pipes, cyen where the water may be moderately aggressive, the overall health risk would-seem to be sensibly zero or at the most, exceedingly low. It has been reported on 17th March 19^3 > in answer to a UK. Parliamentary Question regarding healfch hazards arising from the use of asbestos-cement pipes, that 'the ingestion of water with levels of asbestos such as those found in the UK. present no risk to health' (29). It is worth noting too that the World Health Organization in its forthcoming Guidelines on Drinking Water Qualicy has not specified a guideline value for asbestos in drinking water. 7. CONCLUSIONS Asbestos contamination of water supplies is common; major sources are naturally occurring asbestos and effluent discharges. The methods of analysing asbestos in water involves highly specialized procedures. Typical levels of * chrysotiie asbestos in water arc in the range 0-2 to 2 million fibres per litre of water, although there are several raise-' where several hundreds of millions of fibres per litre of water have been detected as u result of natural asbestos contamination. The fibres detected arc generally very- tiny, often 0*03 to 0*1 pm diameter ana 2 pm long. Food and certain beverages are also sources of ingested asbestos, although little quantitative data is available. Asbestos fibres found in drinking water arise mainly as a result of natural asbestos contamination, effluent discharges to water sources and the use of asbestos-cement pipe distribution systems. As a result of extensive animal experimentation, and a series of human epidemiological studies carried out in areas where asbestos levels iri water are elevated, it has been possible to come to some firm conclusions regarding the health implications of ingested asbestos. Although occupationally inhaled asbestos is associated with various diseases including cancer, there appears to be no firm evidence of adverse health effects from epidemiological studies of populations exposed to asbestos in drinking water, and animal ingestion studies are wholly negative. It can be concluded that at the higher levels in drinking water, eg., from natural f contamination or from effluent discharges to water sources in some areas, any health effects would appear to be sensibly zero or at the most very small indeed; while for the lower- levels in watc-r, eg., those solely due to the use of asbestos-cement pipes, the health risk of ingested asbestos would seem to be sensibly zero or, at the most, exceedingly low. Although there may be no greater health risk for extremely aggressive waters, the levels of asbestos fibre could be increased. (n\ CAPCO JEN 0026073 /. In effect, asbestos-cement piping has been subjected to rigorous testing in the various studies, and properly used it seems to be satisfactory in health terms and the fibres it may release to water, "ew other products have had such exhaustive testing. Thus normally there seems no reason whatsoever not to continue to use asbestos-cement pipes for water distribution systems. Where waters are classified as being highly aggressive however, it would be prudent to seek expert advice in order to avoid any possibility of excessive loss of fibres from the walls,which might lead to operational difficulties in the long term in some situations. Under the appropriate conditions, the use of asbestoscement pipes for conveying potable water appears to be a satisfactory practice for both the Developed and the Developing World. No further research on the subject is planned by the US. EPA, and the World Health Organisation in its Guidelines for Drinking Water Quality has not specified a Guideline value for asbestos in drinking water. Finally it is worth reflecting on the history of the interest in ingested asbestos from drinking water. A great deal of time and money has been spent in the last 10 or so years in evaluating the subject, and now it would seem that the controversy has for all practical purposes ended, and may be the issue can be regarded as essentially a non-problem. Perhaps research effort should now'be sensibly diverted into various other environmental issues. 