Plastics & textile additive — benzotriazole UV absorber

UV-328 in the bedroom

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

UV-328 is a benzotriazole ultraviolet absorber, added to plastics, coatings, adhesives and textiles to stop sunlight breaking them down. Global production runs to more than 1,000 tonnes a year. In May 2023 the Parties to the Stockholm Convention agreed to eliminate it as a persistent organic pollutant, and the EU turned that decision into a prohibition on 4 August 2025. UV-328 is not a legacy residue working its way out of old dust: it is an additive still in use, and it has been measured in the air right at the surface of children's mattresses.

The honest limit sits alongside the finding. Those bedroom concentrations were low, and no published inhalation reference value exists for UV-328, so nobody can say what level in a child's bedroom air would matter. IARC has never evaluated it. Neither has the US National Toxicology Program.

UV-328 — Embr Bedroom Chemistry Atlas

At a glance

Chemical familyBenzotriazole ultraviolet stabiliser (the hydroxy phenol benzotriazole class); a low-volatility semi-volatile organic compound, not a VOC
CAS number25973-55-1
Other identifiersEC 247-384-8. Chemical name 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol. Formula C22H29N3O, molecular weight 351.5 g/mol. Recorded by the Stockholm Convention as a mono-constituent substance, so this entry is one substance and not a group
ClassificationStockholm Convention Annex A (elimination), listed by decision SC-11/11 in May 2023. Prohibited in the EU under Annex I Part A of Regulation (EU) 2019/1021 from 4 August 2025. Not evaluated by IARC. Not evaluated by NTP. No harmonised CLP classification
Where you encounter itPlastics, coatings and adhesives; textiles, leather and coated fabrics; furniture, toys, construction materials, flooring, footwear and electronic equipment; indoor air and house dust, where it rides on fine particles rather than as vapour
Sleep micro-environment relevanceDetected in bedroom air, in the sleeping microenvironment and on the mattress surface itself in 25 Canadian children's bedrooms. Concentrations were low, but it had the highest detection frequency of the six benzotriazoles measured, and its level around the sleeping child correlated with the presence of a mattress protector
Known dose thresholdNone published. No inhalation reference value for UV-328 was found in any source reviewed for this page

