At a glance
| Chemical family | Organophosphate insecticide — acetylcholinesterase inhibitor (the dominant mechanism of organophosphate toxicity) |
| CAS number | 2921-88-2 |
| Classification | Not formally evaluated by IARC (does not appear with a Group classification in the IARC monograph series); EPA Group E — evidence of non-carcinogenicity; residential use banned in the US since 2001; food-crop tolerances revoked 2021 → reinstated 2023 → EPA Dec 2024 proposed partial re-revocation (11 crops retained); Interim Decision expected 2026 |
| Where you encounter it | Persistent dust in homes built before 2001 that received residential pest-control applications; drift from currently-permitted agricultural use (alfalfa, citrus, cotton, soybean, wheat, others per 2024 proposed rule); take-home contamination from agricultural workers; treated wood products from historical termite treatments; lower-frequency exposures from imported foods grown under foreign chlorpyrifos registrations |
| Sleep micro environment relevance | Moderate to high in specific scenarios: pre-2001 homes with original carpets and pre-ban pest-control history; agricultural-region households especially during application season; bedrooms used by occupants who work in agricultural application or live with such workers. Low to negligible for non-agricultural households in post-2001 construction |
| Activated carbon capture | High — chlorpyrifos is a semi-volatile organophosphate with favorable physicochemical properties for granular activated carbon adsorption. Inferred from general activated carbon performance on semi-volatile organophosphates; chlorpyrifos-specific residential breakthrough data is limited |
Regulatory & certification status
Where Chlorpyrifos 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 | Approval of chlorpyrifos as a plant-protection active substance was NOT renewed under Regulation (EC) No 1107/2009 (Commission Implementing Regulation (EU) 2020/18 of 10 January 2020). Member States were required to withdraw authorisations for plant protection products containing chlorpyrifos by 16 February 2020, with any grace period expiring by 16 April 2020. Chlorpyrifos (CAS 2921-88-2, EC 220-864-4) carries a CLP harmonised classification (Annex VI, Index 015-084-00-4): Acute Tox. 3 (H301), Aquatic Acute 1 (H400) and Aquatic Chronic 1 (H410). The non-renewal was enacted under pesticide law, not REACH; chlorpyrifos is not on the REACH SVHC Candidate List or Authorisation List (Annex XIV). Regulatory — EUR-Lex |
| United States | Chlorpyrifos is a pesticide regulated under FIFRA and the FFDCA (not TSCA). EPA's 2021 rule revoking all food tolerances was vacated by the U.S. Court of Appeals for the Eighth Circuit on 2 November 2023; as of the court's mandate on 28 December 2023, all chlorpyrifos tolerances were automatically back in effect. In December 2024 EPA issued a PROPOSED (not final) rule to revoke chlorpyrifos tolerances except those covering 11 specified food/feed crops. It is listed on California Proposition 65 as causing developmental toxicity, effective 15 December 2017. Regulatory — US EPA · Federal Register |
| Canada | Under the Pest Control Products Act (PMRA / Health Canada), the December 2020 environmental re-evaluation decision RVD2020-14 cancelled almost all uses of chlorpyrifos, with most cancelled uses phased out by 10 December 2023 and two uses (canola, garlic) granted an extended phase-out to December 2024. Re-evaluation Note REV2021-04 cancelled the remaining registrations. The sale and any use of chlorpyrifos pesticides in Canada is now prohibited. This is a final pesticide cancellation, not a CEPA Schedule 1 (toxic substances) listing. Regulatory — Government of Canada |
| Australia | As an agvet chemical, chlorpyrifos is regulated by the APVMA (not AICIS). The APVMA's final regulatory decision of 30 September 2024, from its chemical-review reconsideration, removed most agricultural and urban pest-control uses on worker-health-and-safety and environmental grounds (some uses were retained with restrictions). Products bearing the previously approved labels must not be supplied after 30 September 2025. Regulatory — APVMA |
| United Kingdom | Great Britain inherited the EU non-approval position: chlorpyrifos is not an approved plant-protection active substance in GB, with the regime administered by HSE since 1 January 2021. Because an active substance must be on the GB Pesticides Approvals Register before it can be used in any authorised product, no GB authorisations for plant protection products containing chlorpyrifos are in force. Regulatory — HSE |
| International | The Stockholm Convention Conference of the Parties, at COP-12 (Geneva, 28 April–9 May 2025), adopted decision SC-12/9 to list chlorpyrifos in Annex A (elimination) with time-limited specific exemptions. This is a final adopted treaty amendment, not merely a POPs Review Committee (POPRC) recommendation; the amendment enters into force on 9 October 2026 for parties that have not opted out. Regulatory — Stockholm Convention |
