Pyridine
Sounds harmless — smells foul — clings to your sweater.
At a glance
- Also known as
- Azabenzol · Azin
- CAS number
- 110-86-1
- Toxicity
Medium
- Carcinogenic
- Not classified for cancer
- In cigarette smoke
- 6-30 μg per cigarette (DKFZ)
What is Pyridine?
Pyridine is a nitrogen-containing ring compound with a characteristic fishy-pungent smell. It's one of the most important heterocyclic solvents in chemistry. In tobacco smoke it forms as a pyrolysis product from nicotine and other nitrogen-containing components — and is one of the main contributors to the persistent smell of stale smoke in clothing and furniture.
Why is Pyridine in cigarettes?
When heated, nicotine partly breaks down into smaller nitrogen-containing fragments, including pyridine. Each cigarette delivers 6 to 30 micrograms of pyridine into the mainstream smoke (source: DKFZ). Pyridine has an extremely low odour threshold — nanogram traces are enough to contaminate fabrics and hair noticeably. It's the actual „ashtray smell“ in a room.
What Pyridine does to your body — short term
At cigarette-smoke quantities, pyridine causes no noticeable acute symptoms. At higher concentrations it irritates mucous membranes, can trigger nausea and headache, and acts mildly on the central nervous system. Pyridine is broken down by the liver — chronic high exposure has been linked to liver function disturbances, but only in industrial exposure situations.
What Pyridine does long term
Pyridine itself isn't clearly carcinogenic (IARC Group 3, inadequate data), but it contributes to the general burden on liver and nervous system. More important than direct toxicity is its role as sensory marker: anyone who smells pyridine has already inhaled it — and that applies to passive smokers too. Pyridine is one of the prime suspects behind the health effects of „third-hand smoke“ (smoke smell in textiles, furniture, hair).
Where else do you know Pyridine from?
Pyridine is used industrially as a solvent for dyes, plastics and pharmaceuticals and is part of pesticide synthesis steps. In food chemistry it appears as a trace component of the Maillard reaction — the browning process when roasting meat or baking produces small amounts. But the main exposure most people get in daily life comes from tobacco smoke.
How it compares
Germany's DFG MAK Commission has currently suspended the workplace limit for pyridine because the data is considered insufficient for a safe value; historically the limit was 16 mg/m³ (5 ppm). The amounts per cigarette are small but are the main reason smoke smell persists so stubbornly and is detectable in exhaled air hours after the last cigarette.
Workplace exposure limit: DFG MAK derzeit ausgesetzt (unzureichende Datenlage); historisch 16 mg/m³ (5 ppm)
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