Health

Air Pollution Can Have a Greater Effect on Human Gene Expression Than Ancestry

A Canadian analysis found that where a person lived was more significant of a factor in gene expression than their heritage.

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Exposure to air pollution doesn’t just lead to illnesses like asthma and lung ailments, it can also alter the way genes are expressed in our bodies, according to a new study published March 6 in the journal Nature Communications.

The study, conducted by a team of scientists and biostatisticians in Canada, suggests that the impact of air pollution on an individual’s gene expression is much more significant than a person’s ancestry.

Every gene in a DNA molecule provides instructions to build a functional product, like protein, that is needed to perform a task in the cell. Gregor Mendel,  the father of modern genetics, for example, found that a flower color gene provided instructions for a protein that helps make colored molecules in flower petals. This process during which a gene is used to build protein is called gene expression.

The study’s 13-member research team, led by Philip Awadalla of the Ontario Institute for Cancer Research, assembled a cohort of 1,000 individuals living in different parts of Canada’s Quebec province, including Montreal, Quebec City, and Saguenay—Lac-Saint-Jean.

The group was comprised of men and women between the ages of 40 and 70 years. Each of the participants provided information to a biobank and health database called CARTaGENE, including blood pressure, blood cell counts, blood sugar levels, cardiovascular function, and disease history. Participants also shared information on lifestyle habits like, alcohol intake, tobacco consumption, and physical activity. They also reported information on environmental factors like their proximity to green space, residential history, and exposure to ultraviolet radiation. All individuals studied were of French-Canadian descent in order to minimize variability in ethnicity, Awadalla said.

Studying the DNA of individual participants allowed the scientists to establish every person’s ancestry. They then examined each individual’s RNA, which revealed a correlation between where an individual lived and the strength of their gene expression. And, they found, that correlation was stronger than the link between gene expression and ancestry.
Simply put, a person born in Montreal but brought up in Quebec City, was likely to show a gene expression and a related disease risk that was more similar to a person whose place of birth was Quebec City.

“We were surprised to see that we were able to stratify the ancestry within Quebec,” Awadalla said. “The next question to be tackled was what was it about where a person lived that affected the way his or her genes were being expressed.”

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The team took environmental data like levels of PM 2.5 particles and nitrogen and sulfur dioxide from the places where participants lived. They combined this with gene expression data and found that in places with higher levels of particulate matter and nitrogen dioxide, like the Saguenay area, gene expression relating to oxygen pathways and respiratory function was affected. That change in gene expression has led to higher rates of asthma and chronic obstructive pulmonary disease, a condition that makes breathing difficult.

“This helped us show how most gene expression is not derived by ancestry, and that environmental exposures associated with living in a particular city or region are more impactful on gene expression associated with disease traits,” Awadalla said.

He said the findings could help scientists identify irregularities in gene function that cause disease, which could help in designing personalized medical treatments for patients.

“In the world of precision medicine and personalized health, the more information we can capture about an individual on the molecular level, the easier it will be to predict disease risk,” Awadalla said.

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The interaction between air pollution and gene expression demonstrated by Awadalla’s study in Quebec is crucial to many parts of the developing world, particularly in Asia, where pollution levels have spiked in the last few decades. In countries like India, rampant industrialization and a high dependence on fossil fuels coupled with the consequences of climate change, are only going to make air quality more hazardous.

In China, parts of which are also susceptible to notoriously high levels of air pollution, scientists are reportedly working to decode the genetic makeup of one million citizens. According to a recent news report, the Asian powerhouse is pushing hard to overtake the United States in its precision-medicine initiative and reach its data collection target by 2020.