"Long before it's in the papers"
December 03, 2012

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Cleaner air seen continuing to boost life expectancy

Dec. 3, 2012
Courtesy of the Harvard School of Public Health
and World Science staff

Even though U.S. air-pollution regula­tions have been tight­en­ing for a good four de­cades, the re­sult­ing cleaner air is still im­prov­ing pub­lic health, re­search­ers say. That, they add, sug­gests even strict­er rules may be worth their cost, which is sub­stan­tial.

A study by the scientists found an as­socia­t­ion be­tween re­duc­tions in air pol­lu­tion and im­proved life ex­pect­an­cy in 545 U.S. coun­ties from 2000 to 2007. The Har­vard School of Pub­lic Health-led the stu­dy ap­pears in the Dec. 3 on­line is­sue of the jour­nal Ep­i­de­mi­ology.

Even though “the U.S. popula­t­ion as a whole is ex­posed to much low­er lev­els of air pol­lu­tion than 30 years ago—be­cause of great strides made to re­duce peo­ple’s ex­po­sure—it ap­pears that fur­ther re­duc­tions in air pol­lu­tion lev­els would con­tin­ue to ben­e­fit pub­lic health,” said the lead au­thor, An­drew Cor­reia, a doc­tor­al can­di­date in the bio­statis­tics at the school.

Tougher and tougher regula­t­ions since the 1970s have led to U.S. air qual­ity im­prove­ments “that the U.S. En­vi­ron­men­tal Pro­tec­tion Agen­cy has es­ti­mat­ed as high as $25 bil­lion per year,” added sen­ior au­thor Fran­ces­ca Do­minici, a bio­statis­ti­cian at the in­sti­tu­tion. (That’s roughly 60 percent of the aver­age an­nual cost of the U.S. war in Af­ghan­i­stan, as tallied by the U.S. Con­gress­ional Re­search Ser­vice).

But “the ex­tent to which more re­cent reg­u­la­tory ac­tions have ben­e­fited pub­lic health re­mains in ques­tion. This study pro­vides strong and com­pel­ling ev­i­dence.” 

The study looked at the ef­fects of “fine par­tic­u­late mat­ter,” pol­lu­tion par­t­i­cles 2.5 mi­crom­e­ters (mil­lionths of a me­ter) wide or smaller. Many stud­ies have linked ex­po­sure to such con­tam­i­nants with heart and lung dis­eases and mor­tal­ity. Stud­ies have al­so as­sociated re­duc­tions in air pol­lu­tion with bet­ter health, and shown air pol­lu­tion de­clin­ing in the U.S. since 1980. But since the de­clines have been slow­er since 2000, the in­ves­ti­ga­tors wanted to check if life ex­pect­an­cy is still im­prov­ing.

Con­trol­ling for so­ci­o­ec­onomic sta­tus, smok­ing rates, and de­mo­graph­ic char­ac­ter­is­tics, the find­ings linked each decrease of 10 mil­lionths of a gram per cu­bic me­ter in the con­centra­t­ion of the par­t­i­cles to an av­er­age life ex­pect­an­cy boost of about four months, dur­ing the time per­iod un­der focus.

The find­ings al­so point­ed to a stronger link be­tween clean­er air and bet­ter health in ur­ban ar­eas than ru­ral ones—pe­rhaps due to dif­fer­ing types of pol­lu­tion, the re­search­ers said—and fur­thermore sug­gested clean air may ben­e­fit wom­en more than men.

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A study has found an association between reductions in air pollution and improved life expectancy in 545 U.S. counties from 2000 to 2007. The study sheds light on whether costly, increasingly strict clean-air regulations are really helping people—something that has been in question, said Harvard School of Public Health scientists who led the study. The answer, they added, is yes. The findings appear in the Dec. 3 online issue of the journal Epidemiology. Even though “the U.S. population as a whole is exposed to much lower levels of air pollution than 30 years ago—because of great strides made to reduce people’s exposure—it appears that further reductions in air pollution levels would continue to benefit public health,” said the lead author, Andrew Correia, a doctoral candidate in the biostatistics at the school. Increasingly stringent regulations since the 1970s have led to U.S. air quality improvements “that the U.S. Environmental Protection Agency has estimated as high as $25 billion per year,” added senior author Francesca Dominici, a biostatistician at the institution. But “the extent to which more recent regulatory actions have benefited public health remains in question. This study provides strong and compelling evidence.” The study looked at the effects of “fine particulate matter,” pollution particles 2.5 micrometers (millionths of a meter) wide or smaller. Many studies have linked exposure to such contaminants with heart and lung diseases and mortality. Studies have also associated reductions in air pollution with better health, and shown air pollution declining in the U.S. since 1980. But since the declines have been slower since 2000, the investigators wanted to check if life expectancy is still improving. Controlling for socioeconomic status, smoking prevalence, and demographic characteristics, the findings showed that each drop of 10 millionths of a gram per cubic meter in the concentration of the particles during the period 2000 to 2007 was associated with an average increase in life expectancy of about four months in 545 U.S. counties. The findings also pointed to a stronger link between cleaner air and better health in urban areas than rural ones—perhaps due to differing types of pollution, the researchers said—and furthermore suggested clean air may benefit women more than men.