ADAPTATION TO 5MOG AND CAR15' s ^ MONOXIDE 



elude, in particular, the demonstra- 

 tion that a diminution in trypsin 

 inhibitor in the serum (the so-called 

 alphai anti-trypsin deficiency syn- 

 drome) predisposes individuals who 

 were homozygotically deficient to the 

 early onset of pulmonary emphy- 

 sema. Such individuals are infre- 

 quent in the population; studies so 

 far report finding only about one in 

 3,000. However, it is not yet known 

 whether /zeferozygotically deficient 

 individuals (who may comprise 5 to 

 15 percent of the general population) 

 are also more prone to chronic res- 

 piratory irritants. In a few pilot 

 studies, heterozygotically deficient in- 

 dividuals who were also cigarette 

 smokers showed evidence of chronic 

 respiratory disease in a very high 

 proportion, namely 31 out of 33. 



Needed Scientific Activity — Adap- 

 tation to carbon monoxide involves, 

 to a substantial degree, the study of 

 populations of cigarette smokers, 

 since their exposures to this agent 

 are very common and of substantial 

 magnitude — that is, sufficient to in- 

 activate from 5 to 15 percent of the 

 oxygen-carrying capacity of the blood 

 for moderately heavy smokers who 

 inhale. Similarly, there is evidence 

 that cigarette smoking increases the 

 risk of chronic respiratory conditions 

 and respiratory impairment in per- 

 sons exposed both to the sulfur oxide 

 and particulate type of pollution and 

 to photochemical smog. (See Figure 

 XI-8) Thus, we are unable to speak 

 logically of the epidemiologic aspects 

 of studying human adaptation to car- 

 bon monoxide and to smog without 

 considering cigarette smoking. 



Beyond this, however, we must 

 also consider occupational exposures 

 and relevant and related exposures 

 that occur in the home and during 

 recreation and transportation. While 

 there are large numbers of human 

 subjects exposed to both carbon mon- 

 oxide and smog, a longitudinal study, 

 necessary to obtain the best type of 

 data for the study of adaptation, 

 has rarely been undertaken for either 

 of them. In the case of occupational 



exposure to carbon monoxide, some 

 longitudinal data have been obtained; 

 there are, however, few longitudinal 

 data in the case of carbon monoxide 

 associated with cigarette smoking, 

 since the importance of this exposure 

 has been appreciated only since 1960. 

 In the case of smog, there are popu- 

 lations occupationally exposed to two 

 of the major ingredients that have 

 toxic properties — namely, ozone and 

 nitrogen dioxide — but results of the 

 study of occupational groups are not 

 sufficiently clear-cut for an evalua- 

 tion of adaptation. 



Short-term adaptive mechanisms 

 have a more abundant data base. 

 There is a small data base from ex- 

 perimental human studies, and a 

 somewhat larger one from experi- 

 mental animal studies, of adaptive 

 mechanisms for ozone and nitrogen 

 dioxide exposures. Data for carbon 

 monoxide are more abundant, but for 

 neither is the data set adequate. 



Limitations — The data base for 

 studying adaptation to these agents 

 is unfortunately impaired by the 

 view of one sector of the scientific 

 community that adaptation is solely a 

 beneficial process, one that does not 

 carry with it the risks of the long- 

 term consequences suggested above. 

 Thus, a number of scientific papers 

 have cited the ability of patients to 

 increase the oxygen transport in re- 

 sponse to carbon monoxide exposure 

 as evidence that community or ciga- 

 rette-smoking exposures to carbon 

 monoxide are of little consequence to 

 health. 



Recent Scientific Findings 



Impairment of Respiratory Func- 

 tion — It has been demonstrated that 

 nitrogen dioxide, a major product of 

 photochemical smog, is an effective 

 agent for producing emphysema in 

 experimental animals when exposures 



Figure XI-8 — RATES OF CHRONIC BRONCHITIS AND EMPHYSEMA 

 FOR SMOKERS AND NON-SMOKERS 



21 AND OVER 



PRESENT SMOKERS BY NUMBER OF 



CIGARETTES SMOKED PER DAY 



—HEAVIEST AMOUNT 



The diagram shows the substantial contribution of cigarette smoking to chronic 

 respiratory conditions. Heavy smokers have as much as five times the excess 

 morbidity of non-smokers. For females this excess is even greater than for males. 

 The rates are adjusted for age and include data on subjects 17 years of age and 

 over. 



387 



