Document MGmdypNGMyxJEDVMKyXw7YQ2a

Federal Rcglider / Vol. 51* No. 19 / Wednesday, January 29, 1908 / Proposed Rules 8741 pharynx, gastrointestinal tract, kidney, and ovary and respiratory dieeeascs such as pneumonia. Major huulth effects are discussed below. Lynx cancer Is currently responsible fur dm largest number of deaths from exposure to asbestos. llhas been associated with exposure to all the principal commercial asbestos fiber typos, b'xccsv lung cancer has been documented in groups Involved with the mining and milling of asbestos and the manufacture and use of asbestos products. Studios In which tho extent of exposure con be approximated provide evidence that lung cancer Increase linearly with both level end duration of exposure. Cigarette smoking and asbestos have e strong synergistic interaction in development of lung earner. Asbestos exposure appears to multiply the underlying risk orbing cancer. Consequently, when exposed to asbestos, the risk of lung cancer for smokers [far whom the risk oMung cancer U already high) Is much higher than that for nontmokerc exposed to asbestos. Most persons who develop lung cancer dlu witbtn 2 year. Many human studies Have oho shown that exposures to asbestos produce mesotheliomas, which ure cancers that occur us thick diffuse masses in the serous membranes Imesothetin) that lino body cavities. Mesotheliomas occur In the plfturo (tho membranr. that surrounds the lungs ond linos thu lung cavity) und the peritoneum {which surrounds the abdominal organs und lines tiiv ubdomlna) cavity). Most persons who drsvelnp mesothelioma die within the first 2 yours after diogno&is. often after having been in ennatont pain. Epidemiology studies suggest that the incidence of mesothelioma is related lo dose and ilmu from first exposure. Association of mesothelioma with smoking i* weak or nonexistent. Asbestos libers appear, by for. lu be tbn most common uww of mesotheliomas. Asbestos!*. which involves fibrosis of lung and pleural tissues. Is another Mriouo chronic disease associated.with cxpocurn to OHbcstu*. There is no nffectlvu u*atoumi for esUostoste und it is often disabling or latai. Astroslosts lu diagnoacd from firding.t which may int-iude niitiogruphic changes, bswtihlecsuesi,. and obnurmu! lung fum.linn. Smce *<nnc dii.-timl Kymplnms of Hshcstc^is un riinitei to l.hnvu of utlirr ftbrcKing lung discHsuv. u history ni Di.cup'ihoiiai expu&um to Htrtmstos ia often a key fixture of its diagnosis. I Asbeatosin can appear find progress I decades niter exposure, to asbestos ; fihc.n,. Under working conditions where I evontge fiber conc*mtraliunv in the air were high (more than 10 fibers per cubic mesothelioma have been diagnosed centimeter (f/cc)) aabestoaia bae among 62B family contacts of smosile accounted for more than 7percent of workers (Ref. 10). These figures ere observed deaths (Ref. 11), It le muck higher than that expected to lie apparently less common than lung found smong the general population. In cancer or mesothelioma at exposures addition, 35.9 percent of the contacts lower than the current Occupational showed chest x*ny abnormalities as Safety and Health Administration compared with 4.6 percent of control IOSHA) workplace standard of Z.0 f/cc. subject* drawn from the some Some recent data on the Incidence of community. A number of mesothelioma* asbestoais appear compatible with a have also been documented among linear expoaure-responae relationship populations whose only identified with no threshold (Ref. 12). However, it exposure was from living near asbestos Is eliU considered uncertain whether mining areas, asbestos product factories, asbestoais occurs as a result of rtonoccuparfonal exposures. or shipyards where asbestos use had been very heovy (Ref. 4). An estimated In occupational studies where the l00 cases of mesothelioma occur primary route of exposure is through yearly In the U.S. smong various Inhalation, lung cancer ond populations exposed to asbestos (Ref. 6). mosolhcllomes usually account for Lo addition lo exposure to asbestos about 90 percent or the excess cancers fibers to the air, the general population seen among workers exposed to is also exposed through various ore) asbestos. However, as noted la the sources. Including drinking water CHAP report (Ref. 1). a number of other containing asbestos. Because of the earners, principally nf the gastrointestinal tract, have been potential for oral exposure os welt as the excess of gastrointestinal tract associated with osbestos exposure. ' cencefe that has frequently been found These ere cancers of the larynx, in occupational groups exposed to pharynx, oral cavity, esophagus asbestos In the air. there Hbb been much stomach, colon, and rectum. Statistically . study of the possible health effects of significant excesses of cancers of the Ingestion of asbestos fibers. Despite kidney and ovary have also been shown, in addition, the excess of those efforts, evidenceshowing health effect* from ingestion ts xtlH ambiguous. cancers at all other site* combined la 2. Corner risk extrapolation. As statistically significant in some studios. discussed above, numerous human The conclusions from epidemiology studies have demonstrated that studios concerning ihe health effects of exposure to asbestos has increased the asbestos are also supported by results of risk of cancer and aebentosls. Since e laboratory studies. Animats treated with number of epidemiology studios Indicate asbestos nave shown increased a positive relationship natween asbestos incidence ol fibrous, lung cancer, and mesotheliomas- All commercial forms * exposure and the risk of lung cencvr. several models may be used to and several other types of osbestos are extrapolate from risk *| higher exposure implicated from a variety of modes of lo risk at lower exposure. The model exposure. that EPA believes Is most consistent Most occupation*!) studies have been conducted on populations exposed to with the available human und animal dote I* the llnour mm-lbraiihold duse/ high eirtiurno ennuentrutionu of asbestos mapopat* jwudel. ThW mortal assumes for relatively long periods of time. that )11 any exposure increase* rtek, and However, short term occupational (2) the increase In risk is proportional to exposures have also been shown to the background risk in Iho nonoxposod increase the risk of lung cancer and population and to the level of exposure, mesothelioma. One group of asbestos defined as duration of exposure times factory workers with lets than 2 months concentration of axbesios fibers to of occupational exposure bad e twofold which populations may be expound. incruuto in lung cancer risk (Rcfi 9). In The choice of the linear moilvHs addition, thorn urn many documented reueoruihle since there is no evidence of mesothelioma finked tn for a threshold level of asbestos extremely brief exposure to high exposure below which there is no concentrations of Ahbeeios or Jnng>tenn increased risk. It is further supported by exposure to tow concentration* |Ref, 4|. evidence of cancers among populations Direct evidence nl adverse health whose asbestos exposure i* believed to effec ts from non occupational aebiwtos have bnen lower than levels reported in exposure alio exists. Persons who lived the epidemiology studies of uebestos in the housetwlds of osbestor. workers workers mentioned above. buvQ developed pleura) mesothelioma The model adopted by EPA to and asbestos-related radiographic estimate excess mesothelioma Incidence chitngftB. In an ongoing study. 4 casus ol^ dun in asbestos exposure rel-rirs disease FMSI 02432