By NICHOLAS BAKALAR
Researchers studied 3,318 children in 12 Southern California communities beginning at an average age of 10, and then followed them through age 18. They used parental questionnaires to establish exposure to smoking, and data on traffic volume and levels of nitrogen dioxide, ozone and particulates to track pollution.
The study, in Environmental Health Perspectives, controlled for many other factors: sex, initial B.M.I., asthma, physical activity, insurance status, parental education and income, acres of parks and open space nearby, percentage of people living in poverty in each community.