Zinc Pyrithione: Properties, Uses in Plastics and Regulatory Status

Zinc pyrithione (ZnPT, CAS 13463-41-7) is a metal pyrithione used as a fungicide, bactericide and algaecide that protects flexible PVC, polyurethane foam and other polymers from microbial attack. Because the same molecule is also the best-known anti-dandruff active, its legal position in plastics is often confused with its position in cosmetics, which raises the question of what actually applies to a plastic compound.

Since 1 March 2022, zinc pyrithione has carried a harmonised classification as toxic for reproduction category 1B (H360D) under Delegated Regulation (EU) 2020/1182. In plastics it remains an existing active substance in the Biocidal Products Regulation review programme for product-types 2, 6, 7, 9 and 10, with no decision as of 22 September 2026, and the Repr. 1B entry means a future approval is possible only by derogation. Zinc pyrithione is one of the antimicrobial substances, alongside DCOIT, OIT and IPBC, documented in our coverage of plastic additives, each with the same identity, dosage and regulatory fields.

This page sets out the 4 names zinc pyrithione trades under, its 3 recorded modes of action, its 240 °C (464 °F) decomposition point and 8 ppm water solubility, the 6 polymer systems on record without a published let-down rate, the one published plastics test, a 15-row regulatory matrix centred on the 2022 reclassification, 7 hazard classes, 5 competing biocides and 5 trade names.

The identity data for zinc pyrithione, as recorded by PubChem and the EU harmonised classification, are summarised below.

Table T1. Zinc pyrithione identity card.

Footnote: identity and physical data from PubChem CID 26041; classification from Delegated Regulation (EU) 2020/1182; regulatory entries from the legal texts cited in each section. Status as of 22 September 2026.

What Is Zinc Pyrithione?#

Zinc pyrithione is a metal pyrithione: one zinc atom bound to two pyrithione ligands, each a pyridine N-oxide carrying a sulfur thiolate group, which gives the formula C10H8N2O2S2Zn and a molecular weight of 317.7 g/mol. What separates zinc pyrithione from the other zinc compounds used in plastics? Zinc pyrithione is a complete organometallic coordination complex that acts as an intact molecule, while zinc oxide (CAS 1314-13-2) is an inorganic oxide that acts through the release of Zn2+ ions and reactive oxygen species.

In plastics, that complex has one job: material protection of the finished article against fungi, bacteria and algae.

What do ZnPT, ZPT and zinc omadine mean?#

ZnPT and ZPT are both abbreviations of zinc pyrithione, pyrithione zinc is the same substance with the words reversed, and zinc omadine comes from Zinc Omadine, the trade name of Arch Chemicals that Arxada sells it under today. The 4 names a buyer meets on zinc pyrithione documents are listed below.

• ZnPT: the form used in technical and regulatory literature, and on this page.
• ZPT: the same abbreviation without the element symbol.
• Pyrithione zinc: the reversed word order used in US over-the-counter labelling.
• Zinc omadine: the generic use of the Zinc Omadine trade name.

Is zinc pyrithione an organic or an inorganic antimicrobial?#

Zinc pyrithione sits between the two classes: it is an organometallic complex that carries a metal like the inorganic antimicrobials but acts as an intact molecule like the organic biocides, which is why classification schemes for plastics biocides list it in both groups. Our taxonomy lists it under both the zinc inorganics and the organic pyrithiones, beside its sibling copper pyrithione.

For antimicrobial additives for plastics, melt behaviour decides the grouping that matters, and there zinc pyrithione behaves like an organic: it decomposes at about 240 °C (464 °F) and is slowly broken down by UV light, while a silver carrier passes through melt processing unchanged. The overview of antimicrobial additives for plastics counts zinc pyrithione as a type of its own for exactly this reason.

How Does Zinc Pyrithione Protect Plastics from Fungi and Bacteria?#

Zinc pyrithione protects a plastic by poisoning the micro-organisms that settle on it: it disrupts membrane transport through the proton pump, and in fungi it also causes copper-mediated damage to iron-sulfur proteins. The 3 modes of action recorded for zinc pyrithione are listed below.

• Membrane-transport disruption: interference with the proton pump that drives transport across the cell membrane.
• Iron-sulfur protein damage: copper-mediated damage to iron-sulfur proteins in fungi.
• Slow release: gradual release from a low-solubility solid, which sets durability rather than speed of kill.

