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A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis, the formation of cancer.
There are multiple classifications for carcinogenic compounds, depending on their mechanism.
The International Agency for Research on Cancer (IARC) classifies carcinogens into four groups:
- Group 1: Carcinogenic to humans
- Group 2A: Probably carcinogenic to humans
- Group 2B: Possibly carcinogenic to humans
- Group 3: Not classifiable as to its carcinogenicity to humans
- Group 4: Probably not carcinogenic to humans
One classification separates them into genotoxic or nongenotoxic:
- Genotoxins cause irreversible genetic damage or mutations by binding to DNA. Genotoxins include chemical agents like N-nitroso-N-methylurea (NMU) or non-chemical agents such as ultraviolet light and ionizing radiation. Certain viruses can also act as carcinogens by interacting with DNA.
- Nongenotoxins do not directly affect DNA but act in other ways to promote growth. These include hormones and some organic compounds.
- Aldehydes: formaldehyde, acetaldehyde, etc.
- Aromatics: benzene, phenol, etc.
- Ethers: dioxane, ethylene oxide, etc.
- Halocarbons: dichloromethane, chloroform, carbon tetrachloride, methyl iodide, ethyl iodide, etc.
- Metals: beryllium, cadmium, thallium, etc.
- Mycotoxins: aflatoxin, etc.
- Radioactives: radium, radon, uranium, etc.
- Other: asbestos, crystalline silica gel, hexavalent chromium, hydrazine, etc.
How to limit contact with carcinogenic substances in the lab
- Have adequate ventilation
- Wear proper protection in the lab (protection gloves, white coat, respirator/gas mask)
- Work outside or in a fume hood
- Try to work with them only a few times per month or year
- Avoid working with volatile carcinogenic reagents, limit yourself to non-volatile ones