Background Tobacco-specific nitrosamines (TSNAs) are a group of carcinogens, which originate from nicotine and other tobacco alkaloids during fermentation and burning of tobacco. Between 1990 and 2010, the tobacco industry-funded extensive academic research on TSNAs in Germany. The objective was to gain better knowledge of how industry aims and strategies correlate with contents of publications by German toxicologists accepting tobacco industry funding by focusing on one prominent such toxicologist.

Methods and findings The authors analysed previously secret tobacco industry documents that were disclosed following a series of litigation cases in the USA and compared them with peer-reviewed published results of tobacco industry-funded toxicologists. The tobacco industry, in particular Philip Morris, developed sophisticated strategies to downplay TSNA's carcinogenic potential. Over 2 decades, German toxicologist Elmar Richter, faculty member of the renowned Ludwig-Maximilians-University, Munich, received substantial financial support from the tobacco industry. Numerous publications show that his research findings supported the aims of the tobacco industry. In his commissioned work, he suggested that TSNA burden can be explained by misclassification of smokers or assay background levels caused by TSNA-like molecules from food. Other publications cast doubt on the relevance of animal testing for TSNAs to humans claiming a detoxifying effect of nicotine on the metabolism of TSNAs or suggesting that adducts of TSNAs are unsuitable as biomarkers of exposure to tobacco smoke.

Conclusions Economic interests of the tobacco industry have strongly influenced the research activity of Richter and his group. The publications of his working group about carcinogenic effects of TSNAs published between 1992 and 2009 should therefore not be regarded as independent. Scientists and policy makers should consider the long-standing and intensive inter-relation between certain toxicologists and the tobacco industry when assessing the research results and consider ignoring them.