Each week we write about the science behind environmental protection. Previous Science Wednesdays.
A little while ago I visited Dr. Joel Schwartz in his office at the Harvard School of Public Health to find out about his research findings as part of the EPA-funded Harvard Particulate Matter Research Center.
He described enough research topics to fill a dozen blog posts, so I’ll cover one that I found particularly interesting—his research on the role of genes in determining how people respond to air pollution.
Every cell in a person’s body contains all the 25,000-odd genes that make up DNA, Schwartz said. So why then, he asked, don’t your skin cells make liver enzymes?
The answer, I learned, is that we have mechanisms in our bodies that either turn off or turn on our genes.
I couldn’t help but ask: what does this have to do with air pollution?
To answer my question, Schwartz posed an example that seemed to come out of left field—identical twins.
“If you look at identical twins when they are two years old and when they are 60, the 60 year olds don’t look as much alike. But, they have all the same genes! The difference is that some genes got turned on more and some got turned on less and as a result, they didn’t age the same way,” he said, excitedly.
Schwartz explained that the external environment must have some sort of impact on how their genes were activated.
Studies have shown that methyl groups (a carbon and three hydrogen atoms) stuck onto the beginning of a gene can prevent that gene from being turned on, a process called methylation. The number of methyl groups stuck to a gene has been shown to change over time and seems to be related, somehow, to aging and disease.
“We asked the question, does air pollution act, in part, by doing some of that? Clearly environmental things are changing these methylation patterns…maybe that’s part of what’s going on with air pollution,” he explained.
Schwartz and his colleagues analyzed methylation patterns in a large group of people and looked for associations with air pollution. Their results, recently published in The American Journal of Respiratory and Critical Care Medicine, show that particles from traffic DO indeed change a methylation pattern at certain places in the genome.
“We’re starting to see signals that particles in the air can change the methylation of DNA,” Schwartz said.
This finding is a major preliminary step toward understanding whether air pollution makes people sick by acting on their genes.
About the Author: Becky Fried is a science writer with EPA’s National Center for Environmental Research, part of the Office of Research and Development.