Document yryD5Bkk13e1m5MgVQqx5KgV

FILE NAME: Raybestos-Manhattan (RBM) DATE: 1977 May 27 DOC#: RBM058 DOCUMENT DESCRIPTION: Letter to Dr. Goodman at RM Industrial Products Co. from Hilton Lewinsonn RE Opinion on Exposure Levels Needed to Cause Illness Hay 27, 1977 Dr. Joseph L. Goodman RM Industrial Products Co. Garco St. & O'Hear Ave. North Charleston* SC 29^06 Dear Jo g : It Is my personal opinion that a person with diagnosed asbestosis should not continue to work in an occupation which exposes his to asbestos dust containing respirablo fibres. As Ions as there is any airborno asbestos oust in tfco work environment, there cay be aoca small risk to health. Having expressed ay personal opinion, I think that it might bo worth while to explore the alternatives. When dust concentration is hold constant tbo prevalence of asbostosis is highest amongst those with the greatest duratloa of exposure. Asbestosls results because of accumulation of dust in the lungs over a period of time. However, acne of tho dust is receved from the lungs by the normal clearance cechanisrui or by being dissolved in body fluids. Consequently, if it is assumed that none is removed and exposure is limited accordingly, a safety factor is thereby incorporated. In other words, if the present dust levels are such that they have not been associated with evldeoce of asbestosls in those exposed to thes for a substantial period of tice, they 3re unlikely to aggravate the disease already present resulting froa prolonged past-exposure to substantially higher levels held constant ever a period of tiesa. The present standard of 2 fitres/nl (100 fibre/ol years) proposes that one in 100 persons exposed to this concentration for 3 hours per day, W hours per week for 50 years will develop the earliest detectable clinical physical sign of bilatorll basal (pulmonary) rales. It could, therefore, be postulated that continued employment of already affected persons in occupations-where the dust counts are below 2 fibres/ol will not produce further lung caacgss. Coses which give zero respeoses are never, in fact, kr.cwa with absolute certainty si.nco the sensitivity of measurements of respenso is limited. Each person's dose-response line Is different with a different threshold and a different slope. It is, bcvevw*, ay personal oxperionco that asbestesis is a progressive 2 condition even after renoval from further exposure and I cannot bolieve that allowing an asbestosis aufferer to continue wo-Eking in an asbestos exposed occupation, even if it ia below the present standard, will not in none way exagrate his affliction. With regard to lung cancer, I believe that this is highly correlated with the incidence of asbestosis, but that it probably requires smaller concentrations over a longer period of time to cause it. The additional highly significant co-oarcinogenic effect of cigarette smoking makes it difficult to prognosticate in the case of a smoker. I believe that because of the association between lung cancer and asbestos exposure it would be unwlso to allow a person suffering from asbestosis to continue to be exposed, even to low levels. It is conceivable that asbestos accelerates the last stage in a multi stage carcinogenic process. The attached paper by Julian Peto may be of interest to you. Mesothelioma of the pleura in persons solely exposed to chrysofile asbestos is very rare, nevertheless, the dose required to produce this disease appears to be far less than that required to produce lung cancer, especially when it occurs in the absence of asbestosis. The dose induction period, however, is very long and may be 20-H0 years. It is unlikely that low levels of exposure after the diagnosis of asbestosis 'will continue for long enough to produce mesothelioca do novo, because of the cumulative dose already acquired, nevertheless, because of the uncertainties involved and because I deprecate in creasing the lung burden of asbestos in a person already suffering lung damage from expostre to it, r:cy opinion is that further exposure should not be allowed. Medical surveillance of asbestos workers should aim at detecting the earliest biological effects of exposure in order to remevo people from further exposure In the hope of preventing progression to the full-blow syndrome of asbestosis. 1 am afraid that there 1s nor adequately documented epidemiologic evidence to consider which allows one to determine at wr.at stage progression could bo arrested by cessation of exposure. In my experience, asbestosis was certified in 501 of "suspected cases" within a period of 3 years from date of first suspicion, even after removal from further exposure. I hope I have managed to answer your question. The diagnosis of asbestosis is in your hand and, therefore, the final decision is yours la tbo long run. Best wishes Hilton C. Lewinsohn /as