Document MGm14RqzqmNprMyQomNDVeXwy

May 27, 1977 Dr. Joseph L. Goodman RM Industrial Products Co. Garco St. U O'Hear Avo. North Charleston, SC 29406 Doar Joo: It is ay personal opinion that a porson with diagnosed asbe3tosis should not continua to work in an occupation which exposes him to asbestos dust containing respirablo fibres. As long as there is any airborne asbestos dust in tho work environment, thero cay be soma small risk to health. Having expressed ny porsonal opinion, I think that it night bo worth while to explore tho alternatives. Whoa dust concentration is hold constant tho pravalonco of asbastosis is highost amongst those with the greatest duration of exposure. Asbostosis rosults because of accumulation of dust in tho lungs ovar a poriod of time. Hovov-r, some of tho dust is removed rroa tho lungs by tho normal clearance mecnaoi3ms or by boing 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 othor words, if the present dust levels are such that thoy have not been associated with evidooco of asbestosia is those exposed to them far a substantial period of timo, they are unlikely to aggravate tho disease already present resulting from prolonged past-exposuro to substantially higher levels held constant ever a period of timo. The present standard of 2 flbren/nl (100 fibre/nl years) proposes that one in 100 persons exposed to this concentration for Q hours per day, ^0 hours per week for 50 years will develop tho earliest detectable clinical physical sign of bilataril basal (pulmonary) rales. It could, therefore, bo postulated that continuod employment of already affocted persons in oocupatioaolwacro tho dust counts are below 2 fibres/ml will not produce further lung changes. Coses which give icro responses are no/er, in fact, known with absolute certainty since tho sensitivity of measurements of response is limitod. Each person's dose-response line is different with a different threshold and a diffsrent slope. It is, however, / porsonal oxpcrienco that asbestosia is a progressive --jrrrr condition aven after removal from further exposure and I cannot balieva that allowing an asbestosis sufferer to continue working in an asbestos exposed occupation, even if it is below the prsaent standard, will not in soma way exagerato hia affliction. With regard to lung cancer, I boliovo that this la highly correlated with the incidence of aabeatoaia, but that it probably requirea anallor concentrations over a longer period of time to causa it. The additional highly significant co-carcinogonic effect of cigarette smoking makes it difficult to prognoaticata in the caao of a smoker. I believe that because of the association betveea lung cancer and asbostos exposure it would bo unwiao to allow a person suffering from aabentosin to continue to bo exposed, oven to low levels. It is 'conceivable that a3boatos accelerates tho last stago in a multi stage carcinogenic process. Tho attached paper by Julian Poto may be of interest to you. Hoaothallonn of ths pleura in persons solely exposed to chrysotile 'asbestos is very rare. Nevertheless, the doso required to produce this disease appoars to bo far less than that required to produce lung cancer, especially when it occurs In the absence of asbestosis. The doso induction period, hewover, is very long and may be 20-^0 years. It is unlikely that low lovels of exposure after tho diagnosis of asbestosis will continue for long enough to produce mosotheLioma de novo, becauso of tho cumulative dose already acquired. Nevertheless, because of the uncortaintios involved and because I doprecato in creasing tho lung burden of asbestos la a person already suffering lung damage from exposcre to it, ritzy opinion is that furthor exposure should not bo allowed. Medical surveillance of asbestos workers should aim at detecting the oarliest biological affects of exposure in order to remove peoplo from furthor exposure in the hopa of preventing progression to the full-blown syndroca of asbestosis. I am afraid that thoro is nor adequately documented epidemiologic avldenco to consider which allows one to detormino at what stage progression could bo arrested by cossation of exposure. In my experience, asoostosis was certified in 50J of "suspected cases" within a period of 3 yoars from date of first suspicion, oven aftor removal froa further exposura. I hope I havo managed to ansvor your question. Tho diagnosis of asbestosis is in your hand and, therefore, tho final decision is yours in tho long run. Best wishes, Hilton C. Lewinsohn /as