At a glance
| Chemical family | A chlorinated aromatic volatile organic compound (para-dichlorobenzene, p-DCB) — a solid that sublimes to vapor |
| CAS number | 106-46-7 |
| Classification | IARC Group 2B — possibly carcinogenic to humans; a federal Hazardous Air Pollutant and California Toxic Air Contaminant; linked to reduced lung function at population levels |
| Where you encounter it | Mothballs and moth flakes in closets and drawers; toilet, urinal and room deodorizer blocks; some solid air fresheners |
| Sleep micro-environment relevance | Sublimes into closet, drawer and bedroom air wherever these products are used; becomes a dominant indoor VOC and is detectable in nearly everyone's body |
| Activated carbon capture | Adsorbable as a vapor, but the real fix is removing the source product — stop using p-DCB moth and deodorizer products |
Regulatory & certification status
Where 1,4-Dichlorobenzene stands across the major regulatory systems and the certifications a bedroom product might carry. Each row links to the governing instrument; where a jurisdiction has no specific measure, that is stated plainly rather than left blank.
| European Union | REACH Annex XVII restriction (Entry 64, added by Commission Regulation (EU) No 474/2014): 1,4-dichlorobenzene shall not be placed on the market or used, as a substance or in mixtures at a concentration >=1% by weight, where placed on the market for use or used as an air freshener or deodoriser in toilets, homes, offices or other indoor public areas; the restriction applies from 1 June 2015. It carries a harmonised CLP classification in Annex VI (Index 602-035-00-2): Carc. 2 (H351), Aquatic Acute 1 (H400) and Aquatic Chronic 1 (H410). Not on the REACH SVHC Candidate List or the Authorisation List (Annex XIV). Regulatory — EUR-Lex · ECHA |
| United States | TSCA: EPA designated p-dichlorobenzene (CASRN 106-46-7) a High-Priority Substance for risk evaluation effective 20 December 2019; the final scope was published in 2020 and EPA released draft human-health and environmental hazard assessments in April 2026. A High-Priority designation is expressly not a finding of unreasonable risk, and no final risk determination or regulatory action exists yet. California Proposition 65: listed as causing cancer effective 1 January 1989 under the State's Qualified Experts (SQE) listing mechanism. Regulatory — US EPA · Federal Register |
| Canada | Assessed under the CEPA Priority Substances List (PSL1). The Environment Canada/Health Canada assessment concluded 1,4-dichlorobenzene is not 'toxic' under CEPA paragraphs 11(b) and 11(c) (it was not entering the environment in a quantity/concentration or under conditions constituting a danger to human life or health, or to the environment on which human life depends), but found insufficient information to conclude under paragraph 11(a) whether it has immediate or long-term harmful effects on the environment. It is not on CEPA Schedule 1 (List of Toxic Substances) on the basis of this assessment; no CEPA Schedule 1 restriction was identified. Regulatory — Government of Canada |
| Australia | Declared a Priority Existing Chemical by NICNAS on 7 April 1998 over health and environmental concerns about its use in toilet blocks, urinals and as an air freshener; NICNAS published a full assessment as Priority Existing Chemical Assessment Report No. 13 (para-Dichlorobenzene). Industrial chemicals are now administered by AICIS, the successor to NICNAS. Regulatory — AICIS |
| United Kingdom | Great Britain retains the EU air-freshener/toilet-block restriction: Commission Regulation (EU) No 474/2014 was carried over as assimilated (retained EU) law and, per legislation.gov.uk, has not been amended by the UK since IP completion day (31 December 2020), so the >=1% restriction on use as an air freshener/deodoriser continues to apply in GB under UK REACH (HSE is the regulator). Regulatory — UK legislation |
| International | IARC classifies para-dichlorobenzene in Group 2B — possibly carcinogenic to humans (Monographs Volume 73, 1999) — on the basis of sufficient evidence in experimental animals and inadequate evidence in humans. It is not listed under the Stockholm Convention on POPs, and the Minamata Convention (mercury) does not apply. Regulatory — IARC Monographs Volume 73 · IARC |
