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Carcinogen Classification of Pesticides
Pennsylvania componet of the Northeastern IPM Center
This information is taken from EPA's List of Chemicals Evaluated for Carcinogenic Potential, which is only available in hard copy. We have only summarize it here. You can order this publication by going to EPA's web site. In this document, they use three classifications. These classifications are briefly described here. Two of the classifications also have a web site with additional information, which are also listed. A pdf file contains tables with the list of chemicals in all three classifications and the date the classification was made.
- 1986 EPA Weight-of-the Evidence Categories
(Federal Register, Volume 51, Number 185, September 24, 1986 - 1996 Proposed EPA Weight-of-the Evidence Categories
Web Site: http://www.epa.gov/ORD/WebPubs/carcinogen/ - 1999 Draft EPA Weight-of-the Evidence Categories
Web Site: http://www.epa.gov/ncea/raf/car2sab/preamble.pdf
1986 EPA Weight-of-the Evidence Categories
Group A: Human Carcinogen
This group is used only when there is suffcient evidence from epidemiologic studies to support a casual association between exposure to the agents and cancer.
Group B: Probable Human Carcinogen
This group includes agents for which the weight of the evidence of human carcinogenicity based on epidemiologic studies is "limited" and also includes agents for which the weight of the evidence of carcinogenicity based on animal studies is "sufficient." The group is divided into two subgroups. Usually, Group B1 is reserved for agents for which there is limited evidence from epidemiologic studies. It is reasonable, for practical purposes, to regard an agent for which there is "sufficient" evidence of carcinogenicity in animals as if it presented a carcinogenicity risk to humans. Therefore, agents for which there is "sufficient" evidence from animal studies and for which there is "inadequate evidence" or "no data" from epidemiologic studies would usually be categorized under Group B2.
Group C: Possible Human Carcinogen
This group is used for agents with limited evidence of carcinogenicity in animals in the absence of human data. It includes a wide variety of evidence, e.g., (a) a malignant tumor response in a single well-conducted experiment that does not meet conditions for sufficient evidence, (b) tumor responses of marginal statistical significance in studies having inadequate design or reporting, (c) benign but not malignant tumors with an agent showing no response in a variety of short-term tests for mutagenicity, and (d) responses of marginal statistical significance in a tissue known to have a high or variable background rate.
Group D: Not classifiable as to Human Carcinogenicity
This group is used for agents with inadequate human and animal evidence of carcinogenicity or for which no data are available.
Group E: Evidence of Non-Carcinogenicity for Humans
This group is used for agents that show no evidence for carcinogenicity in at least two animal tests in different species or in both adequate epidemiologic and animal studies.
The designation of an agent as being in Group E is based on the available evidence and should not be interpreted as a definitive conclusion that the agent will not be a carcinogen under any circumstances.
1996 Proposed EPA Weight-of-the Evidence Categories
Known/Likely
This category of descriptors is appropriate when the available tumor effects and other key data are adequate to convincingly demonstrate carcinogenic protential for humans; it includes:
Agents known to be carcinogenic in humans based on either epidemiologic evidence of a combination of epidemiologic and experimental evidence, demonstrating causality between human exposure and cancer.
Agents that should be treated as if they were known human carcinogens, based on a combination of epidemiologic data showing a plausible causal association (not demonstrating it definitively) and strong experimental evidence.
Agents that are likely to produce cancer in humans due to the production or anticipated production of tumors by modes of action that are relevant or assumed to be relevant to human carinogenicity.
Modifying descriptors for particularly high or low ranking in the known/likely group can be applied based on scientific judgement and experience and are as follows:
Agents that are likely to produce cancer in humans based on data that are at the high end of the weights of evidence typical of this group,
Agents that are likely to produce cancer in humans based on data that are at the low end of the weights of evidence typical of this group.
Cannot be Determined
This category of descriptors is appropriate when available tumor effects or other key data are suggestive or conflicting or limited in quantity and, thus, are not adequate to convincingly demonstrate carcinogenic potential for humans. In general, further agent specific and generic research and testing are needed to be able to describe human carcinogenic potential. The descriptor cannot be determined is used with a subdescriptor that captures the rationale:
Agents whose carcinogenic potential cannot be determined, but for which there is suggestive evidence that raises concern for carcinogenic effects,
Agents whose carcinogenic potential cannot be determined because the existing evidence is composed of conflicting data (e.g., some evidence is suggestive of carcinogenic effects, but other equally pertinent evidence does not confirm any concern), agents whose carcinogenic potential cannot be determined because there are inadequate data to perform an assessment,
Agents whose carcinogenic potential cannot be determined because no data are available to perform an assessment.
