Dirty Air Kills

I’ve long been struck by how consistently different methods find large health harms from air pollution. Most people seem to think we no longer have an air pollution problem, because we mostly don’t see much air pollution. But the particles that are too small to see continue to cause great harm.

The US Federal EPA standard for air pollution in the form of particles of size 2.5 microns or smaller is an annual average of 15, and a 24 hour average of 35, micrograms per cubic centimeter. Many places are not in compliance with these standards (check your area here and here).

A 2009 paper in the New England Journal of Medicine estimated that decreasing this pollution number by 10 units on average increases lifespan by 0.61±0.20 years. A 2006 paper in the American Journal of Respiratory and Critical Care Medicine estimated that such a change would decrease mortality by about 15%, adding about two years of lifespan. (Quotes below.)

These are huge gains, which could be achieved at a modest expense, especially compared to the vast costs we pay for tiny health gains via medicine. More should be done.

Those promised quotes:

NEJM 2009:

We compiled data on life expectancy, socioeconomic status, and demographic characteristics for 211 county units in the 51 U.S. metropolitan areas with matching data on fine-particulate air pollution for the late 1970s and early 1980s and the late 1990s and early 2000s. Regression models were used to estimate the association between reductions in pollution and changes in life expectancy, with adjustment for changes in socioeconomic and demographic variables and in proxy indicators for the prevalence of cigarette smoking.

A decrease of 10 μg per cubic meter in the concentration of fine particulate matter was associated with an estimated increase in mean (±SE) life expectancy of 0.61±0.20 year (P=0.004). The estimated effect of reduced exposure to pollution on life expectancy was not highly sensitive to adjustment for changes in socioeconomic, demographic, or proxy variables for the prevalence of smoking or to the restriction of observations to relatively large counties. Reductions in air pollution accounted for as much as 15% of the overall increase in life expectancy in the study areas.

AJRCCM 2006:

A small number of studies have assessed the effect of reductions in air pollution on mortality. Mortality in Utah Valley decreased by 3% when average particulate air pollution (PM10) concentrations decreased by 15 microgram/m^3 as the result of a 13-mo strike at a local steel mill. Mortality in Dublin decreased by 8% after a 36-microgram/m^3 decrease in average particulate air pollution (black smoke) due to a ban on coal sales. Restrictions on the sulfur content of fuel oil in Hong Kong resulted in a 45% average reduction in SO2, and the average annual trend in deaths from all causes declined 2% and from respiratory causes declined 3.9%. In these studies, improvements in mortality were observed in the months after well-defined improvements in ambient air quality.

Earlier analysis of the Harvard Six Cities adult cohort study showed an association between long-term ambient PM2.5 and mortality between enrollment in the mid-1970s and follow-up until 1990. We extended mortality follow-up for 8 yr in a period of reduced air pollution concentrations. We found an increase in overall mortality associated with each 10 microgram/m^3 increase in PM2.5 modeled either as the overall mean (rate ratio [RR], 1.16; 95% confidence interval [CI], 1.07–1.26) or as exposure in the year of death (RR, 1.14; 95% CI, 1.06–1.22). PM2.5 exposure was associated with lung cancer (RR, 1.27; 95% CI, 0.96–1.69) and cardiovascular deaths (RR,1.28; 95% CI, 1.13–1.44).

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  • Evan

    not that air pollution isnt an issue that should be looked at as a potential health risk factor, i question your two conclusions.
    increasing lifespan by .61 years is certainly something, but i’m not sure this should be considered ‘huge.’ I question even more your assertion that these gains could be achieved at a modest expense. how are you justifying that claim? we have already made great strides in recent history to reduce air pollution, and as you decrease particulates further, the marginal cost to get cleaner would increase exponentially.

  • So does that mean a home air purifier might be a good idea?

    • I guess the case against that action for me would be, that perhaps the aggregate effect is explained entirely by people with some asthma or similar symptoms. In other words, cleaner air might make a few people much healthier, instead of making everyone a little healthier.

      • zzk

        and sterilizing our environment to help people with Asthma is not necessarily the best strategy either, considering early life microbial exposure is actually negatively correlated with asthma. 

  • richard silliker

    Only four comments on such a subject.. Does this show hopelessness for a fix or acceptance for the orderly elimination of the human species.

  • Aron

    I believe the role of particulates in air was detailed well in the Skeptical Environmentalist.

  • This is very true. The low hanging fruit for this would be reduction in male trees that reproduce via airborne pollen.
    In most first-world cities, human pollution is relatively low, its the natural pollution thats horrible.

  • Anon

    Relatedly, boo coal.

  • floccina

    We humans repress natural fires and live in air-conditioned homes and buildings so we in the USA may already be exposed to much less air pollution than in a state of nature. People in the environmental movement seem to not be bothered by natural levels of pollution.

  • Alicia Reyes


  • John Salvatier

    Apparently woodsmoke is really bad for you too: http://www.ncbi.nlm.nih.gov/pubmed/17127644

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