Confounding or aggravating factors in noise-induced health effects: air pollutants and other stressors.

Different scientific groups have studied and continue to study the health impacts of physical and chemical agents in the environment. In most cases, every study group has considered the health effect as being solely due to the air pollutant(s) under investigation, for example air pollution without due regard for the simultaneous presence of noise pollution whereas both have an impact on the cardiovascular system. Or in the case of noise studies the contribution of solvent, asphyxiant or metal exposures has not been considered, which can have an impact on hearing impairment. One can, therefore, question the stringency of the available evidence of epidemiological studies in both fields to warrant the consideration of air pollutants as confounding or aggravating factors in studies of specific effects due to noise (and vice versa). In this paper we weigh the existing evidence on the association of noise and air pollutant exposure and associated health impacts. In forthcoming publications, the authors will consider the influence of other factors, which can confound noise studies but are currently not included in the analysis.