Time Series Study on Air Pollution and Mortality in Delhi, India

Abstract:

Introduction: Many epidemiological studies provide evidence of an association between short term exposure to air pollution and adverse health effects in humans including: increased mortality, increased rate of hospital admissions and emergency room visits, exacerbation of chronic respiratory conditions and decreased lung function. However such studies are limited in India. In order to bridge the gap in scientific knowledge and add evidence to the ongoing studies in other Asian cities, a retrospective time series study on air pollution and mortality in Delhi has been initiated under the PAPA (Public health Air Pollution in Asian cities) program. The goal of this study was to assess the relationship between daily all cause natural mortality and air quality parameters, primarily respirable particulate matter (PM10), in Delhi after controlling for confounders.

Methodology: The study uses a retrospective time series data (3 years data) on air quality and registered data of naturally occurring deaths in Delhi, to study the change in daily death rate due to change in air quality levels. The methodology involves collection of: (i) data on ambient air quality for major pollutants for all monitored stations for the period of 2002 – 2004 that could represent the population exposure in the city of Delhi. (iii) collection of meteorological data (temperature, humidity and visibility) for the study period; (iv) collection of daily death records from the Registrar of Births and Deaths and data cleaning. (v) Statistical analysis by adopting common protocol with city specific modifications.

Results and Implications: The present study findings show increase in particulate matter with 10 micron size cut off (PM10) and Oxides of nitrogen (NOx) were associated with increase in all cause natural deaths. It was found that for every 10 microgram per cubic meter change in PM10 was associated with only 0.14 percent increase in total all cause natural deaths. When oxides of nitrogen (NOx) alone was considered in the model, daily deaths increased 0.75 percent for every 10 microgram per cubic meter increase in NOx concentration.