Identifying carcinogens is one of the most important steps in cancer prevention. Numerous chemicals, environmental factors, radiation, and even some dietary and lifestyle factors can increase the long-term risk of cancer. The International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), is a global leader in identifying and classifying these factors.
Since 1971, the International Agency for Research on Cancer has studied over 1,000 different substances and agents and classified them into four main categories based on scientific evidence. In this article, we examine this classification in detail, provide key examples, and consider its impact on public health.
Technical data of the saltwater purification system
International Agency for Research on Cancer – Classification of Carcinogens
The International Agency for Research on Cancer classifies substances, compounds, processes, and even human actions into four main categories:
1. Group 1: Carcinogenic to humans
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Definition: There is sufficient scientific evidence that this substance directly causes cancer in humans.
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Example:
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Tobacco and cigarette smoke
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asbestos
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benzene
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alcohol
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Air pollution
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Human papillomavirus (HPV)
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Important: By avoiding or reducing exposure to these factors, you can directly reduce your risk of developing certain types of cancer.
2. Group 2A: May be carcinogenic to humans.
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Definition: There is sufficient evidence from animal studies, but only limited evidence from human studies.
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Example:
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Consumption of large amounts of unprocessed red meat
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I work the night shift.
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UV-A rays
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IMPORTANT: Although data on human exposure are limited, caution should be exercised when handling these substances.
3. Category 2B: May cause cancer in humans.
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Definition: There is evidence that the substance is carcinogenic in animals, but there is insufficient evidence that it is carcinogenic in humans.
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Example:
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Aloe Vera (some special extracts)
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a certain concentration of trichloroethylene
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Some radio waves (such as traveling waves, which are still being researched)
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Important: Further studies are needed in this group and long-term exposure to these agents should be approached with caution.
4. Group 3: Not classifiable with regard to its carcinogenicity to humans.
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Definition: There is insufficient data to determine whether the substance causes cancer.
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Example:
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caffeine
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Chlorophyll
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Some medications and chemicals have not yet been fully researched.
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Meaning: This group does not indicate absolute certainty, but rather a lack of scientific evidence.
What is the IARC evaluation process?
The International Agency for Research on Cancer follows a rigorous scientific procedure for classifying pathogens:
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Data collection: Review of epidemiological studies, animal experiments, and molecular data.
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The scientific evaluation is carried out by a panel of experts: a group of international scientists who do not belong to any industry or political party .
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Analysis of human and animal data: Examines the statistical association between exposure to a substance and cancer incidence.
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Publication of results in monograph form : Each report is published in a separate volume and is publicly accessible.
Important examples of known carcinogens
Some important factors classified as carcinogenic by the International Agency for Research on Cancer are:
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Tobacco and passive smoking (secondhand smoking) → cancer of the lung, larynx and pancreas.
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Alcohol → liver cancer, oral cancer , esophageal cancer, breast cancer.
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Asbestos → lung cancer and mesothelioma.
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Air pollution → lung and bladder cancer.
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Ultraviolet (UV) radiation → skin cancer .
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Processed meat (e.g. sausages and hot dogs) → colon cancer.
The public health impact of the International Agency for Research on Cancer classifications
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Guidance for policymakers: Many environmental and occupational health and safety laws are based on this classification.
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Public awareness: People can choose a healthier lifestyle by understanding risk factors.
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Research funding: This category defines research priorities.
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Reducing the global cancer burden: Eliminating or reducing the burden of the first group of factors can significantly reduce cancer incidence.
Criticism and challenges
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General comments: IARC classifications are sometimes interpreted as indicating the severity of risks, when in reality they simply indicate the presence or absence of scientific evidence.
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Conflicts of interest and industry conflicts: Some industries (e.g., tobacco and agriculture) take specific positions on IARC reports .
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Continuous updating is required: as environmental conditions change and new data become available, classifications must be revised.
The difference between “cancer” and “risk level”
There is a misconception that classifying a substance in Group 1 means it poses a high risk . However, the International Agency for Research on Cancer only considers the likelihood of causing cancer , not the actual level of risk.
For example:
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The first group includes both sunlight (UV) and tobacco .
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However, daily smokers are at much greater risk than those who spend only a few minutes in the sun.
Therefore, a distinction must be made between hazard (carcinogenic properties) and risk (actual degree of risk).
Finally
The International Agency for Research on Cancer (IARC) classification of carcinogens is one of the most reliable scientific systems for identifying carcinogens worldwide. This classification includes four main categories:
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Group 1: Carcinogenic to humans
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Group 2A: Probably carcinogenic
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Group 2B: Probably carcinogenic
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Group 3: Not classifiable
This scientific concept plays an important role in the development of health policy, environmental protection , and lifestyle changes. Despite its limitations and criticism, the International Agency for Research on Cancer remains the leading international organization for the identification of carcinogens.
By understanding this classification and reducing the burden of high-risk factors, we can take effective steps to prevent cancer and improve public health.