| Certifications | No consumer certification commonly applied to mattresses targets this compound by name in its publicly stated criteria. CertiPUR-US is a flexible polyurethane foam program (emissions and a defined list of restricted substances); 1,4-dichlorobenzene is a mothball/deodoriser chemical rather than a foam feedstock or blowing agent and is not called out in its public materials. OEKO-TEX Standard 100 sets limit values for chlorinated/halogenated substance groups but does not name 1,4-dichlorobenzene specifically in public summaries. GREENGUARD/GREENGUARD Gold is a low-VOC emissions certification that would capture it as a measured VOC if emitted, but is not a content prohibition tied to this substance. (For contrast, the Cradle to Cradle Banned Lists do name dichlorobenzenes, but C2C is not a typical mattress certification.) Industry — CertiPUR-US · OEKO-TEX |
| The 72-hour test window | Well captured. 1,4-Dichlorobenzene is a volatile solid that sublimes readily at room temperature (it is the active off-gassing agent in mothballs and toilet deodoriser blocks) and is a routinely measured indoor-air VOC, so a short ~72-hour chamber emissions test detects it reliably. Inferred — from the compound's volatility/emission profile versus the VOC focus of short chamber tests |
What it is
1,4-Dichlorobenzene — para-dichlorobenzene, or p-DCB — is a chlorinated benzene that exists as a white crystalline solid with a sharp, camphor-like smell. Its defining property is that it sublimes: it passes directly from solid to vapor at room temperature, which is how a single mothball slowly disappears while filling its surroundings with vapor. That is the whole point of the product, and also the whole problem. Regulatory — California ARB, PDCB Health Risk Assessment It largely replaced naphthalene as the standard mothball ingredient because it is somewhat less acutely toxic, but it carries its own concerns.
IARC classifies p-DCB as possibly carcinogenic to humans (Group 2B), and U.S. and California regulators list it as a hazardous and toxic air contaminant. It is so widely used that breath, blood, urine, breast-milk and fat samples from the great majority of Americans contain measurable amounts. Regulatory — California ARB, PDCB Health Risk Assessment
How it relates to the bedroom
A product you put in your own closet
What makes p-DCB unusual is that its source is intentional and local. Mothballs and moth flakes go in closets and dresser drawers; deodorizer blocks go in adjoining bathrooms and sometimes the bedroom itself. Each is nearly pure p-DCB, and the vapor accumulates in the enclosed spaces of closets and garment bags before spilling into the bedroom air beside them. Inferred — p-DCB products are concentrated solids placed in closets/drawers; their vapor enters adjacent bedroom air Measurements bear out how skewed this is: across hundreds of homes the median indoor level was modest, but 30% of homes exceeded a concentration corresponding to a one-in-100,000 lifetime cancer risk, 4% exceeded a one-in-1,000 level, and the single highest home reached 4,100 µg/m³ — all driven by active use of these products. Peer-reviewed — Chin et al. 2012 Where the products are used, p-DCB becomes one of the dominant compounds in the indoor air.
The health signal at everyday levels
Two layers of evidence matter here, and it is worth separating them. At ordinary household exposure, the standout finding is respiratory: in a national survey, of eleven VOCs measured in people's blood, 1,4-dichlorobenzene was the only one associated with reduced lung function, with the most-exposed group showing meaningfully lower breathing capacity. Peer-reviewed — Elliott et al. 2006 Combined with its Group 2B cancer classification, that makes chronic low-level inhalation a reasonable thing to reduce. The second layer — severe neurological injury, including brain white-matter damage — is real but belongs to a different world: it comes from extreme misuse, people eating mothballs or deliberately inhaling them, not from a deodorizer block in the bathroom. Speculation — severe neurotoxicity is documented only at extreme ingestion/inhalation exposures, not normal household use Keeping those two layers distinct is the calibrated way to read the risk.
