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The International Agency for Research on Cancer has placed three widely prescribed medicines — hydrochlorothiazide, voriconazole and tacrolimus — in Group 1, its highest category of carcinogenic hazard.
Group 1 means there is sufficient evidence that the agent causes cancer in humans; it is the same category that holds tobacco smoke and asbestos.
Hydrochlorothiazide is linked to non-melanoma skin cancers, particularly squamous cell carcinoma of the skin and lip cancer.
Tacrolimus is associated with non-Hodgkin lymphoma and skin malignancies, while voriconazole acts through a metabolite that makes skin photosensitive.
The evaluation was carried out for Volume 137 of the IARC Monographs, and health authorities have advised patients to continue prescribed treatment and consult their doctors rather than stop medication.
The IARC classifies agents by the strength of the evidence that they can cause cancer, not by how much cancer they actually cause. That distinction is the single most misunderstood point in this story. Group 1 — 'carcinogenic to humans' — says the evidence is conclusive; it says nothing about the size of the risk at ordinary doses. This is why tobacco smoking and processed meat sit in the same group despite wildly different levels of danger. IARC is assessing hazard, the intrinsic capacity to cause harm, whereas risk depends additionally on dose, duration and exposure. For medicines, regulators then weigh that hazard against therapeutic benefit, which is why none of these three drugs has been withdrawn: an untreated organ-transplant rejection or uncontrolled blood pressure kills far more reliably than the elevated skin-cancer risk these drugs carry.
Simple Analogy: A hazard label on a chemical tells you it can burn you; it does not tell you whether a single drop or a full bucket is needed. IARC prints the label; regulators decide the dose.
| Group | Meaning | Example |
|---|---|---|
| Group 1 | Carcinogenic to humans — sufficient evidence in humans | Tobacco smoke, asbestos, and now hydrochlorothiazide, voriconazole and tacrolimus |
| Group 2A | Probably carcinogenic to humans — limited human evidence, sufficient animal evidence | Red meat, high-temperature frying emissions |
| Group 2B | Possibly carcinogenic to humans — limited human evidence and less than sufficient animal evidence | Aloe vera whole leaf extract, pickled vegetables (Asian style) |
| Group 3 | Not classifiable as to carcinogenicity in humans — evidence inadequate | Caffeine, tea |
The specialised cancer agency of the World Health Organization; it conducts and coordinates cancer research and publishes the IARC Monographs, the world's most cited catalogue of carcinogenic hazards
The United Nations specialised agency for international public health, under which the IARC functions
GS Paper 2 > Health; GS Paper 3 > Science and Technology > Developments in Biotechnology and Health
General Awareness > Science > Human Health and International Organisations
General Awareness > General Science > Health
Which one of the following statements is not correct?
Answer: Hepatitis B, unlike Hepatitis C, does not have a vaccine.
An IARC category indicating sufficient evidence that the agent causes cancer in humans; it reflects certainty of hazard, not magnitude of risk.
Hazard is the intrinsic capacity of an agent to cause harm; risk is the probability of harm at a given level of exposure. IARC evaluates hazard.
A class of drugs that increase urinary sodium and water excretion, used to lower blood pressure and reduce oedema; hydrochlorothiazide is the best-known example.
A reaction in which a substance makes skin abnormally sensitive to light, causing damage on sun exposure — the mechanism implicated for voriconazole.
A drug that dampens the immune response, used to prevent transplant rejection; long-term suppression raises the risk of lymphoma and skin cancers.