Air pollution in northern India seen from space

Last week the illustrious scientific journal, Nature, published a study showing that outdoor air pollution kills 1.36 million people in China alone each year. This is “an order of magnitude higher than that attributable to Chinese road transport injuries and HIV/AIDs,” claims the article authored by Jos Lelieveld and his colleagues. Lelieveld and his team estimate that outdoor air pollution kills a total of 3.3 million people each year globally. This number is expected to double by 2050.

So what type of air pollution is killing so many of us, and what do we die of? The answer depends on where in the globe you are living. In Asia, where air pollution mortality rates are the highest, the most deadly type of pollution is from small combustion sources including diesel generators and biofuel use.

Biofuel cakes used for cooking in Tamil Nadu, India

If you’ve ever been in Bangalore when the power cuts out (which happens quite often), then you may have noticed the synchronized belch of black smoke emitted from the surrounding buildings. This is from the diesel generators kicking in to restore electrical power. Lelieveld’s team shows that small combustion sources, such as diesel generators, and others used for heating and cooking, contribute towards a total of 1 million deaths per year world wide. This does not even include the additional 3.54 million deaths per year due to indoor air pollution from the same source.

If you live in Europe or the Eastern United States, the most harmful source of outdoor air pollution is agriculture. To get a more exact number of deaths attributable to agricultural sources requires a better understanding of the toxicity of airborne particles associated with agricultural operations. However, the study does conclude that agriculture is the leading source of mortality in Europe, Russia, Turkey, Korea, Japan, and the Eastern USA. Agricultural emissions of ammonia from fertlizer use and domesticated animals affect air quality by reacting with atmospherically-formed sulfuric and nitric acids to form a cocktail of airborne particles. Unfortunately, the health impacts of these particles are still not fully understood. If one assumes their level of toxicity to be equal to carbonaceous sources, such as those from heating a cooking in Asia, then Lelieveld’s team estimates that agricultural emissions account for one fifth of outdoor air pollution mortality worldwide. This is the second negative effect associated with using synthetic fertilizers discussed thus far on ecosciencewire (see post on how nitrogen fertilizers can reduce biodiversity and thus ecosystem stability).

From this study we can conclude that serious air pollution control measures are needed, particularly in South and East Asia, if we are to avoid the death of millions more people. Additionally, more information is needed on the health effects of sulfates and nitrates to better evaluate the impact of traditional agricultural methods on human health.

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Photo Credit

Air pollution Beijing- Kevin Dooley via Wikipedia Commons; featured image, respiration protection- Nicolò Lazzati iva Flikr; air pollution in north India- NASA; Biofuel cakes, Info Farmer via Wikipedia; tractor- tpmartins via flickr