The third mode is a property, not a reaction, which is why the solubility value matters as much as the biochemistry. The mechanism record is a secondary compilation, so no inhibitory concentrations or species lists are added to it.

Why does flexible PVC need a fungicide such as zinc pyrithione?#

Flexible PVC needs a fungicide because its plasticizer, not the PVC itself, is food for fungi and bacteria, and a flexible compound can contain 5 to 65 wt% of it. Micro-organisms feed on the plasticizers, lubricants and other organic ingredients rather than on the polymer backbone, and the failures they cause are pink and black staining, odour, embrittlement and loss of mechanical properties.

PVC has always been the main host. About two-thirds of plastics biocide volume went into PVC in 2005, and zinc pyrithione entered PVC as a "lower-toxicity alternative" to the arsenical OBPA, as John Markarian reported from the Townsend Polymer Services survey in Plastics Additives and Compounding in 2006. The plasticizer is the nutrient, so switching between plasticizers for PVC does not remove it.

Is zinc pyrithione for material protection or for hygiene claims?#

In plastics, zinc pyrithione is mainly a material-protection biocide, the use the EU classes as product-type 9 for polymerised materials, and a hygiene claim on the same compound changes both the product-type and the evidence the claim needs. Annex V of the Biocidal Products Regulation defines product-type 9 as fibre, leather, rubber and polymerised materials preservatives, including odour prevention, and zinc pyrithione's review covers product-types 2, 6, 7, 9 and 10 but not product-type 4, the food and feed area. In the United States the line runs through the claim instead: protecting the article stays inside the FIFRA treated-article exemption, while a public-health claim requires registration of the article itself.

What Are the Physical and Chemical Properties of Zinc Pyrithione?#

Zinc pyrithione is a fine beige powder or granule that decomposes at about 240 °C (464 °F) instead of melting cleanly, dissolves in water only to about 8 ppm at neutral pH, and is slowly broken down by ultraviolet light. Its density is recorded as 1.782 at 25 °C (77 °F), printed here as the source record prints it. The physical and chemical properties are listed in Table T2.

Table T2. Physical and chemical properties of zinc pyrithione.

Footnote: the °F value is the arithmetic conversion of 240 °C. The 8 ppm solubility comes from a secondary source and is printed as the commonly cited value. Status as of 22 September 2026.

Values follow PubChem (CID 26041), and the NTP record classes the substance as insoluble below 1 mg/mL. Two of these properties set its limits in a plastic: the decomposition point sets the processing window, and the low solubility sets the service life.

What processing temperature can zinc pyrithione withstand?#

Zinc pyrithione stays below its decomposition point of about 240 °C (464 °F) in PVC plastisols, which gel and fuse at 140 to 220 °C (284 to 428 °F), but it reaches that point at the low end of the roughly 240 to 320 °C (464 to 608 °F) used to process engineering polymers such as PA66, PBT, PET and PC. The 240 °C value is a decomposition point, not a maximum processing temperature, and Table T2b sets that processing ceiling against the process windows on record.

Table T2b. Process temperatures against the 240 °C decomposition point.

Footnote: melt temperatures for calendered and extruded flexible PVC, PU foaming and polyolefin moulding are not recorded in our sources for this substance; check the actual melt profile against 240 °C. The engineering-polymer range comes from a secondary source.

Silver carriers pass through melt processing unchanged, so this limit does not apply to them. No decomposition products or residence-time data for zinc pyrithione are recorded in our sources.

How soluble is zinc pyrithione, and why does it matter in a plastic?#

Zinc pyrithione dissolves in water only to about 8 ppm at neutral pH, so a compound loses it slowly to rain, washing or damp contact, which is what gives it long service in outdoor and wet articles. That value is below the 14 ppm recorded for DCOIT and more than 60 times below the 500 mg/L recorded for OIT, both at 25 °C (77 °F), treating ppm and mg/L as equivalent for dilute aqueous solutions.

Low solubility gives slow release, low leaching and outdoor persistence at the cost of speed of kill; no leaching rate or service life is on record.

Which Polymers Use Zinc Pyrithione, and at What Dosage?#

Zinc pyrithione is used in flexible PVC, polyurethane foam, wood-plastic composites and thermoplastic elastomers, and, like every plastics biocide, at very low levels: biocides make up 0.001 to 1 wt% of finished plastic products in the survey by Hahladakis and colleagues (2018). Bio-based HDPE film in research and polyolefin appliance parts in practice extend the host list to the 6 systems in Table T3.

