It’s firmly agreed upon at this point that air pollution isn’t doing anyone’s health any favors. That being said, while air pollution has been linked to cardiovascular and other specific health issues, a firm connection between long-term exposure to smog and a shorter lifespan has never been established — up until now.
Researchers from Harvard University just released a new study offering up the most compelling evidence to date of a causal link between frequent exposure to air pollution and premature, earlier death. In light of their findings, the study’s authors believe that the US’ air quality standards regarding particulate matter (air) pollution are woefully inadequate in their current form.
In fact, the team at Harvard says that if the U.S. air quality standards were to be reformed to match up with the World Health Organization’s (WHO) guidelines, over 140,000 American lives would be saved for the next 10 years!
“Our new study included the largest-ever dataset of older Americans and used multiple analytical methods, including statistical methods for causal inference, to show that current U.S. standards for PM2.5 concentrations are not protective enough and should be lowered to ensure that vulnerable populations, such as the elderly, are safe,” says doctoral student and study co-author Xiao Wu in a university release.
Air pollution is usually measured by assessing the levels of particulate matter (PM 2.5) present in a region’s air. Particulate matter is tiny, microscopic pieces of dust and other pollutants that can irritate the lungs, cardiovascular system, and other parts of the human body if breathed in regularly.
This study picks up where a 2017 research project had left off. That study had concluded at the time that prolonged exposure to PM 2.5, even at fairly low levels considered to be “safe” by US standards, can greatly increase an elderly individual’s chances of dying early.
This time around, a much larger dataset was used; information on 68.5 million Medicare enrollees over 16 years. After adjusting for various potentially influential factors like BMI, smoker status, education, ethnicity, and income, the research team matched each participant’s zip code with corresponding local air pollution levels.
The analysis left no stone unturned. For example, as each zip code’s average PM 2.5 level was agreed upon, researchers were sure to consider additional factors that may influence local air pollution levels such as weather patterns, satellite data, and land-use data. In all, five complex statistical strategies were employed to sort through all that data and determine what effect air pollution has on lifespan.
Across all five statistical approaches, the results remained largely the same. In summation, the study’s authors call their findings “the most robust and reproducible evidence to date” of a causal link between PM 2.5 exposure and early death among Medicare enrollees. This troubling association held even among zip codes with estimated PM 2.5 levels below the air quality standard currently considered “safe” in the US (12 micrograms per cubic meter annually).
According to their calculations, an annual reduction of 10 micrograms per cubic meter in a given area would lower locals’ mortality risk by 6-7%. So, with those numbers in mind, if the US were to lower its yearly PM 2.5 standard to 10 micrograms instead of 12, researchers say 143,257 lives would be saved over the next decade.
As mentioned earlier, this isn’t the first time similar findings have come up. So, why hasn’t the US already addressed this issue? In the past, many have been wary of fully trusting the statistical methods used to come to those conclusions. This time, however, the team at Harvard incorporated extra analyses that allowed them to focus specifically on causation. Thanks to these extra considerations, researchers essentially created a “randomized study,” which is typically thought of in the science community as the “gold standard” of establishing causality.
“The Environmental Protection Agency has proposed retaining current national air quality standards. But, as our new analysis shows, the current standards aren’t protective enough, and strengthening them could save thousands of lives. With the public comment period for the EPA proposal ending on June 29, we hope our results can inform policymakers’ decisions about potentially updating the standards,” concludes co-author Francesca Dominici, Clarence James Gamble Professor of Biostatistics, Population, and Data Science.
The full study can be found here, published in Science Advances.