Airborne Toxic Events: Air Pollution’s Role in Diabetes

Among the environmental disruptors that contribute to the development of diabetes, air pollution is gaining the spotlight. Airborne microscopic endocrine disruptors not only get in the lungs, but also find their way into the bloodstream where they can cause organ damage, specifically to the pancreas.

 

Health professionals uniformly endorse wearing a mask to lower the risk of contracting COVID-19. But have you considered recommending masks for avoiding diabetes?

Air pollution is receiving growing attention as one of the most important endocrine-disrupting chemicals (EDCs) in the environment that contribute to the risk of developing diabetes. And a specific component of air pollution gaining prominence is particulate matter — especially the particles 2.5 micrometers in diameter or smaller known as PM2.5 that can find their way into the lungs and bloodstream.

“A number of researchers have found that air pollution from very fine particulate matter has a strongly supported association with diabetes,” says Namino Glantz, PhD, of the Sansum Diabetes Research Institute in Santa Barbara, Calif. “It is a mixture of organic chemicals — dust, soot, and metals — all compressed together into these tiny particles less than the thickness of a human hair. Those particles are so small we can inhale them. They get deposited in our lungs, and then get passed into the bloodstream.”

“A meta-analysis of seven studies on PM2.5 found that with every 10 micrograms per cubic meter increase in PM2.5 concentration, diabetes risk increased by 25% with chronic long-term exposure,” Glantz says.

“People used to think that when you inhale bad air, it goes to your lungs and gives you asthma or lung disease,” says Ziyad Al-Aly, MD, director of the Clinical Epidemiology Center at Washington University in St. Louis. “That is all true, but it doesn’t stop there because those particles actually make it to your bloodstream. They travel in the bloodstream to the pancreas to suppress insulin secretion and to other organs to impair insulin sensitivity.”

Al-Aly was the lead author of a huge study published in Lancet Planetary Health in 2018 that involved a longitudinal cohort of 1.7 million U.S. veterans, air data from the U.S. Environmental Protection Agency (EPA) and NASA, and a synthesis of previous evidence to calculate the global burden of diabetes attributable to PM2.5. “We tried to figure out how many diabetes cases in the world and in the U. S are attributable to air pollution, and the figure was about 14%,” Al-Aly tells Endocrine News.

And the Other Suspects

Although air pollution has received attention from several studies lately, it should not be forgotten that many other EDCs contribute to diabetes, according to Robert M. Sargis, MD, PhD, an associate professor in the Division of Endocrinology, Diabetes, and Metabolism at the University of Illinois at Chicago who has published extensively on EDCs and diabetes.

“A number of researchers have found that air pollution from very fine particulate matter has a strongly supported association with diabetes. It is a mixture of organic chemicals — dust, soot, and metals — all compressed together into these tiny particles less than the thickness of a human hair. Those particles are so small we can inhale them. They get deposited in our lungs, and then get passed into the bloodstream.” – Namino Glantz, PhD, Sansum Diabetes Research Institute, Santa Barbara, California

“Most, if not all, folks in the developed world are exposed to chemicals like phthalates and bisphenol A, and these chemicals have been associated with diabetes risk,” Sargis says. He notes that problem chemicals associated with diabetes include pesticides like DDT — which was banned in 1972, but whose metabolites are still present in the vast majority of Americans — as well as PCBs, which were also banned in the 1970s but persist in the environment.

Environmental Quality Index

Researchers have been noting for some time that caloric excess and physical inactivity do not fully account for the rise of diabetes prevalence, so there must be other factors at work, according to Jyotsna S. Jagai, PhD, research assistant professor in the Department of Environmental and Occupational Health Sciences at the University of Illinois at Chicago. Jagai was part of a team that developed for the EPA the Environmental Quality Index (EQI), a county-level measure that considers indicators of the quality of air, water, land, the built environment, and sociodemographics. Jagai’s team looked at the association of environmental quality and diabetes in a study published in the Journal of Diabetes Investigation in 2019.

Although overall, counties with poor environmental ratings actually had a lower rate of diabetes prevalence, the researchers discovered urban-rural and wealth-level dichotomies in the results. “In rural environments, poor environmental quality is associated with a higher rate of diabetes prevalence, and areas with relatively worse sociodemographic factors were also associated with higher rates of diabetes,” Jagai says.

Airborne Health Disparities

Sargis, who was a co-author of that study, notes that this association of diabetes, pollution, and sociodemographics is especially poignant at this time of heightened awareness of racial inequity. “We know that communities of color and low-income communities are disproportionately exposed to air pollution as well as a number of different chemicals that have been linked to diabetes,” Sargis says. It’s well-established that African-American, Hispanic-Latino, and Native American populations have higher levels of diabetes.

“People used to think that when you inhale bad air, it goes to your lungs and gives you asthma or lung disease. That is all true, but it doesn’t stop there because those particles actually make it to your bloodstream. They travel in the bloodstream to the pancreas to suppress insulin secretion and to other organs to impair insulin sensitivity.” – Ziyad Al-Aly, MD, director, Clinical Epidemiology Center, Washington University, St. Louis, Missouri

A study in Diabetes in 2017 examined the effects of exposure to nitrogen dioxide and PM2.5 pollution among Latino children in Los Angeles. It concluded that these exposures may contribute to the development of type 2 diabetes through direct effects on insulin sensitivity and pancreatic beta-cell function. Because car and truck exhaust are major contributors to PM2.5, it’s easy to see how an urban environment like Los Angeles could lead to higher risk.

The particulates can affect pancreatic beta-cells, but they also have much more generalized effects on oxidative and inflammatory responses and insulin resistance.

Sargis notes that EDCs can cause “impairments in insulin secretion and action, disruptions in other nuclear hormone receptors that regulate fat development and function, like PPARs and RXR, as well as disruptions of glucocorticoid receptor signaling. They can compromise a whole bunch of different mechanisms, including oxidative stress, endoplasmic reticular stress, sex steroid action, and thyroid hormone action.”

Advice and Action

Endocrinologists can apply this knowledge in advising their patients, these researchers agreed. “It is a little tricky because some of these chemicals are ubiquitous,” Jagai says. “But I think physicians can help patients understand that there are certain products and certain things that might put them at higher risk for endocrine-disrupting chemicals. Physicians can help identify those exposures and explain how to reduce them.” For example, a physician can explain about staying inside on high-air-pollution days or finding different walking routes for exercising that minimize exposure.

“Environments are modifiable,” Sargis says. “What we need to do as a community is to start to recognize that the environment matters.”

Endocrinologists might consider voicing these dangers when it comes to government policies, but back to those masks: Their benefits could be both long-term and immediate; a study published this year in Science of the Total Environment found that during the early days of the pandemic in Milan, Italy, poor air quality and higher particulate levels were associated with increased daily cases of COVID-19. Glantz notes that type 2 diabetes is a pre-existing condition that can exacerbate COVID-19 effects, and the additional stress of PM2.5 exposure could add up to a “perfect storm.”

Seaborg is a freelance writer based in Charlottesville, Va. In the October Endocrine News, he wrote about the use of certain steroids to treat COVID-19 patients.

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