After reanalysing the data from a decade old study by Philip Morris researchers of the University of California said the firm's research "obscured findings of toxicity" and hid the dangers of additives in cigarettes.

The original study by Philip Morris, called Project Mix, resulted in the publication of four papers in a scientific journal that concluded there was "no evidence of substantial toxicity" associated with the additives studied.
The new study, by the Centre for Tobacco Control Research at the University of California, was based on the same data extracted from among 60 million documents released after litigation.
The researchers claim the original studies "cannot be taken at face value" and failed to reveal additives' dangers.
When they conducted their own analysis examining the additives per cigarette – as specified in the original protocol for the Project Mix study but later changed – they found the level of 15 carcinogenic chemicals increased by an average of 20 per cent.
They also discovered that, for what they call "unexplained reasons", Philip Morris had de-emphasised 19 of the 51 chemicals tested in the presentation of their results, including nine that were substantially increased in the smoke on a per cigarette basis.
Stanton Glantz, who led the new research published in the online journal Public Library of Science Medicine, said that if Philip Morris's own data was taken and interpreted correctly, "you could use this data to ban these additives".
A Philip Morris spokesman said: "We believe that the points raised in this recent paper by Stanton Glantz and others do not invalidate the findings of the Project Mix studies. (pi)