1-Hydroxypyrene (1-OHP) in the bedroom

At a glance

Regulatory & certification status

Where 1-Hydroxypyrene (1-OHP) 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.

What it is

1-Hydroxypyrene — 1-OHP, CAS 5315-79-7 — is the principal urinary metabolite of pyrene, a four-ring polycyclic aromatic hydrocarbon (PAH). Regulatory — PubChem CID 21387 When pyrene is absorbed — through inhalation, skin contact, or diet — the liver metabolizes most of it into 1-OHP, which is conjugated and excreted in urine. Because pyrene is present in essentially every real-world PAH mixture (fire smoke, vehicle exhaust, cigarette smoke, grilled food, coal tar), measuring urinary 1-OHP gives a working estimate of total PAH exposure without having to measure every individual PAH compound directly. Peer-reviewed — Jongeneelen 2001, Ann Occup Hyg

1-OHP is not itself a regulated hazard and is not classified by IARC. It is a downstream measurement, not the thing being measured for danger. The compounds of actual health concern in a PAH mixture — most notably benzo[a]pyrene, an IARC Group 1 human carcinogen — are what 1-OHP indirectly indicates exposure to. This page treats 1-OHP the way the Atlas treats cotinine for tobacco smoke: as the measurement tool that proves exposure produced a real, absorbed, biological dose, not as a hazard in its own right.

The ACGIH Biological Exposure Index

ACGIH designates 1-OHP as its Biological Exposure Index (BEI) compound for polycyclic aromatic hydrocarbons, with the recommended sample collected at the end of a work shift, at the end of the work week — the timing intended to capture peak accumulated exposure. Regulatory — ACGIH BEI Documentation, Polycyclic Aromatic Hydrocarbons (2017) Because long-term epidemiological studies directly linking a specific urinary 1-OHP concentration to cancer outcomes are lacking, ACGIH has not set 1-OHP's BEI as a single health-based numeric limit; the designation is used as evidence that occupational PAH exposure occurred, not as a pass/fail toxicity threshold. Peer-reviewed — Jongeneelen 2001

The most detailed published attempt to anchor 1-OHP to concrete reference points is Jongeneelen's 2001 three-level benchmark guideline, built from several hundred published worker studies. It sets: a background reference level (95th percentile in non-occupationally-exposed adults) of 0.24 µmol 1-OHP per mol creatinine for non-smokers and 0.76 µmol/mol for smokers; a no-biological-effect level of 1.4 µmol/mol, the lowest concentration at which genotoxic effects were observed in exposed workers; and industry-specific levels — 2.3 µmol/mol in coke-oven workers and 4.9 µmol/mol in primary aluminum production — corresponding to the occupational exposure limit for airborne PAHs in those sectors. Peer-reviewed — Jongeneelen 2001, Ann Occup Hyg 45(1):3-13 These levels illustrate the scale involved: occupationally exposed workers can run roughly 5–20× the non-smoker background reference.

Firefighter exposure — the on-brand evidence

The strongest, most directly relevant published evidence for 1-OHP as a real-world firefighter exposure tool comes from a 2019 study of firefighters deployed to the 2016 Fort McMurray, Alberta wildfire — an uncontrolled structural and wildland fire that burned for weeks under extreme conditions, with many firefighters working 24-hour-plus shifts with limited access to washing or clean clothing early on. Researchers collected post-deployment urine samples from three fire services and measured 1-OHP alongside self-reported smoke exposure, respirator use, and a "skin exposure mitigation index" built from questions about access to washing, showering, and clean clothes between shifts. Peer-reviewed — Cherry et al. 2019, Ann Work Expo Health 63(4):448-458

Among firefighters whose urine was collected within 48 hours of their most recent exposure, urinary 1-OHP correlated significantly with the researchers' estimated smoke exposure (r = 0.53, p < 0.001) — direct evidence the biomarker tracked real fireground dose. Mean 1-OHP concentrations differed meaningfully between fire services (53.1 to 99.0 ng/g creatinine, p = 0.005), reflecting differences in equipment, conditions, and timing of exposure. Critically, among firefighters with only one deployment rotation before sample collection, respirator use showed no measurable effect on urinary 1-OHP, but firefighters who scored higher on the skin exposure mitigation index — meaning better access to washing, showering, and a change of clothes — had significantly lower 1-OHP (p = 0.003). Peer-reviewed — Cherry et al. 2019

The paper's own interpretation is direct: "skin exposure to PAHs is an important route of absorption in firefighters, which can be mitigated by good skin hygiene." That finding — that the intervention available to a firefighter (showering, clean clothes, mitigating skin contact) measurably moved a real biomarker of absorbed dose — is the same logic behind Embr's broader interest in the sleep-adjacent surfaces (turnout-gear storage, bedding, skin contact overnight) that sit between the fireground and the body's actual PAH burden. It is also consistent with, and complements, the shower-before-bed evidence already discussed on the pyrene entry, which draws on separate dermal-absorption research (Probert et al. 2024).