Not Likely
This is the appropriate descriptor when experimental evidence is satisfactory for deciding that there is no basis for human hazard concern, as follows (in the absence of human data suggesting a potential for cancer effects):
Agents not likely to be carcinogenic to humans because they have been evaluated in at least two well conducted studies in two appropriate animal species without demonstrating carcinogenic effects,
Agents not likely to be carcinogenic to humans because they have been appropriately evaluated in animals and show only carcinogenic effects that have been shown not to be relevant to humans (e.g., showing only effects in the male rat kidney due to accumulation of alpha2u-globulin),
Agents not likely to be carcinogenic to humans when carcinogenicity is dose or route dependent. For instance, not likely below a certain dose range (categorized as likely by another route of exposure). To qualify, agents will have been appropriately evaluated in animal studies and the only effects show a dose range or route limitation or a route limitation is otherwise shown by empirical data,
Agents not likely to be carcinogenic to humans based on extensive human experience that demonstrates lack of effect (e.g., phenobarbital).
1999 Draft EPA Weight-of-the Evidence Categories
Carcinogenic to Humans
This descriptor is appropriate when there is convincing epidemiologic evidence demonstrating causality between human exposure and cancer.
This descriptor is also appropriate when there is an absence of conclusive epidemiologic evidence to clearly establish a cause and effect relationship between human exposure and cancer, but there is compelling evidence of carcinogenicity in animals and mechanistic information in animals and humans demonstrating similar mode(s) of carcinogenic action. It is used when all of the following conditions are met:
There is evidence in a human population(s) of association of exposure to the agent with cancer, but not enough to show a causal association, and
There is extensive evidence of carcinogenicity, and
The mode(s) of carcinogenic action and associated key events have been identified in animals, and
The key events that precede the cancer response in animals have been observed in the human population(s) that also shows evidence of an association of exposure to the agent with cancer.
Likely to be Carcinogenic to Humans
This descriptor is appropriate when the available tumor effects other key data are adequate to demonstrate carcinogenic potential to humans. Adequate data are within a spectrum. At one end is evidence for an association between human exposure to the agent and cancer and strong experimental evidence of carcinogenicity in animals; at the other, with no human data, the weight of experimental evidence shows animal carcinogenicity by a mode or modes of action that are relevant or assumed to be relevant to humans.
Suggestive Evidence of Carcinogenicity, but not Sufficient to Assess Human Carcinogenic Potential:
This descriptor is appropriate when the evidence from human or animal data is suggestive of carcinogenicity, which raises a concern for carcinogenic effects but is judged not sufficient for a conclusion as to human carcinogenic potential. Examples of such evidence may include: a marginal increase in tumors that may be exposure-related, or evidence is observed only in a single study, or the only evidence is limited to certain high background tumors in one sex of one species. Dose-response assessment is not indicated for these agents. Further studies would be needed to determine human carcinogenic potential.
Data are Inadequate for an Assessment of Human Carcinogenic Potential
This descriptor is used when available data are judged inadequate to perform an assessment. This includes a case when there is a lack of pertinent or useful data or when existing evidence is conflicting, e.g., some evidence is suggestive of carcinogenic effects, but other equally pertinent evidence does not confirm a concern.
Not Likely to be Carcinogenic to Humans
This descriptor is used when the available data are considered robust for deciding that there is no basis for human hazard concern. The judgement may be used on:
Extensive human experience that demonstrates lack of carcinogenic effect (e.g., phenobarbital)
Animal evidence that demonstrates lack of carcinogenic effect in at least two well-designed and well conducted studies in two appropriate animal species (in the absence of human data suggesting a potential for cancer effects).
Extensive experimental evidence showing that the only carcinogenic effects observed in animals are not considered relevant to humans (e.g., showing only effects in the male rat kidney due to accumulation of a2u-globulin).
Evidence that carcinogenic effects are not likely by a particular route of exposure.
Evidence that carcinogenic effects are not anticipated below a defined dose range.