General Provisions on Occupational Carcinogens
The problem of chemical exposure in the workplace remains one of the key issues in occupational hygiene. Historical data from the World Health Organization (WHO) Expert Committee published in 1963 emphasize the scale of the problem: approximately 3/4 of all tumor diseases in humans are associated with prolonged contact with chemical carcinogens present in the environment and the workplace.
In addition, as part of the prevention of any occupational injuries (including contact with caustic substances), basic sanitary and hygienic rules must be observed. For example, if the skin is contaminated, specialized cleaning is required: thus, lime dust must be thoroughly removed using oil, after which the worker must take a warm shower and completely change underwear and work clothes.
Classification of carcinogenic factors by IARC: Groups 1 and 2
To systematize knowledge about carcinogenic hazards, the International Agency for Research on Cancer (IARC), founded in 1965 as a specialized WHO body, developed a clear grading system. All studied agents are divided into four main categories depending on the degree of evidence of their hazard.
Group 1: Carcinogenic to humans This category includes certain chemical compounds, groups of compounds, as well as industrial processes and natural exposures whose danger has been scientifically and clinically confirmed. Typical representatives include:
- 4-aminodiphenyl and 2-naphthylamine;
- Arsenic, chromium, and their compounds;
- Asbestos and vinyl chloride;
- Benzene and benzidine;
- Bis(chloromethyl) ether and chloromethyl methyl ether (technical grade);
- Sulfur mustard, as well as various soot, tars, and mineral oils.
Group 2A: Probably carcinogenic to humans This includes factors with a high degree of probability of causing oncological pathology. The list includes:
- Acrylonitrile and benz(a)pyrene;
- Beryllium, nickel, and some of their compounds;
- Diethyl sulfate and dimethyl sulfate;
- o-Toluidine.
Groups 2B, 3, and 4 according to the IARC classification
Group 2B: Possibly carcinogenic to humans This group includes an extensive list of agents for which there is a possibility of a carcinogenic effect, though the evidence base is less convincing than for Group 2A. Examples of substances:
- Amitrole, auramine (technical grade), benzotrichloride;
- Cadmium and its derivatives;
- Halogenated derivatives: carbon tetrachloride, chloroform, chlorophenols (occupational exposure), epichlorohydrin;
- Pesticides and industrial chemicals: DDT, dibromoethane, ethylene oxide, ethylene urea;
- Formaldehyde (gas) and hydrazine;
- Polychlorinated biphenyls and a number of other compounds.
Group 3: Not classifiable In this section, IARC experts place those factors and substances for which insufficient reliable scientific or epidemiological data have been gathered to date. Consequently, they cannot yet be unequivocally classified in terms of their carcinogenicity to the human body.
Group 4: Probably not carcinogenic to humans This is a rare category of agents for which there is reliable and convincing evidence of a complete lack of carcinogenic properties in humans. Currently, according to IARC experts, only one substance is assigned to this group — caprolactam.
Hygienic regulation in the Russian Federation
State sanitary and epidemiological supervision pays close attention to monitoring the factors of the working environment. On the territory of the Russian Federation, the fundamental regulatory document in this area is GN 1.1.725-98.
This document is entitled "List of substances, products, industrial processes, household and natural factors carcinogenic to humans". It is important to note that the methodological basis for developing this hygienic standard included both official materials from the International Agency for Research on Cancer (IARC) and numerous fundamental research results obtained by domestic hygiene scientists.
Briefly: answers to topical questions
Which classes of chemical substances are industrial methemoglobin formers?
Industrial methemoglobin formers include aniline derivatives, as well as nitrites and nitrates.
- Aniline and its derivatives — cause impaired oxygen transport and utilization.
- Nitrites — oxidize iron in hemoglobin, forming methemoglobin.
- Nitrates (e.g., nitroglycerin, saltpeter) — lead to pronounced cyanosis due to the development of methemoglobinemia.
What is the mechanism of hemic hypoxia development upon exposure to methemoglobin formers?
The mechanism of hypoxia development consists in the oxidation of iron in hemoglobin under the action of strong oxidizers. The iron charge changes from Fe(II) to Fe(III), resulting in the formation of methemoglobin. Hemoglobin loses its ability to bind and transport oxygen, leading to hypoxia.
Which antidotes are included in the treatment regimen for acute methemoglobin former intoxication?
Methylthioninium chloride is used as a specific antidote for poisoning by methemoglobin formers (aniline, nitrites).
- Methylthioninium chloride (Methylthioninii chloridum) — methylene blue.
The drug is administered intravenously in a glucose solution at low concentrations. In oxidation-reduction reactions, it acts as a donor or acceptor of hydrogen ions, successfully reducing oxidized methemoglobin back to normal hemoglobin.
Which organs and systems, besides blood, are targets in chronic methemoglobin former intoxication?
In addition to blood, exposure to methemoglobin formers can affect the liver and the urinary system.
- Liver — toxic hepatitis develops, characterized by damage to the liver parenchyma as a result of poison metabolism; aniline is among the causes.
- Urinary bladder and upper urinary tract — aromatic amines, in particular benzidine and 2-naphthylamine, possess carcinogenic resorptive action and can cause bladder cancer; benzidine and β-naphthylamine are also associated with the risk of upper urinary tract urothelial cancer.
Which methemoglobin-forming amino compounds belong to Group 1 carcinogens according to the IARC classification?
According to the IARC classification, Group 1 carcinogens — carcinogenic to humans — include:
- 4-aminodiphenyl;
- benzidine;
- 2-naphthylamine.
What individual prevention measures are used to prevent percutaneous poisoning by methemoglobin formers?
To prevent poison absorption through percutaneous contact, emergency decontamination and sanitary treatment measures are used.
- Skin cleansing — careful washing of the skin with warm soapy water or taking a warm shower is necessary.
- Changing clothes — it is mandatory to change underwear and work clothes.
It is strictly forbidden to rub the skin while washing, as this can provoke hyperemia and increased toxin absorption.
Class and exam questions
In what year was the International Agency for Research on Cancer (IARC) established?
IARC was established in 1965 as a specialized agency within the World Health Organization (WHO).
Which substances are classified in Group 1 by IARC experts?
Group 1 includes agents that are definitely carcinogenic to humans. Examples include asbestos, arsenic, benzene, vinyl chloride, chromium, soot, and mineral oils.
What is included in Group 4 according to the IARC classification?
Group 4 includes agents for which there is evidence of lack of carcinogenicity to humans. Currently, experts place only caprolactam in this category.
Which document regulates carcinogens in Russia?
In the Russian Federation, the regulatory document GN 1.1.725-98 is in effect, developed on the basis of IARC materials and the works of domestic scientists.
What else to study on this topic
- Detailed analysis of the chemical properties of Group 1 compounds
- Differences between probable (2A) and possible (2B) carcinogens
- Sanitary requirements and structure of the GN 1.1.725-98 document
- Mechanisms of action of industrial resins and mineral oils
- Prevention and cleansing of the skin from specific industrial dust
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