Short-term mortality risks of daily PM2.5-bound metals in urban region of Guangzhou, China, an indication of health risks of PM2.5 exposure

Abstract

BackgroundShort-term exposure to fine particulate matter (PM2.5) increases the excess risk (ER) of deaths. The metals are important constituents that are responsible for health risks of PM2.5. However, the short-term mortality risks that are associated with individual PM2.5-bound metals are not comprehensively understood. ObjectiveEstimate the short-term mortality risks and corresponding thresholds of PM2.5-bound metals, with the purpose of advancing our understanding of the health risks of PM2.5 exposure, meanwhile, guiding the policy making of PM2.5 pollution prevention and early warning. MethodsDaily PM2.5 samples, which were collected in the urban region of Guangzhou from 2015 to 2016, were analyzed for metals. Air pollutants, meteorological and mortality data were collected during the same period. A distributed lag non-linear model was used to associate the ER of mortality with individual PM2.5-bound metals. A cluster analysis was processed to classify the cumulative ER of different metals into groups. Results11 PM2.5-bound metals were statistically significantly associated with non-accidental death; the highest cumulative ER of mortality was 2.22%, 1.85%, 1.42%, 2.04%, 1.41%, 1.26%, 0.65%, 2.24%, 1.23%, 2.86%, and 1.84% for an interquartile range (IQR) increase in concentrations of lead (Pb), cadmium (Cd), arsenic (As), selenium (Se), antimony (Sb), manganese (Mn), nickel (Ni), thallium (Tl), barium (Ba), aluminum (Al), and iron (Fe), respectively. The metals were classified into high (Pb, Cd, Se, Tl, and Al), middle (As, Sb, Mn, Ba, and Fe), and low (Ni, copper, and zinc) ER groups according to their highest cumulative ER values. No threshold was found for concentration-response relationships between all the metals and mortality. ConclusionPb, Cd, Se, Tl, and Al had more contributions to PM2.5-related mortality risk than the other metals. Specific emission source-control measures were needed to reduce the mortality risk of PM2.5 exposure. The mortality risks, which were associated with low-level exposure of PM2.5-bound metals, deserve attention in the design of early warning and self-prevention. Comprehensive exposure assessment of PM2.5-bound metals is required to understand and reduce the PM2.5-related health risks.