Evaluation of traffic noise-related cardiovascular risk.

In this paper we discuss the risk of myocardial infarction induced by traffic noise within the conceptual framework for risk assessment suggested by the US National Research Council. The characterisation of cardiovascular risk is evaluated using a four-dimensional set of evaluation criteria: severity of health effect, frequency of exposures considered relevant for health, size of estimated risk, and validity of risk assessment. For quantification of risk we calculated lifetime risks using standard methods applied for quantitative cancer risk estimation. In evaluation of validity we refer to criteria that the International Agency for Research on Cancer has developed for classification of epidemiological evidence. Compared to other adverse effects regarded in regulatory toxicology, myocardial in-farction is a severe health effect. Assuming that sound pressure levels Leq, 6-22 hr above 65 dB(A) are associated with an increased cardiovascular risk, a major portion of the German population (about 16 %) is exposed to health relevant noise levels. Estimated lifetime risk amounts to 20:1,000 and exceeds considerably the lifetime risk induced by other environmental hazards or tolerable risk levels suggested in other contexts. A causal association between noise exposure and infarction risk, however, cannot be taken as proven scientifically, because chance, bias or con-founding cannot be ruled out with reasonable confidence. Methodological quality of the studies performed, consistency of findings, dose-response relations, coherence with a recent occupational study and biological plausibility nevertheless support a causal interpretation. Thus, an integrative evaluation of all available information may justify the conclusion that a causal interrelationship is probable. The conclusions for regulation strongly depend on how the high risk potential is balanced against the uncertain causality assessment. This question cannot be answered by science but must be decided politically. From a public health perspective noise exposure should be reduced in order to protect human health.