Outdoor pollution is not primarily an urban problem, and ambient air is as toxic in rural India as it is in urban areas, according to a new study funded in part by NASA that combined satellite data with models to estimate levels of air pollution. small particles (PM2. 5> 2.5 μm) that damage health and cause premature death.
In the rest of India, average PM2.5 levels are similar in rural and urban areas, the study by researchers from Colorado State University and the Indian Institute of Technology in Bombay found. It found that the majority of people in India (84% of the population) are exposed to contamination well above the limit of the Indian standard (40 μg / m3), and almost the entire country is exposed to levels higher than the WHO standard (10 μg / m3). m3), with “a long tail of very high concentrations (> 160 μg / m3) in the urban regions of the Indo-Gangetic Plains and parts of non-urban areas in eastern and western India”.
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Around 16% of the population of India is unaffected by this pollution (below 40 μg / m3), and it is mainly confined to the northwestern parts of India, the Western Ghats and some regions of India. The fraction that is below WHO standards is very small (<0.001%), the study said, which has implications for air quality monitoring, regulations, public health and policy. It was published in the journal Proceedings of the National Academy of Sciences (PNAS) on Tuesday.
“I was a bit surprised (with the results), although our previous work indicated this. We calculated them using satellite data, so no, there are no significant gaps, ”lead author R. Ravishankara, Distinguished University Professor, Colorado State University Departments of Chemistry and Atmospheric Sciences, USA, said in an email.
“Only the very north-western part of India appears to be below the PM2.5 threshold. We have used premature mortality as a metric to measure the impact on health. In addition to premature mortality, there are other negative impacts such as asthma, hospital visits, medical costs, etc. Ravishankaran said.
The findings are in line with the State of Global Air 2020 report released in October, which said India recorded exposure to the world’s highest annual average PM2.5 concentration in 2019, followed by Nepal, Niger, Qatar and Nigeria.
For the PNAS study, the researchers calculated the aerosol optical depth (AOD) averaged annually from three satellite instruments (methods) that were converted to surface PM2.5 abundances using the model’s PM2.5: AOD ratios. of GEOSChem chemical transport. They then compared daily and annual PM2.5 obtained by satellite with surface PM2.5 measured by the Central Pollution Control Board of India at 20 monitoring sites, most of which were in urban areas.
Annual premature deaths attributable to PM2.5 alone for urban and rural India is 1.05 million, the study found, which took into account six causes of death: ischemic heart disease, stroke, lower respiratory infections, lung disease. chronic obstructive disease, lung cancer and type 2 diabetes.
Long-term exposure to outdoor and domestic air pollution contributed to more than 1.67 million premature deaths annually from stroke, heart attack, diabetes, lung cancer, chronic lung diseases and neonatal diseases in India in 2019, according to the 2020 Global Air Report.
The analysis revealed that the risk of premature death attributable to PM2.5 is similar in rural and urban regions, but there were more deaths in rural areas, which are home to 69% of the country’s population.
“We have used premature mortality as a metric to measure the impact on health. These are quantified in the article. In addition to premature mortality, there are other negative impacts such as asthma, hospital visits, medical costs, etc. Ravisankaran said.
The findings suggest that efforts to monitor and reduce air pollution should not be limited to urban areas in India. Improving monitoring and regulation in rural areas, which are practically non-existent, could help to better assess risks and inform policy for reducing PM2.5 levels across India, taking into account the lower capacity of rural areas. rural populations to reduce risks due to economic reasons.
“The Global Burden of Disease 2019 shows us that possibly 100% of India is exposed to air that does not meet WHO guidelines, and between 69% and 85% of the population is exposed to air that does not meet with the national standard. Now there is a combination of satellite data, chemical transport and ground monitors to prove it. Currently, there are studies that show that between 30% and 50% of outdoor air pollution comes from domestic emission sources. Impacts on the health of rural and urban populations can range from cardio-respiratory, cardiovascular, diabetes, low birth weight, preterm birth and neonatal mortality, ”said Kalpana Balakrishnan, director of the Council’s Center for Advanced Air Research. Indian Medical Research. Quality, climate and health, Chennai.
“My key message is: don’t forget non-urban India when it comes to air pollution. The second key message is: science, measurement and analysis can help overcome this problem with good information for policy makers, ”said Ravisankaran.
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