Black Smoke as an Additional Indicator to Evaluate the Health Benefits of Traffic-related Policy Measures: A Systematic Review of the Health Effects of Black Smoke Compared to PM Mass

Abstract

PP-29-044 Background/Aims: Literature suggests that black smoke (BS) or elemental carbon (EC) may be better indicators of health effects compared to PM mass. However, this suggestion is not based on a systematic review of the literature on the effects of the different indicators. We therefore conducted a systematic review, comparing the health effects estimated with PM mass versus BS/EC within the same studies. Methods: Medline as well as the Air Pollution Epidemiology Database (APED) were searched for studies that included estimates for (a measure of) PM as well as (a measure of) black smoke. Thirty-three suitable papers on time-series studies on daily mortality or hospital admission or emergency department visits were identified. All papers were skimmed through for possible information on results of multi-pollutant models. Results: Pooled estimates of the percentage change in mortality or hospital admissions per interquartile range (IQR) were generally similar for BS compared to PM10. For example, the pooled estimated percentage change in all cause mortality (9 single-city estimates) was 0.9% (0.4%–1.3%) per 20 μg/m3 increase in PM10 and 0.9% (0.4%–1.4%) per 12 μg/m3 increase in BS. Ten papers provided information on multi-pollutant models, 4 of which provided only qualitative information. In all 4 papers, as well as in 3 of 4 papers that provided quantitative results for PM10 adjusted for BS (and vice versa), the effect of BS was suggested to be more robust. Conclusion: Single pollutant effect estimates for daily mortality or hospital admissions were similar for BS and PM10 when expressed per IQR. Limited evidence from multi-pollutant models suggests that the effect of BS/EC may be more robust. As traffic-related policy measures will result in larger reductions in BS, relative to reductions in PM mass, estimated health benefits of such measures will be larger when expressed per achievable reductions in BS.