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ON CANCER, |
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The cry of carcinogen is raised often by the dollar drive press or
the regulatory crazed OSHA. Thus California Skeptics has only written on the
most significant causes (obesity, air quality, and tobacco). We would like to
look into occupational trades (especially painting and automotive) but have not at present the time to properly research them. Industries who fear regulations published studies for the sake of undermining the
credibility of valid, published studies. Thus research is made arduous. Below is an excellent listing of standards of evaluation, from http://monographs.iarc.fr/monoeval/eval.html. |
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Evaluations of the strength of the evidence for carcinogenicity arising from human and experimental
animal data are made, using standard terms. It is recognized that the criteria for these evaluations, described below, cannot encompass all of
the factors that may be relevant to an evaluation of carcinogenicity. In considering all of the relevant scientific data,
the Working Group may assign the agent, mixture or exposure circumstance to a higher or lower category than a strict interpretation
of these criteria would indicate. (a) Degrees of evidence for carcinogenicity in humans and in experimental animals and supporting
evidence These categories refer only to the strength of the evidence that an exposure is carcinogenic and not
to the extent of its carcinogenic activity (potency) nor to the mechanisms involved. A classification may change as new information
becomes available. An evaluation of degree of evidence, whether for a single agent or a mixture, is limited to the materials
tested, as defined physically, chemically or biologically. When the agents evaluated are considered by the Working Group to
be sufficiently closely related, they may be grouped together for the purpose of a single evaluation of degree of evidence.
(i) Carcinogenicity in humans The applicability of an evaluation of the carcinogenicity of a mixture, process, occupation or industry
on the basis of evidence from epidemiological studies depends on the variability over time and place of the mixtures, processes,
occupations and industries. The Working Group seeks to identify the specific exposure, process or activity which is considered
most likely to be responsible for any excess risk. The evaluation is focused as narrowly as the available data on exposure
and other aspects permit. The evidence relevant to carcinogenicity from studies in humans is classified into one of the following
categories: Sufficient evidence of carcinogenicity: The Working Group considers that a causal relationship has been established between exposure
to the agent, mixture or exposure circumstance and human cancer. That is, a positive relationship has been observed between
the exposure and cancer in studies in which chance, bias and confounding could be ruled out with reasonable confidence. Limited evidence of carcinogenicity: A positive association has been observed between exposure to the agent, mixture or exposure
circumstance and cancer for which a causal interpretation is considered by the Working Group to be credible, but chance, bias
or confounding could not be ruled out with reasonable confidence. Inadequate evidence of carcinogenicity: The available studies are of insufficient quality, consistency or statistical power to
permit a conclusion regarding the presence or absence of a causal association between exposure and cancer, or no data on cancer
in humans are available. Evidence suggesting lack of carcinogenicity: There are several adequate studies covering the full range of levels of exposure that
human beings are known to encounter, which are mutually consistent in not showing a positive association between exposure
to the agent, mixture or exposure circumstance and any studied cancer at any observed level of exposure. A conclusion of 'evidence
suggesting lack of carcinogenicity' is inevitably limited to the cancer sites, conditions and levels of exposure and length
of observation covered by the available studies. In addition, the possibility of a very small risk at the levels of exposure
studied can never be excluded. In some instances, the above categories may be used to classify the degree of evidence related to carcinogenicity
in specific organs or tissues. (ii) Carcinogenicity in experimental animals The evidence relevant to carcinogenicity in experimental animals is classified into one of the following
categories: Sufficient evidence of carcinogenicity: The Working Group considers that a causal relationship has been established between the
agent or mixture and an increased incidence of malignant neoplasms or of an appropriate combination of benign and malignant
neoplasms in (a) two or more species of animals or (b) in two or more independent studies in one species carried out at different
times or in different laboratories or under different protocols. Exceptionally, a single study in one species might be considered to provide sufficient evidence of
carcinogenicity when malignant neoplasms occur to an unusual degree with regard to incidence, site, type of tumour or age
at onset. Limited evidence of carcinogenicity: The data suggest a carcinogenic effect but are limited for making a definitive evaluation
because, e.g. (a) the evidence of carcinogenicity is restricted to a single experiment; or (b) there are unresolved questions
regarding the adequacy of the design, conduct or interpretation of the study; or (c) the agent or mixture increases the incidence
only of benign neoplasms or lesions of uncertain neoplastic potential, or of certain neoplasms which may occur spontaneously
in high incidences in certain strains. Inadequate evidence of carcinogenicity: The studies cannot be interpreted as showing either the presence or absence of a carcinogenic
effect because of major qualitative or quantitative limitations, or no data on cancer in experimental animals are available.
