A California agency voted on Thursday to classify second-hand tobacco smoke as a "toxic air contaminant", a first-in-the-nation move that could ultimately toughen state regulations against smoking.
The designation by California's Air Resources Board starts a process that could lead to further smoking bans in the nation's largest state, which has often pioneered in health and environmental regulation.
"I think there is no question that this puts California way ahead," said John Froines, chairman of the Air Resources Board's Scientific Review Panel.
"To actually have the major air pollution agency in the state of California to list ETS (environmental tobacco smoke) as a toxic air contaminant is going to have immense impact, we think, in terms of public education around other states," he said. "It will clearly lead to regulatory changes within the state."
The panel's 2005 study found that about 16 per cent of all Californians smoked, but 56 per cent of adults and 64 per cent of adolescents were exposed to second-hand smoke.
The decision in the California state capital kicks off a process that will likely take two or three years as officials study ways to reduce exposure to second-hand smoke.
In 1994, California became the first US state to bar smoking in the workplace, and then followed up with bans on smoking in restaurants and bars. Other American cities and states have since adopted similar prohibitions.
Several California cities have enacted wider bans, such as San Francisco, which now prohibits smoking in city parks, and Los Angeles, which bars smoking at piers and beaches.
Some health experts say the ultimate impact of California's decision to classify second-hand smoke as a toxin could reach beyond the United States.
Some foreign countries, including Ireland, Norway and Sweden, have workplace smoking bans. (pi)