The World Health Organization has released a new estimate of the number of premature deaths linked to air pollution: In 2012, approximately seven million deaths — one in eight of those occurring worldwide — resulted from exposure to air pollution. The vast majority of these deaths occurred in low- and middle-income countries, with much of the burden falling in South East Asia and the Western Pacific.

This report deals separately with deaths from indoor and outdoor air pollution, although of course many people are exposed to both forms. Indoor, or household, air pollution comes mainly from the burning of wood, coal, dung, or other biomass fuels, which is why there’s so much urgency behind the global push for cleaner cookstoves. Strategies to reduce outdoor, or ambient, air pollution include reducing industrial smokestack emissions, prioritizing rapid urban transit, and increasing the use of renewable combustion-free power sources. These recommendations aren’t new, but perhaps the recognition of air pollution as the world’s largest single environmental health risk might give some momentum to pollution-reduction efforts.

Here’s the WHO’s breakdown of pollution-related deaths:

Outdoor air pollution-caused deaths – breakdown by disease:

• 40% – ischaemic heart disease;
• 40% – stroke;
• 11% – chronic obstructive pulmonary disease (COPD);
• 6% – lung cancer; and
• 3% – acute lower respiratory infections in children.

Indoor air pollution-caused deaths – breakdown by disease:

• 34% – stroke;
• 26% – ischaemic heart disease;
• 22% – COPD;
• 12% – acute lower respiratory infections in children; and
• 6% – lung cancer.

Read more here. And for those interested in learning more about active transportation — something that can help reduce ambient air pollution while increasing physical activity — check out the National Public Health Week Active Transportation Hangout on Air, hosted online by the American Public Health Association on Friday.