Banding carcinogenic risks in developed countries: A procedural basis for qualitative assessment

Our plain-English summary of Banding carcinogenic risks in developed countries: A procedural basis for qualitative assessment, by B.W. Stewart (Mutation Research, 2008).

The study

• Author: B.W. Stewart
• Journal: Mutation Research
• Published: 2008;658(1-2):124-151
• Type of article: Review
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Readily achieved comparative assessment of carcinogenic risks consequent upon environmental exposures may increase understanding and contribute to cancer prevention. Procedures for hazard identification and quantitative risk assessment are established, but limited when addressing novel exposures to previously known carcinogens or any exposure to agents having only suspected carcinogenic activity. To complement other means of data evaluation, a procedure for qualitative assessment of carcinogenic risk is described. This involves categorizing the relevant carcinogen and circumstances under which exposure occurs. The categories for carcinogens are those used for hazard identification and involve whether the agent is (1) a recognized carcinogen for humans; (2) probably or (3) possibly carcinogenic for humans; (4) characterized by inadequate evidence of carcinogenicity; or (5) lacking carcinogenicity. Exposure is categorized by whether it is one which (1) establishes the agent as a recognized carcinogen; (2) is taken into account in establishing carcinogenicity status; (3) is distinct from those providing clearest evidence of carcinogenicity; (4) is not characterized in relation to carcinogenicity; or (5) involves an exposure in which absence of carcinogenic outcome is observed. These two categories of evidence allow the risk inherent in a situation to be banded as indicative of a proven, likely, inferred, unknown or unlikely carcinogenic outcome, and further characterized using sub-bands. The procedure has been applied to about fifty situations. For recognized carcinogens, including asbestos and polycyclic aromatic hydrocarbons, risks consequent upon occupational exposure, the impact of point source pollution, residence near contaminated sites and general environmental exposure are allocated across the proven band and a likely sub-band. For solvents, pesticides and other compounds having less clearly established carcinogenicity, impact on residents living near a production site, or near earlier related industrial activity is allocated to certain inferred sub-bands. Unknown carcinogenic outcome, which identifies exposure to an agent with inadequate evidence of carcinogenicity rather than being indicative of equivocal or negative data in any context, indicates both the impact of certain pollutants and user-exposure to some consumer products. Situations allocated to the unlikely risk band principally involve certain consumer products. Overall, such risk assessment may be of greatest worth in focusing community attention on proven causes of cancer and associated preventive measures.

In plain English

This article, labelled a review, described a procedure for ranking cancer risks qualitatively. Each situation combined an IARC-based category for the evidence that the agent causes cancer with a category for the exposure circumstances, from those that established carcinogenicity to those showing no carcinogenic effect. Situations fell into five bands: proven, likely, inferred, unknown and unlikely carcinogenic outcome. It was applied to more than 50 example situations in developed countries. Assessments drew on IARC and NTP evaluations and published reviews, not fresh appraisals of the studies; the stated innovation was grouping situations with qualitatively similar risks. Occupational asbestos exposure was placed in the proven band. So was living near point sources of asbestos causing extreme local pollution, though some studies failed to establish risk there. Asbestos in drinking water was placed in a likely sub-band and described as reasonably identified with negative studies. Asbestos was noted as consistently linked with mesothelioma. Lower-exposure jobs such as auto mechanics and telephone linemen were not assessed. The author concluded the approach may help reduce confusion and raise awareness of proven cancer prevention measures.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: review proposing a procedure for qualitative (non-numerical) carcinogenic risk assessment, illustrated with example situations
• Who was studied: more than 50 example exposure situations, restricted to situations as they exist in developed countries; no human subjects were studied directly
• Exposure: a wide range of agents (tobacco, alcohol, drugs, radiation, metals, solvents, pesticides, consumer products and others). Asbestos was assessed for occupational inhalation exposure, residence near point sources of pollution, and asbestos in drinking water. No fiber types were specified.
• Main results:
  • Evidence of carcinogenicity was categorized using IARC criteria. Exposure circumstances were categorized from those establishing the agent as a recognized carcinogen to those identifiable with lack of a carcinogenic effect. Some agents had not been evaluated by IARC or NTP.
  • The author stated that the contribution of the tables was grouping situations whose risks are qualitatively similar, not characterizing risk for any particular situation.
  • For several recognized carcinogens, including asbestos, the author placed occupational exposure in the alpha-band (proven carcinogenic outcome) and environmental-pollutant exposures in the beta-band (likely carcinogenic outcome).
  • Residing near point sources causing extreme local pollution, including asbestos, was placed in the alpha-band (proven carcinogenic outcome). The author commented that studies indicate increased risk in local populations, though some fail to establish it.
  • Asbestos in drinking water was placed in sub-band beta2 (a recognized carcinogen in circumstances distinct from those giving the clearest evidence). The route was ingestion and the likely target was given as colo-rectum and possibly other sites. The author's comment cited inference of hazard from bioassay data.
  • The author described drinking water containing asbestos as a situation reasonably identified with negative studies. It was nonetheless excluded from the unknown (delta) band because asbestos is a recognized carcinogen.
  • Across the situations listed in the proven and likely bands, the author noted that asbestos was consistently associated with mesothelioma.
  • The author stated that for asbestos and some other recognized carcinogens, decreasing risk can be correlated with decreasing dose because distinct modes of exposure have been studied.
• The authors' conclusion: The author concluded that a means of describing widely differing cancer risks may help reduce confusion and increase community awareness of proven cancer preventive measures.
• Limitations the authors state:
  • The assessments were derived from existing IARC and NTP evaluations and published reviews, not from fresh appraisals of the underlying data for each situation.
  • The procedure relies heavily on epidemiological data and has limited power to discriminate when only experimental data exist.
  • Only situations in developed countries were considered.
  • The tables are examples, not a complete listing.
  • Jobs with lower levels of asbestos exposure, such as auto mechanics and telephone linemen, were not addressed.
  • Band allocations depend on the data currently available and must be reviewed as new data are published.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Environmental Exposure, Occupational Exposure.

Related studies

• Geological occurrence, mineralogical characterization, and risk assessment of potentially carcinogenic erionite in Italy — M. Giordani, M. Mattioli, et al. (2017)
• Transfer of occupational health problems from a developed to a developing country: lessons from the Japan-South Korea experience — J. Park, N. Hisanaga, et al. (2009)
• Sources of uncertainty in dose-response modeling of epidemiological data for cancer risk assessment — L. Stayner, A.J. Bailer, et al. (1999)
• Occupational exposures and cancer: a review of agents and relative risk estimates — C. Marant Micallef, K.D. Shield, et al. (2018)
• Does qualitative examination of Elongated Mineral Particles (EMP) recovered from human and animal lungs provide reliable information on their carcinogenic and other effects? — B.W. Case (2018)
• Pleural mesothelioma and occupational and non-occupational asbestos exposure: a case-control study with quantitative risk assessment — D. Ferrante, D. Mirabelli, et al. (2016)

Browse more research in Mutation Research, or return to medical research.