Antimicrobial Additives for Plastics: 6 Types, Mechanisms, Dosage and Selection

Antimicrobial additives are biocides compounded into a polymer so that the plastic article, or its surface, resists the growth of bacteria, fungi, algae and yeasts, and in the European Union every plastic that contains one is legally a treated article. Six chemical types do this work, from silver carriers that release ions when the surface gets wet to isothiazolinones that react with enzyme thiols, so which one belongs in which polymer, and what may you claim about it? Biocides make up 0.001 to 1 wt% of a finished plastic product, the lowest content range of any functional additive family except colorants.

The 6 types, in the order used throughout this page, are silver-based carriers such as silver zinc zeolite, zinc and copper inorganics such as zinc oxide, zinc pyrithione, the isothiazolinones such as DCOIT, the carbamate and benzimidazole fungicides such as IPBC, and the legacy actives such as OBPA. A biocide goes into a plastic for one of two reasons: material protection, which stops microbes feeding on the compound itself, or a surface-hygiene claim about the finished article. Only one active holds a current European approval for polymer preservation, silver zinc zeolite, approved for product-types 2, 7 and 9 from 1 March 2026.

This reference separates the antimicrobial additive from the antimicrobial polymer, explains how silver carriers, organic biocides and contact-active surfaces act, sets out the 6 types with CAS numbers and European status, matches each to the polymers that use it, publishes the measured dosage evidence and states where no published dosage exists, gives 7 selection steps, compares the wet ISO 22196 test against the dry ISO 7581 test, sets out the EU treated-article regime and the US FIFRA exemption active by active, and closes with the complete list of 10 antimicrobial substances.

The table below compares the 6 types on chemistry, example actives with CAS numbers, target organisms, typical use and their position under the EU Biocidal Products Regulation.

Contact-active polymers and natural biocides such as chitosan are described in the mechanism section. They are research-stage or emerging in plastics and are not counted as commercial types here.

What Is an Antimicrobial Additive for Plastics?#

An antimicrobial additive for plastics is a biocidal substance or mixture compounded into a polymer so that the finished article, or its surface, resists growth of bacteria, fungi such as mould and mildew, algae and yeasts. The same product carries several names depending on who is speaking: antimicrobial agent and antibacterial additive in converter specifications, fungicide and mildewcide where the target is mould, preservative in the compounding trade, biocide in the legal texts, and antimicrobial masterbatch where the active arrives as a concentrate. The spelling splits as well, since anti-microbial, mold and odor appear in North American documents where mould and odour appear in European ones.

Why does the same additive have three different legal names depending on what the label says? The claim, not the chemistry, decides the regime. An article that intentionally incorporates a biocidal product is a treated article under Article 3(1)(l) of Regulation (EU) No 528/2012, an article whose primary function is biocidal is itself a biocidal product, and an article that carries no biocidal claim is simply an article. Antimicrobials are one of the 43 families of plastic additives covered on this site, and the only family in which the wording on the packaging changes the approval the product needs.

Material protection or surface hygiene? The distinction that decides the law#

A biocide goes into a plastic for one of two reasons, and the reason decides the law: either it protects the plastic itself from microbes that feed on its plasticizer and lubricants, which is product-type 9 in the European Union and a treated article in the United States, or it supports a hygiene claim about the surface, which moves the article into product-type 2 or 4 in the EU and out of the US treated-article exemption altogether. Material protection is the older and larger of the two uses. Fungi and bacteria metabolise the organic components of a compound rather than the polymer backbone, which is why the failures are visible: pink and black staining on flooring and wallcoverings, odour in foam, embrittlement and loss of mechanical properties.

The nutrient is the reason soft PVC needs a biocide and rigid PVC usually does not. Fungi metabolise the plasticizers that make PVC flexible, together with lubricants and other organics, so the microbial load scales with the plasticizer content of the recipe. Surface hygiene is the other route and a different legal animal: in Europe a hygiene claim points at product-type 2, or product-type 4 where the article sits in a food and feed area, and in the United States a public-health claim voids the treated-article exemption and requires full registration of the article under FIFRA. Product-type 9 also covers odour, because Annex V of the Biocidal Products Regulation defines it to include products that antagonise the settlement of micro-organisms on materials and so prevent the development of odour.

Antimicrobial odour control is a material-protection claim in the EU: Annex V includes products that antagonise the settlement of micro-organisms on materials and so prevent odour in PT9.

Antimicrobial, antibacterial, antifungal, biocide: what each word commits you to#

Antimicrobial, antibacterial and antifungal describe which organisms an additive acts on, while biocide is the regulatory word for the same substance, and the word that appears on the product decides which approval the product needs. There is no ranking of actives behind these words and no single best antimicrobial agent, because the target organism and the legal route decide the choice: a fungicide that controls mould in a roofing membrane says nothing about bacteria on a kitchen surface.

The 5 words that appear on plastics antimicrobial documentation, and what each commits the label to, are listed below.

