The pollution wafting out of exhaust pipes and billowing from smoke stacks is menacing enough, even before knowing about its links to physical and psychological illness, and poor brain health. The US Environmental Protection Agency has set a hard limit on how many of those airborne particles are safe for humans to tolerate. New Plos Medicine research published Tuesday, however, suggests that they may not be enough to keep the public safe.
In the world of air pollution research there’s rarely good news. This paper starts with some: Since 1999, the average levels of fine particulate matter that can impact health (PM2.5) have declined from 13.6μg/m^3 to 8 μg/m^3 . But it’s all downhill from there: The authors, from Imperial College London, reports that even those relatively lower levels of air pollution are associated with decreased life expectancy and death.
Between 1999 and 2015, they estimate, levels of PM2.5 greater than at least 2.8 μg/m^3 were linked with 15,612 deaths in women and 14,757 deaths in men. Considering that the EPA’s standard for acceptable levels of PM2.5 accumulation is 12 μg/m^3 , lead study author Mazzid Ezzati, Ph.D., argues it’s time to rethink what levels we deem safe.
“This study suggests even at seemingly low concentrations — mostly below current limits — they still cause tens of thousands of deaths,” Ezzati said. “Lowering the PM2.5 standard below the current level is likely to improve the health of the US nation, and reduce health inequality.”
Ezzati’s results are coming a particularly important time for the EPA, which was involved in funding the study.
In early July, two prominent public health groups, the American Lung Association and the American Public Health association, filed a lawsuit against the EPA for repealing the Obama-era Clean Power Plan and replacing it with the Trump administration’s Affordable Clean Energy Rule, which supports coal-fired power plants.
As Inverse previously reported, the groups argue that this policy move will not only walk back efforts to control carbon pollution, but could cause allow new coal plants to be built. Janice Nolen, American Lung Association’s vice president of national policy, argued that this move could open the door for higher levels of dangerous air pollution in the future.
“So it will not only allow carbon dioxide emissions to continue, it will allow for an extraordinary amount of pollution that can literally kill people in the interim,” Nolen told Inverse.
Ezzati’s paper presents an even more dire perspective. Though it notes that “the findings might not be causal,” it illuminates a distressing pattern: Even our current levels of air pollution may be robbing Americans of a few precious months of life expectancy.
How Air Pollution Impacts Life Expectancy
This paper measures annual levels of PM2.5 in the air gathered from 750 air quality stations across thousands of US counties. Almost every county that they analyzed had levels that were below that crucial 12μg/m^3 mark except four (which are unnamed).
Poorer counties saw greater pollution-related harms, underscoring the idea that exposure to air pollution is in itself a public health inequality. But even after controlling for covariates like income, there is still evidence that there are still about 30,000 cases of cardiorespiratory disease that can trace their origins back to unhealthy air.
"Lowering the PM2.5 standard below the current level is likely to improve the health of the US nation."
Life expectancy loss was highest in the Los Angeles area and southern states like Oklahoma, Arkansas, and Alabama, where more than 0.3 years (about 3.6 months) of life expectancy are lost to poor air conditions. By comparison, the Rocky Mountain counties in states like Arizona, New Mexico and Colorado had losses in life expectancy of less than .05 of a year (a little over half of a month).
The team argues that those losses could slightly reduce average American life expectancy, which right now, is 78.6 years. The reductions are small — about 0.13 years (1.56 months) for men and 0.15 (1.8 months) for women under our current air pollution situation. Generally, American life expectancy has already dropped slightly, a trend the CDC attributed to overdose deaths and suicide.
But our current levels of air pollution, as the authors note, may also contribute to “mortality and loss of longevity in the USA.”
That’s in part why Ezzati argues in the paper that it may be time to revisit what we deem acceptable. Especially in light of recent policy moves made by the EPA, it’s worth keeping a closer eye on the nation’s air.
Methods and Findings:
We used vital registration and population data with information on sex, age, cause of death, and county of residence. We used four Bayesian spatiotemporal models, with different adjustments for other determinants of mortality, to directly estimate mortality and life expec- tancy loss due to current PM2.5 pollution and the benefits of reductions since 1999, nation- ally and by county. The covariates included in the adjusted models were per capita income; percentage of population whose family income is below the poverty threshold, who are of Black or African American race, who have graduated from high school, who live in urban areas, and who are unemployed; cumulative smoking; and mean temperature and relative humidity. In the main model, which adjusted for these covariates and for unobserved county characteristics through the use of county-specific random intercepts, PM2.5 pollution in excess of the lowest observed concentration (2.8 μg/m3) was responsible for an estimated 15,612 deaths (95% credible interval 13,248–17,945) in females and 14,757 deaths (12,617–16,919) in males. These deaths would lower national life expectancy by an esti- mated 0.15 years (0.13–0.17) for women and 0.13 years (0.11–0.15) for men. The life expectancy loss due to PM2.5 was largest around Los Angeles and in some southern states such as Arkansas, Oklahoma, and Alabama. At any PM2.5 concentration, life expectancy loss was, on average, larger in counties with lower income and higher poverty rate than in wealthier counties. Reductions in PM2.5 since 1999 have lowered mortality in all but 14 counties where PM2.5 increased slightly. The main limitation of our study, similar to other observational studies, is that it is not guaranteed for the observed associations to be causal. We did not have annual county-level data on other important determinants of mortality, such as healthcare access and quality and diet, but these factors were adjusted for with use of county-specific random intercepts.
Conclusions: According to our estimates, recent reductions in particulate matter pollution in the USA have resulted in public health benefits. Nonetheless, we estimate that current concentrations are associated with mortality impacts and loss of life expectancy, with larger impacts in counties with lower income and higher poverty rate.