Effects of long-term exposure to particulate matter and metal components on mortality in the Rome longitudinal study

BACKGROUND: The effect of long-term exposure to metal components in particulate matter on mortality are still controversial.

OBJECTIVES: To study the association between long-term exposure to PM10, PM2.5, PM2.5 absorbance, particulate matter components (copper, iron, zinc, sulfur, silicon, potassium, nickel, and vanadium) and non-accidental, cardiovascular (CVD), and ischemic heart disease (IHD) mortality.

METHODS: All 30+ year olds from the Rome Longitudinal Study were followed for vital status from October 2001 until December 2010. We used land use regression models to estimate annual average concentrations at residences and Cox models to estimate the associations between pollutants and cause-specific mortality, adjusting for individual and contextual characteristics. Hazard ratios (HRs) were expressed per increments equal to the 5(th)-95(th) percentile range of each pollutant distribution.

RESULTS: We analyzed 1,249,108 residents and found strong associations between all exposure indicators and mortality. We observed higher mortality risk with increasing exposure to PM2.5 absorbance (HR=1.05; 95% CI: 1.03-1.06) and to tracers of non-tailpipe traffic emissions such as tire and brake wear (Cu, Fe, and Zn); for PM2.5Zn, we found HR=1.06 (95% CI: 1.04-1.08) for non-accidental mortality, HR=1.07 (95% CI: 1.04-1.10) for CVD, and HR=1.11 (95% CI: 1.06-1.16) for IHD mortality. With increasing levels of nickel in PM10, we found HR=1.07 (95% CI: 1.05-1.09) for non-accidental mortality, HR=1.08 (95% CI: 1.05-1.11) for CVD, and HR=1.13 (95% CI: 1.08-1.18) for IHD mortality. Results were robust when we adjusted for PM mass and for cardiovascular mortality when we adjusted for NO2.

CONCLUSIONS: In addition to vehicular exhaust pollutants, PM related to non-tailpipe emissions and mixed oil burning/industry plays an important role in mortality.