Reducing Environmental and Occupational Cancer Risks Toolkit


Authoritative Scientific Reviews and Classifications of Carcinogens

There are dozens of known and suspected environmental risk factors for cancer, based on authoritative reviews of the available scientific evidence, including those published by the World Health Organization’s International Agency for Research on Cancer (IARC) and the U.S. National Toxicology Program’s (U.S. NTP) Report on Carcinogens. These scientific institutions convene panels of experts to review published studies and assess the strength of the evidence that an agent can cause cancer in humans. As of this writing, IARC has evaluated ~1,000 agents (drugs, industrial chemicals, exposure circumstances, among others), while the U.S. NTP has evaluated ~100 in its Report on Carcinogens.

See here the growing number of agents/substances evaluated by IARC and their classifications..

Authoritative Evidence Resources

Has a chemical/agent of interest to your cancer coalition been classified as it its carcinogenicity? Screen using these resources:

Although screening techniques may be used to simply understand whether a given environmental agent has been reviewed and classified (search by name or Chemical Abstract Service (CAS) number), those agents classified have detailed summaries of the evidence. For IARC, review the associated Monograph. For U.S. NTP’s Report on Carcinogens, read the substance profiles

New reviews are undertaken every year to reevaluate agents based on new evidence and to evaluate new agents/substances. In the US, over 3,000 High Production Volume chemicals (defined as manufactured or imported in amounts greater or equal to 1 million pounds). The vast majority are untested regarding carcinogenicity. 

  • Industrial chemicals (e.g., benzene, formaldehyde, trichloroethylene) 
  • Mineral dusts (e.g., asbestos, silica)
  • Heavy metals (e.g., arsenic, beryllium, cadmium)
  • Radioactive substances (e.g., uranium, radium, radon)
  • Combustion products (e.g., particulate matter, diesel exhaust, polyaromatic hydrocarbons (PAHs))

Much of the evidence supporting classification as a “known human carcinogen” tends to be from studies of exposures in the workplace, with some exceptions. Yet these same agents are released into the air and water as contaminants because of industrial emissions and disposal, and they remain in consumer products. Environmental epidemiologic studies continue to demonstrate increased cancer risks from exposures in non-occupational settings. Click the image below to see examples of such studies.

Although authoritative scientific entities such as the U.S. NTP and IARC issue classifications of carcinogens based on the state of the science at the time of their review, hundreds of new studies are published monthly that examine emerging chemicals of concern, adding to the base of knowledge about associated cancer risks.

To explore a range of research investigating environmental and occupational cancer risk factors over the last 5-years, see the following searches in PubMed. These general searches include some articles that address health outcomes other than cancer. 

Having the most up-to-date information about environmental exposures is important. There are numerous chemicals used in industrial manufacturing, agriculture, and in consumer products that have been identified as potential cancer risks. These include flame retardants, per- and polyfluorinated alkyl substances (PFAS), pesticides and other agricultural chemicals, and endocrine disrupting chemicals, such as phthalates (which are used in hundreds of products, from personal care products to vinyl flooring). These chemicals are ubiquitous given the products and places where they are used, so many residents in our states may be exposed.

Recordings of recent conferences focused on the science linking cancer with environmental and occupational exposures are valuable resources.

Why are there some studies that show elevated risks of cancer from a specific occupational and environmental exposure and others that don’t? Does it matter who funded the research? YES.

There are two primary funders of scientific research related to environmental and occupational health – (1) governments and (2) corporations. Evidence demonstrates clear ties between studies with results that favor commercial and industrial entities and corporate sources of funding, including well-documented examples of the chemical industry conducting research to deny, ignore, or marginalize the adverse health effects caused by chemicals they produce. Examples include industry interference in the science concerning health impacts from asbestos, lead, endocrine-disrupting chemicals and pesticides, glyphosate/Roundup, and atrazine. This strategic interference in science has its origins in the tobacco industry, which sowed confusion and uncertainty about the science documenting harms to public health over many years.

It is important to be a discerning reviewer of the science. Look at the affiliations of the authors. Look to see who funded the research as most journals (but not all) require disclosures of financial conflicts of interest. Use this knowledge to help interpret results in studies you are reviewing.

For more nuance on this topic, watch a talk by Dr. David Michaels, former Administrator of the Occupational Safety and Health Administration (OSHA) and author of two books, Doubt is Their Product and the Triumph of Doubt exploring the industry’s influence on the science and policy of public health.

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