Polycyclic Aromatic Hydrocarbons (PAHs): How They Affect Human Health Indoors, Outdoors, and Through Everyday Products

Polycyclic aromatic hydrocarbons (PAHs) are a group of chemicals most people have never heard of but almost everyone is exposed to. Among them, benzo[a]pyrene (BaP) stands out as one of the most potent environmental carcinogens known. Found in polluted air, tobacco smoke, consumer products, and even indoor dust, PAHs quietly contribute to cancer risk and other chronic diseases across Europe and globally.

Let’s unpack where PAHs come from, how they affect the body, and why indoor exposure is often more dangerous than people realize, before closing with a practical overview of EU regulations designed to limit their harm.

What makes PAHs so dangerous?

PAHs are formed whenever organic material burns incompletely, whether that’s diesel fuel, wood, coal, tobacco, or food on a grill. Benzo[a]pyrene is especially hazardous because:

o   It is a known human carcinogen (IARC Group 1),

o   It is not directly toxic, but becomes dangerous after metabolism,

o   Its metabolites bind to DNA (Deoxyribonucleic Acid), the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms, causing mutations that initiate cancer.

PAHs are lipophilic (fat-loving), persistent, and easily transported on fine particles (PM2.5), making them ideal “stealth pollutants” in air and dust. Fine particles, also known as PM2.5, are tiny airborne pollutants with an aerodynamic diameter of 2.5 micrometres or less, small enough to penetrate deep into the lungs and bloodstream, posing significant health risks like respiratory and cardiovascular issues.

Fine particles of benzo[a]pyrene (BaP) are typically found attached to airborne particulate matter (PM) and are often in the sub-micrometer range (below 1 µm), with significant concentrations found in PM smaller than 0.5 µm or 0.49 µm, though they can also form larger aerosols, generally falling into the <2.5 µm (PM2.5) or even <2 µm size classes, allowing deep lung penetration. The most hazardous BaP is usually associated with the finest particles from combustion sources, such as vehicle exhaust.

Main sources of benzo[a]pyrene include burning coal, wood, and waste in old stoves, with a health impact that is strongly carcinogenic, damaging DNA, and increasing the risk of lung and bladder cancer. This pollutant is especially high in winter evenings in residential areas.

How PAHs harm the human body

Once inhaled or absorbed through the skin, PAHs undergo metabolic activation, mainly in the lungs and liver.

Key steps of toxicity:

1. PAHs enter the body via air, skin, or ingestion

2. Enzymes (CYP450) convert them into reactive epoxides

3. These metabolites bind to DNA, forming DNA adducts

4. If DNA repair fails, mutations persist

5. Over time, this leads to cancer and systemic disease.

Chronic low-dose exposure, typical of urban life, is often more harmful than short, high-dose exposure.

Indoor vs. outdoor PAH exposure: what’s the difference?

Outdoor PAH Exposure

Main sources

• Vehicle exhaust (especially diesel)

• Industrial emissions

• Residential wood and coal heating

• Wildfires

• Asphalt and road dust.

Characteristics

• PAHs are diluted by atmospheric mixing

• Exposure varies with traffic density and season

• Often regulated and monitored

Health impacts

• Lung cancer

• Cardiovascular disease

• Chronic respiratory inflammation

• Increased mortality linked to PM_2.5 bound PAHs

Outdoor exposure is especially relevant in urban and industrial regions, but regulation has reduced levels in many EU cities over the last two decades.

Indoor PAH exposure (often underestimated)

Main sources

• Tobacco smoke (dominant indoor source)

• Cooking (frying, grilling, charbroiling)

• Candles and incense

• Fireplaces and wood stoves

• Off-gassing from rubber, plastics, and treated wood

• Contaminated house dust

Why indoor exposure can be worse

• PAHs accumulate in dust and surfaces

• Poor ventilation traps pollutants

• Exposure duration is longer (hours per day)

• Children have higher inhalation rates per body weight

Health impacts

• Lung and skin cancer

• Childhood asthma and reduced lung development

• Endocrine disruption

• Neurodevelopmental effects

• Increased lifetime cancer risk starting early in life

In many European homes, indoor PAH exposure now exceeds outdoor exposure, particularly where smoking, solid fuel heating, or poor ventilation is present.

PAHs in consumer products: a hidden source

PAHs are also found in:

• Rubber and plastic goods (tires, footwear, tools)

• Toys and childcare articles

• Cosmetics (carbon black pigments, contaminated mineral oils)

• Soot-containing inks and coatings

Skin contact allows PAHs to penetrate directly into the bloodstream, bypassing lung defenses.

