[6] In late February 1963, after he experienced his spouse suffering and dying of cancer, journalist and peace activist Yves Poggioli sent a letter to Emmanuel d'Astier de la Vignerie relating his story, and urging support for the creation of an international center to fight against cancer, whose funding was to be directly debited from the national budgets allocated to nuclear weaponry.

Touched by the letter, d'Astier assembled a group of French prominent figures, among which Pierre Auger, Francis Perrin, Jean Hyppolite, François Perroux, Pierre Massé, Louis Armand, François Bloch-Lainé [fr], Jean Rostand, François Mauriac, Antoine Lacassagne, Ambroise-Marie Carré and Le Corbusier, to reach for French president Charles de Gaulle[7] in national newspaper Le Monde on the 8 November 1963. de Gaulle answered positively to the call and reached for the World Health Organization director Marcolino Gomes Candau on the 11 November.

[8] The first IARC Director was John Higginson (1966–1981), who was followed by Lorenzo Tomatis (1982–1993), Paul Kleihues (1994–2003), Peter Boyle (2004–2008), Christopher Wild (2009–2018) and Elisabete Weiderpass (2019–present).

The categorization is a matter of scientific judgement that reflects the strength of evidence derived from studies in humans, experimental animals and other relevant data.

[12] Examples of agents classified as Group 1 include tobacco smoke, alcoholic beverages, Chinese-style salted fish and consumption of processed meat.

[12] Examples of agents classified as Group 2A include emissions from high-temperature frying of food, the occupational exposures as a hairdresser or barber, consumption of red meat and night shift work .

[12] Examples of agents classified as Group 2B include occupational exposures in working in the textile manufacturing industry, printing processes, traditional Asian pickled vegetables, and radiofrequency electromagnetic fields.

[16] 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.

[16] 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,[18] as "probably carcinogenic to humans" (Group 2A).

In April 2016, internal IARC officials told its experts to not release documents or comply with the legal requests related to its review of glyphosate.

[24] Additionally, Congressman Robert Aderholt (Republican), chairman of the House Appropriations Subcommittee on Agriculture, wrote a letter in June 2016 to the head of the NIH questioning the funding of IARC.

[citation needed] However, IARC respond that the Working Groups methods are "widely respected for their scientific rigor, standardized and transparent process and for freedom from conflicts of interest.

[29] IARC answered in a press release their mission was not to evaluate potency or to assess the risks but only to determine scientifically the strength of carcinogenetic evidence of glyphosate.

[31] In July 2023, an IARC committee concluded that there was "limited evidence" for aspartame causing cancer in humans, classifying the sweetener as possibly carcinogenic.