THE JOURNAL’S July 15 editorial “RIPTA’ s rationality” was an audacious and welcome plea for the importance of public transit, especially to our state’s economic vitality.

As a public-health specialist I want to emphasize how support for (and expansion of) public transit is a principal prevention strategy for a range of health-related disorders — some of epidemic proportion.

An astonishing amount of climate-change pollution comes from privately driven motor vehicles in the United States. (Roughly 10 percent nationally, 40 percent in New England.) Leaving the car at home just two days a week will reduce greenhouse-gas emissions, according to the American Public Health Association, by an average of 1,600 pounds a year.

Parenthetically, it also reduces the risk of traumatic death and injury. According to Centers for Disease Control and Prevention, 2,831 kids under 16 were killed by motor vehicles in 2000. Another 332,000 were injured.

We are all well acquainted with our society’s struggle with obesity. Obesity plays a major role in a wide range of health epidemics, from diabetes to heart disease to asthma. To combat obesity the U.S. surgeon general’s office recommends, among other things. at least 30 minutes of walking or bicycling a day — the equivalent of 1.5 miles of walking, or a commute by bicycle of 5 miles round trip. Yet fewer than 6 percent of kids walk or bike to school, compared with 66 percent in 1974. (Maybe that is a rational decision: Of the 2,800 kids killed by cars in 2000 over 700 were walking or biking.)

Note a simple and elegant experiment conducted by the CDC during the 1996 Summer Olympic Games, in Atlanta. Atlanta restricted private automobiles in and around the Olympic venue. (Crowds were directed to public transit.) CDC investigators decided to find out what impact that policy might have on air quality and asthma in the surrounding neighborhoods.

Asthma acute-care events decreased 41.6 percent as measured by Medicaid claims, there was a 44.1 percent decline of asthma events in a local health-maintenance organization, an 11.1 percent drop in two pediatric-emergency departments, and a 19.1 percent decline in admissions for asthma as measured by the Georgia Hospital Discharge Database. A remarkable public-health success.

Most motor vehicles run on gasoline. Gasoline-fueled engines produce significant amounts of carbon monoxide. In urban traffic, daily average carbon-monoxide concentrations reach levels that (in controlled experiments) impair coordination, tracking, driving ability, vigilance and cognitive performance among healthy subjects. In studies involving patients with coronary disease, higher carbon-monoxide levels were associated with angina, increased electrocardiographic changes and impaired left ventricular function during exercise.

Any erosion in our public-transit system will not only hurt our economy and quality of life, it would probably damage our hearts, livers, brains and lungs. By getting people out of cars, we improve public health, reduce global warming, improve air quality, encourage safe walkable communities and protect open space. The overall benefit of public transit is massive.

James Celenza is director of the Rhode Island Committee on Occupational Safety and a founder of the New Public Transit Alliance.