Use of human and animal data

Under 1990.143(a) a single positive human epidemiologic study (or more) will be used to establish the qualitative inference that a substance poses a carcinogenic hazard to workers (Positive human studies).

• This means OSHA will rely on positive human evidence even if other evidence is limited.
• If you want to challenge reliance on a specific human study, you must meet the criteria for consideration in 1990.144.

Yes — under 1990.143(b) positive results in one or more experimental studies in one or more mammalian species will be used to establish the qualitative inference of carcinogenic hazard to workers (Positive animal studies).

• OSHA relies on well-conducted mammalian studies to identify potential workplace carcinogens.
• Arguments against relying on such animal evidence must meet the criteria in 1990.144.

Yes — under 1990.143(c) OSHA will generally use positive results from human or mammalian studies to identify potential occupational carcinogens even when non‑positive human studies exist (Non-positive human studies).

• Non‑positive human studies will be considered by the Secretary only if those studies meet the criteria in 1990.144(a).

Yes — under 1990.143(d) positive results in one or more mammalian studies will be used for qualitative identification of potential occupational carcinogens even if non‑positive studies exist in other species (Non-positive animal studies).

• However, if both positive and non‑positive studies exist within the same species, OSHA will evaluate the non‑positive results as part of its assessment.

OSHA will use positive results that show induction or acceleration of tumors that occur “spontaneously” in unexposed individuals as evidence for qualitative identification of a potential occupational carcinogen (Spontaneous tumors).

• In plain terms: even if a tumor type can occur naturally, if a substance increases its occurrence or speeds its appearance in studies, OSHA will count that as evidence.

Yes — under 1990.143(f)(1) OSHA will use positive results from studies where mammals were exposed via the oral, respiratory, or dermal routes to identify potential occupational carcinogens (Routes of exposure).

• This applies whether tumors appeared at the exposure site or at sites distant from it.

Yes — under 1990.143(f)(2) positive results in studies where tumors occur at sites distant from the site of administration will be used to identify potential occupational carcinogens (Distant-site tumors).

• This means systemic effects demonstrated in animals are relevant even when they are not localized to the exposure point.

Under 1990.143(f)(3)(i) such studies will be treated as “concordant” evidence that a substance is a potential occupational carcinogen, and per 1990.143(f)(3)(ii) arguments against relying on those studies must meet the criteria in 1990.144(b).

• In short: even non-occupational administration routes that produce tumors at the administration site can support an inference of hazard unless successfully challenged under the specified criteria.

Yes — under 1990.143(g) positive carcinogenicity results from mammals exposed to high doses will be used to establish a qualitative inference of hazard to workers (Use of high doses in animal testing).

• If you want to argue such high-dose studies are not relevant, that challenge must meet the criteria in 1990.144(d).

No — under 1990.143(h) OSHA will not determine that a threshold or no‑effect level exists for carcinogens in general or for any specific substance ("Threshold" or "No-effect" Levels).

• This means OSHA does not assume there is a safe low level of exposure for carcinogens without specific and convincing evidence meeting the administrative criteria.

Yes — under 1990.143(i) results based on induction of benign tumors, malignant tumors, or both will be used to establish a qualitative inference of carcinogenic hazard to workers (Benign tumors).

• To argue that benign tumors do not present a carcinogenic risk, the proffered evidence must meet the criteria in 1990.144(e).

No — under 1990.143(j) statistical evaluation will be used in determining whether results provide positive evidence for carcinogenicity, but it will not be the exclusive means of evaluation (Statistical evaluation).

• OSHA considers the totality of evidence, including study design, biological plausibility, dose‑response patterns, and other scientific factors in addition to statistics.

Yes — under 1990.143(k) a substance that is metabolized in mammals to yield one or more potential occupational carcinogens will itself be identified and classified as a potential occupational carcinogen (Carcinogenicity of metabolites).

• Evidence of such metabolism will normally come from in vivo mammalian studies, although in vitro mammalian tissue studies may be used in appropriate circumstances.
• Challenges to the relevance of in vivo metabolic evidence must meet the criteria in 1990.144(c).

Arguments that positive results in mammalian species should not be relied upon will be considered only if the supporting evidence meets the criteria in 1990.144(c) or 1990.144(f).

• In practice this means you must present high‑quality, specific evidence that directly addresses the relevance, reliability, or applicability of the mammalian data according to the procedural criteria set out in those sections.

When positive and non‑positive studies exist in the same species, 1990.143(d) says OSHA will evaluate the non‑positive results as part of its assessment (Non-positive animal studies in same species).

• That evaluation looks at study quality, design differences, and whether the non‑positive findings are robust enough to change the overall inference.

Employers can make that argument, but under 1990.143(g) positive results from high‑dose animal studies will be used to infer hazard unless the challenge satisfies the criteria in 1990.144(d).

• To succeed you must submit evidence meeting the procedural and substantive requirements in 1990.144(d) that show the high‑dose results are not applicable to human occupational exposures.

Yes — 1990.143(j) states that statistical evaluation will be used in determining whether results in human, animal, or short‑term studies provide positive evidence for carcinogenicity, so short‑term and mechanistic data are part of the weight‑of‑evidence approach (Statistical evaluation and short‑term studies).

• OSHA does not rely solely on short‑term studies, but they can support or clarify findings from longer‑term animal or human studies.

Non‑positive human studies will be considered by the Secretary only if those studies meet the criteria outlined in 1990.144(a).

• If you want OSHA to give weight to a non‑positive human study, present the study and supporting evidence in the format and with the detail required by 1990.144(a) so it can be formally considered.