January 21, 2009
Lower Air Pollution Increased US Life Expectancies 5 Months

When a smelly old diesel truck or car goes past I get annoyed at the thought that I'm briefly breathing poisonous exhaust air. When the coal electric power industry manages to delay new air pollution regulations my reaction is similar and my support for nuclear power is in part due to a desire to live longer. Well, reductions in particulate pollution probably have raised US life expectancies by 5 months in recent decades.

A new study by researchers at Brigham Young University and Harvard School of Public Health shows that average life expectancy in 51 U.S. cities increased nearly three years over recent decades, and approximately five months of that increase came thanks to cleaner air.

"Such a significant increase in life expectancy attributable to reducing air pollution is remarkable," said C. Arden Pope III, a BYU epidemiologist and lead author on the study in the Jan. 22 issue of the New England Journal of Medicine. "We find that we're getting a substantial return on our investments in improving our air quality. Not only are we getting cleaner air that improves our environment, but it is improving our public health."

The research matched two sets of data from 51 cities across the nation: changes in air pollution between about 1980 and about 2000; and residents' life expectancies during those years. The scientists applied advanced statistical models to account for other factors that could affect average life spans, such as changes in population, income, education, migration, demographics and cigarette smoking.

In cities that had previously been the most polluted and cleaned up the most, the cleaner air added approximately 10 months to the average resident's life. On average, Americans were living 2.72 years longer at the end of the two-decade study period; up to five months, or 15 percent, of that increase came because of reduced air pollution. Other studies show that these gains are likely coming from reductions in the cardiovascular and cardiopulmonary disease that typically accompany air pollution.

A reduction of 10 micrograms per cubic meter of particulate pollution will increase life expectancies by 7 months. Indoor air filtration devices anyone?

"Life expectancy is the single most comprehensive summary of how people's longevity is affected by factors like air pollution that cause early death," said co-author Majid Ezzati, associate professor of international health at Harvard School of Public Health. "We were able to use routine mortality statistics to track longevity in all cities over a long period of time and analyze how it has been influenced by changes in air pollution."

The analysis found that for every decrease of 10 micrograms per cubic meter of particulate pollution in a city, its residents' average life expectancy increased by more than seven months. During the 1980s and 1990s the average PM2.5 levels in the 51 U.S. cities studied dropped from 21 to 14 micrograms per cubic meter. In cities such as Pittsburgh and Buffalo, the decrease was closer to 14 micrograms per cubic meter.

Long commutes in crowded traffic are probably bad for your health to the exhaust particulates of older cars and trucks.

Here's a more technical overview and here's a NEJM commentary that accompanied the original NEJM paper.

Share |      Randall Parker, 2009 January 21 09:25 PM  Aging Studies

Jerry Martinson said at January 21, 2009 10:10 PM:

Many people I know who are worried to death about global warming seem to whine about the restrictions on fireplaces, construction equipment, 2 stroke engines, and old cars. But this study is one of many that show how PM's are a serious health problem. The fact is that running an old 2 stroke weed wacker can generate far more PMs than running an SUV for a year. In fact I would say that most granola types I know think having a wood-burning stove fed with wood cut from a 2 stroke chainsaw is better for the environment than insulating your house better and using a natural gas furnace. We're getting marginal returns by making clean new cars slightly cleaner and if we really want to make progress against PMs we need to go after the big sources and those big sources are NOT SUVs.

Jerry Martinson said at January 22, 2009 1:59 AM:

You suggested indoor air filtration.

I'm not sure we have figured out how to do this well yet. Sure, you can buy a product that makes bogus claims, but do they really work well? It might be better to figure out where the harmful PMs in indoor air are coming from (i.e. fraying fabrics, cooking) and attack it at the source. General air filtering is already being done but I'm not sure I trust that the systems are efficient enough at removing PMs from a room. If a system is installed that is that effective at turning over the air, it might make sense in offices to find a way to combat droplet nuclei as well which are the likely carrier particles of almost all airborne disease like TB, colds, and influenza. Reducing the transmission R of these diseases in most communal settings would really take the bite out of the cold and flu outbreaks.

Joe said at January 23, 2009 3:51 PM:

This is nonsense. An increase of five months means that a small group of vulnerable people lived longer, but that it had little effect on the rest of the population.

The other point is that five months in a lifetime means that PM isn't nearly as bad as many claim. In fact, they're largely irrelevant.

Jerry Martinson said at January 24, 2009 7:56 AM:


I disagree. 5 months of life is a lot. This is far more life years than Pneumo vaccine for the elderly or colonoscopy. Most of these excess PM2.5 deaths weren't pure "harvesting" of the already demented in nursing homes or some sort of modern "Lebensunwertes Leben" euthanasia of the hopelessly infirm. If we just use GDP per head with the US at about $45k/year/head as a way to value a life year, this comes to about $20k of life lost. This implies that government interventions that cost people thousands of dollars per head(over the course of a lifetime) to reduce PM exposure are probably worth it. This is a big deal. I know it is hard to comprehend if one uses basic "proximate cause" reasoning but major PM sources like diesel engines, wood burning, and 2 stroke engines are as real of a cause of premature death as asbestos. I'm not a hippie, I grew up reading "Popular Mechanics" by firelight too.

Most other environmental interventions both real and proposed do not have nearly as strong of an improvement in human life expectancy. In fact, most of them are probably irrelevant to human life. Probably only the environmental interventions of basic plumbing, using landfills, and modern sewers exceed the cost-effectiveness of PM2.5 reduction.

Graham Cliff said at April 2, 2009 10:08 AM:

Folks, Particulates are evaluated by a management that only looks at the fiscal costs of evaluation. How do I know? I co-authored the paper "The Identification Of Asbestos" in the Journal of Microscopy, in 1976. What I see today appalls me. Particulate evaluation studies today employ PCM and PLM and NOT AEM. Why? - because it costs. PM1 particulates cannot be evaluated by light microscopy. I am reminded of NOT regulating the banking and fiscal management failures. The trouble is that innocent victims of particulates will have to pick up the tab?

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