How studying the ‘exposome’ can reveal harmful environmental exposures

Woman at window in silhouette

April 8, 2024 – In the not-too-distant future, doctors may be able to determine what sort of damaging exposures their patients have faced—everything from toxic chemicals to unhealthy foods—all from a blood test.

Andrea Baccarelli, dean of the faculty at Harvard T.H. Chan School of Public Health, wrote about the largely invisible collection of exposures that can affect a person’s health across their lifetime—known as the exposome—in an April 4 Boston Globe Ideas article.

Such exposures, Baccarelli wrote, can range from the lead paint on a childhood train set to toxins in drinking water to soot in the air. Studying these exposures is feasible, he explained, because they cause slight changes to people’s DNA—a process called DNA methylation—that can in turn lead to changes in gene expression that can affect health. These changes are recorded in a layer on top of a person’s DNA called the epigenome. Using standard lab technology, scientists can look at how people’s epigenomes change in response to hazardous exposures, and how these changes relate to their health.

For example, some research teams that Baccarelli has worked with have found that cigarette smoking is linked with DNA methylation affecting the expression of thousands of genes. The genes in question have been linked to smoking-related diseases such as cancer and cardiovascular disease. Baccarelli and colleagues have also identified epigenetic changes linked with exposure to car exhaust, poor diet, stress, and other factors.

Knowing more about how the exposome impacts health means that experts can focus more on prevention—for example, with improved nutrition policy, stronger environmental regulation, or better building design. “The more we know about the damage caused by everyday exposures, the more we can do to protect against them,” Baccarelli wrote.

Read Baccarelli’s Boston Globe Ideas article: Public Health’s new frontier: unlocking the exposome