So what is the dosage of zinc pyrithione in PVC? No published supplier let-down rate for it in a named polymer survived our source check, and the 0.001 to 1 wt% range, compiled again by Chea and colleagues in 2025, covers all biocides; ask the supplier for the grade's active content and recommended let-down.

Competing pages print no plastics dosage level either, only cosmetic levels that have nothing to do with a PVC compound. Typical ranges for every family are collected under additive dosage levels in plastics.

The polymers on record, the evidence for each and the dosage position are compared in Table T3.

Table T3. Zinc pyrithione by polymer: role, evidence and dosage position.

Footnote: "no published let-down rate" means no primary source on file gives a value. We do not estimate.

Zinc pyrithione in flexible PVC#

In flexible PVC, zinc pyrithione is one of the fungicides that took over from OBPA, and it usually arrives dispersed in a plasticizer carrier such as DINP rather than as a neat powder. Liquid biocides for PVC generally arrive in DINP, DIDP or DIHP carriers. The rest of the recipe around the biocide is set out under flexible PVC formulations.

The substitution became structural in Europe. OBPA is not in the review programme of the Biocidal Products Regulation, so it cannot be the active in treated articles placed on the EU market, while zinc pyrithione remains an existing active under review, product-type 9 included.

Choosing between zinc pyrithione and OIT, DCOIT, IPBC or BBIT in flexible PVC is a package decision rather than a substance decision. The full fungicide (or mildewcide) package is compared under antimicrobials for flexible PVC.

Zinc pyrithione in polyurethane foam#

In polyurethane foam, zinc pyrithione again replaced OBPA, and for foams that sit in damp soil it is sold blended with the isothiazolinone BBIT as Vanquish SL-10. Polyurethane foam took under 10 % of plastics biocide volume in 2005 in the Townsend survey, and BBIT itself is used in flexible foams, gaskets and insulation.

The fungicide does not shape the foam; it protects it, as one line in the package described under additives for polyurethane.

Zinc pyrithione in TPE, polyethylene and polypropylene#

In thermoplastic elastomers, zinc pyrithione has the clearest published efficacy result of any polymer in our sources: Pittol and colleagues (2017) reported a 99.9 % reduction of Escherichia coli and a 99.7 % reduction of Staphylococcus aureus on an SEBS compound under JIS Z 2801, together with a fungal inhibition zone. The loading is not stated in the study abstract, so the figure belongs to that compound and that method.

Thermoplastic elastomer grips are one of the 5 application areas on record. SEBS grip compounds and the rest of their package are covered under additives for thermoplastic elastomers.

In polyethylene, Mesquita and colleagues (2024) studied zinc pyrithione with organoclay in bio-based HDPE film; no result from that study is recorded in our sources.

In polypropylene and polyethylene parts for appliances, kitchenware, food-processing boards and water coolers, zinc pyrithione is one of three actives, alongside silver carriers and zinc oxide, compared under antimicrobials for polypropylene and polyethylene. EU food-contact use is a separate legal question, answered in the regulatory section.

How is zinc pyrithione dosed: masterbatch let-down, plasticizer carrier or powder?#

Zinc pyrithione reaches a plastic compound in 3 forms: as a masterbatch concentrate, as a dispersion in a plasticizer carrier such as DINP, or as a neat powder dosed into the dry blend. The 3 supply forms are listed below.

• Masterbatch concentrate: most plastics biocides, zinc pyrithione included, are sold as an additive masterbatch at 1 to 20 % active, so the let-down ratio sets the final level.
• Plasticizer-carrier grade: for PVC, the carrier counts in the plasticizer budget of the recipe; Sanitized PL 21-60, in DINP, is the example on record.
• Neat powder: the whole thermal load falls on the active, so the 240 °C (464 °F) decomposition point applies directly.

A concentrate percentage is not the active level in the part: a concentrate at 10 % active let down at 1:50 gives 0.2 % active (10 % divided by 50), an illustration rather than a recommended level.

Quotations for a powder, a dispersion and a masterbatch are comparable only after conversion to active content. Convert every offer with the let-down ratio calculator before comparing prices.

