09 Mar 2016

Review of recent health effect studies with sulphur dioxide

Report no. 4/16: This report focuses on published toxicology and epidemiology studies that have examined the relationship between sulphur dioxide exposures and the occurrence of acute and chronic health effects in laboratory animals and humans. All relevant studies published since the World Health Organization issued their Air Quality Review in 2005 were taken into consideration. A total of 225 environmental epidemiology and toxicology studies were individually examined and summarized in the course of preparing this report.

Whereas an appreciable number of new morbidity and mortality investigations have been conducted on both acute and chronic health outcomes, the focus of most studies continues to be on the relationship between SO2 exposures and respiratory disease and asthma exacerbation. In addition, there has been a large increase in the number observational focusing on associations between SO2 exposure and variety of birth outcomes such low body weight, malformations, and infant mortality.Although a tremendous amount of new information has been published there are many problems with a majority of the observational studies including a heavy over reliance on concentration measurements from central monitoring sites as a surrogate for personal exposures. Despite the existence of studies showing that there is no relationship between these measures and personal SO2 exposures, central monitoring site measurements continue to be used unabated.

In addition, most of the studies have been performed used a single pollutant modelling approach that did not take into consideration the correlations between ambient SO2 levels and the concentrations of other pollutants such as PM 10 and PM 2.5. Those studies that have incorporated a multi-pollutant design have generally shown that and observed health associations emerging from a single pollutant model are not robust to the inclusion of a correlated co-pollutant.

As a result, a majority of the epidemiological studies conducted with SO2 suffer from a very high degree of exposure misclassification that renders them unusable for a hazard or risk determination. Given these circumstances, there is no good justification for making any adjustment to current limit values.

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