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Air pollution may damage every organ in the human body, research review finds

Fine particulates are linked to cataracts; also, they may travel directly from nose to brain, bypassing lungs.

car exhaust
The “new analytical model” will reduce the official estimate of deaths attributable to inhaling fine soot particles from smokestacks and vehicle exhausts by 1,400 per year.
REUTERS/Peter Nicholls

Maybe you saw a headline on this, because it made some big ones on Monday: The Trump-transformed Environmental Protection Agency is cooking the books —I mean, refining its calculations — on air pollution’s lethal harm to Americans.

As reported by the New York Time’s Lisa Friedman, the “new analytical model” will reduce the official estimate of deaths attributable to inhaling fine soot particles from smokestacks and vehicle exhausts by 1,400 per year.

That’s the direct effect. An indirect effect, and the transparent purpose, of the change is to justify a rollback of the Obama administration’s Clean Power Plan into a set of less stringent requirements (not the first time the new regime has attempted to reshape policy by re-doing the math). The result will be marketed as the Affordable Clean Energy Rule, due for rollout in June.

As it happens, this news broke only days after publication of a new and sweeping analysis of health damage traceable to air pollution, prepared by actual medical experts for CHEST, the official journal of the American College of Chest Physicians. They reach the startling conclusion that emissions from the burning of fossil fuels, fine particulates especially, are likely to damage just about every organ in the human body.

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Livers and kidneys, that is. Skin and eyes. Joints and bones. The bladder, brain and pancreas. Also, particulate exposure appears to cause or aggravate systemwide problems of allergy, inflammation and autoimmune disorder, not to mention developmental problems in children.

The largest portion of medical research on airborne pollutants has long focused, understandably, on the tissues they touch directly, like the lungs, and others whose function is closely related to respiration, like the heart. But less heralded inquiry has found clear correlations between fossil-fuel pollution and disease across a far wider spectrum. The new, two-part paper pulls these together into a groundbreaking, comprehensive portrait that is causing considerable buzz in public-health circles.

The lead researcher, pulmonologist Dean Schraufnagel of the University of Illinois-Chicago, told the UK Guardian that he himself was surprised at the breadth of harm laid out in CHEST. Any organs unmentioned in the report aren’t at all in the clear, he said; rather, it’s safe to assume their  absence is “probably because there was no research yet.”

Sample impacts gathered by the Schraufnagel team:

  • Osteoporosis-related fractures in Medicare-aged Americans were more common in areas with higher particulate exposures; in middle-aged people, high exposures are associated with mineral loss from their bones.
  • Liver impacts include unusual cancers, various inflammatory conditions, and the incurable buildup of fat deposits known as steatosis.
  • In the kidneys, “oxidative stress” correlated with exposure to particulates and diesel exhaust damages both large and small blood vessels; in people whose kidneys are already diseased, the stress “exacerbates chronic renal failure.”
  • Bad air can make the eyes water, of course, but beyond the various irritations and inflammations associated with sulfur and nitrogen oxides as well as ozone, exposure to fine particles has been linked cataract formation.
  • Chronic exposure to those oxides were shown in a UK study to raise the odds of Crohn’s disease afflicting the intestines of young people; elsewhere, it has been linked to inflammatory bowel disease, enteritis, gastric ulcer and appendicitis.
  • Among blood diseases, fine particles have been shown to promote “an imbalanced coagulative state” that interferes with normal clotting in ways that increase the risk of heart attack and stroke.

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As for the brain and central nervous system:

Older adults more heavily exposed to air pollution perform more poorly on cognitive testing and are at increased risk of dementia compared with less exposed adults. Long-term exposure to PM 2.5 [the especially worrisome particulates with a diameter of 2.5 microns, about half the thickness of a human hair] was associated with a smaller brain volume… and higher odds of subclinical strokes among generally healthy adults. Short-term exposure to fine particles increased the risk of hospitalizations and all-cause mortality in Parkinson’s disease.

Studies in animals have shown that inhaled ultrafine particles can travel from the nose via the olfactory nerve directly into the brain, where they may cause inflammation and oxidative stress.

No human-subject studies

And in that reference we encounter a major limitation on researching the health impacts of bad air: the inability, for ethical reasons, to use human subjects in experimental designs that expose them to suspected harmful agents and compare the effects to patterns in a control group. Instead we have statistical correlations at the population level and animal testing at the organism level.

Still, it’s hard to think of a reason why human noses and olfactory nerves would behave differently from lab animals’ in conveying fine particulates directly from ambient air to the brain, bypassing the lungs and their filtration altogether.

Beyond organ-specific damage, researchers have gathered evidence of other types of harm that can be grouped roughly in two sets: systemic effects and developmental impacts.

Dalhousie University, Aaron van Donkelaar
Average global distribution of particulate matter concentrations (2001-2006).
Several studies suggest that air pollution increases both the incidence and severity of type 2 diabetes, the review found, as well as related “metabolic syndrome”; in adults, the problem seems to be that it promotes the accumulation of visceral fat and heightens insulin resistance. A study of children in Mexico City (which has been going through a particularly horrible siege of filthy air this month), found a variety of disruptions to normal regulation of appetite, metabolism and fat storage, along with vitamin deficiencies.

Then there is the mysterious sphere of allergies, inflammation and autoimmune disorders, in which research suggests an important if yet unclear role for air pollution:

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The lung has an enormous surface area that comes into contact with a myriad of antigens. It has an efficient sensitization and antigen-presenting system that could make individuals prone to autoimmune disorders. Air pollution is a potential contributor to diseases such as rheumatoid arthritis and systemic lupus erythematosus.

A Canadian study found increased odds of having a diagnosis of a rheumatic disease with increased ambient PM exposure. Air pollutants have also been implicated in triggering or exacerbating juvenile idiopathic arthritis, but autoimmunity related to air pollution exposure has largely been understudied.

The burden on children

As always, the health burdens of these pollutants are borne unfairly, weighing most heavily on the poor, the elderly,  the already ill – and, especially, children:

Lung and immune system development occurs over the entire prenatal period, beginning with embryogenesis and continuing for many years after birth. Infants are born with only about 20% of the alveoli that they will eventually make once they have reached adulthood. Exposures to air pollutants during the prenatal period and during childhood can have harmful and irreversible effects on the lung and other organ systems.

Postnatal exposures to air pollutants … have been associated with increased infant mortality, even in developed countries such as the United States. The strongest associations have been with postneonatal respiratory mortality, which in part may be related to respiratory infections that have links to pollution.

In all, the paper notes, reliable statistics suggest that outdoor exposure to fine particulates alone accounts for 4.2 million deaths worldwide each year, ranking it fifth among risk factors for death globally. Ozone may add another quarter-million deaths, while indoor air pollution, from cigarettes and wood cookstoves and a wide range of other sources, is estimated to kill 3.8 million per year.

All of these figures are likely to rise as a research continues to expand beyond the heart and lungs.


The two-part paper, Air Pollution and Noncommunicable Diseases, can be read online without charge;  Part 1, a survey of overall damage, is here, and Part 2, a discussion of specific organs and illnesses, is here.