Average human life is about one year shorter because of PM2.5 ambient air pollution, with lives shortened by 1.5-2 years in the most polluted Asian and African countries, a new study that uses data from the Global Burden of Disease Project has found.
In many countries in South Asia, especially India, the loss is more than 1.5-1.75 years, with the impact of air pollution on human lifespan in India being much larger than that of all cancers combined, the study finds.
In May, the WHO Global Ambient Air Quality Database for 2018, showed that India had 14 out of the 15 most polluted cities in the world in terms of PM2.5 concentrations. Kanpur was the worst at 173 micrograms per cubic metre (mg/m3), while Delhi was at 143 mg/m3. Kanpur was followed by Faridabad (172), Varanasi (151), Gaya (149) and Patna (144). The Central Pollution Control Board hasn’t released the annual average PM2.5 concentrations for 2017 so far.
The finding also notes the disproportionate effect air pollution has on the elderly. “Across South Asia, the probability of surviving from age 60 to 85 would have been 20% higher if PM2.5 exposure were removed as a mortality risk factor,” the study notes.
Titled ‘Ambient PM2.5 Reduces Global and Regional Life Expectancy’, the study published in the Environmental Science and Technology Letters on Wednesday systematically identifies how air pollution leads to shorter lives in each country.
It applies an actuarial standard life table method and combines it with data from the Global Burden of Disease Project to estimate global and national reductions in life expectancy for 185 countries that can be attributed to ambient PM2.5.
“The life expectancy is based on a survival curve. We start by evaluating how a population survives over time from birth onwards to estimate the baseline life expectancy. We then consider a hypothetical scenario where air pollution is no longer a health risk. In that scenario, the probability of surviving from each age to the next is incrementally higher than in the baseline,” lead author Joshua S Apte from the University of Texas told The Indian Express. “The difference between this hypothetical life expectancy and the baseline life expectancy is what we interpret as the life expectancy impact of air pollution.”
Apte said this is more pronounced in “most polluted countries” like Bangladesh, Pakistan and India, where people are losing more than 1.5 years from air pollution. “A year doesn’t sound like a lot but considered across population, this is a truly immense loss of lives, which has economic impacts as well,” he said.
“In addition to looking at outdoor PM2.5 air pollution, we looked at the combined effect of all air pollution, including outdoor ozone pollution and indoor sources like cooking and heating. Here, South Asia is in a particularly unfavourable position, since household air pollution, and outdoor pollution are both major issues,” he said.
Apte said the results “clearly show how cleaner air can lead to longer lives. If India were to meet the WHO air quality guidelines, the average Indian would live more than a year longer”. “If there are more India-led studies of the health effects of air pollution, it will increase the need for taking this problem seriously,” he said.
The study, however, is cautious while discussing improvements in life expectancy. “Mortality for any risk factor will evolve over time as a result of demographic and epidemiological transitions. Life expectancy is strongly dependent on age-specific death rates, which tend to decrease over time in countries where general population health is improving,” it notes. “Thus, the life expectancy benefit of PM2.5 reductions in many polluted lower-and middle-income countries might be 20-40% lower than our core estimates if those countries also had age-specific death rates that were typical of high-income economies,” it points out.
The study is co-authored by Apte along with Michael Brauer from the School of Population and Public Health, University of British Columbia; Aaron J Cohen from the Health Effects Institute in Boston; Majid Ezzati from the Centre for Environment and Health, Imperial College London; and C Arden Pope from Brigham Young University in Utah.
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