The International Agency for Research on Cancer (IARC) is internationally recognized for evaluation of compounds, complex mixtures with a carcinogenic potential. For the current state of the science of classification and evaluation see Annexure 2. The IARC evaluations rank the compounds and complex mixtures into five groups. Select examples of workplace carcinogens are enlisted below:
- Group 1: Carcinogenic to humans, which are based mainly on studies in humans. This group comprised 28 definite occupational carcinogens, including asbestos, crystalline silica, wood dust, arsenic and arsenic compounds,beryllium, cadmium and cadmium compounds, hexavalent chromium compounds, nickel compounds, benzene, vinyl chloride monomer, 4-aminobiphenyl, benzidine, 2-naphthylamine, ethylene oxide, 1,3-butadiene (recently reclassified to Group 1, cf. below), and coal tars and pitches.
- Group 2A: Probably carcinogenic to humans, which are based on sufficient evidences from animal studies. This group comprised 27 probably occupational carcinogens, including benzo[a]pyrene, tetrachloroethylene, trichloroethylene,acrylamide, epichlorohydrin, benzidine-based dyes, diethyl sulphate, and formaldehyde.
- Group 2B: Possibly carcinogenic to humans, which are based on a combination of effects in humans, animals and other evidences. This group comprised more than 100 occupational exposures, including antimony trioxide, cobalt and cobalt compounds, lead and inorganic lead compounds, naphthalene, acrylonitrile, ethylacrylate, isoprene, styrene, toluene diisocyanate, acetaldehyde, acetamide,chloroform, 1,2-dichloroethane, dichloromethane, some aromatic amine dyes, some azo dyes (including trypan blue), butylated hydroxyanisole (BHA), catechol,1,4-dioxane, and hydrazine.
- Group 3: Not classifiable as to its carcinogenicity to humans due to limitations in the data set.
- Group 4: Probably not carcinogenic to humans, which are based on a combination of effects in epidemiologic and animal studies together with othere vidences.
For more details on classifications and the various categories and examples of carcinogenic compounds see article in Annexure 3. The summary and overall evaluations by IARC are available from the home web of the International Programme on Chemical Safety [http://www.inchem.org/pages/cicads.html and
http://www.inchem.org/pages/icsc.htmlDf]. Another comprehensive list with documentations of carcinogenic compounds is available from the U.S. Department of Health and Human Services through the home web of the National Toxicology Program [http://ntp.niehs.nih.gov/ntp/roc/toc11.htm].The list is published biennially and distinguishes between compounds ‘‘known to be human carcinogens”, which is based on epidemiological studies, and compounds‘‘reasonably anticipated to be human carcinogens”, which is based on human and/or animal studies as well as on other relevant data. The lists are useful as a first choice of information about potential carcinogenic effects.