Is benz[a]anthracene as dangerous as benzo[a]pyrene?

No. While both are carcinogenic PAHs, benz[a]anthracene has lower carcinogenic potency than benzo[a]pyrene. BaP is classified IARC Group 1 (carcinogenic) while BaA is Group 2B (possibly carcinogenic). In PAH mixture risk assessments, benzo[a]pyrene typically drives most of the estimated cancer risk, with BaA contributing a smaller fraction.

What is a bay region in a PAH?

A bay region is a concave area in the molecular structure of a PAH, formed by the angular arrangement of fused rings. This structural feature is important because PAHs with bay regions can be metabolised to bay-region diol-epoxides — reactive intermediates that bind to DNA and initiate carcinogenesis. Not all PAHs have bay regions, and those that do tend to be more carcinogenic.

Benz[a]anthracene: An IARC Group 2B PAH in Combustion Dust

At a glance

Chemical family	Polycyclic aromatic hydrocarbon (PAH) — four-ring alternant structure with a bay region
CAS number	56-55-3
Classification	IARC Group 2B (possibly carcinogenic to humans, Monographs Vol. 92, 2010). EU CLP Carc. 1B (H350). One of the 8 EU REACH Entry 50 restricted PAHs
Where you encounter it	Combustion products (tobacco smoke, wood smoke, vehicle exhaust, coal tar); found in household dust; grilled/smoked food; coal tar pitch
Sleep micro-environment relevance	Found in household dust from combustion sources. One of the carcinogenic PAHs that contributes to the cancer risk from PAH mixtures in indoor environments

Regulatory & certification status

European Union	CLP Carc. 1B (H350). REACH Annex XVII Entry 50 restricts 8 priority PAHs (including BaA) to 1 mg/kg in rubber and plastic components with prolonged skin contact. Regulatory
United States	EPA Priority Pollutant. Clean Water Act listed. California Proposition 65 listed (cancer). Regulatory
Canada	CEPA Schedule 1 (toxic substance) as part of the PAH group. Regulatory
International	IARC Group 2B (possibly carcinogenic, Monographs Vol. 92, 2010). One of the 8 EU priority PAHs restricted in consumer articles. Regulatory

What it is

Benz[a]anthracene (BaA) is a four-ring PAH with an angular structure that creates a bay region — a concave area in the molecule that is structurally associated with carcinogenic activity in PAHs. IARC evaluated BaA in Monographs Vol. 92 (2010) and classified it as Group 2B based on sufficient evidence of carcinogenicity in animals and inadequate evidence in humans. The EU takes a more precautionary approach, classifying BaA as Carc. 1B. BaA is formed during incomplete combustion of organic matter and is found in tobacco smoke, wood smoke, vehicle exhaust, and coal tar. It is one of the 8 priority PAHs restricted in rubber and plastic components of consumer articles under REACH.

Where it shows up in bedding

Benz[a]anthracene is not an ingredient in bedding products. It enters the bedroom as a component of combustion-derived particulate matter that settles in dust. Sources include tobacco smoke (both secondhand and thirdhand residue on surfaces), fireplace and wood stove emissions, and outdoor vehicle exhaust that infiltrates through windows and ventilation. BaA is one of several carcinogenic PAHs that co-occur in these combustion mixtures. The EU restricts BaA to 1 mg/kg in rubber and plastic components of consumer articles with prolonged skin contact under REACH Entry 50.

The Embr Exposure Ledger: Benz[a]anthracene

One chemical, several public questions, answered from independent datasets and joined here — the environment it shows up in, the body burden it carries, how it is regulated, and what actually reduces it.

This compound appears in 6 of the Embr Exposure Ledger’s 10 exposure datasets.

Is it in smoke?

Measured in the emissions of residential wood smoke. This is what the source gives off, not a level in anyone's home: it says the compound is present in that smoke, not how much of it reaches a person. What smoke leaves behind indoors.Source: US EPA, SPECIATE 5.4 — the EPA repository of source-emission composition profiles (air toxics, criteria and greenhouse pollutants)

At what level would it matter?

Published benchmarks exist: a residential indoor-air screening level of 0.017 µg/m³, set on a cancer endpoint (1-in-a-million excess lifetime risk). A screening level is the concentration at which EPA would look further, not a boundary between safe and harmful. The ledger holds no measured sleeping-environment concentration for this compound, so there is nothing here to compare the benchmark against — it tells you what would matter, not what is in any room.Source: US EPA, Regional Screening Levels (RSL) Summary Table — consolidated toxicity values from IRIS, PPRTV, ATSDR, Cal EPA and OPP

Who releases it?

351 Canadian facilities have reported it (2000-2024). These are self-reported quantities leaving a facility, not levels anyone encountered, and the two national programs are not added together — they use different reporting thresholds.Source: US EPA, Toxics Release Inventory (TRI) Basic Data File, 2024 reporting year; Environment and Climate Change Canada, National Pollutant Release Inventory (NPRI), releases 1993-present

Does the law flag it?

Listed under California Proposition 65 for cancer since 1987. On the EU REACH Candidate List as a substance of very high concern for carcinogenic, persistent, bioaccumulative and toxic (PBT), very persistent and very bioaccumulative (vPvB) since 15-Jan-2018. That is a formal identification, not a ban: it triggers supply-chain disclosure above 0.1% by weight. Carries an EU-wide binding classification as carcinogenic (category 1B). That classifies the substance itself; it does not restrict any product.Source: California OEHHA Proposition 65 List (Safe Drinking Water and Toxic Enforcement Act of 1986)Source: ECHA Candidate ListSource: EU CLP Annex VI

Has a regulator acted?

Regulators have acted on products over this compound: 2 EU safety alerts. These are actions against specific products, not a measure of the substance in general — and counts follow enforcement attention as much as they follow prevalence.Source: EU Safety Gate (RAPEX), European Commission rapid alert system for dangerous non-food products

Detection and body-burden figures are occurrence data, not a personal measurement or a health diagnosis. Part of the Embr Exposure Ledger — an open, cross-dataset chemical join (download the data), reusable with attribution.

Citations

IARC (2010). Some Non-Heterocyclic Polycyclic Aromatic Hydrocarbons and Some Related Exposures. IARC Monographs Vol. 92. Source Regulatory
ATSDR (1995). Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). Source Regulatory
EU REACH Annex XVII, Entry 50 — PAHs in consumer articles. Source Regulatory

Frequently asked questions

Is benz[a]anthracene as dangerous as benzo[a]pyrene?
No. While both are carcinogenic PAHs, benz[a]anthracene has lower carcinogenic potency than benzo[a]pyrene. BaP is classified IARC Group 1 (carcinogenic) while BaA is Group 2B (possibly carcinogenic). In PAH mixture risk assessments, benzo[a]pyrene typically drives most of the estimated cancer risk, with BaA contributing a smaller fraction.
What is a bay region in a PAH?
A bay region is a concave area in the molecular structure of a PAH, formed by the angular arrangement of fused rings. This structural feature is important because PAHs with bay regions can be metabolised to bay-region diol-epoxides — reactive intermediates that bind to DNA and initiate carcinogenesis. Not all PAHs have bay regions, and those that do tend to be more carcinogenic.

Related compounds

Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.

Last reviewed 2026-07-08. If you find a factual error, contact us.

Benz[a]anthracene in the bedroom