| Certifications | OEKO-TEX Standard 100: restricted — chlorpyrifos (listed as chlorpyrifos-ethyl, CAS 2921-88-2) appears among the regulated pesticides in the STANDARD 100 limit-values criteria, which set pesticide-residue limits (strictest for Product Class 1, baby/toddler articles) for textiles made of natural fibres. CertiPUR-US: not addressed — its foam program screens for CMR (carcinogenic/mutagenic/reprotoxic) chemicals and heavy metals such as lead and mercury, not agricultural insecticides, so chlorpyrifos is not a listed analyte. GREENGUARD/GREENGUARD Gold: a low-VOC chamber-emissions certification that does not specifically screen for a semi-volatile pesticide like chlorpyrifos. Industry — OEKO-TEX |
| The 72-hour test window | Largely missed. Chlorpyrifos is a semi-volatile organic compound (SVOC) with very low vapour pressure that partitions onto surfaces and house dust rather than off-gassing freely, so a short (~72-hour) VOC emissions chamber test does not reliably capture it; dust/wipe sampling or targeted residue analysis is the appropriate method. Inferred — from the compound's volatility/emission profile versus the VOC focus of short chamber tests |
What it is
Chlorpyrifos — CAS 2921-88-2, O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate — is an organophosphate insecticide synthesized by Dow Chemical in 1965 and marketed for decades under the trade names Dursban and Lorsban. The molecule contains a phosphorothioate group (the basis for organophosphate insecticide chemistry) attached to a chlorinated pyridine ring. It is a colorless to white crystalline solid at room temperature, with low water solubility, moderate volatility, and high affinity for organic matter — properties that drive its environmental fate: chlorpyrifos partitions strongly to soil and indoor dust, persists in those compartments for months to years, and reaches indoor air at lower concentrations than dust loadings would suggest.
The mechanism of action — the chemistry that makes chlorpyrifos useful as an insecticide and dangerous as a human exposure — is inhibition of acetylcholinesterase, the enzyme that breaks down the neurotransmitter acetylcholine at nerve synapses. Chlorpyrifos itself is a relatively weak inhibitor; the active toxicant is the metabolic activation product chlorpyrifos-oxon, formed by cytochrome P450 oxidation in the liver and other tissues. The acetylcholinesterase-inhibition mechanism is shared across the broader organophosphate insecticide class (malathion, diazinon, parathion, acephate, naled, and others) and is responsible for the characteristic acute organophosphate poisoning syndrome.
Where you encounter it
In persistent indoor dust from pre-2001 residential applications
Chlorpyrifos was the dominant US residential insecticide of the 1990s, applied for termite treatments, ant and cockroach control, and routine pest management in millions of homes. The EPA phase-out agreement of 2000 took effect December 31, 2001 for most residential uses. Regulatory The compound persists in carpet dust, baseboard dust, attic insulation, and crawl-space dust for years to decades after the original application. Homes built before 2001 that received termite treatments may still have measurable chlorpyrifos in dust today, and the dust pathway is the dominant route for current bedroom exposure in these households.
In drift and take-home contamination from agricultural use
Chlorpyrifos retains agricultural registrations in the US for the 11 food crops specified in the EPA's December 2024 proposed rule: alfalfa, apple, asparagus, tart cherry, citrus, cotton, peach, soybean, strawberry, sugar beet, and spring and winter wheat. EPA Federal Register, December 10, 2024. Regulatory Households in agricultural regions where these crops are grown can receive drift exposure during application season and take-home contamination via the clothing, hair, and skin of agricultural workers in the household.
In imported food and lower-frequency dietary exposure
Foods grown under foreign chlorpyrifos registrations and imported to the US carry residues consistent with the application history in the country of origin. The dietary exposure pathway is smaller than the dust and drift pathways for households in active agricultural regions or pre-2001 homes, but it is non-zero for general populations.
The current regulatory status
The chlorpyrifos regulatory record since 2000 has been complicated:
- 2000-2001: EPA phase-out agreement ends most residential uses; full residential ban takes effect December 31, 2001.
- 2002: Diazinon, the other dominant residential organophosphate, withdrawn from residential use following the same EPA process.
- 2021: EPA finalizes rule revoking all chlorpyrifos food-crop tolerances, effective February 2022.
- November 2023: 8th Circuit Court of Appeals vacates the 2021 final rule, finding EPA acted arbitrarily by not considering partial tolerance modifications.
- December 28, 2023: 8th Circuit mandate issues; all chlorpyrifos tolerances automatically reinstated.
