In response to your April 18 editorial, "Oceanside ought to butt out," outdoor environmental tobacco smoke is much more than annoying. It is a complex mixture of thousands of gases and fine particles, with some constituents that persist in the air even when there is a breeze. People should not be forced to be exposed to known carcinogenic substances.

Outdoor drifting tobacco smoke can trigger asthma attacks, bronchial infections and other serious health problems in nonsmokers.

Personal liberties are precious and by all means should be protected and preserved. However, special conditions must be implemented when the personal rights and freedoms of one cause harm to another.

Also, the great majority of Californians, more than 85 percent, do not smoke and have a basic right to breathe clean air. This is especially true if they have a health condition such as asthma, cancer or cardiovascular disease that can be negatively impacted by exposure to environmental tobacco smoke.

Asthma is the No. 1 reason that children enter our hospital emergency rooms in San Diego. Many of the 96 million Americans who have chronic conditions like asthma and bronchitis, which make them especially susceptible to environmental tobacco smoke, have been held to be entitled to protection under the Americans with Disabilities Act.

The Centers for Disease Control and Prevention has warned that breathing drifting tobacco smoke for as little as 30 minutes (less than the time one might be exposed outdoors on a beach or in a park) can raise a nonsmoker's risk of suffering a fatal heart attack to that of a smoker.

The scientific basis regarding the toxicity of outdoor environmental tobacco smoke is extensive and has come from a large body of scientific evidence and has been endorsed by major science and health organizations throughout the world.

Walter Williams, in his column, "Science goes up in smoke" (April 19), trivialized the scientific process used by the Environmental Protection Agency. In January 2006, the California Air Resources Board declared outdoor tobacco smoke as a Toxic Air Contaminant. The findings are well-documented and conclusive.

The Air Resources Board assessed the level of environmental tobacco smoke exposure to Californians and the Office of Environmental Health Hazard Assessment evaluated the health effects associated with environmental tobacco smoke exposure. The report was then submitted to an independent scientific review panel.

The Air Resources Board's outdoor nicotine monitoring results are comparable to those found in some smokers' homes. Smokers' homes can have indoor nicotine levels 30 times higher than nonsmokers' homes.

Under state law, the Air Resources Board is authorized to identify a substance as a Toxic Air Contaminant if it determines the

substance is "an air pollutant which may cause or contribute to an increase in mortality, in serious illness, or which may pose a present or potential hazard to human health."

Federal agencies, national scientific, medical and health organizations promote policies that protect human health through the creation of smoke-free environments.

Lawmakers are clearly making the intelligent choice to protect the health, safety and environment for San Diegans from environmental tobacco smoke.

Candice M. Porter is director of the Youth Tobacco Prevention Corps, a group of teens from San Dieguito Academy and La Costa Canyon and Torrey Pines high schools who work toward the prevention of tobacco use by teens.