Hydroquinone
EU-banned in skin-whitening cosmetics — present in every cigarette.
At a glance
- Also known as
- Hydrochinon · 1,4-Dihydroxybenzol
- CAS number
- 123-31-9
- Toxicity
Medium
- Carcinogenic
- Not classified for cancer
- In cigarette smoke
- 40-90 μg per cigarette (DKFZ)
What is Hydroquinone?
Hydroquinone (1,4-dihydroxybenzene) is the para-isomer of catechol and chemically closely related. The IARC classifies hydroquinone as Group 3 („not classifiable for cancer“) — data is insufficient for a clear human carcinogen classification, although animal studies show hints. In cosmetics, hydroquinone is largely EU-banned.
Why is Hydroquinone in cigarettes?
Like catechol, hydroquinone also forms during pyrolysis of plant phenols in tobacco. Each cigarette delivers 40 to 90 micrograms of hydroquinone into the mainstream smoke (source: DKFZ). Hydroquinone and catechol typically appear together — both are oxidised to quinones and contribute to the oxidative burden on lung cells.
What Hydroquinone does to your body — short term
Acutely, hydroquinone acts as a skin lightener because it inhibits melanin production — exactly this effect made it the main component of whitening creams in many countries for decades. On the airways it irritates mucous membranes and can cause eye irritation. At cigarette-smoke quantities these acute symptoms are not perceptible.
What Hydroquinone does long term
Chronic hydroquinone exposure on skin can lead to ochronosis — paradoxical darkening of the treated skin areas through pigment deposition. Via the airways, long-term effect in the tobacco context is hard to separate from general phenol exposure but contributes to kidney damage and oxidative stress in the lung. At high doses, hydroquinone also has inhibitory effects on blood formation.
Where else do you know Hydroquinone from?
Hydroquinone was for decades the main active ingredient in skin-whitening creams used en masse in African, Asian, and some Latin American markets. The EU has banned hydroquinone in cosmetic whiteners since 2001 (with exceptions only in salon and nail-art products); in many other countries it remains on the market. Industrially it's a photographic developer and antioxidant in plastics.
How it compares
Germany's workplace exposure limit for hydroquinone is 2 mg/m³ (DFG MAK 2023). The amounts per cigarette fall well below this in absolute terms — what matters here is the combination with catechol and other phenols, whose effects add up.
Workplace exposure limit: 2 mg/m³ (DFG MAK 2023)
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