Contribution of heavy metals in PM2.5 to cardiovascular disease mortality risk, a case study in Guangzhou, China

Heavy metals play an important role in inducing fine particulate matter (PM2.5) related cardiovascular disease (CVD). However, most of the past researches concerned the associations between CVD mortality and the PM2.5 mass, which may not reveal the CVD mortality risk contributed by heavy metals in PM2.5. This study explored the correlations between individual heavy metals in PM2.5 and CVD mortality, identified the heavy metals that significantly contribute to PM2.5-related CVD, heart disease (HD), and cerebrovascular disease (CEV) mortality, and attempted to establish corresponding source control measures. Over a 2-year study period, PM2.5 was sampled daily in Guangzhou, China and analyzed for heavy metals. The airborne pollution and weather data, along with CVD, HD, and CEV mortality, were obtained at the same time. The excess risk (ER) of mortality was linked to the individual heavy metals using a distributed lag non-linear model. PM2.5 and most heavy metals showed significant correlations with the CVD, HD, and CEV mortality; the largest cumulative ER (LCER) values of CVD mortality associated with an interquartile range increase in the levels of lead, cadmium, arsenic, selenium, antimony, nickel, thallium, aluminum, iron, and PM2.5 were 2.43%, 2.23%, 1.66%, 2.39%, 1.19%, 1.21%, 2.69%, 3.29%, 1.74%, and 2.40%, respectively. Most heavy metals showed comparable LCER values of HD and CEV mortality. Heavy metals with the addition of PM2.5 were divided into three groups following their LCER values; lead, cadmium, arsenic, antimony, thallium, zinc, aluminum, and iron, whose contributions were greater than or equal to the average effect of the PM2.5 components, should be limited on a priority basis. These findings indicated that heavy metals play roles in the CVD, HD, and CEV mortality risk of PM2.5, and specific control measures which aimed at the emission sources should be taken to reduce the CVD mortality risk of PM2.5.