Evidence suggesting lack of carcinogenicity: Adequate studies involving at least two species are available which show that, within
the limits of the tests used, the agent or mixture is not carcinogenic. A conclusion of evidence suggesting lack of carcinogenicity
is inevitably limited to the species, tumour sites and levels of exposure studied. (b) Other data relevant to the evaluation of carcinogenicity and its mechanisms Other evidence judged to be relevant to an evaluation of carcinogenicity and of sufficient importance
to affect the overall evaluation is then described. This may include data on preneoplastic lesions, tumour pathology, genetic
and related effects, structure-activity relationships, metabolism and pharmacokinetics, physicochemical parameters and analogous
biological agents. Data relevant to mechanisms of the carcinogenic action are also evaluated. The strength of the evidence
that any carcinogenic effect observed is due to a particular mechanism is assessed, using terms such as weak, moderate or
strong. Then, the Working Group assesses if that particular mechanism is likely to be operative in humans. The strongest indications
that a particular mechanism operates in humans come from data on humans or biological specimens obtained from exposed humans.
The data may be considered to be especially relevant if they show that the agent in question has caused changes in exposed
humans that are on the causal pathway to carcinogenesis. Such data may, however, never become available, because it is at
least conceivable that certain compounds may be kept from human use solely on the basis of evidence of their toxicity and/or
carcinogenicity in experimental systems. For complex exposures, including occupational and industrial exposures, the chemical composition and
the potential contribution of carcinogens known to be present are considered by the Working Group in its overall evaluation
of human carcinogenicity. The Working Group also determines the extent to which the materials tested in experimental systems
are related to those to which humans are exposed. (c) Overall evaluation Finally, the body of evidence is considered as a whole, in order to reach an overall evaluation of
the carcinogenicity to humans of an agent, mixture or circumstance of exposure. An evaluation may be made for a group of chemical compounds that have been evaluated by the Working
Group. In addition, when supporting data indicate that other, related compounds for which there is no direct evidence of capacity
to induce cancer in humans or in animals may also be carcinogenic, a statement describing the rationale for this conclusion
is added to the evaluation narrative; an additional evaluation may be made for this broader group of compounds if the strength
of the evidence warrants it. The agent, mixture or exposure circumstance is described according to the wording of one of the following
categories, and the designated group is given. The categorization of an agent, mixture or exposure circumstance is a matter
of scientific judgement, reflecting the strength of the evidence derived from studies in humans and in experimental animals
and from other relevant data. This category is used when there is sufficient evidence of carcinogenicity in humans. Exceptionally,
an agent (mixture) may be placed in this category when evidence of carcinogenicity in humans is less than sufficient but there
is sufficient evidence of carcinogenicity in experimental animals and strong evidence in exposed humans that the agent
(mixture) acts through a relevant mechanism of carcinogenicity. This category includes agents, mixtures and exposure circumstances for which, at one extreme, the degree
of evidence of carcinogenicity in humans is almost sufficient, as well as those for which, at the other extreme, there are
no human data but for which there is evidence of carcinogenicity in experimental animals. Agents, mixtures and exposure circumstances
are assigned to either group 2A (probably carcinogenic to humans) or group 2B (possibly carcinogenic to humans) on the basis
of epidemiological and experimental evidence of carcinogenicity and other relevant data. This category is used when there is limited evidence of carcinogenicity in humans and sufficient
evidence of carcinogenicity in experimental animals. In some cases, an agent (mixture) may be classified in this category
when there is inadequate evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in
experimental animals and strong evidence that the carcinogenesis is mediated by a mechanism that also operates in humans.
Exceptionally, an agent, mixture or exposure circumstance may be classified in this category solely on the basis of limited
evidence of carcinogenicity in humans. This category is used for agents, mixtures and exposure circumstances for which there is limited
evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals.
It may also be used when there is inadequate evidence of carcinogenicity in humans but there is sufficient evidence
of carcinogenicity in experimental animals. In some instances, an agent, mixture or exposure circumstance for which there
is inadequate evidence of carcinogenicity in humans but limited evidence of carcinogenicity in experimental
animals together with supporting evidence from other relevant data may be placed in this group. This category is used most commonly for agents, mixtures and exposure circumstances for which the evidence
of carcinogenicity is inadequate in humans and inadequate or limited in experimental animals. Exceptionally, agents (mixtures) for which the evidence of carcinogenicity is inadequate in
humans but sufficient in experimental animals may be placed in this category when there is strong evidence that the
mechanism of carcinogenicity in experimental animals does not operate in humans. Agents, mixtures and exposure circumstances that do not fall into any other group are also placed in
this category. This category is used for agents or mixtures for which there is evidence suggesting lack of carcinogenicity
in humans and in experimental animals. In some instances, agents or mixtures for which there is inadequate evidence
of carcinogenicity in humans but evidence suggesting lack of carcinogenicity in experimental animals, consistently
and strongly supported by a broad range of other relevant data, may be classified in this group. Last updated: |
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