The US EPA sets National Ambient Air Quality Standards for criteria air pollutants, recognizing that air pollution in the environment exists as a complex mixture. Potential interactions between mixture components within biological systems are not well characterized. We reviewed past literature investigating the effects of mixtures of criteria air pollutants, starting with mixtures containing NOX (nitrogen oxides), and evaluated the presence of in vivo toxicological interactions. All endpoints and NOX-containing mixtures were considered, however, most studies evaluated respiratory effects of NOX+O3 (ozone). Studies were classified into two categories: complete or incomplete response data. Complete data included the number of observations, mean response, and variance for each treatment group in the study. Studies lacking single pollutant exposures or complete response data were reviewed qualitatively. Of the 13 animal studies and 7 human studies in the qualitative analysis, 6 animal studies and 0 human studies suggested there may be interactions, though no pattern of response among the endpoints or exposures was apparent. Studies with complete data were analyzed quantitatively, and the response to the mixture was compared statistically to the sum of the responses to individual pollutants; the absence of a difference was defined as additive (H0: combined effects = sum of individual effects, p=0.05). Of the studies in the quantitative analysis, all animal studies (n=17) had at least one non-additive endpoint, while the majority of endpoints evaluated in human studies (n=9) were additive. Among the studies that deviated from additivity, no pattern of response emerged in endpoints or exposure conditions. Thus, this analysis suggests that deviations from additivity exist in criteria air pollutant mixtures; however, many of the studies did not demonstrate interactions other than additivity.
Toxicology; Air-quality; Pollutants; Pollution; Environmental-pollution; Biological-factors; In-vivo-study; Respiration; Respiratory-irritants; Respiratory-system-disorders; Pulmonary-system; Pulmonary-system-disorders; Pulmonary-function; Exposure-levels; Laboratory-animals; Animals; Humans; Men; Women
The Toxicologist. Society of Toxicology 53rd Annual Meeting and ToxExpo, March 23-27, 2014, Phonex, Arizona