letters Carbon monoxide hazards Reply by Bernard Weinstock My discussion of the California standard was based on the “Technical Report of California Standards for Ambient Air Quality and Motor Vehicle Exhaust,” California Department of Public Health (1959). This report states on page 70: “It therefore seems proper to consider persons with severe coronary heart disease as the most sensitive group for standard setting purposes.” Later it states: “ most observers agree that 10% carboxyhemoglobin would be a level significantly affecting oxygen transport in the blood. It seems reasonable to set a standard such that community air pollution could coniribute not more than half of this. . . ,” Mr. Silver probably is aware that the standard for industrial CO exposure at that time was 100 p.p.m. for eight hours; it has since been lowered to 5 p.p.m. Presumably, these industrial standards are set for a less sensitive part of the population. Concerning the altitude effect, the same California report specifically equates a hemoglobin desaturation of 5% to an altitude of about 6000 feet. With respect to Silver’s comments about my wandering away from the medical evidence, I believe the weight of medical evidence would, in fact, support my comment. Mr. Silver might be interested in a paper by J. H. Schulte in Military Medicine, 125, 40-48 (1961). Schulte performed careful physiological, biochemical, and psychometric evaluations on 108 men who lived for 72 days on a submarine in an atmosphere containing 44 p.p.m. CO. No significant changes whatsoever that could be attributed to their exposure to CO were found in these men.
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Bernard Weinstock Fuel Sciences Department Ford Motor Co. Dearborn, Mich. 48121
DEARSIR: I wish to call to your attention a number of errors--of fact or emphasis -in the Weinstock discussion of Ralph Smith‘s paper on carbon monoxide in your July issue (page 635 +). In his first paragraph, Weinstock speaks of the 30 p.p,m. California standards for eight hours as being very conservative so as to protect the especially sensitive. On the contrary, the California standards consider this exposure as serious, based on medical evidence, and not as conservative o r as protecting the more sensitive. Farther on in the same paragraph, Weinstock speaks of 30 p.p.m. as resulting in 5 % carboxyhemoglobin (correct), but, then, he says (incorrectly) that this corresponds to 6000 feet altitude. Drabkin and associates demonstrated rather dramatically the error of assuming that the formation of carboxyhemoglobin was no more damaging than simple oxygen deficiency of the same magnitude: “The presence of carbon monoxide in the hemoglobin molecule seems to fix the remaining oxygen more tightly. This effect seems to suggest that carbon monoxide is about twice as damaging as would be expected if the mechanism was simple replacement.” (Am. J . Med. Sci., 205 ( 5 ) , 755-6,May 1943). Weinstock‘s statement (near the bottom of page 636) that carbon monoxide evinces no biological symptoms until rather high levels of carboxyhemoglobin are reached, wanders away from the medical evidence. Perhaps, the best refutation of this statement is contained in my own review of the medical evidence at lower levels and my own observations on the behavior of highly trained brain workers under exposures to gas exhaust of 15-20 p.p.m.
Francis Silver 5th Consulting Environmental Engineer Martinsburg, W . Vu. 25401