What Is Zinc Pyrithione Used For in Plastics?#

Zinc pyrithione is used in 5 plastics application areas: PVC flooring, roofing membranes and wallcoverings; polyurethane foams; wood-plastic composites; thermoplastic elastomer grips; and sponges. All 5 are material-protection uses that keep the article from staining, smelling or degrading, not health claims. The 5 application areas on record are listed below.

• PVC flooring, roofing membranes and wallcoverings: high-plasticizer vinyl in damp service.
• Polyurethane foams: foams protected against fungi, including the BBIT blend for soil burial.
• Wood-plastic composites: mould control alongside DCOIT.
• Thermoplastic elastomer grips: SEBS compounds held in the hand.
• Sponges: wet, porous articles that hold moisture between uses.

PVC flooring, roofing membranes and wallcoverings#

Flooring, roofing membranes and wallcoverings are the classic zinc pyrithione articles in PVC, because each combines a high plasticizer content with damp service, the condition under which fungi stain and degrade a vinyl surface. The failures prevented are pink and black staining, odor and embrittlement.

On an exposed roof, zinc pyrithione is slowly decomposed by UV light, while DCOIT is recorded with better UV resistance than OBPA (Markarian 2006); the two records measure different things, so neither ranks zinc pyrithione against DCOIT. The fungicide sits alongside the plasticizer, stabilizer and filler choices covered in additives for PVC.

Wood-plastic composites#

In wood-plastic composites, zinc pyrithione is one of two fungicides used against mould, the other being DCOIT, for which Rohm and Haas launched dedicated Vinyzene grades. No zinc pyrithione grade or dosage specific to composites is recorded in our sources.

Mold control is one of four additive tasks in a composite. Biocides are one of four additive groups in additives for wood-plastic composites, alongside coupling agents, lubricants and UV stabilizers.

Grips, sponges and foam articles#

Grips, sponges and foam articles use zinc pyrithione to prevent the odour and discoloration that follow from skin contact and trapped moisture, and in the EU an odour-prevention purpose of this kind falls inside product-type 9. An anti-odour grip compound is therefore a material-protection use, and the SEBS result of Pittol and colleagues (2017) is its efficacy evidence.

Foam-specific packages, from PU to PE foam, are compared under additives for plastic foams.

How Well Does Zinc Pyrithione Work? Test Results and Test Methods#

In the one published plastics test in our sources, an SEBS compound containing zinc pyrithione reduced Escherichia coli by 99.9 % and Staphylococcus aureus by 99.7 % under JIS Z 2801 and also produced a fungal inhibition zone (Pittol and colleagues, 2017). That result belongs to one compound, method, organism and contact time, not to zinc pyrithione in general. Does a 99.9 % result mean the plastic is protected from mould?

No: JIS Z 2801 and ISO 22196:2011 measure antibacterial activity on a wet surface over 24 hours at 35 ± 1 °C (95 °F) and at least 90 % relative humidity, reported as the activity value R, the log10 reduction in viable count against an untreated control. Fungal resistance needs fungal tests such as ASTM G21 and ISO 846, which are compared with the wet and dry methods under antimicrobial plastics testing.

The evidence on record and the methods that apply to zinc pyrithione compounds are summarised in Table T4.

Table T4. Zinc pyrithione test evidence and methods.

Footnote: a result belongs to a compound, a method, an organism and a contact time. It is not a property of zinc pyrithione.

A zone of inhibition shows that an active moves into the agar, so for a low-solubility active such as zinc pyrithione its width says little about surface activity. Outdoor compounds are qualified after accelerated weathering tests as well as as-moulded, because zinc pyrithione is slowly broken down by UV; no weathering result for it is on record.

How Does Zinc Pyrithione Interact with Plasticizers, UV Stabilizers and Other Additives?#

Zinc pyrithione interacts with 4 parts of a formulation that are on record: the plasticizer that feeds the fungi and often carries the biocide, the UV package, the co-biocide it is blended with, and the melt temperature of the process. No interaction data with colorants, fillers or heat stabilizers are recorded, and no source describes zinc pyrithione being deactivated by a named additive.

The plasticizer carrier is the interaction a compliance reviewer misses: DINP is not an SVHC and is not banned in the EU, but REACH Annex XVII entry 52 covers it in mouthable toys and childcare articles, and it has been on the California Proposition 65 cancer list since 20 December 2013 (No Significant Risk Level 146 µg/day). A grade dispersed in DINP (diisononyl phthalate) brings DINP's own toy and Proposition 65 status into the compound.

The 5 co-additives and conditions on record, their effect and the action each calls for are compared in Table T5i.