- December 2024: EPA issues proposed rule revoking all chlorpyrifos food-crop tolerances except the 11 specified crops. Comment period extends into March 2025.
- 2026 (expected): EPA Interim Decision implementing the partial revocation framework.
The EPA's current-status FAQ is the cleanest single source for tracking the trajectory. Regulatory
What the research says
Acute toxicity — the acetylcholinesterase mechanism
Acute chlorpyrifos poisoning produces the classic organophosphate cholinergic syndrome — salivation, lacrimation, urination, defecation, gastrointestinal cramps (the SLUDGE mnemonic), pinpoint pupils, muscle twitching, and at extreme doses respiratory failure from diaphragm paralysis. The clinical management uses atropine to block cholinergic receptor activation and pralidoxime to reactivate inhibited acetylcholinesterase before the inhibition becomes irreversible through "aging." Eaton and colleagues 2008 in Critical Reviews in Toxicology produced the foundational 125-page review of chlorpyrifos toxicology with the most comprehensive coverage of the acute and chronic mechanisms. Peer-reviewed
Developmental neurotoxicity — the residential-ban driver
The chlorpyrifos developmental neurotoxicity evidence base is unusually rich for a single pesticide, anchored by two long-running prospective birth cohort studies: the Columbia Center for Children's Environmental Health (CCCEH) cohort in New York City and the CHAMACOS cohort in California's Salinas Valley agricultural region. Rauh et al. 2006 in Pediatrics documented the first three-year follow-up from the Columbia cohort, showing dose-dependent associations between prenatal chlorpyrifos exposure and delayed mental and motor development. Peer-reviewed
Rauh et al. 2012 in Proceedings of the National Academy of Sciences extended the Columbia findings to structural neuroimaging — MRI evidence of brain anomalies in children with the highest prenatal exposures, including thinning of the cerebral cortex and abnormalities in regions involved in attention and executive function. Peer-reviewed The combination of biochemical mechanism, animal toxicology, and structural human neuroimaging produced a coherent enough case for the EPA to finalize the residential ban.
The CHAMACOS cohort provided the agricultural-population counterpart. Eskenazi, Marks and colleagues 2008 in Neurotoxicology and Teratology documented organophosphate exposure and neurodevelopment associations in Mexican American farmworker children. Peer-reviewed Eskenazi et al. 2014 in Environmental Research demonstrated that the developmental impact was modified by maternal PON1 genotype — children of mothers with low-activity paraoxonase 1 (which metabolizes organophosphates) showed the largest exposure-related deficits. Peer-reviewed Whyatt and colleagues 2009 in Environmental Health Perspectives validated the prenatal biomarker measurements that anchored the Columbia cohort findings. Peer-reviewed
Carcinogenicity
Chlorpyrifos has not been formally evaluated by the International Agency for Research on Cancer; it does not appear with a Group classification in the IARC monograph series. The US EPA classified chlorpyrifos as "Group E — evidence of non-carcinogenicity for humans" based on the available animal data showing no significant tumor formation in chronic rodent bioassays. Regulatory The dominant chronic concern for chlorpyrifos is developmental neurotoxicity rather than cancer, which is the inverse of the framing for many other widely-used pesticides.
Regulatory reference values
The ATSDR Toxicological Profile for Chlorpyrifos sets a chronic oral Minimal Risk Level (MRL) at 0.001 mg/kg/day based on plasma cholinesterase inhibition in human volunteer studies. Regulatory EPA's chronic Reference Dose (RfD) is set at the same order of magnitude based on similar endpoints. The reference values are derived from cholinesterase inhibition rather than the developmental neurotoxicity endpoint, which has been the subject of considerable scientific and regulatory debate about whether the cholinesterase-based reference adequately protects against developmental effects.
What helps reduce exposure
For pre-2001 homes: HEPA-vacuum carpets and upholstery weekly. Chlorpyrifos partitions to dust at high affinity and persists for years in the dust reservoir. Frequent HEPA vacuuming with a sealed-system vacuum reduces the airborne re-entrainment of dust during normal activity and reduces the surface dust load directly.
Damp-mop hard floors regularly. Dry sweeping re-entrains dust into the air; damp mopping captures it without aerosolization.
Consider replacing original wall-to-wall carpets in pre-2001 homes. Carpet is the largest indoor reservoir for semi-volatile organic pesticides including chlorpyrifos. Replacing original carpets with hard flooring removes the dominant reservoir; replacing with new carpet substantially reduces the historical pesticide load.
For agricultural-region households: enforce a strict shoes-off and outerwear-change policy. Drift and take-home contamination from agricultural application is meaningfully reduced by leaving outdoor footwear and work clothing at an entry mudroom or laundry area rather than carrying them into living spaces and bedrooms.
