An alarmingly high number of people on Earth now breathe polluted air, according to an air quality map released on Tuesday by the World Health Organization.
The interactive map, based on global air pollution data, confirms that 92% of the world's population lives in places where outdoor air quality fails to meet WHO guidelines.
This is a concerning public health issue, as air pollution can harm your lungs, heart and even brain—with the potential to cause premature death, said Dr. Maria Neira, director of the organization's Department of Public Health, Environmental and Social Determinants of Health.
The study said that air pollution could have killed at least 600,000 Indians in 2012—about a fifth of the 3 million who died worldwide because they were exposed to fine particulate matter (PM2.5) that may have aggravated or been directly responsible for cardiovascular diseases and lung cancer.
India comes just behind China – which witnessed an estimated 800,000 deaths – says the study, which relied on mathematical modelling to arrive at its figures.
India is second among all countries in the absolute number of deaths caused due to exposure to air pollution.
About 2,49,388 Indians died of Ischemic heart disease;1,95,001 of stroke; 1,10,500 of Chronic Obstructive Pulmonary Disease (COPD) and 26,334 of lung cancer, the study relying on publicly available national data on pollutant levels showed.
The actual impact of air pollution, says the report, is a “conservative figure,†as it does not include the separate impacts on health from other air pollutants such as nitrogen oxides (NOx) or ozone (O3), and excludes health impacts where evidence is still limited (such as pre-term birth or low-birth weight), the authors note.
Industries, households, cars and trucks emit complex air pollutants, including invisible PM2.5 particulates.
PM2.5 causing chronic illnesses
The impact of fine particulate matter (PM2.5) highlighted by the WHO study is felt through a broad spectrum of acute and chronic illnesses that cause premature death.
These include lung cancer, chronic obstructive pulmonary disease, and cardiovascular diseases. Worldwide, it is estimated to cause about 16 per cent of lung cancer deaths, 11 per cent of COPD deaths, and more than 20 per cent of ischaemic heart disease and stroke. Particulate matter pollution is an environmental health problem that affects people worldwide, but low- and middle-income countries disproportionately experience the burden.
A WHO South East Asian Region statement said, “Air pollution is the world’s biggest environmental risk to health and must be addressed on a priority basis as it continues to rise, causing long lasting disease and illness.â€
PM2.5 includes pollutants such as sulfate, nitrates and black carbon, which can sneak deep into the lungs and cardiovascular system.
Separate studies have shown associations between increased PM2.5 levels and increased risk of mortality and morbidity, said Jim Zhang, professor of global and environmental health at Duke University's Nicholas School of the Environment and the Duke Global Health Institute. He was not involved in the new WHO map.
"We also have data to show how PM2.5 affects the lung and the cardiovascular health. For example, PM2.5 exposure increases tissue and systemic inflammation, increases oxidative damage to DNA and cell membrane lipids, increases the risk for thrombosis," he said. "We also started to see cumulating evidence that PM2.5 lowers birth weight and impairs metabolic, cognitive and immune function."
These smaller particles can enter and deposit deep into your lungs, and cause the most health effects, said Stuart Batterman, professor of environmental health sciences at the University of Michigan, who was not involved with the new WHO map.
"Those health effects can include aggravation or causation of asthma, cardiovascular and respiratory disease, hospitalizations and death," he added.
The study findings, based on data derived from satellite measurements, air transport models and ground station monitors for more than 3,000 locations, both rural and urban, were developed by WHO in collaboration with the University of Bath in UK.
Urban trauma
In instances where accurate PM2.5 (that is, 2.5 micrometers or less) measurements were unavailable, the researchers derived their averages based on PM10, which are larger dust particle-concentrations. It notes that more than 80 per cent of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed the WHO limits. The study gave the WHO air quality guidelines for PM2.5 as 10 micrograms per cubic metre annual average, and 25 micrograms per cubic metre 24-hour average.
While all regions of the world are affected, populations in low-income cities are the most impacted. Overall, 98 per cent of cities in low- and middle income countries with more than 100,000 inhabitants do not meet WHO air quality guidelines. However, in high-income countries, that percentage decreases to 56 per cent.
Earlier this year too, the WHO had warned that nearly 1.4 million Indians may have succumbed to diseases caused by indoor air pollution. The numbers released on Tuesday were specific to outdoor air pollution.
Of all of pollutants, fine particulate matter has the greatest impact on health. A lot of the fine particulate matter comes from fuel combustion, both from mobile sources such as vehicles and from stationary sources such as power plants, industry, households or biomass burning.
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