Benzo[a]pyrene

What is Benzo[a]pyrene?

Benzo[a]pyrene (BaP for short) is a polycyclic aromatic hydrocarbon (PAH) and one of the most thoroughly researched cancer triggers in existence. IARC classifies BaP as a Group 1 carcinogen. It forms anywhere organic material burns incompletely — in tobacco smoke, on grilled meat, in wood-stove soot and in vehicle exhaust.

Why is Benzo[a]pyrene in cigarettes?

During pyrolysis of tobacco constituents, aromatics and phenols form polycyclic compounds with 4 to 7 fused benzene rings — benzo[a]pyrene with five rings is the most important indicator substance of this class. Each cigarette delivers 8 to 40 nanograms of BaP into the mainstream smoke (source: DKFZ). BaP belongs to the tar fraction and deposits exactly where lung cancer typically arises later.

What Benzo[a]pyrene does to your body — short term

BaP causes no noticeable acute symptoms — its action is purely genetic. In the body, BaP is enzymatically converted to reactive epoxides that bind directly to DNA, forming so-called „BaP-DNA adducts“. These adducts disrupt DNA reading during cell division and can lead to mutations — especially in the p53 tumour suppressor gene, which is mutated in the majority of all smoker lung tumours.

What Benzo[a]pyrene does long term

BaP is one of the most important substances behind smokers' lung cancer risk. Studies can trace the typical mutation patterns in the p53 gene directly to BaP-DNA adducts — a rare situation where the molecular damage chain from carcinogen via genetic damage pattern to tumour is gap-free. The effect is dose-dependent, with risks already at very low concentrations.

How it compares

Germany's workplace acceptance concentration for benzo[a]pyrene is 0.00007 mg/m³ (70 ng/m³, TRGS 910) — the tolerance concentration (uppermost acceptable level) sits at 700 ng/m³. Both rank among the lowest workplace limits in existence, because even trace amounts contribute significantly to cancer risk. Concentrations in cigarette smoke exceed these values during the brief seconds of inhalation by orders of magnitude.

Workplace exposure limit: 0.00007 mg/m³ (70 ng/m³ Akzeptanzkonzentration, 700 ng/m³ Toleranzkonzentration, TRGS 910)