The third category of secondary pollutants is peroxyacetyl nitrate PAN, which, like ozone, is formed by a photochemical reaction and is one of the common constituents of smog. It is believed that PAN serves as a stable storage form of NO and other nitrogen oxides, allowing these highly reactive compounds to be transported in the colder, high regions of earth’s atmosphere. Once transported, PAN can easily release free NO in warmer, low-altitude air layers. The quantities of PAN in the air of large cities depends on the intensity and duration of daily sunshine, air temperature, the concentration of PAN and other photochemical oxidants such as ozone at the beginning of the day, as well as the emission rates and concentrations of primary pollutants NO. In fact, the increase in ozone in the late morning and early afternoon of hot summer days, as shown in figurepageis accompanied by an increase in PAN and a decrease in NO.
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PAN was initially identified in automobile exhaust as a pollutant in the early s. Since that time, it has been recognized as an eye irritant with a distinctive odor that results in blurred vision and eye fatigue at levels as low as. In comparison, PAN concentrations in Los Angeles have exceeded when environmental conditions were favorable for a great buildup of photochemical smog.
Changes in pulmonary function tests PFT, maximal exercise responses, and symptoms reported. Days – represent consecutive daily exposures. FA, initial O, and day were randomly presented, – days apart. Reprinted from Folinsbee et al. .
Only a few studies have investigated the effects of PAN during submaximal exercise. One involved light treadmill walking VO max lasting for while breathing air containing PAN. The results showed no changes in oxygen consumption, ventilation, heart rate, rectal temperature, or skin temperature in both younger – years old and older – years old healthy males. Values recorded durmg PFT FeW als revealed n change due to PAN exposure
Two studies have observed the effects of a PAN exposure of on VOmax. These experiments found no decrement in the VOmax values of two groups of smokers and nonsmokers: healthy younger – years and older – years men. Further, no changes in VEmax, exercise time, maximal heart rate, or blood lactate concentration after exercise was observed. The investigators cautioned, however, that PAN might impair PFT or maximal exercise performance in unhealthy individuals those with respiratory disease or compromised pulmonary function. In summary, the research regarding PAN exposure is sparse, particularly regarding maximal exercise performance. It appears unwise to form conclusions until higher concentrations are tested and persons with pulmonary impairment are evaluated.
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