Studies Show Links Between Built Environment, Accelerated Aging, and Environmental Sensitivity
Published April 19, 2021
The places we live can change us—in many cases, down to the molecular level. Exposure to chemicals and other harmful substances in our environment can affect our health in myriad ways over time, aggravating existing health problems, contributing to new disease such as cancer and even impacting how our genes work. Scientists are studying the way our genomic and biological processes change in response to the environment or other external factors in the growing field of epigenetics.
In a pair of 2020 studies, EPA scientists found that 1) epigenetic changes related to aging and mortality are impacted by the environment and 2) epigenetic changes may reveal whether a person is more susceptible to health risks in their environment. Led by EPA's Dr. Cavin Ward-Caviness, the studies are among the first to link these biological indicators of accelerated aging, called molecular biomarkers, to both the quality of the environment and environmental health risks.
"These biomarkers could help us understand how the environment initially gets under our skin, then how the environment gets literally coded into our DNA," said Dr. Ward-Caviness. "These are changes that impact what genes get expressed and cell and tissue function, making individuals more sensitive to pollution exposure."
Gene expression is the process that takes information coded in our DNA and converts it into the molecules that keep our bodies functioning. Dr. Ward-Caviness said disadvantaged communities are especially susceptible to epigenetic changes through a combination of environmental characteristics, like chemical exposure, lack of greenspace, and lack of places to exercise like parks, all of which can influence biological processes.
One study assessed participants from different urban neighborhoods and found an association between an epigenetic biomarker that indicates overall mortality risk and the physical condition of the participants' neighborhoods. The link was strongest in neighborhoods with non-art graffiti, abandoned cars, poorly maintained roads and other objective measures of disadvantage. The researchers saw the same results regardless of whether the participants had a positive or negative view of where they lived, pointing to an external cause for the higher mortality risk. On the other hand, the researchers saw some evidence that the presence of large, mature trees could help counteract the adverse health risks. While research is still needed to understand how the built environment impacts individuals on a molecular level, this research helps evaluate how biomarkers respond to environmental characteristics. Additionally, the study involved predominantly African American participants, a historically understudied group in epigenetics.
The second study determined that a biomarker indicating a person's biological age, which is based on biological factors rather than actual age, may predict their sensitivity to air pollution from traffic. Many studies, some led by Dr. Ward-Caviness, have shown that a person's biological age can accelerate faster than their chronological age based on factors in their environment. The larger the difference between biological and chronological age, the higher the risk for health impacts like cancer and mortality.
In this study, the researchers examined whether environmental health risks for cardiovascular disease patients living near roadways differ based on their biological age. Researchers found those patients with accelerated aging who lived closer to a major roadway had a three times greater risk of peripheral arterial disease, which causes narrowed arteries in the arms and legs.
"Both of these studies feed into each other," said Dr. Ward-Caviness. "The built environment seems to accelerate aging, and aging can make you more sensitive to environmental stressors, so there are aspects of individual sensitivity and environmental justice issues in both."
He explained that disadvantaged communities are often exposed to higher levels of pollution, which in turn makes these groups more sensitive to future exposure, creating a feedback loop. Dissecting these issues, he said, will help us understand the relationship between environmental justice concerns and individual health.
For individuals, biomarkers could be a way to better predict future health outcomes and take steps to prevent them. For neighborhoods, measures like creating more greenspace could help protect residents. Neighborhood greenspace seemed to moderate the environmental health risk on the aging and mortality indicators studied. By providing evidence that neighborhood characteristics can change biological processes, these studies provide a path towards reducing the health disparities disadvantaged communities face.
Ward-Caviness, C.K., Pu, S., Martin, C. et al. Epigenetic predictors of all-cause mortality are associated with objective measures of neighborhood disadvantage in an urban population. Clin Epigenet 12, 44 (2020). https://doi.org/10.1186/s13148-020-00830-8
Ward-Caviness CK, Russell AG, Weaver AM, Slawsky E, Dhingra R, Kwee LC, Jiang R, Neas LM, Diaz-Sanchez D, Devlin RB, Cascio WE, Olden K, Hauser ER, et al. Accelerated epigenetic age as a biomarker of cardiovascular sensitivity to traffic-related air pollution. Aging (Albany NY). 2020; 12:24141-24155. https://doi.org/10.18632/aging.202341