The EPA believes two unregulated chemical cleaners, methyl chloroform and carbon tetrachloride, probably are major contributors to ozone depletion and controls on them may be necessary, officials confirmed.

The officials confirmed Monday the Environmental Protection Agency last week warned industry against using the two chemicals, saying new scientific evidence indicates they play a larger role than previously believed in erosion of the Earth's protective ozone layer, which screens out harmful radiation."The analyses show they contribute to the problem in a way that is probably unacceptable," John Hoffman, director of the EPA's global change division, said.

Hoffman's remarks followed an EPA announcement in the April 17 Federal Register in which the agency served notice on industry that methyl chloroform and carbon tetrachloride may be added to the list of ozone-depleting chemicals regulated by international treaty.