• Studies have consistently shown an association between elevated ambient levels of fine particulate matter (PM2.5) and increased mortality.
• In a longitudinal study of the population of six United States cities followed for 14 to 16 years (mid-1970s through 1990), increased air pollution was associated with increased mortality; this increased mortality was most closely associated with the increase in fine particulate pollution [N Engl J Med. 1993;329(24):1753.] 
• A dose response was observed, with an increased mortality rate of 13 percent for every 10 mcg/m3 rise in PM2.5.
• With extended follow-up in the same cities, there were improvements in air quality with a decrease in PM2.5; this decrease was associated with improvements in mortality risk [Am J Respir Crit Care Med. 2006;173(6):667].
• Even a short-term increase in levels of particulate pollution is associated with a rise in daily all-cause mortality. In a time-series study including over 650 cities in 24 countries, increases of 10 mcg/m3 in the two-day average PM2.5 and PM10 were associated with an increase in daily all-cause mortality (0.68, 95% CI 0.59-0.77; and 0.44, 95% CI, 0.39-0.50 respectively) [N Engl J Med. 2019;381(8):705].
• In regions with better overall air quality, the observed dose response effect was greater with no threshold for effects, thus implying that even countries with relatively good air quality could still see public health benefits from further reduction in PM [N Engl J Med. 2019;381(8):774].

• In a cohort study evaluating the pulmonary function of children ages 11 to 15 years with and without asthma, better air quality (decreased levels of nitrogen dioxide and particular matter) was associated with improvements in both forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) [N Engl J Med. 2015 Mar;372(10):905-13].

Dr KK Aggarwal

Padma Shri Awardee

President Confederation of Medical Associations in Asia and Oceania (CMAAO)

Group Editor-in-Chief IJCP Publications

President Heart Care Foundation of India

Past National President IMA