Regulatory & certification status

European UnionProhibited. Commission Delegated Regulation (EU) 2025/843 of 5 May 2025 added UV-328 (CAS 25973-55-1, EC 247-384-8) to Annex I Part A of the POPs Regulation, (EU) 2019/1021. Manufacture, placing on the market and use are banned from 4 August 2025, subject to the specific exemptions the Annex records. The unintentional-trace-contaminant limit under Article 4(1)(b) is phased down over time, starting at 100 mg/kg. This supersedes the earlier REACH route, under which UV-328 had been on the Candidate List as a PBT and vPvB substance of very high concern since 17 December 2014 and was entry 51 on the Authorisation List with a sunset date of 27 November 2023. Annex I is a genuine prohibition; the Candidate List was only an identification. Regulatory — European Union authority
European Union — hazard classificationNo harmonised classification. UV-328 does not appear in the CLP Annex VI table, though several other benzotriazoles do. Absence from Annex VI is not absence of hazard: Annex VI covers only the harmonised subset of substances, and everything outside it is left to industry self-classification. Regulatory
United StatesNo federal restriction. UV-328 is on the TSCA Inventory and was reported under the Chemical Data Rule at a national aggregate production-plus-import volume of roughly 450 to 4,500 tonnes a year across the 1986 to 2006 and 2011 to 2015 reporting periods, with most reporting sites declaring import rather than domestic manufacture. Not listed under California Proposition 65. Not evaluated by NTP. The United States signed the Stockholm Convention in 2001 but never ratified it and has no statutory mechanism for implementing new listings, so the 2023 decision creates no US obligation. Regulatory
CanadaNot restricted. Environment and Climate Change Canada and Health Canada screened UV-328 under CEPA as BDTP and published the final decision in the Canada Gazette Part I on 21 May 2016, concluding that it meets none of the criteria in section 64 of the Act and that the Ministers proposed to take no further action under section 77. UV-328 is consequently absent from CEPA Schedule 1 and from the Prohibition of Certain Toxic Substances Regulations, 2025 (SOR/2025-270). The 2016 assessment noted UV-328 is not manufactured in Canada and that imports had fallen from a range of 100 to 1,000 tonnes in 2000 down to a range of 10 to 100 tonnes a year in 2012 and 2013. A separate Benzotriazoles and Benzothiazoles Group assessment was published in March 2025; whether it revisits UV-328 could not be confirmed for this page. Regulatory — Government of Canada authority
United KingdomProhibited in Great Britain. The Persistent Organic Pollutants (Amendment) Regulations 2025 (SI 2025/296) added UV-328 to the retained POPs Regulation with effect from 1 April 2025. The Article 4(1)(b) unintentional-trace-contaminant threshold is 10 mg/kg, or 0.001% by weight, a stricter starting point than the EU's. Exemptions cover mechanical separators in blood collection tubes until 26 February 2030, and replacement parts for land-based motor vehicles where UV-328 was in the original part, until the earlier of the end of the vehicle's service life and 2044. Regulatory — United Kingdom authority
AustraliaListed on the IChEMS Register by the Industrial Chemicals Environmental Management (Register) Amendment (2024 Measures No. 2) Instrument 2024, F2024L01577, made 2 December 2024, following IChEMS Advisory Committee advice of 11 June 2024 that recommended scheduling on the basis of the Stockholm Annex A listing. The fact of the listing is well corroborated. The schedule number is not stated here: the primary instrument could not be opened during research and secondary summaries disagree, so this page will not print a number it has not verified. Regulatory
InternationalStockholm Convention Annex A, Part I, listed for global elimination by decision SC-11/11 in May 2023. Switzerland proposed the listing in May 2020, and the POPs Review Committee concluded at its 16th meeting in January 2021 that UV-328 met the Annex D screening criteria. UV-328 is the first non-halogenated substance listed under the Convention. Specific exemptions cover parts of land-based motor vehicles, industrial coatings for vehicles, engineering machines, rail vehicles and heavy-duty steel structures, mechanical separators in blood collection tubes, triacetyl cellulose film in polarizers, photographic paper, and replacement parts running to the end of an article's service life or 2044, whichever is earlier. Not evaluated by IARC, which means no cancer assessment exists rather than that one found no hazard. Regulatory — UNEP / Stockholm Convention Secretariat

What it is

UV-328 belongs to a family of ultraviolet absorbers built on a benzotriazole ring. Sunlight breaks polymers apart. A UV absorber soaks up the ultraviolet part of that light and releases it as heat, so a plastic window frame does not chalk, a coated fabric does not yellow, and a printed surface holds its colour. UV-328 does that job well enough that global production passes 1,000 tonnes a year. It is a single mono-constituent substance, CAS 25973-55-1, and not a mixture or a group.

The properties that make it useful are the ones that got it banned. UV-328 is persistent, it bioaccumulates, and it does not stay where it was put. Switzerland proposed it for the Stockholm Convention in May 2020. The POPs Review Committee agreed in January 2021 that it met the screening criteria, and the Parties listed it for elimination in May 2023. UV-328 was the first non-halogenated substance the Convention ever listed. Every POP listed before it carried a halogen.

Two findings from human toxicology are worth holding together. Three volunteers given a single oral dose of 0.3 mg per kilogram absorbed it well: blood levels of the parent compound peaked around eight hours, but only about 0.1% of the dose came back out in urine over 72 hours, which implies the rest leaves by bile and faeces rather than through the kidneys. Separately, work on human CYP3A4 metabolism found that metabolising UV-328 makes it more antiandrogenic, not less. At 0.25 micromolar the metabolised compound was roughly twice as antiandrogenic as the parent. Screening the parent compound alone understates the hazard.

Where it shows up in bedding

The Stockholm Convention's own guidance lists fabric, textile and leather products among UV-328's uses, alongside indoor articles such as furniture, toys, construction materials, footwear, flooring and electronic equipment. That is a long list, and the guidance is candid that the typical loading in textiles is not known. The only textile measurement it cites found UV-328 in 2 of 26 clothing articles, at 8.05 and 108 ng/g, both primarily cotton.

