Association of air pollution and mortality in the Ludhiana city of India: A time-series study.

ABSTRACT

Background: With rapid industrialization, the quality of the air is being compromised in several Indian cities. Hence, the effect of air pollution on mortality was studied in the Ludhiana city of Punjab in northern India. Materials and Methods: Air quality and meteorological and mortality data were obtained for 2002-2004. Punjab Pollution Control Board monitored air quality on specific week days at different sites. Respirable suspended particulate matter (RSPM) (equivalent of PM 10 ) was measured by the gravimetric method and NOx and SO 2 by chemical method. The estimation of the daily average RSPM level was attempted by combining 24-h average of the monitoring stations working on a particular day. Sahnewal Airport records temperature, dew point, and relative humidity at 8.30 am, 11.30 am, and 5.30 pm. Visibility of fixed landmarks is observed manually every hour from 6.30 am to 6.30 pm. Daily death records were obtained from the civil registration system. The association between visibility as proxy for RSPM and mortality was established using the generalized additive model (GAM) with natural spline smoothers at 6, 3, 3 df in R software with deaths (excluding accidents) as a dependent variable. Smoothers for day of the week, temperature, and relative humidity were also included in the model. Results: Air quality monitoring days for different monitoring stations ranged from 86 to 138 per year. The annual mean RSPM ranged from 226.7 to 269 μg/m 3 , SO 2 from 11.6 to 20.9 μg/m 3 , and NOx from 32.2 to 46.3 μg/m 3 . The mean (SD) temperature was 25.6 (7.9)°C, relative humidity was 58.1 (19.3)%, and visibility was 3398 (1418) m. Overall 28,007 deaths were registered, with an average of 25.4 deaths (SD 5.8) per day. The association between air quality as indicated by visibility (haze) and daily mortality was found to be statistically significant. For every 1 km decrease in visibility at midday, mortality due to natural causes increased by 2.4%. Conclusions: In Ludhiana, air pollution levels were quite high. The air quality (as measured by visibility) was significantly associated with mortality.