limited in experimental animals. Exceptionally, agents (or mixtures) where evidence is inadequate in humans but sufficient in experimental animals may be placed in this category only if there is strong evidence that the mechanism of carcinogenicity in experimental animals does not operate in humans. Substances that do not fall into any other group are placed in this category. This is not a determination of non-carcinogenicity or overall safety. It means that further research is needed, especially when exposures are widespread or the cancer data are consistent with differing interpretations. As of August 2019, roughly 50% of all substances analyzed by IARC fall into this category. Group 4: The agent is probably not carcinogenic to humans. There is evidence suggesting lack of carcinogenicity in humans and in experimental animals. In some instances, agents or mixtures for which there is inadequate evidence in humans but evidence suggesting lack of carcinogenicity in experimental animals, consistently and strongly supported by a broad range of mechanistic and other relevant data may be classified group 4. Until recently, only caprolactam fell under this category, but it was recently upgraded. This currently leaves no agent or substance classiified as probably not carcinogenic to humans by the IARC. Controversies Transparency (1998–2004) Lorenzo Tomatis, IARC director from 1982 to 1993, was allegedly "barred from entering the building" in 2003 after "accusing the IARC of softpedaling the risks of industrial chemicals" in a 2002 article. In 2003 thirty public-health scientists signed a letter targeting conflicts of interest and the lack of transparency. Tomatis accused the IARC of "highly irregular" voting procedures, alleging industrial interferences, and called for the agency to publish voting procedures and names in details for independent scrutiny. The IARC rejected these criticisms, highlighting that only 17 of 410 of the working-group participants were consultants to industry and these people never served as chairs, nor were allowed to vote. The reason the details of the voting names were not published was to avoid political pressures on the participating Working Group scientists, and to protect the integrity of the deliberative process. Glyphosate monograph (2015–2018) On 20 March 2015, IARC classified glyphosate, the most widely used weed killing substance in the world sold under the brand name of Roundup by Monsanto, as "probably carcinogenic to humans" (Group 2A). Subsequently, many national regulatory authorities underwent a reevaluation of the risk posed by the exposure to glyphosate. Regulators in Europe (ECHA, EFSA),