The easiest fix in the Atlas
Because the exposure comes from a chosen product, removing it removes the exposure almost entirely. Regulators are explicit: the CPSC and EPA advise that items being protected from moths be stored in containers kept somewhere ventilated separately from living space — an attic or detached garage — rather than a bedroom closet. Regulatory — California ARB, PDCB Health Risk Assessment Simpler still is not using p-DCB products at all. Inferred — source removal eliminates the dominant exposure
What the research says
- Group 2B carcinogen and Hazardous Air Pollutant. The active solid in mothballs and deodorizer blocks. Regulatory — California ARB
- Reduced lung function at population levels. The only one of 11 blood VOCs linked to lower breathing capacity. Peer-reviewed — Elliott et al. 2006
- Indoor levels are highly skewed by product use. A minority of homes reach cancer-risk levels of 1-in-1,000 or higher. Peer-reviewed — Chin et al. 2012
- Severe neurotoxicity is an abuse phenomenon. Brain injury cases involve ingestion or huffing, not normal use. Speculation
What helps reduce it
Stop using p-DCB moth and deodorizer products. Source removal is the decisive step; cedar, lavender or airtight storage are alternatives for moths. Inferred
If you must use them, store them away from living space. Sealed containers in an attic or detached garage, per CPSC/EPA guidance — never the bedroom closet. Regulatory — California ARB
Air out anything stored with them. Clothes and linens kept with mothballs should be aired before being worn or put on the bed. Inferred
What does NOT help
- Masking the smell. Adding another air freshener does nothing about the p-DCB and may add more VOCs; remove the source instead. Inferred
- Assuming "deodorizer" means harmless. The block is a near-pure Group 2B compound subliming into the room, not a benign fragrance. Regulatory — California ARB
Open research questions
- Whether the population-level lung-function association reflects causation and at what exposure it begins. Speculation
- The contribution of closet and garment-bag use specifically to bedroom-air p-DCB over a sleeping night. Speculation
The Embr Exposure Ledger: 1,4-Dichlorobenzene
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.
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
- California Air Resources Board (2004). Health Risk and Needs Assessment for the Airborne Toxic Control Measure for Para-Dichlorobenzene Solid Air Fresheners and Toilet/Urinal Care Products. PDCB = IARC Group 2B; federal HAP & CA Toxic Air Contaminant; mothball/deodorizer use; body burden in most US persons; CPSC/EPA separate-ventilation storage advice. Via Consensus. Reference record Regulatory
- Elliott L, et al. (2006). Volatile organic compounds and pulmonary function in NHANES III. Environmental Health Perspectives. Of 11 blood VOCs, only 1,4-DCB was associated with reduced lung function in the US population. Via Consensus. DOI 10.1289/ehp.9019 Peer-reviewed
- Chin JY, et al. (2012). Concentrations and risks of p-dichlorobenzene in indoor and outdoor air. Indoor Air. Median indoor 0.36 µg/m³; 30% of homes > 1-in-100,000 cancer-risk level, 4% > 1-in-1,000; max 4,100 µg/m³; driven by product use. Via Consensus. DOI 10.1111/j.1600-0668.2012.00796.x Peer-reviewed
Frequently asked questions
What is 1,4-dichlorobenzene?
It is the white, camphor-smelling crystalline solid that makes up modern mothballs, moth flakes, and the deodorizer blocks placed in closets, garment bags, toilets and urinals. Chemically it is para-dichlorobenzene (p-DCB), a chlorinated volatile organic compound. It does its job by subliming — turning directly from solid to vapor — which fills the surrounding air with it, and is exactly why it shows up in the air you breathe.
Why is it a bedroom concern specifically?
Because the products that contain it live in the bedroom: mothballs and moth flakes in closets and dresser drawers, deodorizer blocks in adjoining bathrooms. The vapor builds up in enclosed closets and garment bags and spills into the bedroom air next to them. Where these products are used, p-DCB becomes one of the dominant indoor VOCs, and it is detectable in the bodies of nearly all Americans from this kind of everyday use.
How harmful is it?
IARC classifies p-DCB as possibly carcinogenic to humans (Group 2B), and it is a federal Hazardous Air Pollutant. At the levels found in the general US population, it is the one common indoor VOC that has been linked to measurably reduced lung function. Severe neurological harm has been reported, but those cases involve extreme exposure — ingesting or deliberately inhaling mothballs — not normal household use. The everyday concern is a possible cancer risk and respiratory effect from chronic low-level inhalation.
What should I do about it?
This is one of the most fixable entries in the Atlas, because the source is a product you choose to use. The simplest step is to stop using p-DCB mothballs and deodorizer blocks, or switch to alternatives like cedar or proper airtight storage. If you do use them, the CPSC and EPA advise keeping protected items in containers stored somewhere ventilated separately from living space — an attic or detached garage — never in the bedroom closet, and airing out anything that has been stored with them.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-06-27. If you find a factual error, contact us.