Washington : Tobacco firm Phillip Morris underplayed the dangers from cigarette additives, including menthol, masking toxicity levels and increasing chances of heart, cancer and other diseases for smokers.

Researchers from University of California San Francisco (UCSF) said that they have found that hundreds of additives, including menthol, should be eliminated from cigarettes on public health grounds.

"When we conducted our own analysis by studying additives per cigarette-following Philip Morris' original protocol-we found that 15 carcinogenic chemicals increased by 20 percent or more," said senior author Stanton A. Glantz, director of the Centre for Tobacco Control Research and Education at the UCSF.

In the independent study, Glantz and team reassessed data from Philip Morris' 'Project MIX,' which detailed chemical analyses of smoke and animal toxicology studies of 333 cigarette additives. Philip Morris is the largest tobacco company in the US.

Researchers also found after obtaining evidence that additives increased toxicity, that tobacco scientists adjusted the protocol for presenting their results in a way that obscured these increases.

Additionally, in the independent study, the researchers discovered the reason behind Philip Morris' failure to identify many toxic effects in animal studies: its studies were too small.

Researchers used documents made public as a result of litigation against the tobacco industry. The documents are available to the public through UCSF's Legacy Tobacco Documents Library.