Ventilate aggressively during agricultural application season. When neighboring fields are being actively treated, indoor air can briefly carry drifted chlorpyrifos vapor and particles. Cross-ventilation during off-application hours and closed windows during active spraying reduce the indoor accumulation.
For households with historical termite treatment: consider professional dust sampling. Pre-2001 termite treatments using chlorpyrifos can leave very high residues in crawl spaces, basements, and the soil immediately around foundation walls. Quantitative dust sampling informs whether targeted remediation makes sense.
What does NOT help
- Air purifiers alone. Chlorpyrifos is primarily in dust and on surfaces, not in air at residential concentrations. Air filtration captures the airborne fraction but does not address the dominant dust-reservoir exposure pathway.
- Generic "non-toxic" or "natural" pest control labels. These terms are unregulated. Effective alternatives exist (integrated pest management, boric acid for cockroaches, mechanical traps), but the labels themselves don't certify anything specific. Look for OMRI or similar verified certifications when product-specific verification matters.
- Organic farming labels on imported food. Organic certification addresses the production process but does not affect historical residential chlorpyrifos contamination, which is the bedroom-relevant exposure for pre-2001 homes.
- "Pesticide-free" mattress claims without specification. Some marketing claims address the manufacturing process; others specifically address application during use; very few address legacy contamination of the home environment the mattress will be placed in. Read the specific certification language.
Open research questions
- Neurodevelopmental effects at chronic low-dose exposure below the cholinesterase-inhibition threshold — the unresolved scientific question driving the developmental-vs-cholinesterase regulatory debate. Speculation — the prospective cohort data establishes the association; the dose-response in households with only dust-reservoir exposure has not been precisely characterized
- Residential dust persistence decay curves at multi-decade timescales — most monitoring data extends a few years post-application; multi-decade persistence in pre-2001 homes is documented qualitatively but not characterized with detailed decay-curve studies. Inferred from general organophosphate persistence literature; chlorpyrifos-specific multi-decade residential measurements are sparse
- Drift exposure dose-response in agricultural communities — the proximity and meteorological factors that drive household drift exposure are documented; the resulting dose-response for chronic neurodevelopmental endpoints has not been disentangled from the broader rural-pesticide co-exposure picture. Speculation
- Interaction effects with co-exposed organophosphates — agricultural communities are typically exposed to multiple organophosphates simultaneously (malathion, diazinon legacy, others). The cholinesterase-inhibition mechanism is shared, raising questions about additive or synergistic effects that single-compound regulatory assessment may understate. Speculation
Citations
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Chlorpyrifos. atsdr.cdc.gov/ToxProfiles/tp84.pdf Regulatory
- US Environmental Protection Agency. Frequently Asked Questions about the Current Status of Chlorpyrifos and Anticipated Path Forward. epa.gov Regulatory
- US Environmental Protection Agency (2024). Chlorpyrifos; Tolerance Revocation — Proposed Rule. Federal Register, 89(237):97558-97607. federalregister.gov Regulatory
- Eaton DL, Daroff RB, Autrup H, Bridges J, Buffler P, Costa LG, Coyle J, McKhann G, Mobley WC, Nadel L, Neubert D, Schulte-Hermann R, Spencer PS (2008). Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment. Critical Reviews in Toxicology, 38(Suppl 2):1-125. DOI 10.1080/10408440802272158 Peer-reviewed
- Rauh VA, Garfinkel R, Perera FP, Andrews HF, Hoepner L, Barr DB, Whitehead R, Tang D, Whyatt RW (2006). Impact of prenatal chlorpyrifos exposure on neurodevelopment in the first 3 years of life among inner-city children. Pediatrics, 118(6):e1845-e1859. DOI 10.1542/peds.2006-0338 Peer-reviewed
- Rauh V, Arunajadai S, Horton M, Perera F, Hoepner L, Barr DB, Whyatt R (2012). Brain anomalies in children exposed prenatally to a common organophosphate pesticide. Proceedings of the National Academy of Sciences USA, 109(20):7871-7876. DOI 10.1073/pnas.1203396109 Peer-reviewed
- Eskenazi B, Marks AR, Bradman A, Harley K, Barr DB, Johnson C, Morga N, Jewell NP (2008). Organophosphate pesticide exposure and neurodevelopment in young Mexican-American children. Neurotoxicology and Teratology, 30(2):130-137. DOI 10.1016/j.ntt.2008.03.012 Peer-reviewed — CHAMACOS cohort
- Eskenazi B, Kogut K, Huen K, Harley KG, Bouchard M, Bradman A, Boyd-Barr D, Johnson C, Holland N (2014). Organophosphate pesticide exposure, PON1, and neurodevelopment in school-age children from the CHAMACOS study. Environmental Research, 134:149-157. DOI 10.1016/j.envres.2014.07.001 Peer-reviewed
- Whyatt RM, Garfinkel R, Hoepner LA, Andrews H, Holmes D, Williams MK, Reyes A, Diaz D, Perera FP, Camann DE, Barr DB (2009). A biomarker validation study of prenatal chlorpyrifos exposure within an inner-city cohort during pregnancy. Environmental Health Perspectives, 117(4):559-567. DOI 10.1289/ehp.0800041 Peer-reviewed
- US Environmental Protection Agency. Chlorpyrifos — main pesticide-product ingredient page (chemistry, regulatory history, current label status). epa.gov/ingredients-used-pesticide-products/chlorpyrifos Regulatory
Frequently asked questions
Is chlorpyrifos banned?
