Long-term trends and health impact of PM and O in Tehran, Iran, 2006-2015.

The main objectives of this study were (1) investigation of the temporal variations of ambient fine particulate matter (PM) and ground level ozone (O) concentrations in Tehran megacity, the capital and most populous city in Iran, over a 10-year period from 2006 to 2015, and (2) estimation of their long-term health effects including all-cause and cause-specific mortality. For the first goal, the data of PM and O concentrations, measured at 21 regulatory monitoring network stations in Tehran, were obtained and the temporal trends were investigated. The health impact assessment of PM and O was performed using the World Health Organization (WHO) AirQ+ software updated in 2016 by WHO European Centre for Environment and Health. Local baseline incidences in Tehran level were used to better reveal the health effects associated with PM and O. Our study showed that over 2006-2015, annual mean concentrations of PM and O varied from 24.7 to 38.8 μg m and 35.4 to 76.0 μg m, respectively, and were significantly declining in the recent 6 years (2010-2015) for PM and 8 years (2008-2015) for O. However, Tehran citizens were exposed to concentrations of annual PM exceeding the WHO air quality guideline (WHO AQG) (10 μg m), U.S. EPA and Iranian standard levels (12 μg m) during entire study period. We estimated that long-term exposure to ambient PM contributed to between 24.5% and 36.2% of mortality from cerebrovascular disease (stroke), 19.8% and 24.1% from ischemic heart disease (IHD), 13.6% and 19.2% from lung cancer (LC), 10.7% and 15.3% from chronic obstructive pulmonary disease (COPD), 15.0% and 25.2% from acute lower respiratory infection (ALRI), and 7.6% and 11.3% from all-cause annual mortality in the time period. We further estimated that deaths from IHD accounted for most of mortality attributable to long-term exposure to PM. The years of life lost (YLL) attributable to PM was estimated to vary from 67,970 to 106,706 during the study period. In addition, long-term exposure to O was estimated to be responsible for 0.9% to 2.3% of mortality from respiratory diseases. Overall, long-term exposure to ambient PM and O contributed substantially to mortality in Tehran megacity. Air pollution is a modifiable risk factor. Appropriate sustainable control policies are recommended to protect public health.