Identification of Subpopulations That Are Sensitive to Ozone Exposure: Use of End Points Currently Available and Potential Use of Laboratory-Based End Points under Development

Abstract

A number of epidemiological studies have attempted to assess the effect of recurrent ozone exposure in humans. For the most part, they have failed to document convincingly an association between chronic ozone exposure and differences in lung function performance or respiratory symptoms. This is not surprising given the small respiratory effects observed in animals chronically exposed to ozone and assuming that people with abnormal respiratory function resulting from other occupational or environmental exposures, such as tobacco smoke, would make up a much larger percentage of the population than people with respiratory effects attributable to ozone. Therefore, either more sensitive end points must be developed to detect subtle changes due to chronic ozone exposure, or ways of selecting subpopulations that are especially sensitive to ozone must be devised. It has been well documented that there are large and reproducible differences in the acute response of individuals to ozone as measured by pulmonary function tests. Recently, it has also been shown that there are large differences in the acute response of individuals to ozone as measured by inflammatory and other biochemical parameters. This paper discusses the problems of selecting individuals who are sensitive to ozone depending on the end point chosen. It also describes potential new sensitive end points that might be available for ozone epidemiology studies in the near future. -Environ Health Perspect 101 (Suppl 4): 225-230 (1993).

8-hydroxy-2'-deoxyguanosine, a major mutagenic oxidative DNA lesion, and DNA strand breaks in nasal respiratory epithelium of children exposed to urban pollution.

“…The significant interindividual variation in biomarkers apparently reflects the modulating effect of genetic and acquired susceptibility factors (12). Identification of subpopulations at higher risk of detrimental effects from air pollutant exposure is needed (13).…”

Sensitivity to ozone: could it be related to an individual's complement of antioxidants in lung epithelium lining fluid?

“…In exposure chamber studies, ozone has been demonstrated to elicit a broad spectrum of pathophysiological responses in animals and human subjects. Responses include transient decrements in pulmonary function, 8 .9 pronounced airway inflammation, 10 -12 increased airway reactivity to bronchoconstrictor agents, 13 • 14 alterations in airway epithelial permeability,I 5 and cellular damage with epithelial remodelling in the respiratory tract. 16 • 17 Spirometric decrements 18 and airway inflammation 19 have also been observed in 'naturally' exposed individuals, namely children and adults engaged in out-door activities.…”

“…Subsequently, a considerable body of work has been undertaken to define the effects of ozone upon the human population, 4 groups perceived as being at risk within it, 5 and in a wide range of animal models. 6…”

Possible mechanisms for the respiratory tract effects of noncarcinogenic indoor-climate pollutants and bases for their risk assessment

“…Several epidemiologic studies have investigated the effect of recurrent ozone exposure on humans. In general, a convincing association between chronic exposure and differences in lung function performance or respiratory symptoms has not been demonstrated (50).…”