PAHs : from chimney soot
to occupational cancer

The first toxic fumes

Ancient civilisations burned wood and coal for heating and metallurgy. Soot deposits in dwellings and workshops already exposed populations to polycyclic aromatic hydrocarbons (PAHs), though the danger went unrecognised.

Percivall Pott — the first occupational cancer in history

British surgeon Percivall Pott publishes his observations on scrotal cancer in London chimney sweeps. These young boys, sent up chimneys from the age of 4, developed tumours after 20 to 25 years of exposure to soot. This is the first time a cancer was linked to an environmental exposure — and the first occupational cancer ever documented.

Source : Chirurgical Observations, Percivall Pott, 1775

The Chimney Sweepers Act

In direct response to Pott's work, the British Parliament passes the Chimney Sweepers Act, banning the employment of children under 8 as chimney sweeps. It is one of the first worker-protection laws inspired by medical research.

Source : Parlement britannique, 1788

The coal tar era

The Industrial Revolution multiplied gasworks, coking plants, and foundries. Coal tar, a massive by-product of gas lighting manufacture, was used to waterproof roofs, pave roads, and protect timber. Every major city had its gasworks, creating thousands of PAH-contaminated sites.

Scrotal cancer recognised as an occupational disease

A century after Pott, scrotal cancer is officially recognised as an occupational disease in Great Britain for workers exposed to soot, coal tar, and mineral oils. Recognition comes a century too late for thousands of victims.

Source : Factory and Workshop Act, 1875

Yamagiwa and Ichikawa — experimentally induced cancer

Japanese researchers Katsusaburō Yamagiwa and Kōichi Ichikawa succeed for the first time in inducing cancer in the laboratory by applying coal tar to rabbits' ears for several months. This fundamental experiment proves that chemical substances can directly cause cancer.

Source : Tokyo Imperial University, 1915

Ernest Kennaway identifies benzo[a]pyrene

British biochemist Ernest Kennaway and his team at the Cancer Hospital Research Institute isolate benzo[a]pyrene (BaP) from coal tar and demonstrate that it causes cancer in mice. It is the first pure chemical carcinogen ever identified. Cook, Hewett and Hieger confirm its structure in 1933. BaP would become the benchmark among the 16 priority PAHs.

Source : Cook, Hewett & Hieger, Journal of the Chemical Society, 1933

Tarred roads and mass exposure

The post-war period saw a massive expansion of the road network. Coal tar was widely used as a binder in road asphalt. Construction workers, asphalt layers, and roofers were exposed daily to high concentrations of PAHs, without any protection.

PAHs identified in cigarette smoke

Research demonstrates that tobacco smoke contains more than 500 different PAHs, including benzo[a]pyrene. A smoker inhales approximately 0.26 µg of BaP per pack of 20 cigarettes. PAHs are identified as one of the main carcinogenic agents in tobacco smoke — the first chemical carcinogen isolated from cigarettes.

Source : Cancer Research, études des années 1950-1960

Growing environmental awareness

The ecology movement brings widespread PAH contamination to light. Their presence is discovered in urban air, surface water, soils near roads and industrial sites. The US EPA establishes a list of 16 priority PAHs that would become the global benchmark for environmental monitoring.

Source : US EPA, Priority Pollutant List

IARC classifies BaP as carcinogenic to humans

The International Agency for Research on Cancer (CIRC/IARC) classifies benzo[a]pyrene in Group 1 — confirmed carcinogen in humans. Occupational exposure in foundries, coking plants, aluminium production facilities, and road surfacing is directly linked to lung, bladder, and skin cancers.

Source : IARC Monographs, Volume 32, 1983 (réévalué en 2010, Vol. 92)

Discovery of PAHs in older buildings

Building-pollutant surveys reveal the widespread presence of PAHs in pre-1990 structures: coal-tar waterproofing membranes, black adhesives for parquet and floor tiles, floor coverings, expansion joints, and protective coatings. Coal tar was ubiquitous in Swiss construction until its gradual replacement by petroleum bitumen.

EU bans coal tar in construction

The European Union restricts the use of coal-tar-based products (creosote, coal pitch) in construction and consumer products. However, millions of existing buildings still contain these materials — the challenge now lies in managing the existing older building stock.

Source : Directive REACH, règlement CE n° 1907/2006

IARC: diesel engine emissions are carcinogenic

The IARC classifies diesel engine exhaust in Group 1 (confirmed carcinogen). Diesel exhaust fumes are a major source of PAHs in urban environments. Road traffic remains today the primary source of PAH exposure for the general population.

Source : IARC Monographs, Volume 105, 2012

New Swiss regulations on asphalt containing PAHs

The OLED (Ordinance on the Reduction and Disposal of Waste / Ordonnance sur la limitation et l'élimination des déchets) sets thresholds for the management of PAH-containing bituminous asphalt. Above 250 mg/kg: restricted recycling. Above 1,000 mg/kg: specialised treatment with PAH elimination is mandatory. These thresholds apply to all renovation and demolition projects.

Source : OLED, annexe 4, ch. 3.3

The challenge of renovating Switzerland's existing building stock

In Switzerland, any building constructed before 1990 may contain materials with PAHs. Pre-work surveys are mandatory (Art. 16 OLED). SUVA imposes strict protective measures: from 100 mg/kg of BaP or 2,500 mg/kg of total PAHs, full protection with air filtration is required for workers. Remediation costs can range from a few thousand to several hundred thousand Swiss francs.

Source : SUVA, Fiche thématique HAP, 2024