On Monday, Maine will take one more step in protecting its citizens from secondhand smoke.

Secondhand smoke contains more than 4,000 chemicals and more than 50 cancer-causing agents. Every day in Maine, seven people die from tobacco use, one of whom is a nonsmoker who has been exposed to secondhand smoke.

There is no safe level of exposure to secondhand smoke. Even brief exposure can be dangerous.

Now, drivers and passengers statewide will be prohibited from smoking in vehicles when children younger than 16 are present, even if the windows are open. This law builds on other great successes the state has experienced in fighting for healthy air for its citizens; Maine is one of 23 states where smoking in workplaces and indoor public places is banned.

Why the legislative effort to control secondhand smoke?

The smoke from a lit cigarette can go anywhere and affects everyone in its path -- not just smokers, who comprise only 25 percent of the population statewide. No air filter or ventilation system can totally remove it.

In a car, even rolling down a window won't stop smoke from reaching other passengers. After the smoke disappears, the poisons remain and cling to carpets, walls, and furniture -- even plastic toys and stuffed animals. That's why you can still smell smoke long after the smoke is gone.

Children are at greater risk from the threats of secondhand smoke because their organs are growing and developing. For a child, even brief exposure is dangerous and can cause lung problems, ear infections, asthma and the threat of sudden infant death syndrome (SIDS).

Secondhand smoke exposure in childhood is known to permanently decrease lung efficiency and function. Children who are exposed to smoke in their homes are more likely to develop asthma, bronchitis, pneumonia, colds, sore throats, ear and eye infections and allergies.

Although secondhand smoke exposure has declined significantly in Maine, children's exposure is still a serious public health issue. Forty-one percent of middle school children and 53 percent of high schoolers report having been in the room with someone smoking within the past week. An average of 13 percent of middle and high school students report being exposed to secondhand smoke in a car, every day.

Here are some ways you can protect yourself and your family from secondhand smoke:

* The best protection against secondhand smoke is to live smoke-free. Set firm rules against smoking in your home and car. If anyone asks to smoke, be polite but firmly refuse. Offer smokers a substitute -- keep sugar-free gum or mints on hand.

* Ask family and friends to never smoke around your children. Make sure that your sitters and daycare providers know, too.

* Talk to your children about secondhand smoke. Tell them it's OK to politely say to adults, "Please don't smoke around me."

You can make a change in the health of Maine citizens. Wherever you live and breathe, go smoke-free.

Joanne Joy is executive director of Healthy Communities of the Capital Area and Renee Page is program manager for Youth and School Initiatives. 588-5020. rpage@mcd.org For more information, www.tobacco freemaine.org.