International Agency for Research on Cancer (IARC) - Summaries & Evaluations

(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 53 (1991) (p. 481)

CAS No.: 1918-02-1
Chem. Abstr. Name: 2-Pyridinecarboxylic acid, 4-amino-3,5,6-trichloro-

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Picloram is a systemic herbicide used to control broad-leaved weeds on pasture, rangeland, rights-of-way, forestland and some grains. It was first registered for use in 1963.

Picloram has been formulated as granules and soluble concentrates in the form of amine and potassium salts and esters.

Exposure to picloram may occur during its production and application and, at much lower levels, from consumption of foods containing residues.

5.2 Carcinogenicity in humans

No data were available to the Working Group.

5.3 Carcinogenicity in experimental animals

Technical-grade picloram was tested for carcinogenicity in one experiment in mice and in two experiments in rats by administration in the diet. No increase in tumour incidence was observed in mice. In rats, it increased the incidence of liver-cell tumours (mainly benign) in males in one study and in males and females in another, and of C-cell adenomas of the thyroid in female rats in one study.

5.4 Other relevant data

The liver is the primary organ for picloram toxicity following chronic administration to rats.

No data were available on the genetic and related effects of picloram in humans.

Picloram did not induce chromosomal aberrations in mouse bone-marrow cells in vivo nor in cultured human cells. With the exception of a single report in which forward mutation was induced in Streptomyces coelicolor, picloram gave negative results in all short-term tests for mutation. It induced mitotic recombination in yeast but not in fungi.

5.5 Evaluation

No data were available from studies in humans.

There is limited evidence for the carcinogenicity of picloram of technical grades in experimental animals.

Overall evaluation

Picloram is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of the italicized terms, see Preamble Evaluation.


Last updated: 21 November 1997

    See Also:
       Toxicological Abbreviations
       Picloram (ICSC)