There is not one regulatory agency mandated with protecting public health in the world that identifies 2,4-D as a human carcinogen.
“The Agency [EPA] determined, based on several reviews of epidemiological studies, in addition to the animal studies, that the existing data did not support a conclusion that links human cancer to 2,4-D exposure.”
United States Environmental Protection Agency
"Health Canada also consulted an independent Science Advisory Panel comprised of government and university experts/researchers in toxicology, epidemiology and biology. The Panel agreed with Health Canada’s assessment that 2,4-D can be used safely when used according to label directions, with some uses requiring additional protective measures."