State bans home ozone air purifiers - Air Resources Board says the regulation, which takes effect in 2009, is the first of its kind in the nation. Health risks are cited.

The California Air Resources Board on Thursday banned popular in-home ozone air purifiers, saying studies have found that they can worsen conditions such as asthma that marketers claim they help to prevent.

The regulation, which the board said is the first of its kind in the nation, will require testing and certification of all types of air purifiers. Any that emit more than a tiny amount of ozone will have to be pulled from the California market.