The study also notes an important caveat worth stating plainly: 1-OHP's elimination half-life is not settled. Some literature suggests a fast-clearing component (roughly 1–2 days) and a slower-clearing component that may persist much longer; ACGIH's own BEI documentation tabulates published half-lives ranging from under 4 hours to well over 100 hours. Peer-reviewed — Cherry et al. 2019, citing Jongeneelen et al. 1988 and others That uncertainty is why the standard protocol specifies end-of-shift, end-of-week sampling — it is trying to catch the compound before it has had time to fully clear.

General-population background levels

Away from occupational exposure, essentially everyone has some measurable 1-OHP, because PAHs are unavoidable in ordinary life: charred and grilled food, vehicle exhaust, wood smoke, and general urban air all contribute. The US CDC tracks 1-OHP as part of its National Report on Human Exposure to Environmental Chemicals, using data from the National Health and Nutrition Examination Survey (NHANES). Regulatory — CDC Biomonitoring: Population Exposures The ATSDR Toxicological Profile for Polycyclic Aromatic Hydrocarbons reports a geometric mean urinary 1-OHP concentration of 74.2 nanograms per gram creatinine in the US population aged 6 and older, based on the 1999–2000 NHANES survey cycle — with the profile also noting much higher levels in occupations such as aluminum smelting, diesel mechanics, professional driving, and coke-oven work. Regulatory — ATSDR Toxicological Profile for PAHs

The takeaway for a non-occupational household: a detectable 1-OHP level in a healthy adult is normal and expected, not a sign of something wrong. It reflects the unavoidable, low-level PAH exposure of ordinary life — cooking, traffic, occasional wood smoke — sitting well below the benchmark levels associated with occupational risk. The biomarker becomes clinically interesting only when it is elevated well above this background range, which is the pattern seen in firefighters and other PAH-exposed workers.

Why it's in the Atlas

1-OHP earns a place in the Atlas for the same reason cotinine does for nicotine exposure: it is the biomarker that turns "this environment probably had PAHs in it" into a measured, individual, absorbed dose. It is not a bedroom contaminant, does not off-gas, and is not something activated carbon or ventilation addresses directly — the relevant interventions are upstream, on the parent PAHs and the exposure pathways (fireground smoke, contaminated turnout gear, contact with contaminated skin or bedding) that 1-OHP is measuring the downstream effect of. See the pyrene entry for the parent compound and the sleep-environment transfer pathway, and the benzo[a]pyrene entry for the specific IARC Group 1 carcinogen that a PAH mixture — and therefore an elevated 1-OHP reading — most often signals exposure to.

What helps reduce the exposure 1-OHP measures

For firefighters and PAH-exposed workers — the evidence-backed intervention. The Cherry et al. 2019 finding is specific and actionable: better access to washing, showering, and a change of clothes between shifts significantly lowered urinary 1-OHP, independent of respirator use. Showering and changing out of contaminated clothing as soon as practical after a fire response — rather than waiting until the next scheduled shower — is the single most directly evidenced step for reducing absorbed PAH dose.

Keep contaminated gear away from rest and sleep areas. The same logic that applies on the pyrene and benzo[a]pyrene pages applies here: turnout gear and PAH-contaminated clothing stored or worn near sleeping areas extends the exposure window into hours when decontamination has stopped.

For general households, this is largely a background-exposure story. Reducing indoor combustion sources (wood-burning stoves, heavy indoor grilling), ventilating during and after cooking, and reducing tobacco smoke exposure all lower the ordinary, low-level PAH exposure that 1-OHP reflects in a non-occupational population — but this is a modest, background-level concern, not an urgent one, for households without occupational or wildfire-smoke exposure.

What does NOT help

• Trying to affect 1-OHP directly. 1-OHP is a downstream metabolite on a fixed metabolic and excretion timeline; there is no intervention that "clears" 1-OHP faster. The only way to lower it is to reduce the upstream PAH exposure that produces it.
• Treating a single spot urine test as definitive. Because 1-OHP's elimination half-life is not fully settled and may include a slower-clearing component, a single measurement is a snapshot, not a complete exposure history. ACGIH's end-of-shift, end-of-week protocol exists specifically to standardize timing for this reason.
• Assuming respirator use alone is protective. The Fort McMurray data found no measurable effect of respirator use on urinary 1-OHP among single-rotation firefighters, while skin hygiene measures did show an effect — evidence that dermal absorption is a meaningful, independent exposure route that respiratory protection alone does not address.

