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Polluted city.

While we don’t often think about the air we breathe, we should. Clean air is important to all of us. It is important for your health. Thankfully, there are things you can do to protect yourself from dirty air.

Indoor air pollution and outdoor air pollution

Air can be polluted indoors and it can be polluted outdoors, but it’s not the same things that are making the air dirty in both places. Check out this chart to see what things cause indoor air pollution and what things cause outdoor air pollution!

Indoor pollutantsOutdoor pollutants
Animal dander (skin and fur)Ground-level ozone (smog)
Dust mitesDust*
Secondhand smokeLiquids*
(either tracked in from outside or used in the house)
Industrial emissions
(like smoke and chemicals from factories)
Household cleaners
(spray cleaners, air fresheners)
Car emissions
(like carbon monoxide)
*All of these things make up “particle pollution.” They mostly come from cars, trucks, buses, and power plants.

Good ozone versus bad ozone

If you have already read the Sun section of this module, you are probably thinking, Wait a second. Isn’t ozone good for us? Isn’t it what protects us from UV radiation? You’re right! The ozone that is in our upper atmosphere is good ozone that protects us from the sun. Ground-level ozone is different, though, even though it sounds the same. Ground-level ozone is a summertime air problem that comes from a chemical reaction between certain chemicals and heat and sunlight. Ground-level ozone is bad for our health, and can make it hard to breathe. People who are active outdoors on hot summer days may be affected by high levels of ozone.

Air Quality Index (AQI)

How do you know if the air you are breathing is clean? You can check on the Internet for your local Air Quality Index (AQI). The AQI is a guide for reporting daily air quality. It tells you how polluted or clean your air is, and if you need to do anything to protect your health. If the AQI is poor, you may need to stay indoors that day. You can also walk, ride your bike, get a ride from a friend, or take the bus to reduce air pollution from cars on days when the AQI is bad.

Carbon monoxide

Did you know that one of the biggest dangers that may be in your house is invisible and has no smell? It’s called carbon monoxide (CO). CO is a gas that is formed when a fuel like gas, oil, kerosene, wood, or charcoal is burned. Things that you have in your house — like a clothes dryer, stove, or hot water heater — may use these fuels. If the appliance fumes can get out of the house through a vent, then the amount of CO in your house is probably not dangerous. But if the appliances are not vented the right way, CO can become very dangerous! CO poisoning can cause serious injury and even death. Here are a few things you can do to prevent CO poisoning:

  • Make sure that if you use a gas or kerosene space heater, that the room is well vented. This means that the windows must be opened. Never use these things in a closed off room.
  • Ask your parents to have your appliances checked once a year by a professional.
  • Have an adult in your house place CO detectors (they look like smoke detectors) in the rooms where you and your family sleep. CO detectors should be placed near the floor.
  • Never barbeque inside the house or garage.
  • Let the drivers in your house know that running a car or lawnmower in a closed garage is dangerous.
  • Make sure that car and truck tail pipes are not clogged with snow or other things.


Radon is a cancer-causing, radioactive gas. It is natural and comes from the earth. You can't see radon. And you can't smell it or taste it. But it may be a problem in your home. Radon levels may be highest in the lowest parts of your home, like the basement.

Radon is thought to cause many thousands of deaths each year. That's because when you breathe air containing radon for many years, you can get lung cancer. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today. Only smoking causes more lung cancer deaths. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.

Radon comes from the natural breakdown of uranium in soil, rock, and water and gets into the air you breathe. Radon can be found all over the U.S. It can get into any type of building — homes, offices, and schools — and result in a high indoor radon level. But you and your family are most likely to get your greatest exposure at home, where you spend most of your time.

Testing is the only way to know if you and your family are at risk from radon. Testing is cheap and easy. Some tests can be done in a few minutes or it can take a couple of days. Radon can be reduced in your home if you find out there are high levels. Talk to your parents or guardian and ask if they have ever tested for radon.

Secondhand smoke

Most smokers know that smoking is bad for them. But smoke can also hurt the people around the person smoking. This smoke is called “secondhand smoke.” It’s a mix of the smoke exhaled by smokers and smoke from cigarettes, pipes, and cigars. Babies and young children, especially those with asthma, are most at risk from secondhand smoke. If someone in your house smokes, talk to them about quitting. If you smoke, learn some tips for quitting in the Drugs, Alcohol, and Smoking section of


Content last reviewed July 20, 2010
Page last updated October 31, 2013