Polycyclic aromatic hydrocarbon

Dibenz[a,h]anthracene in the bedroom

By — 19-year firefighter and entrepreneur. Published July 2026.

Dibenz[a,h]anthracene (DBA) is a five-ring PAH classified by IARC as Group 2A (probably carcinogenic to humans, Monographs Vol. 92, 2010). It is the only commonly monitored PAH classified at Group 2A besides benzo[a]pyrene (which is Group 1). DBA is among the most potent carcinogenic PAHs by relative potency factor, despite occurring at low environmental concentrations. It is one of the 8 PAHs restricted in consumer articles under EU REACH Annex XVII Entry 50. In the bedroom, DBA is found in combustion-derived dust at very low concentrations, but its high potency means even small amounts contribute meaningfully to PAH cancer risk.

Dibenz[a,h]anthracene — Embr Bedroom Chemistry Atlas

At a glance

Chemical familyPolycyclic aromatic hydrocarbon (PAH) — five-ring alternant structure with multiple bay regions
CAS number53-70-3
ClassificationIARC Group 2A (probably carcinogenic to humans, Monographs Vol. 92, 2010). EU CLP Carc. 1B (H350). One of the 8 EU REACH Entry 50 restricted PAHs. Among the highest relative potency factors of any PAH
Where you encounter itCombustion products at very low concentrations; tobacco smoke; diesel exhaust; coal tar; grilled food; household dust from combustion sources
Sleep micro-environment relevanceFound in household dust at very low concentrations but with high carcinogenic potency. Despite low abundance, DBA can contribute significantly to the total PAH cancer risk in indoor environments

Regulatory & certification status

European UnionCLP Carc. 1B (H350). REACH Annex XVII Entry 50 restricts 8 priority PAHs (including DBA) to 1 mg/kg in rubber and plastic components with prolonged skin contact. Regulatory
United StatesEPA Priority Pollutant. Clean Water Act listed. California Proposition 65 listed (cancer). EPA assigned DBA a relative potency factor of 1.0 (equal to BaP). Regulatory
CanadaCEPA Schedule 1 (toxic substance) as part of the PAH group. Regulatory
InternationalIARC Group 2A (probably carcinogenic, Monographs Vol. 92, 2010). The only common PAH at Group 2A besides BaP (Group 1). One of the 8 EU priority PAHs restricted in consumer articles. Regulatory

What it is

Dibenz[a,h]anthracene is a five-ring alternant PAH with multiple bay regions in its molecular structure. IARC classified it as Group 2A in 2010 — probably carcinogenic to humans — based on sufficient evidence of carcinogenicity in animals and limited evidence in humans. DBA is notable for its high carcinogenic potency relative to other PAHs: in relative potency factor (RPF) approaches used for PAH mixture risk assessment, DBA is assigned a factor of 1.0-5.0 relative to benzo[a]pyrene (depending on the study), meaning it is as potent or more potent than BaP per unit mass. However, DBA is found at much lower environmental concentrations than BaP, so the total cancer risk contribution from DBA, while significant, is modulated by its low abundance.

Where it shows up in bedding

DBA is not a bedding ingredient. It enters the bedroom as part of combustion-derived particulate matter at very low concentrations. Sources are the same as for other PAHs: tobacco smoke, diesel exhaust infiltration, fireplace emissions, and wood stove smoke. DBA is particle-bound due to its high molecular weight and low vapour pressure. Its significance in the bedroom is not its abundance — it is typically found at nanogram-per-gram levels in dust — but its potency. In PAH mixture risk assessments, DBA can contribute a disproportionate share of the estimated cancer risk despite its low concentration.

Citations

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

Frequently asked questions

  • Why is DBA classified higher than most PAHs?

    DBA is classified IARC Group 2A (probably carcinogenic) while most other PAHs are Group 2B (possibly carcinogenic) or Group 3 (not classifiable). This reflects stronger evidence of carcinogenicity in animal studies — DBA was one of the first PAHs shown to cause tumours in animal experiments (in the 1930s). Its multiple bay regions create particularly reactive diol-epoxide metabolites that bind to DNA.

  • If DBA is so potent, should I be worried about dust?

    DBA is found at very low concentrations in household dust — typically nanograms per gram, much less than benzo[a]pyrene. While its potency is high, the actual risk at these trace levels is small. The most effective way to reduce PAH exposure in the bedroom is to eliminate combustion sources (no smoking, use of fireplace only with good ventilation) and to regularly clean dust from surfaces and floors.

Related compounds

  • Benzo[a]pyrene — the reference carcinogenic PAH (IARC Group 1)
  • Chrysene — a four-ring PAH with weaker carcinogenic activity
  • Benz[a]anthracene — another IARC Group 2B PAH with a bay region
  • Fluoranthene — one of the most abundant environmental PAHs

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.