Summer can bring more than just sunshine and swimming opportunities. In many urban areas, summer is also associated with smog, a form of air pollution that becomes particularly hazardous on hot days.

Why worry about smoggy days? According to the Environmental Protection Agency (EPA), it can be dangerous to breathe in too much smog. Smog contains a health-harming pollutant called ozone. Elevated levels of ozone have been shown to cause a variety of negative health effects in the lungs.

Smog is most common in big cities; however, even those who live in suburban areas need to be conscious of its dangers. If you need to pass through a major metropolitan area during a family vacation or road trip, it's wise to be aware of smog conditions.

No matter where you live, there are precautions you can take to protect your family on extra-hot days, particularly when smog warnings are in effect.

What Is Smog?
The term "smog" describes a mixture of emissions--including emissions from industry pollutants, cars and other vehicles, open burning, and incinerators--under specific climate conditions. In the United States, the first smog is usually noticed in the summer. In London, England, smog is often more noticeable in the winter months.

Summer smog is sometimes also known as "photochemical smog." This type of smog is caused when sunlight mixes with chemicals in the atmosphere called hydrocarbons and nitrogen oxides. Summer smog contains pollutants such as a colorless, odorless gas called ozone.

Though ozone can be good when it is found in the upper atmosphere, it can be harmful when it occurs at near ground level. Ozone formed in the Earth's lower atmosphere can lead to smog, and can affect your health when you breathe it.

How Can Smog Affect My Health?
Because of the effects of ozone on your lungs, smog exposure may lead to several different types of short-term health problems:

  • Coughing and throat/chest irritation: High levels of ozone can irritate your respiratory system. Generally, these types of mild symptoms only last for a few hours after you've been exposed to smog. However, ozone can continue to harm your lungs even after symptoms disappear.
  • Worsening asthma symptoms: If you suffer from asthma, being exposed to high levels of ozone from smog can trigger asthma attacks.
  • Difficulty breathing and lung damage: Because of ozone's effect on lung function, smog can make it feel difficult to breathe deeply, especially during exercise. Research has shown that ozone exposure can also damage the lining of your lungs.

It's important to note that smog affects everyone differently, and some groups are especially at risk. Children, seniors, and people with asthma need to be especially careful on smoggy days.

How Can I Protect Myself from Smog?
The EPA notes that the majority of people only need to be concerned about smog when ozone exposure reaches sufficiently high levels. In order to protect yourself and your family, you need to stay informed about the ozone levels in your area. If you are vacationing, you should check on the ozone levels wherever you are traveling.

Organizations like the EPA, as well as many state and local air agencies, have tools available to help you look up ozone levels in a particular region. You can also access tools that will help you understand the possible health effects of smog. For example, the EPA has developed an index called the Air Quality Index (AQI) that reports on the levels of ozone and other pollutants nationally. The index has colors assigned to ozone levels to make it easy to understand the air quality in your community.

The AQI ranks air quality from zero to 300. Levels above 150 are considered unhealthy for anyone, and levels above 200 are considered very unhealthy. These exposure levels correspond to red and purple colors on the index, respectively.

Two simple precautions can help protect you when ozone levels are high:

  1. Limit your outdoor activities as ozone levels rise to unhealthy levels. The EPA notes that elevated ozone levels increase your chances of being affected by smog the longer you stay outside.
  2. Keep your activities gentler on smoggy days. The more vigorous your activity level, the greater your chances of experiencing respiratory problems.

HealthAhead Hint: Take Precautions
Don't take chances with smog on days when air quality is low. The best approach is to spend less time outdoors, and replace vigorous activities, like running or biking, with gentler options, such as walking. It can also help to schedule your outside activities for the early morning or evening, since ozone levels are usually lower at those times. These simple steps can help protect you and your family on smoggy days, whether you live in a major city or you're just passing through.