Ozone and your lungs

Respiratory health can be affected by air conditions

/ Author:  / Reviewed by: Joseph V. Madia, MD

Before you step outside on a sunny day for a run, think about taking precautions for your health. Sure, you stretched, but did you check the day's ozone level?

Ground-level ozone, a widespread air pollutant, can have serious effects on your lungs. The amount of ozone in the air changes from day to day. Spending time outside on a high ozone day can can cause or worsen conditions like asthma and COPD.

Children and the elderly – particuarly those with asthma or emphysema - are the most vulnerable to ozone, but it can also affect healthy adults during exercise. Ozone, which you breathe in with the surrounding air, reacts with tissues in your lungs to cause reddening, swelling, and inflammation. As a result, it causes difficulty breathing, coughing, wheezing, and can spur on asthma attacks.

Knowing when to stay indoors

Ozone is regulated by the Environmental Protection Agency (EPA), and levels in the air are monitored on a daily basis. Currently, the standard is 75 parts per billion (ppb) of ozone – that is, how much ozone is considered safe to breathe in the air. When ozone reaches above 75 ppb, air quality is considered to be unhealthy.

“Ozone is pretty much invisible,” says Janice Nolen, of the American Lung Association. “It's easier to think about drinking water. If it had unhealthy amount of lead in it, you would be unhappy. What we have is air, and it has an unhealthy amount of ozone.”

Nolen recommends checking out airnow.gov, a government-run website where you can find the air quality forcast in your area. Ozone levels are color-coded and easy to understand. She said that people with heightened sensitivities should be cautious when the ozone level is orange. Red is unhealthy, purple is very unhealthy, and brown is hazardous – the entire population is likely to be affected.

The levels are likely to be higher in the summer, when it's sunny and hot.

What is ozone?

We're not talking about the ozone layer in Earth's atmosphere. Ozone is a gas produced by the things we need and use everyday: Power generation and vehicle transportation. Ozone is the product of two chemical compounds, nitrogen oxides and volatile organic compounds (VOCs). Nitrogen oxides are the more active ingredient.

“Nitrogen oxides are formed whenever you combust some kind of fuel,” explains Dr. Cyril Durrenberger, an air quality researcher at the University of Texas at Austin. “Fuel is burned to create energy, and you use oxygen for energy that causes that burning. In presence of the heat, you have some of the nitrogen and oxygen molecules to form nitrogen oxides.”

VOCs are a pollutant that seep out of your fuel tank when you fill up. In the presence of sunlight – most often on days that are 85 degrees Farenheit or above – VOCs combine with nitrogen oxides to form ozone.

How does ozone affect your lungs?

Scientists have studied the effect of ozone on health for many years. They've found that it primarily affects the respiratory system. According to the EPA, one out of every three people in the United States is at a higher risk of experiencing ozone-related health effects.

Children are at greater risk because they're likely to spend a good chunk of their time being active and running around outdoors. Kids' respiratory defenses haven't reached their full capability, and they breathe in more air per pound of body weight than adults do. That means they're getting higher doses of ozone, and their bodies are less prepared to protect themselves from it.

Elderly adults are known to have higher sensitivity to ozone. Those with respiratory diseases such as as asthma, bronchitis, pneumonia, and COPD (Chronic Obstructive Pulmonary Disease) are particuarly susceptible, as well as those with allergies.

Even healthy adults may experience health effects from ozone. In 2001, a study from the National Institutes of Health found that a 5 to 10 percent reduction in lung capacity occurred in volunteers engaged in moderate exercise for 6.5 hours at just 80 parts per billion (ppb). 80 ppb is a level commonly reached during warm weather in many parts of the world.

The future of ozone

Since the Clean Air Act was passed in the 1970s, air pollution has significantly decreased and air quality has improved. The Clean Air Act mandates that national standards for ozone levels be revisited every five years. A committee reviews the current scientific literature to determine how much ozone is safe for public health.

The standard was last set in 2008, to the current level of 75 ppb. The EPA considered revising the standard to between 60 – 70 ppb in 2011, but President Obama ultimately rejected the tougher standard, leaving it at 75 ppb. The EPA estimates that lowering to 60 ppb would have saved up to 12,000 lives every year, prevented 58,000 asthma attacks and avoided 21,000 hospital and emergency room visits. Nolen's organization, the American Lung Association, reacted by suing the EPA, along with other environmental groups.

But even at the 75 ppb standard, many American towns and cities are already close to violating the standard. According to Dr. Cyril Durrenberger, it would be very difficult to achieve the lower levels if they were enforced by the EPA.

“How many days of the year does ozone really cause problems? Not too many,” said Dr. Durrenberger. “People who are susceptible have to stay in doors when ozone is higher, and be careful about when or how long they stay outside.”

What you can do to reduce ozone in the air

There are things that you can due to help reduce ozone in the air, particuarly during the summer months when ozone is likely to be higher. Fuel up in the evening rather than during the day, when ozone cooks in the air. Avoid using solvent-based products in your home, like spray paints and other aerosols. Use your gasoline-powered lawn mower less often, or switch to an electric, battery, or human-powered mower. Don't idle your vehicle. By doing these things, you can do your part to contribute to greater public health.

Reviewed by: 
Review Date: 
October 14, 2011
Last Updated:
October 24, 2011