A new UCSF analysis of tobacco industry documents shows that Philip Morris USA manipulated data on the effects of additives in cigarettes, including menthol, obscuring actual toxicity levels and increasing the risk of heart, cancer and other diseases for smokers.

Tobacco industry information can't be taken at face value, the researchers conclude. They say their work provides evidence that hundreds of additives, including menthol, should be eliminated from cigarettes on public health grounds.

By investigating the origins and design of Project MIX, the UCSF researchers conducted their own inquiry into the Philip Morris results. They stressed that many of the toxins in cigarette smoke substantially increased after additives were added to cigarettes.

They 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.

"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," he said.

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.

In the new study, the 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.