A new University at Buffalo (UB) study based on levels before, during and after the Beijing Olympics has shown how air pollution affects the human body at the level of metabolites. Metabolites are small molecules that are the end products of environmental exposures, such as air pollution, and body metabolism. The human metabolome is a collection of exogenous chemicals and metabolites from cellular processes that may reflect the body’s response to environmental exposures; studies of air pollution and metabolomics are limited.

Think of our body as a society. These metabolites fulfill different positions, such as teacher, farmer, worker, soldier. We need each one functioning properly in order to maintain a healthy system.

—lead author Lina Mu, PhD, associate professor of epidemiology and environmental health in UB’s School of Public Health and Health Professions

The researchers found that 69 metabolites changed significantly when air pollution changed. Their results are published in an open-access paper in the journal Environmental Health Perspectives.

The study identified two major metabolic signatures: one consisting of lipids and a second that included dipeptides, polyunsaturated fatty acids, taurine, and xanthine. Many of those metabolites are involved in oxidative stress, inflammation, cardiovascular and nervous systems, the researchers note.

The findings are based on the Beijing Olympics Air Pollution study, conducted during the 2008 Olympic Games in China, when temporary air pollution controls were implemented.

The study enrolled 201 adults prior to Beijing’s air quality improvement initiative, when air pollution was high. Researchers followed them during the Games, when air pollution was low, and afterward, when levels returned to their usual high in the city of 21 million people. A subset of 26 non-smokers aged 30 to 65 was selected for the metabolomics analysis.

Our study found that the human body had systemic changes at the metabolite level before, during and after the 2008 Beijing Olympics, when ambient air pollution changed drastically.

— Zhongzheng Niu, PhD candidate and paper co-author

The molecules mostly belonged to the lipid and dipeptide families.

The study provides researchers with a broader view of the molecular mechanism underlying the impact of air pollution on the human body. Most previous studies only looked at a small number of molecules. However, the human body is complex and molecules affect one another.

Mu and her colleagues used the “omics” method, a new platform that can measure a whole collection of all detectable metabolites—886 in their study—simultaneously. Instead of examining these molecules one by one, Mu and her team used network analysis to analyze them all together.

We found that these metabolites together depicted a relatively comprehensive picture of human body responses to air pollution.

—paper co-author Rachael Hageman Blair, associate professor of biostatistics at UB

Blair and her team developed the novel analysis method used in the study.

The responses include cellular stability, oxidative stress, anti-oxidation and inflammation.

Researchers measured metabolomics repeatedly when air pollution was high, low and high. Such a design mimicked a “natural experiment” while controlling for variations unrelated to air pollution changes. This provided stronger evidence than previous studies.

Once inhaled, air pollutants stimulate the body’s respiratory system, including the nose and lungs. Some cells in the body may be directly insulted by these air pollutants, their membrane may be broken, their secretion may be disordered, and they may send out signaling molecules to other organs for subsequent responses, Mu explains. Metabolites are all these broken membranes, secreted products and signals.

Air pollution also induces cellular oxidative stress, which breaks cell membranes.

Researchers found that some molecules that serve as building blocks of cell membranes were elevated when air pollution levels rose. Broken cell membranes release different kinds of lipid molecules. Some of these lipid molecules, with the help of enzymes, turn to inflammatory molecules, which could be harmful to the body.

The good thing is that we also found some protective molecules, namely antioxidants, also increased when air pollution is high, indicating our body has a defense system to reduce harm.

—Lina Mu

Studies such as this one may help identify individuals most vulnerable to air pollution, as well as finding potential biological pathways to guide treatment that reduces harm to the body, Mu said.

Mu’s UB co-authors include Richard Browne, associate professor of biotechnical and clinical laboratory sciences, Jacobs School of Medicine and Biomedical Sciences; Matthew Bonner, associate professor of epidemiology and environmental health; and Mya Swanson, data manager/statistician, Department of Epidemiology and Environmental Health.

Furong Deng of Peking University is also a co-author.

Resources

• Lina Mu, Zhongzheng Niu, Rachael Hageman Blair, Han Yu, Richard W. Browne, Matthew R. Bonner, Tiffany Fanter, Furong Deng, and Mya Swanson (2019) “Metabolomics Profiling before, during, and after the Beijing Olympics: A Panel Study of Within-Individual Differences during Periods of High and Low Air Pollution” Environmental Health Perspectives 127:5 doi: 10.1289/EHP3705