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Air pollution cuts short the lives of far more people in the US each year—estimates range from 107,500 to over 200,000—than do traffic accidents. Together, indoor and outdoor air pollution caused one in every nine deaths globally in 2016—far more than the number felled by malnutrition, alcohol use, or malaria.
The bulk of all that damage, as Smedley explains in a dense but illuminating early chapter of Clearing the Air, can be traced to PM2.5. Most of these fine particles are a byproduct of our civilizational dependence on burning stuff: coal, gasoline, diesel, wood, trash, you name it. These particles can get past the defenses of our upper airways to penetrate deep into our lungs and reach the alveoli, the tiny air-filled sacs where oxygen is exchanged for carbon dioxide. From there, they cross into the bloodstream and spread throughout the body. They can travel through the nose, up the olfactory nerve, and lodge themselves in the brain. They can form deposits on the lining of arteries, constricting blood vessels and raising the likelihood of blockages that lead to strokes and heart attacks. For decades, scientists have understood that they exacerbate respiratory illnesses like asthma and chronic obstructive pulmonary disease, but—as with tobacco smoking—the biological mechanisms have been elusive. It is now thought that much of the havoc PM2.5 wreaks is through systemic inflammation, caused by an overreaction by the immune system.
Scientists keep learning that there is no part of the body that these particles cannot reach, and no phase of life, from gestation to advanced age, they do not touch. Last year, researchers found inhaled soot particles in the placentas of five women who gave birth in London hospitals. In Choked, Gardiner interviews Beate Ritz, an epidemiologist at UCLA who has led groundbreaking studies of air pollution’s links with adverse birth outcomes. When she first started analyzing data in the early 1990s, Ritz was motivated by her own experience giving birth to an underweight child while living next to a busy freeway. Since her early studies on the subject, a large body of literature has developed showing strong associations between air pollution exposure and a wide range of adverse pregnancy outcomes, including low birth weight and prematurity, as well as child cancers and even autism. There’s also convincing evidence linking air pollution exposure to an increased risk of Alzheimer’s and other forms of dementia.....
....On April 3, in its annual State of the Air report, the American Lung Association reported that 141 million Americans live with unhealthy levels of ozone and particle pollution, an increase of seven million from 2018. It attributed much of the rise to the effects of climate change. Even Trump’s EPA acknowledges in a new report that “most of the northern half of the country will experience greater air pollution because of climate change.”
New evidence seems to ratchet only in one direction: revising today’s global death toll of air pollution upward, and widening the scope and variety of its damage. A recent study in the European Heart Journal concluded that ambient air pollution is responsible for 8.8 million premature deaths per year—more than double previous estimates, and 1.5 million more than smoking causes.8....
....The Clean Air Act stipulates that, every five years, the EPA must review and update the scientific assessment on which national ambient air quality standards are based. That process is currently underway for particulate matter. EPA staff have compiled a draft Integrated Science Assessment for Particulate Matter (ISA) and sent it for review to the Clean Air Scientific Advisory Committee (CASAC), an independent panel of experts, mandated by the CAA, that provides scientific guidance on how much pollution is safe for us to breathe.
The ISA scrutinizes an enormous body of scientific literature on the health effects of particulate matter. Researchers have developed a set of rigorous, quantitative tools with which to access and analyze the treasure trove of observational data assembled by the Six Cities and other long-term studies. In the decades since its publication, the Six Cities findings have been gone over with several fine-toothed statistical combs: in 2000 an extensive reanalysis of the data by an independent team at the Health Effects Institute confirmed the results; another analysis in 2012 confirmed them yet again. The PM–mortality relationship has been repeatedly confirmed by large cohort studies, including one by the American Cancer Society that surveyed air quality in 150 US cities. The result is one of the most robust points of consensus in modern public health research: breathing particulate matter shortens lives.
Yet for the first time in its history, the CASAC is questioning the scientific consensus that exposure to fine particles causes mortality. Not coincidentally, for the first time in its history, the CASAC has no epidemiologists among its seven members—all of them appointed since 2017. Last year, Tony Cox Jr. was appointed its chair. A statistician and risk analyst with no training or background in health or medicine, Cox has consulted for the American Petroleum Institute, the Truck and Engine Manufacturers Association, mining companies, and the tobacco conglomerate Philip Morris....
....It would be a profound statement, confirming the judgment of so many scientists: that air pollution acts in concert with other factors to tip human bodies over into crisis, illness, and death, and that behind the staggering statistics, air pollution curtails and corrodes individual lives. But whether or not officialdom puts it on a death certificate, the larger truth remains: these pollutants are robbing us of time, our most precious resource, on an unimaginable scale. A study in the Lancet found that 122 million years of lost life were due to exposure to PM2.5 in 2015. Children in sub-Saharan Africa and South Asia were its primary victims, suffering nearly 20 percent of all those lost years.9 They, too, have no memorial.
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