Residential use has been banned in the United States since 2001 — that ban is still in effect. Agricultural food-crop tolerances have followed a more complex path: EPA revoked all food-crop tolerances in 2021, the 8th Circuit Court of Appeals vacated that rule in November 2023, all tolerances were automatically reinstated in December 2023, and EPA proposed a new partial revocation in December 2024 that would keep 11 food-crop uses while revoking the rest. EPA plans to issue an Interim Decision in 2026.
Why was chlorpyrifos banned for residential use?
The 2001 residential ban was driven by developmental neurotoxicity evidence — particularly the Columbia Center for Children's Environmental Health prospective cohort studies showing associations between prenatal chlorpyrifos exposure and altered neurodevelopment in inner-city children. Rauh and colleagues subsequently documented brain anomalies on MRI in children with the highest prenatal exposures. The acetylcholinesterase-inhibition mechanism, well-characterized for acute toxicity, raised concerns about subtler developmental effects at exposure levels well below the acute threshold.
If chlorpyrifos was banned in 2001, why does it still matter for bedroom chemistry?
Chlorpyrifos persists in household dust for years after the original application — multiple studies have detected chlorpyrifos in indoor dust decades after pre-ban residential treatments. Homes built before 2001 that received chlorpyrifos termite treatments or routine pest control sprays may still have measurable residue in carpets, baseboards, attic insulation, and crawl-space dust. Households in agricultural areas can also receive drift and take-home contamination from currently-permitted agricultural uses.
How does chlorpyrifos affect the brain?
The proximate mechanism is inhibition of acetylcholinesterase, the enzyme that breaks down the neurotransmitter acetylcholine at nerve junctions. Acute high-dose exposure produces classic organophosphate poisoning: SLUDGE symptoms, muscle twitching, and at extreme doses respiratory failure. The developmental neurotoxicity concern that drove the residential ban is a different mechanism — effects on developing brain at exposures well below those that produce measurable acetylcholinesterase inhibition in adults. The Rauh 2012 PNAS paper documented MRI-visible brain structural differences in children with high prenatal exposure.
What should I do if I live in a home built before 2001?
HEPA-vacuum carpets and upholstery weekly to remove accumulated dust where chlorpyrifos partitions. Damp-mop hard surfaces. Replace original wall-to-wall carpets when feasible — carpet is the largest reservoir for persistent semi-volatile organic pesticides. If termite treatment was applied historically (typical pre-2001 pest control), professional dust sampling can quantify current concentrations and inform whether crawl-space remediation makes sense for your specific home.
Does chlorpyrifos cause cancer?
Chlorpyrifos has not been formally evaluated by the International Agency for Research on Cancer (IARC) — it does not appear with a Group classification in the IARC monograph series. The US EPA classified chlorpyrifos as "Group E — evidence of non-carcinogenicity" based on the available animal and human data. The dominant chronic concern for chlorpyrifos is developmental neurotoxicity rather than cancer.
Are organophosphate pesticides still in use?
Yes — multiple organophosphate insecticides remain registered for agricultural use in the US (malathion, acephate, naled, and others). Diazinon, like chlorpyrifos, was withdrawn from residential use in 2002 but retains some agricultural uses. The class as a whole shares the acetylcholinesterase-inhibition mechanism and the associated acute toxicity profile; developmental neurotoxicity concerns are documented for several class members and remain an active regulatory question.
Related compounds
Embr is a sleep environment company researching the chemistry of the bedroom. See the methodology page for how this Atlas tags claims by evidence strength. For broader context on agricultural and farm-family exposure, see farm family sleep; for dust-reservoir exposure framing, see non-toxic bedroom.
Last reviewed 2026-05-25. If you find a factual error, contact us.