A study by the University of California Los Angeles (UCLA) Institute of the Environment said the film industry was responsible for sending 140,000 tonnes of pollutants into the atmosphere every year.

Ozone and diesel emissions from trucks and generators used on movie sets as well as pyrotechnic explosions for special effects all contributed to the layer of smog that hangs over Los Angeles.

"Many industries are moving toward more environmentally sustainable operations, and it's important that we monitor their progress," said institute director Mary Nichols.

Nichols said researchers noted that although several studios and production companies were taking steps to minimise damage, the industry's lack of a unified environmental strategy was a barrier to improvement.

Two UCLA professors who conducted an analysis as part of the study concluded that Hollywood could be doing more, the report said.

"Our overall impression is that, with a few notable and inspiring exceptions, environmental considerations are not high on the agenda in the film and television industry, and that more could be done within the industry to foster environmentally friendly approaches," the professors said.

The researchers cited the example of the makers of "The Day After Tomorrow", who paid for a 200,000-dollar package of environmental measures to offest damage caused by vehicles used in the 2004 blockbuster.

The makers of the last two "Matrix" films were also praised for arranging for more than 97 percent of set materials to be recycled.

The study found the problem was attributable to the transient nature of production companies, saying that "the degree to which work is controlled by short-lived ever-changing production companies" made it "difficult to institutionalize best practices."

Business groups warned against using the report to crackdown on the film and television industry, which generates around 29 billion a year in combined revenues and employs around 252,000 people.

Jack Kyser, chief economist for the Los Angeles County Economic Development Corp, cautioned against further regulation, saying it could force movie and television studios out of California.

"There would be a risk because you have other states out there quite anxious to get a piece of the film industry," he told the Los Angeles Times. "This would just be another nudge."

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.