Air Pollution: Health Hazards and Prevention
31 January 2020 (online)
Air pollution is as old or probably older than humanity itself. Charaka Samhita provides one of the earliest descriptions of polluted air and its ill effects on human health. John Evelyn wrote one of the first books in Western literature attributing chronic respiratory ailments to air pollution in 1661. However, rapid industrialization, urbanization, and increased use of fossil fuels coupled with climate change and air pollution have become a health emergency in India. Smog is an annual occurrence in New Delhi, and has been seen even in coastal areas like Chennai ([Figs. 1] ). Annual mean particulate matter 2.5 (PM2.5) exposure in India has been estimated to be nearly 90 μg/m3, more than twice the national ambient air quality standard (NAAQS) upper limit of 40 μg/m3. More than 75% of our population has higher exposure to air pollution. Of these, New Delhi, Haryana, and Uttar Pradesh had exposure of around 125 μg/m3, that is, more than three times the upper limit. More than thrice the recommended exposure to pollutants. In India (2017), of the 1.24 million (1.09–1.39 million) deaths, that is, 12.5% of total deaths, were attributable to air pollution. Of these, 0.48 million (0.39–0.58 million) were attributable to household air pollution. Importantly, 51.4% deaths have been reported in persons below 70 years of age. In 2017, 26.2% of the global disease adjusted life years (DALYs) associated with air pollution were contributed by India. The highest DALYs due to ambient air pollution were in Uttar Pradesh, Haryana, New Delhi, Punjab, and Rajasthan; household air pollution DALYs were highest in Chhattisgarh, Rajasthan, Madhya Pradesh, and Assam. Improvement in air pollution is estimated to improve life expectancy in 2017 by 1.7 years (1.6–1.9 years); and >2 years in Rajasthan, Uttar Pradesh, and Haryana ([Fig. 2]).
The major air pollutants are PM, ozone, nitrogen oxides, carbon monoxide (CO), and sulfur dioxide (SO2). The larger particulate matter (PM 10, that is, particulate matter < 10 µm diameter) is entrapped in upper airways, and causes rhinitis, sinusitis, and throat irritation. The finer PM, that is, PM < 2.5 mm (PM2.5) bypasses the natural defense of upper airways and is deposited in distal airways, enters systemic circulation, and causes increased acute cardiovascular, cerebrovascular, and respiratory events, and also chronic diseases such as asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. PM exposure has also been linked to low birth weight and poor lung development. Ozone, a powerful oxidant, causes oxidative damage, leads to increased neutrophils, and inflammatory cytokines in the bronchial tree causes increased acute respiratory morbidity (pneumonia and asthma). Increasing ambient temperatures due to climate change coupled with air pollution poses a very grave public health challenge. Upper respiratory symptoms, namely sinusitis, running or stuffy nose, sneezing, sore throat, and common cold with fever were 1.8 times more prevalent in residents of New Delhi in the months of October and November of 2019 (personal observation, unpublished).
Vehicle exhaust, forest fires, fossil fuels, dust particles, pollution, spores, and volcanoes all aid in hastening air quality deterioration. The ongoing climate change crisis adds on to the adverse health effects of air pollution. Productivity loss from all of the above retards economic growth. A recent World Bank study estimated that for the year 2013, premature air pollution attributable deaths led to a loss of 225 billion dollar in labor income, and $5.11 trillion welfare losses worldwide; for India, these losses accounted for more than 8% of its GDP.
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