Cause and Age-specific premature mortality attributable to PM_2.5 Exposure: An analysis for Million-Plus Indian cities

In India, a majority population is exposed to high levels of ambient PM_2.5 resulting in adverse health outcomes. Epidemiological studies have associated diseases such as Ischemic Heart Disease (IHD), Cerebrovascular Disease (Stroke), Chronic Obstructive Pulmonary Disease (COPD), Lower Respiratory Infection (LRI), and Lung Cancer (LNC) to long-term PM_2.5 exposure resulting in premature mortality. In the present work, the Integrated Exposure Response (IER) model is used to estimate such premature deaths for the year 2016 in 29 million-plus Indian cities. The city-specific registered deaths data along with information of percent share of cause-specific deaths in the total deaths and measured ambient PM_2.5 concentrations are used to estimate cause-specific baseline mortality in a city. The premature mortality attributable to PM_2.5 exposure is estimated from this baseline mortality. The premature mortality burden attributable to PM_2.5 exposure in these cities is 114,700 (104,100-125,500) deaths from the five causes (IHD, Stroke, COPD, LRI, and LNC). IHD is the leading cause of death accounting for 58% of PM_2.5 related premature deaths, followed by Stroke (22%), COPD (14%), LRI (4%), and LNC (2%) in these 29 cities. The estimated number of PM_2.5 related deaths in productive age group (25 - 50 years) is quite low compared to older people, but the percentage share of these deaths in the cumulative cause-specific baseline deaths is higher for productive age group. Thus, the productive population is considerably at a higher risk of mortality due to PM_2.5 exposure. There is approximately 18% and 70% reduction in premature mortality if these cities can attain National Ambient Air Quality Standards (NAAQS) (40 μg/m³) and the World Health Organization (WHO) guidelines (10 μg/m³) of annual PM_2.5, respectively. The estimates of air pollution related mortality at the city level could assist in city-specific policy formulation for better air pollution control.