The bedroom evidence is Canadian and recent. Vaezafshar and colleagues placed passive samplers in the bedrooms of 25 children aged six months to four years in Toronto and Ottawa, sampling three places at once: room air, the sleeping microenvironment immediately around the sleeping child, and the mattress surface itself. UV-328 turned up in all three. That cohort is the subject of our longer read on what the 2025 children's mattress study found.

Read that finding with its limits attached, because they carry as much weight as the headline. The authors state plainly that UV-328 concentrations were low in all three sampler types. Benzotriazoles as a class had detection frequencies below 50% in room air, so this is a widely-but-faintly present compound rather than a dominant one; the phthalates and organophosphate esters measured in the same bedrooms were present at far higher levels. What stood out about UV-328 was its consistency: it had the highest detection frequency of the six benzotriazoles measured.

One household item tracked with it. Of everything the parents were asked about, the presence of a mattress protector showed the strongest association with UV-328 in the sleeping microenvironment, at a Spearman rho of 0.75. A correlation across 25 households names a candidate source. It does not prove one, and nobody has yet measured UV-328 content in mattress protectors directly. The mechanism is at least plausible, since UV absorbers are added to the plastic films and coatings that make a protector waterproof.

What the research says

Air and dust are the most contaminated media for benzotriazole UV stabilisers as a class, and UV-328 is among the congeners occurring at elevated concentrations. House dust in a residential area of Manila carried up to 1,020 ng/g dry weight of seven benzotriazole UV stabilisers including UV-328. Low-volatility congeners such as this one partition onto fine particulate matter rather than existing in the vapour phase, which decides how exposure happens and what reduces it. The route is particle-bound dust and skin contact with treated surfaces, not inhaled vapour.

The gap that matters most is a missing number. UV-328 is measured in people, measured in bedrooms, and agreed by the Parties to the Stockholm Convention to be persistent and bioaccumulative enough to eliminate. What no one can supply is the concentration in bedroom air at which any of it would matter. No published inhalation reference value for UV-328 appeared in any source reviewed for this page. Presence is not dose, and on this compound the dose side of the ledger is empty. That is the same absence the Dose Gap tracks across the Atlas.

What helps

  • Wash bedding on a routine cycle and keep the sleeping surface uncluttered. This is the study authors' own recommendation, and it follows from their finding that the sleeping microenvironment held higher concentrations than the surrounding room. The material in the bed is the source. Fewer soft and plastic items in it, plus a regular wash, physically removes particle-bound residue instead of trying to filter it out of the air.
  • Prefer a woven cotton, wool or untreated fabric mattress protector over a laminated or coated plastic one. Across the 25 Toronto and Ottawa homes, the mattress protector was the item whose presence correlated most strongly with UV-328 around the sleeping child. That is a correlation, not proof of causation, but UV absorbers are added to the plastic films and coatings that make a protector waterproof, so the mechanism fits.
  • Damp-dust and vacuum the bedroom with a sealed HEPA machine. UV-328 partitions onto fine particles and settles into dust, so removing dust removes the compound. That is not true of a genuine VOC. A damp cloth beats dry dusting, which mostly redistributes what it picks up.
  • In the EU and Great Britain, new purchases now carry legal protection. Both jurisdictions prohibit UV-328 above trace levels, from 4 August 2025 and 1 April 2025 respectively, so newly-manufactured plastics, coatings and textiles placed on those markets should not contain it. Articles already in the home are unaffected, and neither rule applies in Canada or the United States.