8.SELECTED BIBLIOGRAPHY (1) 1 Asbestos Fibres in Drinking Water1, Scientific and Technical Report, STR1. COMMINS,B.T. Published May 1932 by Commins Associates, 'Pippins', Altwood Close,Maidenhead,Berkshire,SL6 4PP,England. (2) 'Asbestiform amphibole mineral: Detection and Management of high concentrations in Municipal Water Supplies. C00K,P.M.,GLASS,G.E,.TUCKER,J.H., Science(l97z), 185 853-55 (5)'Exposure to Asbestos from Drinking 'Water in the United States', MlLLETTE,JrR CLARK,P.J.,PANSING,M.F. Environmental Protection Agency, Cicinnati, Ohio, August 1979. EPA-600/1/-79-028 (4) 'Asbestos and Drinking Water in Canada'. T0FT,P.,WIGLE,D,.MERA.VGER,J.C and MAY0,Y. Science of the Total Environment.(1981) ^8 77-89 (5)'Asbestos-cement: the facts'. Asbestos Information Centre, London. (1982). (6)'Asbestos analysis case history: surface water supplies in Southern California. McGUIRE,M.J.,BOWERS,A.E.,DOWERS,D.A. J.Amer.Wat.Works.Assoc. (1982), 74 471-78 (7)'Asbestos Fibres in beverages and Drinking Water. CUNNINGHAM,II.M., PONTEFRACT,R. Nature (1971) 232 332-35 (8)'Structural Performance of Asbestos Cement Pipe in Corrosive Potable Water Environment' HOUCK,D.H. Corrosion/8l Int, Forum Nat. Assoc. Corrosion Eng. (1981) Toronto, Canada. (9) Rationale behind a proposed asbestos .air quality standard.' DRUCKMAN,L., RUBINO.R.A.", J .Air Poll. Contr. Assoc. (1975) 25 1207 (10)'Indoor Pollutants'. National Academy Press, Washington, D.C (1981). (11)'Asbestos air pollution in Now York City'. NICHOLSON,V.J., R0HL,A-N., FERRAND,E.F. Ih-oc. Int.Clean Air Congress, New Yoi'lc. Acad.Press Inc. (1971). (9) CAPCO JEN 0026074 (12)'Drinking Water and Health', Volume 4. National Academy Press, Washington D.C. (190s) (3.3)'Asbestos:Ambient Water Quality Criteria' Criteria and Standards Division, Office of Water Planning and Standards, US.,EPA.,Washington, DC. (1980) (14) 'Asbestos in cistern water'. MILLETTE,J.R.,BOONE,R.,ROSENTHAL,M. Res. Brief. USA, EPA, Cincinnati (1980) Environ. (15) 'Health effects and prevalence of asbestos fibres in drinking water' McCABE,L.J, MILLETTE,J.R. Proc.Aiter.Wat.Works.Assoc. San Francisco. (1979) (16) 'Pipes in the third world'. World Water. (1981) 59-6i* (17) 'Asbestos Cement materials used in water supply. MILLETTE,J.R, PANSING,M.F BOONE,R.L. Water/Engineering and Management. (1981) 48,51,60,97* (18) 'Asbestos in drinking water' ELZEN'GA,C.i{.J,METET-,P.B. Water Research Centre, UK. Colloquium. Drinking Water Quality and Health(l9?6) (19) 'Corrosion in potable water systems' DeBKRRf,D.W,KIDWEI.L,J.R, MALISH,D.A. Sum X Corporation, P.0. Box 14864/1500,E.Braker.Ln,Austin, Texas,USA.(1982). (20) 'A national survey for asbestos fibre in Canadian drinking water supplies' ClIATFIELD,E.J., DILLON.MJ. Nat.Health and Welfare,Canada (1979) 79-EHD-34. (21) 'A/C Pipe and drinking water'. A/CPipa Producers Assoc. Arlington,USA(1979) (22) 'Preparation and analysis of particulate samples by electron microscopy with special reference to asbestos'.C!IATFIELD,E.J. Scanning Electron Microscopy. SEM Inc. AMF. O'Hare. 111.USA. (1979) (25)'Interim method for determining asbestos in water' ANDERSON,C.H MACART1IURL0NG,J. US.EPA., Athens, Georgia.(1980) EPA-600/4-80-005 (24) 'Public Health risks of Exposure to asbestos' Commission of the European Communities. Rapporteur, Professor R.L.Zielhuis(l977).Pergamon Press. UK. (25) 'The nature,hazards and assessment of occupational exposure to airborne asbestos dust': a review. Annals Occupat. Hygiene(1982) 25 No:2. (26) 'Evaluation of carcinogenic risk of chemicals to man'.Vol.l4. Asbestos. Internet. Agency for Research on Cancer, WHO, Lyon. (1-977) (27) 1 Fate of Ingested Particulates'. MILLETTE,J-R. ROSENTHAL,M. Proc. Nat. Workshop Substitutes for Asbestos, Arlington. (1980).El'A-560/5-80-001. (23) 'Summary Workshop on Ingested Asbestos.' US.EPA. 15/14 Oct.(1982) Cincinnati Ohio, (to be. published in Environmental Health Perspectives, Oct. 1985) (29)Ueply by the UK. Under-Secretary, UK.Department of the Environment, in answer to a question regarding any hazard arising from the use of asbestoscement water mains. Extract from Hansard 17th March 1983 of Parliamentary Questions for written answers. Q CAPCO JEN 0026075