Table T5i. Zinc pyrithione interactions in a plastic formulation.

No protection factor for any of the UV stabilizers for plastics, such as HALS or benzotriazole absorbers, is recorded against zinc pyrithione loss, so the whole package is qualified outdoors rather than a stabilizer being picked by name. The stabilizer classes are compared under UV stabilizers for plastics.

What Is the Regulatory Status of Zinc Pyrithione?#

Zinc pyrithione has carried a harmonised Repr. 1B classification in the EU since 1 March 2022, is an existing active substance in the Biocidal Products Regulation review programme for product-types 2, 6, 7, 9 and 10 with no decision as of 22 September 2026, is not a Substance of Very High Concern, is listed in REACH Annex XVII Appendix 6, and is not on the EU food-contact Union list. It may be used in EU treated articles while the review continues, but claims, consumer supply and food contact each meet a separate rule. The 15 instruments that apply are listed in Table T5.

Table T5. Zinc pyrithione regulatory matrix, status as of 22 September 2026.

Footnote: tonnes are the arithmetic conversion of the reported pound bands (1 lb = 0.4536 kg). Biocidal review positions change; check the date before relying on a row.

The three layers, biocide law, chemical law and food-contact law, are mapped on plastic additive regulations.

Does zinc pyrithione need approval under the EU Biocidal Products Regulation?#

Yes: zinc pyrithione is a biocidal active substance, so its use in plastics needs approval under Regulation (EU) No 528/2012 for each product-type, and as of 22 September 2026 it is still an existing active in the review programme for product-types 2, 6, 7, 9 and 10, with no decision published. Article 58(2) allows a treated article to contain only actives approved, or under review, for the relevant product-type, so the review entry is what keeps zinc pyrithione usable in plastics.

"In review" is a transitional status, not an approval. Under the Article 94 transitional rule, treated articles on the EU market on 1 September 2013 may stay there if the active-substance application was submitted by 1 September 2016, and actives in review keep that status until a decision, which can go either way. For zinc pyrithione that decision is harder than usual, for the reason set out next.

One classification, three consequences: what the 2022 Repr. 1B entry changed#

A single EU decision, the harmonised Repr. 1B classification of zinc pyrithione under Delegated Regulation (EU) 2020/1182, applicable from 1 March 2022, produced three separate legal consequences: a ban in cosmetics, a hurdle in its biocide approval and a restriction on selling concentrates to consumers. Each consequence follows from a different instrument that cites the same toxic-for-reproduction entry, as Table T6 shows.

Table T6. One classification, three consequences.

The classification did not put zinc pyrithione on the REACH Candidate List, so a plastic article containing it carries no Article 33 duty and no SCIP notification on its account. How a harmonised entry and its M-factors are applied to a mixture is explained under CLP classification of plastic additives.

What may a plastic article treated with zinc pyrithione claim?#

A plastic article treated with zinc pyrithione may claim that it is protected against microbial deterioration, and in the EU that claim obliges the label to name zinc pyrithione as the active substance and to state the substantiated property. The 5 elements Article 58(3) requires on the label of a treated article that makes a biocidal claim are listed below.

• Biocide statement: a statement that the article incorporates biocidal products.
• Biocidal property: the property attributed to the article, where it is substantiated.
• Active substances: the names of all active substances, here zinc pyrithione.
• Nanomaterials: the name of any nanomaterial, followed by "(nano)".
• Instructions and precautions: any relevant instructions for use and precautions.

Article 58(5) also gives consumers information on the treatment free of charge within 45 days of a request.

In the United States, "protects the product from microbial deterioration" stays inside the FIFRA treated-article exemption of 40 CFR 152.25(a), while "protects you from germs" is a public-health claim that requires registration of the article. The full wording rules for both markets are set out under treated articles.

Is zinc pyrithione an SVHC?#

No: zinc pyrithione is not on the REACH Candidate List, which held 253 entries at its update of 4 February 2026, even though its Repr. 1B classification is the kind of hazard on which a Candidate List entry can be based. As a general rule, Article 57(c) of REACH makes Repr. 1A or 1B a ground for SVHC identification, but no procedure has listed zinc pyrithione.

Without that entry it triggers no Article 33 duty or SCIP notification, and it is not on Annex XIV either. Every plastic additive on the SVHC Candidate List is tabulated there; zinc pyrithione is not among them.

