Is IARC and the WHO the same thing?
IARC is an agency under the WHO but is not responsible for regulating pesticides.

The body responsible for conducting risk assessments of pesticides for regulatory purposes is the Joint FAO/WHO Meeting on Pesticide Residues, or the “JMPR” for short.

“JMPR meets regularly since 1963 to review residues and analytical aspects of the pesticides, estimate the maximum residue levels, review toxicological data and estimate acceptable daily intakes (ADIs) for humans of the pesticides under consideration."

The Joint FAO/WHO Meeting on Pesticide Residues reviewed 2,4-D most recently in 1996/97. Previously 2,4-D was reviewed in 1970, 1971, 1974, and 1975. 2,4-D was tested for a wide range of health impacts. The JMPR continues to conclude that 2,4-D is not genotoxic and that there is no evidence of carcinogenicity.