Revision of Swiss noise exposure limits in the wake of the WHO environmental noise guidelines: methodology matters

The current concept for the protection of the population against noise in Switzerland was defined in the 1980s in the Environmental Protection Act and subsequently substantiated with exposure limit values. To review and revise these nowadays outdated values, we were appointed by the Federal Noise Abatement Commission to update the pertinent scientific foundations and to suggest new exposure limits if necessary. For our recommendations, we took into account exposure-response relationships from the (Switzerland-specific) SiRENE study and from the WHO evidence reviews for annoyance, sleep disturbance, cardiovascular and metabolic outcomes as well as risk estimates from a recent meta-analysis on cardiometabolic outcomes. In deriving new limit values, the working group followed a similar heuristic as did the WHO Guideline Development Group for informing their recommendations, but explicitly considered two categories of effects that were both given the same weight for deriving the limit values: Self-reported ("subjective") effects like annoyance and self-reported sleep disturbances on one hand, and on the other hand ("objective") cardiometabolic effects for which the evidence was considered scientifically sound enough, namely ischemic heart disease (IHD), diabetes, and cardiovascular disease mortality. This paper discusses the proposed methodological courses of action to derive updated exposure limits.