Is zinc pyrithione restricted under REACH Annex XVII?#

Yes, in one narrow way: zinc pyrithione is listed in Appendix 6 of REACH Annex XVII entries 28 to 30, which forbid supplying it to the general public on its own or in mixtures at or above the concentration limit, but the entries do not restrict industrial compounding or finished plastic articles.

Regulation (EU) 2021/2204 made the entry, and the latest appendix update is Regulation (EU) 2025/1731 of 8 August 2025; the applicable concentration limit is not recorded in our sources, so no number is printed. Entries 28 to 30 are explained with the other REACH Annex XVII restrictions.

The entries reach a consumer-sold concentrate, a repair kit or a hobby mixture, not a compounder supplying masterbatch to a converter.

Restriction is separate from registration. Zinc pyrithione is registered with 5 active full dossiers, the lead Article 10 dossier dating from 2010, and as a biocidal active it is also regarded as registered for its biocidal use under Article 15(2). Registration, restriction and authorisation are set out under REACH and plastic additives.

Is zinc pyrithione allowed in food-contact plastics?#

No, not in the EU: zinc pyrithione is not on the Union list of Regulation (EU) No 10/2011 (consolidation of 14 July 2026), and its biocide review does not include product-type 4, the food and feed area, so there is no European route for it in a food-contact plastic.

The Union list is a positive list, and no pyrithione antimicrobial appears on it. The list and its metal limits are explained under EU 10/2011.

The biocide route is closed as well, because the review covers product-types 2, 6, 7, 9 and 10 only, so an EU cutting board or water-cooler part compounded with zinc pyrithione can rely on neither regime.

In the United States the only FDA rule recorded for zinc pyrithione is 21 CFR 358.710, which governs over-the-counter anti-dandruff drugs, not food-contact plastics, and no food-contact clearance is recorded in our sources. The 21 CFR routes for plastics additives are set out under FDA food contact rules.

What is the US status of zinc pyrithione: EPA, TSCA and Proposition 65?#

In the United States, zinc pyrithione is a registered pesticide active under FIFRA with EPA pesticide code 088002, it is reported under TSCA Chemical Data Reporting at 75,000 to under 100,000 lb (34 to 45 t) for 2023, and it was not found on the California Proposition 65 list when we last checked on 22 September 2026.

The CDR figures cover all uses, plastics and non-plastics together, and the 2022 band was 250,000 to under 400,000 lb (113 to 181 t). Chemical Data Reporting is explained under TSCA and plastic additives.

Protected plastic articles rely on the FIFRA registration of the active as long as the claim stays with protecting the article.

The Proposition 65 status is re-checked against each new OEHHA list edition and tracked under California Proposition 65.

Is zinc pyrithione banned in plastics?#

No: zinc pyrithione is not banned in plastics in the EU or the United States; in the EU it is an existing biocidal active under review for 5 product-types, whose approval is possible only by derogation because of its Repr. 1B classification, and the ban that headlines refer to is the EU cosmetics ban of 1 March 2022. That cosmetics ban is explained below the contextual border of this page.

Is Zinc Pyrithione Hazardous? GHS Classification and Environmental Profile#

Zinc pyrithione carries a harmonised EU classification as a category 1B reproductive toxicant (H360D, may damage the unborn child), as acutely toxic by inhalation in category 2 (H330) and by ingestion in category 3 (H301), and as very toxic to aquatic life with an acute M-factor of 1,000. The entry, index 613-333-00-7 in Annex VI of Regulation (EC) No 1272/2008, also covers STOT RE 1 (H372) and Eye Dam. 1 (H318). Does zinc pyrithione cause cancer? Its harmonised classification contains no carcinogenicity class, and no IARC or Proposition 65 cancer entry is recorded in our sources, so this page makes no carcinogenicity statement. The 7 harmonised hazard classes are listed in Table T5h.

Table T5h. Harmonised CLP classification of zinc pyrithione.

Footnote: hazard-statement wording follows the standard text of CLP Annex III; the classification codes come from Delegated Regulation (EU) 2020/1182, applicable 1 March 2022. No LD50, LC50, NOAEL, DNEL or occupational exposure limit is recorded in our sources, so none is printed.

