PART XI — HUMAN ADAPTATION TO ENVIRONMENTAL STRESS 



of ozone, 3 hours a day, 6 days a 

 week, for 12 weeks. The individuals 

 so exposed had a gradual decrease 

 in the forced expiratory volume in 

 one second which began to occur 

 after 8 weeks of exposure and con- 

 tinued to be depressed for 8 weeks 

 after the termination of exposure. 

 A lower dose failed to produce this 

 effect. 



Prevailing Controversy and 

 Needed Research 



Cohen, Deane, and Goldsmith, 

 utilizing data obtained for other pur- 

 poses, studied the possible effect of 

 carbon monoxide exposure on the 

 case fatality rate among persons ad- 

 mitted to Los Angeles hospitals with 

 myocardial infarction. They showed 

 that the rate increased during the 

 high pollution period and in the 

 higher of the two pollution areas of 

 Los Angeles County. Without addi- 

 tional studies, however, they were 

 reluctant to attribute this increase 

 only to carbon monoxide. Contro- 

 versy also exists concerning the effect 

 of carbon monoxide on the central 

 nervous system and, hence, its pos- 

 sible role in the performance of com- 

 plex tasks requiring accurate time 

 evaluation, such as driving an auto- 

 mobile. There has been no decisive 

 evidence concerning the role of car- 

 bon monoxide in general in motor- 

 vehicle accident frequency. 



The interaction of the various com- 

 ponents of both forms of smog in 

 producing health effects remains con- 

 troversial. Of particular interest is 

 the hypothesis recently put forward 

 by Pitts, among others, that one of 

 the essential mechanisms in the early 

 oxidation of nitric oxide to nitrogen 

 dioxide is the absorption of energy 



by atmospheric oxygen and conver- 

 sion of some of the normal triplet 

 oxygen to a singlet delta form that 

 may have a finite half-life and could 

 be of biological importance. 



A cross-sectional study of the fre- 

 quency of emphysema in several cities 

 in relation to the history of smoking 

 and of pollution exposure is going 

 to be necessary in order to resolve 

 some of the questions about the 

 effects of smog on chronic respiratory 

 disease. The identification of active 

 atmospheric species produced by 

 photochemical processes is an im- 

 portant one that may have powerful 

 interactions with radiological health 

 and carcinogenesis. Closely related 

 is the possibility that agents in photo- 

 chemical smog may be mutagenic or 

 teratogenic, though such reactions 

 would scarcely be considered adap- 

 tive ones. 



Relationship to Environmental 

 Management 



It is clear that community exposure 

 to carbon monoxide would be sub- 

 stantially diminished if automobiles 

 in operation were decreased either 

 in number or in the amount of car- 

 bon monoxide that they emit. Re- 

 duction in emissions of hydrocarbons 

 and oxides of nitrogen should also 

 have a substantial effect on the in- 

 tensity of photochemical smog, al- 

 though the effect will take a number 

 of years to be fully evident. Since 

 1956, the United Kingdom has 

 greatly reduced the amount of par- 

 ticulate matter in many of its urban 

 areas, and since 1967 there has been a 

 pronounced decrease in sulfur oxide 

 and particulate emissions in coastal 

 cities of eastern United States. Stud- 

 ies by Fletcher and his colleagues 



have shown that, in parallel with the 

 decrease in particulate matter in Lon- 

 don, there has been a decrease in 

 the frequency of chronic bronchitis 

 and in the amount of sputum pro- 

 duced by groups of people who had 

 comparable smoking exposures all 

 during this period. 



The attention paid to atmospheric 

 pollutants is responsive largely to 

 public concern with air pollution as 

 a menacing and offensive substance. 

 The public has not felt it necessary 

 to know the precise health effects. 

 The possibility exists, therefore, that 

 some questions that are of great sci- 

 entific importance will never be an- 

 swered, since it is hoped that the 

 increasingly vigorous control meas- 

 ures advocated by the Environmental 

 Protection Agency will reduce com- 

 munity exposures and thus make 

 some of the longitudinal studies un- 

 likely to reflect present or increased 

 exposures. 



Thus, the greatest priority should 

 be given to the specific exploration 

 of the hypothesis that pollutant ex- 

 posures which lead to impairment of 

 function may also increase the risk 

 of developing chronic cardiac and 

 respiratory disease through the mech- 

 anisms of adaptation which they pro- 

 voke. Longitudinal research on ex- 

 posed populations and their adaptive 

 mechanisms has been inadequately 

 supported because of the difficulty of 

 assembling teams of competent in- 

 vestigators over the longer periods of 

 time necessary for this sort of re- 

 search. From two to ten research 

 groups, some of which are not in 

 the United States, will be needed to 

 plan and carry out longitudinal 

 studies to evaluate the adaptation of 

 human subjects to smog and to car- 

 bon monoxide. 



390 



