Type 2 diabetes is a major public health concern rising rapidly, with the number of people diagnosed with the disease worldwide more than doubling in the past 20 years. Researchers from the Mount Sinai Institute for Exposomic Research found that exposure to air pollution was associated with higher risks for developing diabetes.
Research by
Maayan Yitshak-Sade, PhD, Assistant Professor, Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai
Background
Type 2 diabetes mellitus is a major public health concern rising rapidly, with the number of people diagnosed with the disease worldwide more than doubling in the past 20 years. It may cause major complications, including blindness, cardiovascular damage, and premature mortality, and it is therefore important to identify risk factors for the disease. Like many other chronic conditions, diabetes has genetic components – but genetics alone explains only a small portion of the cases. In recent years we find more and more evidence linking diabetes to environmental exposures, specifically air pollution. Although air pollution levels are regulated, many studies show that current air pollution standards in the U.S. are not sufficient to protect human health. In this study, we leveraged the national Medicare cohort, including over 40 million older adults in the U.S., and investigated whether higher exposure to three types of air pollutants was associated with higher risk of developing diabetes. We also simulated a scenario in which air pollution levels did not exceed the U.S. Environmental Protection Agency (EPA) national ambient air quality standards to see whether we still find harmful air pollution effects in these lower exposure levels.
What did we find?
We went back in time and followed 41,780,537 Medicare beneficiaries annually between 2000 and 2016. We estimated the annual air pollutants exposures at their zip code of residence using satellite-based air pollution models and obtained records of newly diagnosed diabetes in this population. We found higher risks for developing diabetes among those exposed to higher levels of nitrogen dioxide (NO2) and fine particulate matter (PM2.5) pollution. PM2.5 are fine inhalable particles originating from different sources such as traffic, industry, smoke, and dust. NO2 is an air pollutant that originates mostly from traffic and high-temperature combustion processes. Higher PM2.5 exposure was associated with 7% increase in the risk of developing diabetes among older adults, and higher NO2 exposure was associated with 5% increase in the risk of developing diabetes among older adults.
Most importantly, these higher risks remained even when restricting the population to people exposed only to exposure levels below the national air pollution standards set by the U.S. EPA.
Older adults, who already face higher rates of chronic diseases as well as underlying social and economic factors, are particularly vulnerable to air pollution health effects. Our study adds evidence of the harmful consequences of air pollution exposure on diabetes risk, which can in turn be translated into higher risk of cardiovascular diseases and premature mortality.
Dr. Maayan Yitshak Sade
Why is it important?
Older adults, who already face higher rates of chronic diseases as well as underlying social and economic factors, are particularly vulnerable to air pollution health effects. Our study adds evidence of the harmful consequences of air pollution exposure on diabetes risk, which can in turn be translated into higher risk of cardiovascular diseases and premature mortality. Moreover, we provide further evidence to strength the World Health Organization (WHO) recommendations to lower air pollution standards. In 2021, the WHO concluded that harmful PM2.5 effects on health are observed at even lower concentrations than previously thought and have markedly reduced the recommended pollutants threshold levels. For example, the annual level for PM2.5 was reduced to 5 µg/m3. For comparison, in the U.S., the current primary (health-based) annual standard is 12 µg/m3. Following a recent scientific review of air pollution health effects literature, in January 2023 the EPA has proposed to revise their 2020 decision to retain the PM standards and recommended to reduce the annual standard for PM2.5 to levels between 9-10 µg/m3. Although this is a step in the right direction, these levels are still higher than the WHO guidelines, and further research will help determine whether these new proposed standards provide adequate protection to human health.
What’s next?
Currently, PM2.5 is regulated by its size rather than its chemical composition. However, these particles may contain different chemical components (such as lead, nitrate, sulfate, elemental and organic carbon, and others) depending on air pollution sources, climate, and other factors. We know that PM2.5 mass is associated with adverse health effects, but each PM2.5 chemical component might have different toxicity, and some may be more harmful than others. Still, most current studies evaluate PM2.5 exposure based on particle size alone without addressing the differential toxicity depending on its chemical composition. Due to lack of consistent scientific evidence, currently, there are no national standards for chemical components of particulate matter in the U.S. Although lead may be found in particulate matter, it is regulated as a separate pollutant and not as a PM chemical component. In several ongoing studies, we are currently investigating the cardiometabolic health effects of PM2.5 chemical components. We investigate which chemical components are associated with higher risks of heart disease, stroke, diabetes, hypertension, and other conditions. These will add scientific evidence which can be used in the review of air quality standards and help focus regulation efforts on specific chemical components and pollution sources.
The information is for educational purposes only and is not intended as a substitute for medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you have regarding your medical care.