An M-factor of 1,000 multiplies the zinc pyrithione content of a mixture by 1,000 before comparison with the classification threshold, so a masterbatch reaches the aquatic hazard classes at a far lower content than the active alone suggests, and the chronic M-factor of 10 works the same way. The Repr. 1B entry is also why consumer supply of concentrates is restricted under REACH Annex XVII Appendix 6. Zinc pyrithione sits on our list of toxic plastic additives because of its CMR and aquatic classifications, not because of any measured exposure from plastic articles.

What Are the Alternatives to Zinc Pyrithione in Plastics?#

The 5 biocides that compete with zinc pyrithione in plastics are DCOIT, OIT, IPBC, silver zinc zeolite and the legacy arsenical OBPA, and the differentiator that matters most in Europe is product-type 9: only silver zinc zeolite holds a current approval for it. Each alternative trades a different property, such as water solubility, target organisms, thermal behaviour or regulatory status, and none is a drop-in replacement. The 6 biocides, zinc pyrithione included, are compared attribute by attribute in Table T7.

Table T7. Zinc pyrithione and its alternatives compared.

Footnote: melting points are not processing limits; only zinc pyrithione's value is a decomposition temperature. "Not recorded" means the value is not in our sources; we do not estimate. BPR positions change: check the date.

Zinc pyrithione vs OBPA#

Zinc pyrithione is one of the fungicides that replaced OBPA, the arsenical that held more than a third of plastics biocide volume in 2005, and in the EU the replacement is no longer optional, because OBPA is not in the Biocidal Products Regulation review programme and cannot be used in treated articles at all.

Markarian (2006) called zinc pyrithione a "lower-toxicity alternative" to OBPA, a relative description, since zinc pyrithione itself has carried a harmonised Repr. 1B classification since 1 March 2022. Like zinc pyrithione today, OBPA (CAS 58-36-6) was supplied in DIDP, DIHP and DINP carriers.

Zinc pyrithione vs DCOIT and OIT#

DCOIT and OIT are the isothiazolinone alternatives to zinc pyrithione in flexible PVC, and the main difference is where they go in the compound: their octyl chains make them lipophilic enough to stay in the plasticized phase, while zinc pyrithione is a low-solubility solid that releases slowly. Longer alkyl chains make isothiazolinones both more fungicidal and more lipophilic, according to the review by Silva and colleagues (2020).

Of the pair, DCOIT (CAS 64359-81-5) dissolves to 14 ppm at 25 °C (77 °F) and was recorded with better UV resistance than OBPA by Markarian (2006).

None of the three holds an EU approval for product-type 9: DCOIT holds product-types 8 and 21, OIT product-type 8, and zinc pyrithione none yet.

The liquid of the pair, OIT (octhilinone) (CAS 26530-20-1), melts at 15 °C (59 °F) and dissolves to 500 mg/L, and it is in review for product-type 9.

Zinc pyrithione vs IPBC#

IPBC is the carbamate alternative to zinc pyrithione, a fungicide sold as a solid grade for polyolefins and styrenics and as a non-metallic liquid grade for flexible PVC, and like zinc pyrithione it is still in review for product-type 9. The grades on record are Micropel 612 (solid) and Micropel A285 (liquid).

Elsewhere in the BPR, IPBC (CAS 55406-53-6) holds approvals for product-types 6, 8 and 13 and stays in review for 7, 9 and 10, so for polymerized materials it stands where zinc pyrithione stands.

Zinc pyrithione vs silver zinc zeolite#

Silver zinc zeolite does a different job from zinc pyrithione: it is an antibacterial carrier that releases silver ions in the presence of moisture, it passes through melt processing unchanged, and since 1 March 2026 it is the only antimicrobial in this comparison with an EU approval for product-type 9.

Implementing Regulation (EU) 2024/2635 approves silver zinc zeolite (CAS 130328-20-0) for product-types 2, 7 and 9 until 29 February 2036, excluding non-textile polymer articles in direct skin contact above 300 cm2 for adults and children over 2 years or 200 cm2 for toddlers and infants, with a mandatory Article 58(3) label.

Silver zinc zeolite is recorded as antibacterial only and holds no approval for product-type 4, while zinc pyrithione also acts on fungi and algae but holds no approval yet.

Who Supplies Zinc Pyrithione? Trade Names, Grades and Sourcing#

Zinc pyrithione is sold to the plastics industry under 5 trade names on record, Zinc Omadine, Omacide, Acticide PZ, Vanquish SL-10 and Sanitized PL 21-60, by Arxada, Thor and Sanitized AG, and the first thing to check on any offer is the active content of the grade. Arxada is the former Lonza and Arch Chemicals business. Producers of every active in this family are listed among antimicrobial additive suppliers.