What does not help

  • Airing out or off-gassing a mattress. UV-328 has very low volatility and moves bound to fine particles rather than as vapour. The 72-hour airing that genuinely clears a fresh-foam VOC does essentially nothing for a particle-bound semi-volatile.
  • Activated carbon bags, charcoal sachets and carbon filter elements. Carbon adsorbs volatile organic compounds. UV-328 is not one. A HEPA particle filter has a plausible mechanism against a particle-bound compound; a carbon element does not.
  • Reading "no Proposition 65 warning" or "no EU hazard classification" as reassurance. UV-328 is on neither list, and neither absence is a finding of safety. CLP Annex VI covers only the harmonised subset of substances. Absence from Prop 65 usually means nobody has taken a substance through the listing process. IARC has never evaluated UV-328 and neither has NTP.
  • Assuming the Stockholm listing means it has already gone. Annex A elimination governs production and new use. Exemptions run to 2030 for several applications and to 2044 for motor-vehicle replacement parts, articles already in circulation are not recalled, and a persistent compound sitting in existing household plastics stays put.
  • Switching to a product advertised as using a different benzotriazole UV absorber. The Stockholm guidance warns explicitly about regrettable substitution here. UV-234, UV-326, UV-327, UV-329 and UV-928 are all under PBT assessment in the EU, and several have been flagged as candidates for vPvB identification.

Open research questions

  • What concentration in bedroom air would matter? No published inhalation reference value for UV-328 was found in any source reviewed here. It is measured in humans, measured in bedrooms and listed for global elimination, and the dose number does not exist.
  • Does the mattress-protector correlation reflect the protector, or a confounder? A Spearman rho of 0.75 across 25 households in a single study is a signal, not an attribution. Nobody has yet measured UV-328 content in mattress protectors directly.
  • How much UV-328 is in textiles? The Stockholm Convention's own guidance states that the typical loading in textiles is not known. Its only cited textile measurement found UV-328 in 2 of 26 clothing articles, at 8.05 and 108 ng/g.
  • Will North American bedroom concentrations fall anyway? The EU, Great Britain and Australia have acted. Canada concluded in 2016 that UV-328 met no CEPA section 64 criterion, and the United States has neither ratified the Convention nor restricted the substance under TSCA. Whether the global market shift drags North American product content down regardless is untested.
  • Which IChEMS schedule did Australia assign? The primary instrument, F2024L01577, could not be opened during research for this page, and secondary summaries disagree between two schedules. The listing itself is well corroborated; the number is not stated here until someone reads the instrument.
  • Does Canada's March 2025 Benzotriazoles and Benzothiazoles Group assessment revisit UV-328? Or does the 2016 no-action conclusion still stand unchanged? This page could not confirm either way.

The exposure ledger for UV-328 (2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol)

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 1 of our 10 exposure datasets.
At what level would it matter?
This compound does not appear in EPA’s consolidated screening-level table at all, so no published inhalation reference value exists to set against the findings on this page. That is common for newer substances and for replacements brought in after an older compound was restricted. What this page documents is that the compound is present, not how much of it would matter. Presence is not dose.Source: US EPA, Regional Screening Levels (RSL) Summary Table
Does the law flag it?
Banned in the EU under the persistent organic pollutants Regulation: manufacture, sale and use are prohibited. Specific exemptions apply.Source: California OEHHA Prop 65 listSource: EU POPs Regulation

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.

Where you meet Uv 328 across your home

The same compound turns up in more than one place you live. Here's where it shows up in Embr — each links to the full breakdown for that part of your home.

