Environment and Breast Cancer: Science Review

The list(s) or database(s) in which the chemical was identified as showing an increase in mammary gland tumors. CPDB: Carcinogenic Potency Database, IARC: International Agency for Research on Chemicals Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man summaries, NTP TR: National Toxicology Program (NTP) Technical Reports, NTP 11ROC: NTP 11th Report on Carcinogens, CCRIS: Chemical Carcinogenesis Research Information Service.

Names of closely related chemicals discussed in the "originating list" are listed here if they were not separately reviewed.

We assigned each chemical into one of the following groups based on its major sources and uses: industrial chemicals, chlorinated solvents, products of combustion, pesticides, dyes, radiation and drinking water disinfection, pharmaceuticals, hormones, natural products, and research chemicals.

If a chemical is a High Production Volume chemical, added to food, found in air pollution or consumer products, or causes greater than 5000 women to be exposed occupationally, it was judged to cause a likely widespread exposure to women in the United States.

Information describing pathways of exposure for the general population was obtained from a variety of sources, including IARC Monographs (9), NTP 11th ROC (4), NTP Study Reports (3), and Hazardous Substance Database (10). Summaries of chemical use in consumer products were developed from information found in US EPA's Source Ranking Database (SRD) (11), the NLM Household Product Database (HPD)(12), Scorecard (12), and Pesticide Action Network (PAN) Pesticides Database (13). If a chemical could not be found in these sources, we searched ToxNet (14), PubChem (15), and The Merck Index (16), and conducted searches by both name and CAS No. using Google.

A summary of findings related to mammary gland tumors, most often excerpted from IARC Monographs or the NTP 11th ROC, and, in some cases, supplemented by our evaluation of individual studies and reviews, is available for the priority chemicals and 67 others.

Overall evaluation: Group 1: The agent is carcinogenic to humans. Group 2A: The agent is probably carcinogenic to humans. Group 2B: The agent is possibly carcinogenic to humans. Group 3: The agent is not classifiable as to carcinogenicity in humans. Group 4: The agent is probably not carcinogenic to humans. NA: not evaluated by IARC (9).

Strength of the evidence in humans (summary of epidemiologic evidence) and animals: sufficient, limited, or inadequate. If IARC has not reviewed the chemical, this field will be labeled "NA".

If tumors were found in humans, the entry in this field will be labeled "(human)." Unlabeled terms are from animal studies. Tumor sites are abbreviated and can be referenced in the key (Table 1). NA: not evaluated by IARC.

Strength of the evidence in humans (summary of epidemiologic evidence) and animals: sufficient, limited, or inadequate. If IARC has not reviewed the chemical, this field will be labeled "NA".

The US EPA Weight of Evidence Characterization of the chemical’s carcinogenic potential is listed: Group A: Carcinogenic to humans; Group B: Probably carcinogenic to humans. Group C: Possibly carcinogenic to humans. Group D: Not classifiable as to human carcinogenicity. Group E: Evidence of non-carcinogenicity for humans. NA: Not evaluated by US EPA (17).

The National Toxicology Program Technical Reports include a determination of the carcinogenicity of the test chemical in each sex and species tested. Designations prior to 1983 are "positive" or "negative". After 1983, NTP assigned designations of "clear evidence of carcinogenicity," "some evidence of carcinogenicity," "equivocal evidence of carcinogenicity," "no evidence of carcinogenicity," or "inadequate study of carcinogenicity." The words "of carcinogenicity” are removed from the field in this database to conserve space. "NA" indicates no NTP technical report for the chemical (3).

This summary of evidence from the Carcinogenic Potency Database is labeled “Yes” if the agent is mutagenic or weakly mutagenic in the Salmonella assay and “No” if not. NA: Not listed in CPDB. NA-S: Listed in CPDB, but no assessment of mutagenicity in Salmonella is included (1).

This summary of evidence from the Registry of Toxic Effects of Chemical Substances database (NIOSH 2005) is labeled “Yes” if the agent is listed as mutagenic, “No” if not. NA: Not listed in RTECS (18).