By Ellen Considine
Overview: The Health Impacts of Air Pollution
The World Health Organization (WHO) reports that approximately 7 million people worldwide die each year as a result of exposure to air pollution. Unsurprisingly, this health burden is distributed extremely unequally across the world. The following maps were obtained from the Global Burden of Disease (GBD) – Compare visualization tool.
The map also looks quite different when we consider disability adjusted life years (DALYs) instead of deaths. DALYs account for the total reduction in length and quality of life attributable to an exposure. The DALYs map shows an even more unequal distribution of the health burden due to air pollution, indicating that while many deaths in lower-income countries are officially attributed to other causes, air pollution is a major contributing factor to overall morbidity (suffering from a health condition) in these countries. Also, even though the scaling on the DALYs map obscures some variability among higher- and middle-income countries, the WHO reports that 91% of the world’s population live in places where the air pollution exceeds WHO guidelines.
Of the previously-mentioned 7 million deaths, about 4.2 million are attributed to ambient (outdoor) air pollution and about 3.8 million are attributed to household (indoor) air pollution. Ambient air pollution is due to a combination of natural and anthropogenic sources. Natural sources include smoke from wildfires and particles from dust storms. Anthropogenic sources (which dwarf natural sources) include fuel combustion from vehicles, heat and power generation, industrial facilities, and waste processing / incineration. Indoor air pollution is mostly due to smoke from dirty cookstoves and fuel use, which also contributes to ambient air pollution.
You may have noticed that the ambient air pollution plot specified “particulate matter pollution”. Two main kinds of air pollution that can have large health impacts are particulate matter (PM) and ground-level ozone. In contrast to the PM map, the world map of deaths attributable to ground-level ozone highlights countries with high and middle income levels. This is because ground-level ozone is created when chemicals emitted by machines or industrial processes react with sunlight, so countries with more motorized transportation and manufacturing generate more of this pollutant.
Together with nitrogen dioxide and sulfur dioxide, PM and ground-level ozone are the air pollutants for which the strongest evidence of adverse health effects has been collected. Another phrase you might encounter is “criteria air pollutants”. In the US, the criteria air pollutants (these four plus carbon monoxide and lead) are regulated by the Clean Air Act, which requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for each pollutant.