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A year ago, I went to California to participate in a scientific conference. After a couple of days, my mentor and I started to have trouble breathing. As two healthy adults, we wondered why this was happening. I did not know the answer at that time, but I did notice a pattern: Other female colleagues, especially those with asthma, were also struggling to breathe, but not many men were. Our symptoms got better once we left the conference. A research study we later performed in our lab helped us understand what had happened. We discovered some differences in lung function among male and female mice exposed to ozone and other air pollutants, and we learned that females had worse symptoms than males. So something in the air caused our breathing problems.

In the past decade, air pollution has become the world’s single biggest environmental health risk, causing about 7 million deaths—nearly one of every eight—worldwide each year. According to the Air Quality-Life Index, increased air pollution concentration levels may shorten your lifespan by one month if you live in New York and by up to eight months if you live in California. Exposure to pollutants such as ozone, biomass fuels, and fine particles like soot and smoke has been strongly associated with increased mortality from lung disease. As the evidence piles up, we are starting to realize what a big problem these little molecules create—and that what you can’t see can kill you.

Researchers have shown that women are more susceptible to the negative effects of air pollution than men are. The exact reason remains unclear, but we know that men have more relative fat mass, which gives them a larger distribution volume for chemical particles in the environment. Women’s bodies also metabolize pollutants more quickly than men’s, resulting in higher toxicity. A recent study in the American Journal of Physiology—Lung Cellular and Molecular Physiology has shown that sex steroid hormones are somewhat responsible for the male and female differences, indicating that both sex and air pollution may alter the effectiveness of lung immunity.

The American Lung Association offers these and other tips to help protect you from unhealthy air:

• Check daily air pollution forecasts.
• Avoid exercising outdoors when pollution levels are high.
• Avoid exercising near high-traffic areas.
• Use less energy in your home.
• Explore other alternatives to driving your car (bike, walk).
• Don’t burn wood or trash.
• Don’t allow anyone to smoke indoors.

October 22–28 is Respiratory Care Week. Let’s help the world breathe better. Your life and the lives of your loved ones may depend on it.

Nathalie Fuentes is a PhD candidate in the biomedical sciences program at Penn State College of Medicine. Her studies in Dr. Patricia Silveyra’s lab include the development of sex-specific therapies to treat lung diseases, sex differences in asthma-related lung inflammation triggered by ground-level ozone and the role of male and female sex hormones in lung disease. Nathalie is originally from Caguas, Puerto Rico.