Narrator: This is Science Today. The next time you're cleaning the house, you may want to make sure you have a window open. A University of California , Berkeley study has found that chemicals in certain household cleaning products could be dangerous if used in areas that are not well-ventilated. Environmental engineering professor William Nazaroff, who led the study, explains.

Nazaroff: The kinds of situations where one might be at high risk include those where the ventilation of the space is poor, where a high amount of the product is used where, and especially if it's used in a small space, where the products are used with high frequency.

Narrator: Nazaroff says a high risk of air pollution exposure comes from the mixture of ozone with chemicals called terpines, which are found in scented cleaning products and air fresheners.

Nazaroff: Examples of the steps that one can take to reduce exposures include, using the product in dilute form whenever that's appropriate. Not using more than the amount necessary to do a good job of cleaning.

Narrator: For Science Today, I'm Larissa Branin.