Buyers should ask for the active content, the carrier, the technical data sheet, the safety data sheet and the product-types the supplier supports in the EU review, because a grade without a supported product-type has no long-term EU route.

No zinc pyrithione price is recorded in our sources, and quotes for a powder, a carrier dispersion and a masterbatch compare only after conversion to active content. No price guide covers biocides yet; the drivers for other families are tracked under plastic additive prices.

The 5 trade names on record, their owners and their form are listed in Table T8.

Table T8. Zinc pyrithione trade names.

Footnote: we list a company only where our sources record it. Grade-level details beyond these are being verified; see our sourcing standards.

Where Does Zinc Pyrithione Sit in the Family of Plastics Biocides?#

Zinc pyrithione belongs to the organic and organometallic side of a plastics biocide market that the Townsend Polymer Services survey put at 15.4 million kg (34 million lb) in 2005, a market then led by the arsenical OBPA and the isothiazolinones and only beginning to shift towards silver. The survey, reported by Markarian in 2006, gave OBPA more than a third of volume, the isothiazolones about a third or more and inorganic actives, mostly silver, under 10 %.

No current market size for plastics biocides is recorded in our sources, so the 2005 figures are not extrapolated. The organic class as a whole, with OBPA, the isothiazolinones and IPBC, is compared under organic biocides and fungicides for plastics.

Pyrithiones, isothiazolinones and silver carriers#

Zinc pyrithione has one close chemical sibling, copper pyrithione, and two neighbouring classes in plastics: the isothiazolinones, which attack enzyme thiol groups, and the silver carriers, which release silver ions when moisture reaches the surface. OIT, DCOIT, BIT and BBIT are covered together as isothiazolinone biocides for plastics.

Silver carriers, such as zeolite, zirconium phosphate and phosphate glass hosts, release Ag+ by ion exchange and survive melt processing. Each silver carrier's approval or refusal is set out under silver-based antimicrobials.

Why was zinc pyrithione banned in EU cosmetics?#

Zinc pyrithione was banned in EU cosmetics from 1 March 2022 because it was classified as toxic for reproduction category 1B, and Regulation (EU) 2021/1902 added it to Annex II, the list of substances prohibited in cosmetic products. The classification came from Delegated Regulation (EU) 2020/1182, applicable the same day, and the Scientific Committee on Consumer Safety had issued opinion SCCS/1614/19 on the substance.

The same classification did not ban zinc pyrithione in plastics; it turned the biocide approval into a derogation question, and a PVC floor, foam or grip containing it remains legal in the EU while the review continues.

Zinc pyrithione outside plastics: anti-dandruff products and film preservation#

Outside plastics, zinc pyrithione is best known as an over-the-counter anti-dandruff drug ingredient in the United States, permitted under 21 CFR 358.710 at 0.3 to 2 % in rinse-off and 0.1 to 0.25 % in leave-on products, and in the EU its biocide review also covers film preservation (product-type 7). Neither use is a plastics use, and neither is covered further on this site.

Does zinc pyrithione wear off a plastic article?#

Zinc pyrithione leaves a plastic slowly rather than wearing off at a fixed rate: its water solubility of about 8 ppm limits how much contact with water removes, and its slow decomposition under UV light limits how long it lasts on an exposed surface. The physics behind it is the same as for any additive migration in plastics.

Does a plastic article containing zinc pyrithione need a SCIP notification?#

No, not on account of zinc pyrithione: SCIP notification under Article 9(1)(i) of the Waste Framework Directive, required since 5 January 2021, applies to Candidate List substances above 0.1 % w/w in an article, and zinc pyrithione is not on the Candidate List. Another substance in the article, such as DEHP, can still trigger it, because a substance on the REACH Candidate List above 0.1 % w/w is what triggers the notification.

Is zinc pyrithione the same as zinc oxide?#

No: zinc oxide (CAS 1314-13-2) is an inorganic oxide authorised for EU food-contact plastics as FCM No 402 under a zinc migration limit of 5 mg/kg, while zinc pyrithione (CAS 13463-41-7) is an organometallic biocide that is not on the food-contact Union list and carries a Repr. 1B classification. Beyond antimicrobial use, zinc oxide also works as a UV absorber, an activator and a white pigment.