EU Regulatory limits: what is controlled?

Ambient Air (Outdoor)

Directive 2004/107/EC

• Benzo[a]pyrene target value: 1.0 ng/m³ (annual average in PM₁₀)

BaP is used as a marker compound for carcinogenic PAHs in air. There is no “safe” threshold—this value reflects risk management, not zero risk.

Consumer products (REACH Regulation – Annex XVII)

Limits for rubber and plastic articles

Product category	Benzo[a]pyrene limit
General consumer articles	≤ 1 mg/kg
Toys & childcare articles	≤ 0.5 mg/kg

Sum of 8 carcinogenic PAHs (including BaP, chrysene, benzo[b]fluoranthene, etc.)

• ≤ 10 mg/kg (general articles)

• ≤ 1 mg/kg (toys and childcare articles)

These limits apply to products with direct and prolonged skin contact.

Indoor Air

• No binding EU-wide indoor air limits for PAHs

• WHO recognizes PAHs as major indoor carcinogens

• Regulation is left largely to national guidelines and building standards

This regulatory gap means personal behavior and building design play a major role in exposure reduction.

Who is most at risk?

• Smokers and those exposed to secondhand smoke

• Children (especially crawling infants)

• Pregnant women

• People living near traffic or industry

• Workers exposed to combustion products

• Low-income households using solid fuels indoors

Reducing PAH exposure in daily life

Indoors

• Eliminate smoking indoors

• Improve ventilation when cooking

• Reduce candle and incense use

• Use clean heating technologies

• Regular wet cleaning to reduce dust

Outdoors

• Avoid heavy traffic areas during peak hours

• Support clean air policies

• Use air filtration where pollution is high

Consumer awareness

• Choose certified toys and products

• Avoid cheap rubber or plastic goods of unknown origin

  
  

Final thoughts

PAHs like benzo[a]pyrene are not rare industrial accidents, they are routine by-products of modern life. While outdoor air quality has improved in much of Europe, indoor exposure and consumer product contact now represent major, under-recognized health risks.

Understanding where PAHs come from, and how regulation, lifestyle, and environment interact, is essential for reducing long-term cancer and chronic disease risk.

Support and cooperation

Safety and environmental assessments. Let`s do more for safety!

References

1. International Agency for Research on Cancer (IARC).

   IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 92: Some Non-heterocyclic Polycyclic Aromatic Hydrocarbons and Some Related Exposures. Lyon, France: IARC; 2010.

2. World Health Organization (WHO).

   Air Quality Guidelines for Europe, 2nd ed. Copenhagen: WHO Regional Office for Europe; 2000.

3. Boström, C.-E., Gerde, P., Hanberg, A., et al.

   Cancer risk assessment, indicators, and guidelines for polycyclic aromatic hydrocarbons in the ambient air.

4. Kim, K.-H., Jahan, S. A., Kabir, E., & Brown, R. J. C.

   A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects.

5. European Commission.

   Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air.

6. European Environment Agency (EEA).

   Air Quality in Europe — Benzo[a]pyrene (BaP) Assessment. Copenhagen: EEA; latest edition.

7. Agency for Toxic Substances and Disease Registry (ATSDR).

   Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). Atlanta, GA: U.S. Department of Health and Human Services; 1995 (updated).

8. European Chemicals Agency (ECHA).

   Annex XVII to REACH — Restrictions on the Manufacture, Placing on the Market and Use of Certain Dangerous Substances, Mixtures and Articles (PAHs). Helsinki: ECHA.

9. Umweltbundesamt (German Environment Agency).

   Restricted limit values for polycyclic aromatic hydrocarbons (PAHs) in consumer goods. Dessau-Roßlau, Germany.

10. Bundesinstitut für Risikobewertung (BfR).

    PAH levels in consumer products should be as low as possible. Opinion No. 010/2010. Berlin, Germany.

11. European Food Safety Authority (EFSA)

    Polycyclic aromatic hydrocarbons in food — Scientific Opinion of the Panel on Contaminants in the Food Chain.

12. Perera, F. P., Rauh, V., Whyatt, R. M., et al.

    Effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons on neurodevelopment in children.

13. Jędrychowski, W., Perera, F., Mrozek-Budzyn, D., et al.

    Intrauterine exposure to polycyclic aromatic hydrocarbons, fine particulate matter, and early wheeze.

    European Respiratory Journal. 2010;35(2):306–312.

14. United Kingdom Health Security Agency (UKHSA).

    Benzo[a]pyrene and PAHs: Toxicological Overview. London, UK.