Open research questions

• The relative contribution of bedding-mediated dermal re-absorption (contaminated skin or turnout gear transferring PAHs to bedding, then continuing to absorb into skin overnight) to a firefighter's total post-shift 1-OHP has not been isolated from other exposure pathways in any published study. Speculation
• 1-OHP's true elimination half-life, including whether a genuine slow-clearing compartment exists, remains unresolved in the literature — the original multiphasic half-life observation has not been replicated in a larger cohort. Peer-reviewed — Cherry et al. 2019, discussing this gap
• Whether a formal, health-outcome-based numeric BEI for 1-OHP will ever be feasible depends on long-term epidemiological data linking cumulative urinary 1-OHP to cancer incidence — data that Jongeneelen 2001 already flagged as lacking, and which remains an open gap. Speculation

Citations

1. Jongeneelen FJ (2001). Benchmark guideline for urinary 1-hydroxypyrene as biomarker of occupational exposure to polycyclic aromatic hydrocarbons. Annals of Occupational Hygiene, 45(1):3-13. PMID 11137694 Peer-reviewed
2. Cherry N, Aklilu YA, Beach J, Britz-McKibbin P, Elbourne R, Galarneau JM, Gill B, Kinniburgh D, Zhang X (2019). Urinary 1-hydroxypyrene and Skin Contamination in Firefighters Deployed to the Fort McMurray Fire. Annals of Work Exposures and Health, 63(4):448-458. DOI 10.1093/annweh/wxz006 · PMID 30753267 Peer-reviewed
3. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Polycyclic Aromatic Hydrocarbons — Analytical Methods chapter (1-hydroxypyrene as standard PAH biomarker) and NHANES 1999–2000 background urinary concentration (74.2 ng/g creatinine). NCBI Bookshelf NBK598179 Regulatory
4. American Conference of Governmental Industrial Hygienists. Polycyclic Aromatic Hydrocarbons — Biological Exposure Indices (BEI) Documentation, 1-hydroxypyrene (2017). Regulatory
5. PubChem. 1-Hydroxypyrene, CID 21387 — CAS 5315-79-7. PubChem CID 21387 Regulatory
6. Centers for Disease Control and Prevention. Biomonitoring: Population Exposures — National Report on Human Exposure to Environmental Chemicals, Polycyclic Aromatic Hydrocarbons topic area. CDC Environmental Public Health Tracking Regulatory

Frequently asked questions

• What is 1-hydroxypyrene, in plain terms?

  It is the main breakdown product the human body makes from pyrene, a polycyclic aromatic hydrocarbon (PAH) found in essentially all smoke and combustion exposure. After pyrene is absorbed — by breathing it in, through skin contact, or in food — the liver converts most of it to 1-hydroxypyrene, which is then excreted in urine. Measuring 1-OHP in a urine sample is the standard way occupational health researchers estimate how much PAH exposure a person has had recently. It is a measurement tool, not a hazard itself.

• Is 1-hydroxypyrene dangerous?

  1-OHP itself is not classified by IARC and is not the compound of health concern — it is what the body makes after processing pyrene, which is itself IARC Group 3 (not classifiable as a human carcinogen). What 1-OHP indirectly signals is exposure to the broader PAH mixture, which includes benzo[a]pyrene, an IARC Group 1 (confirmed human) carcinogen. A high 1-OHP reading means meaningful PAH exposure occurred; it does not mean 1-OHP itself caused harm.

• Why is 1-OHP used for firefighter monitoring specifically?

  Structure fires and wildfire smoke are dense in PAHs, and firefighters absorb them both by inhalation and through skin contact with soot and contaminated turnout gear. A 2019 study of Fort McMurray wildfire firefighters found urinary 1-HP correlated with estimated smoke exposure (r = 0.53, p < 0.001) and was significantly lower in firefighters with better access to washing, showering, and clean clothing between shifts (p = 0.003) — direct evidence that skin hygiene reduces absorbed dose, measured through this one biomarker. ACGIH recommends collecting the sample at the end of a work shift, at the end of the work week, when absorbed dose is expected to be highest.

• What counts as a normal, non-occupational 1-OHP level?

  Background levels are low but not zero — everyone absorbs some PAHs from grilled food, traffic exhaust, wood smoke, and ambient air. A 2001 benchmark analysis set the 95th-percentile reference level for non-occupationally-exposed adults at 0.24 micromol 1-OHP per mol creatinine for non-smokers and 0.76 for smokers (smoking is itself a meaningful PAH exposure route). The CDC's National Report on Human Exposure to Environmental Chemicals tracks 1-OHP in the general US population through NHANES; the 1999–2000 survey found a geometric mean of about 74 nanograms per gram creatinine. Occupationally exposed workers can run many times higher than this background range.

Related compounds

• Pyrene — the parent compound 1-OHP is metabolized from; the firefighter transfer-to-bedding pathway lives on this page
• Benzo[a]pyrene — the family's IARC Group 1 flagship; the carcinogen a PAH mixture, and therefore an elevated 1-OHP reading, most often signals
• Cotinine — the closest structural analog in the Atlas: another exposure biomarker, not a hazard, used to prove real absorbed dose from tobacco smoke
• The Smoke That Stays — the flagship article on third-hand smoke and firefighter take-home contamination this entry supports

This page describes documented chemistry and the biomarker science used to quantify PAH exposure. It does not provide medical advice. Firefighters or other workers concerned about occupational PAH exposure should consult their occupational health program or physician.

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