Citations

  1. Vaezafshar S, Wolk S, Arrandale VH, Sühring R, Phipps E, Jantunen LM, Diamond ML (2025). Young Children's Exposure to Chemicals of Concern in Their Sleeping Environment: An In-Home Study. Environmental Science & Technology Letters. DOI 10.1021/acs.estlett.5c00051. Source Peer-reviewed
  2. UNEP / Secretariat of the Basel, Rotterdam and Stockholm Conventions (2024). Guidance on best available techniques and best environmental practices relevant to UV-328 listed under the Stockholm Convention on Persistent Organic Pollutants. Source Regulatory
  3. European Commission (2025). Commission Delegated Regulation (EU) 2025/843 of 5 May 2025 amending Annex I to Regulation (EU) 2019/1021 as regards UV-328. Official Journal of the European Union, OJ L, 2025/843, 15.7.2025. Source Regulatory
  4. Department for Environment, Food and Rural Affairs (2025). The Persistent Organic Pollutants (Amendment) Regulations 2025 (SI 2025/296). UK Statutory Instruments, legislation.gov.uk. Source Regulatory
  5. Department of the Environment and Department of Health, Canada (2016). Publication of final decision after screening assessment of Phenol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)- (BDTP), CAS RN 25973-55-1, under subsection 77(6) of CEPA 1999. Canada Gazette, Part I, 21 May 2016. Source Regulatory
  6. Denghel H, Hiller J, Leibold E, Göen T (2021). Human metabolism and kinetics of the UV absorber 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV 328) after oral administration. Archives of Toxicology. DOI 10.1007/s00204-021-03093-1. PMID 34180011. Source Peer-reviewed
  7. Zhuang S, Lv X, Pan L, Lu L, Ge Z, Wang J, Wang J, Liu J, Liu W, Zhang C (2017). Benzotriazole UV 328 and UV-P showed distinct antiandrogenic activity upon human CYP3A4-mediated biotransformation. Environmental Pollution. DOI 10.1016/j.envpol.2016.10.011. PMID 27743791. Source Peer-reviewed
  8. Ling T, Fang Y, Zong L, Tang Z, Fan K, Chen D, Jin P, Guan M (2025). Review of Environmental Occurrence and Toxicity of Benzotriazole Ultraviolet Stabilizers. Environment & Health. DOI 10.1021/envhealth.5c00139. PMID 41446764. Source Peer-reviewed

Frequently asked questions

  • Is UV-328 in my mattress?

    Nobody has measured UV-328 content inside mattresses directly. What has been measured is UV-328 in the air right at the mattress surface: a 2025 study of 25 children's bedrooms in Toronto and Ottawa detected it on mattress-mounted samplers, in the sleeping microenvironment and in room air. Concentrations were low in all three, but UV-328 had the highest detection frequency of the six benzotriazoles measured. The household item whose presence tracked most closely with UV-328 around the sleeping child was the mattress protector, at a Spearman rho of 0.75. That is a correlation across 25 homes, not proof that the protector is the source.

  • Is UV-328 banned?

    It depends entirely on where you live. The Parties to the Stockholm Convention agreed in May 2023 to list UV-328 in Annex A for global elimination. The EU turned that into a prohibition on 4 August 2025 through Commission Delegated Regulation (EU) 2025/843, which added UV-328 to Annex I Part A of the POPs Regulation, and Great Britain did the same on 1 April 2025. Canada assessed UV-328 in 2016, concluded it met none of the CEPA section 64 criteria, and has not restricted it. The United States has never ratified the Stockholm Convention and has no federal restriction on UV-328.

  • Will airing out a mattress get rid of UV-328?

    No. UV-328 has very low volatility and travels bound to fine particles rather than as vapour, so the airing that genuinely clears a fresh-foam VOC does almost nothing here. For the same reason, activated carbon bags and charcoal sachets have no plausible mechanism: carbon adsorbs volatile organic compounds, and UV-328 is not one. Physical dust removal is the route that matches the chemistry. Wash bedding on a routine cycle, keep the sleeping surface uncluttered, and damp-dust and vacuum with a sealed HEPA machine.

  • How much UV-328 is too much to breathe?

    No published inhalation reference value for UV-328 appeared in any source reviewed for this page. It is measured in people, measured in bedrooms and listed for global elimination, and there is still no number for the air a person sleeps in. Human volunteers given a single 0.3 mg/kg oral dose excreted only about 0.1 percent of it in urine over 72 hours, implying the rest leaves by other routes, and human CYP3A4 metabolism makes UV-328 roughly twice as antiandrogenic as the parent compound rather than less. Presence is not dose, and on this compound the dose side of the ledger is empty.

Related compounds

  • TBOEP — the organophosphate ester measured alongside UV-328 in the same 25 children's bedrooms
  • 2-Mercaptobenzothiazole — a benzothiazole, the neighbouring ring class to the benzotriazoles
  • PFAS textile finishes — another persistent additive applied to coated and treated fabrics
  • Phthalates — the semi-volatile plasticiser family that dominated that same bedroom dataset
  • BHT — another additive put into polymers to stop them degrading

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

Last reviewed 2026-07-25. If you find a factual error, contact us.