• Antimicrobial. The broadest word, covering bacteria, fungi, algae and yeasts. In Europe it is a biocidal property, so under Article 58(3) of Regulation (EU) No 528/2012 it may appear on a treated article only where it is substantiated and every active substance is named.
• Antibacterial. A narrower claim limited to bacteria, and the one most often tied to a hygiene purpose, which moves an article toward product-type 2 or 4.
• Antifungal, mildewcide, fungicide. A claim about fungi, which in plastics almost always means material protection of a plasticized or filled compound, and therefore product-type 9.
• Biocide, biocidal product, active substance. The regulatory vocabulary. A biocidal product is placed on the market to destroy or control a harmful organism, and the active substance inside it is what gets approved, per product-type.
• Antimicrobial masterbatch. A supply form, not a claim: a concentrate carrying the active at 1 to 20 %, which the compounder lets down into the polymer.

How Do Antimicrobial Additives Work in a Polymer?#

Almost every antimicrobial additive in commercial use works by releasing an active species at the surface of the plastic, either a metal ion from an inorganic carrier or an organic molecule that diffuses out of the matrix, while a small and newer group kills on contact without releasing anything. The two mechanism families behave differently in every respect that matters to a compounder. A leaching system depends on water reaching the surface and on how much active remains in the matrix, and it survives processing only if the active tolerates the melt temperature. Silver carriers are thermally stable through melt processing, which is their main practical advantage over the organic actives, several of which decompose well below common extrusion temperatures.

How silver carriers release silver ions#

A silver carrier works in 4 steps: moisture reaches the surface of the plastic, sodium and hydrogen ions exchange with silver in the carrier lattice, silver ions migrate to the surface, and there they bind enzyme thiol groups, disrupt membranes and generate reactive oxygen species. The 4 steps are set out below.

1. Absorb moisture at the polymer surface, which is the trigger for the whole sequence and the reason a dry surface shows no activity.
2. Exchange sodium and hydrogen ions from that moisture against silver held in the zeolite, zirconium phosphate or glass lattice.
3. Release the freed silver ions (Ag+) into the water film at the surface of the article.
4. Attack the micro-organism, as silver ions bind the thiol groups of enzymes, disrupt cell membranes and generate reactive oxygen species.

Release rate, not silver content, governs what the surface actually does. Humberto Palza at the University of Chile set out this dependence on water uptake and matrix crystallinity in a 2015 review of metal nanoparticles in polymers: a hydrophobic, highly crystalline polyolefin such as polypropylene or polyethylene takes up little water, so silver ions reach the surface only slowly, and the concentration at that surface governs activity rather than the loading in the bulk. Carrier chemistry also matters legally, because European approval is granted to a named carrier substance and never to silver as a class, and carrier-by-carrier data sits on silver-based antimicrobials.

How organic biocides kill: thiol chemistry and membrane transport#

Organic biocides attack enzymes rather than membranes first: an isothiazolinone opens its sulfur-nitrogen bond against a thiol group in an enzyme active site and forms a mixed disulfide, while zinc pyrithione disrupts membrane transport through the proton pump and damages iron-sulfur proteins in fungi. The electrophilic sulfur-nitrogen bond is what makes the isothiazolinone class work, and the alkyl chain is what decides where it works. Silva and co-workers described this structure-activity pattern in their 2020 review of isothiazolinone biocides: longer alkyl chains, as in octhilinone (OIT) and DCOIT, raise both fungicidal activity and lipophilicity, which is exactly what a plasticized PVC compound needs, because the fungi feed in the plasticized phase and a lipophilic active stays there.

Zinc pyrithione takes a different route to the same end. Its water solubility of about 8 ppm at neutral pH gives slow release and outdoor persistence rather than a fast kill, it is slowly decomposed by ultraviolet light, and it decomposes at about 240 °C, which sets the practical ceiling on the melt temperature of any compound that carries it. OBPA, the arsenical that once dominated flexible PVC, is a broad-spectrum fungicide and bactericide that works by preventing microbes from feeding on the plasticizer itself. The class page covers OIT, DCOIT, BIT and BBIT together as isothiazolinone biocides for plastics.

Thermal values are melting or decomposition points from the substance records, not processing recommendations.

Does the antimicrobial effect wear off?#

An antimicrobial additive keeps working as long as the polymer can still deliver the active species to the surface, which is why a leaching system is limited by what is left in the matrix and by how fast water can reach it. Three matrix properties set that limit. Water uptake decides whether a silver carrier exchanges at all, crystallinity decides how quickly anything migrates through the bulk, and the solubility of the active decides how much leaves per unit of contact. Zinc pyrithione shows the trade-off: its low water solubility of about 8 ppm gives slow release and good outdoor durability, and it is slowly decomposed by ultraviolet light, so the exposure class matters as much as the organism. DCOIT has better ultraviolet resistance than OBPA, a difference recorded in the 2006 Townsend Polymer Services survey published by John Markarian.

A leaching biocide is governed by the same physics as any other additive migration, which means diffusion, solubility in the matrix and surface contact conditions rather than a fixed service life. This page publishes no service life, no number of wash cycles and no lifetime-of-the-product claim, because no primary source on file gives service-life or wash-off data for any antimicrobial additive in a finished plastic. Every page-1 competitor makes that claim; none of them cites a measurement behind it.

Contact-active polymers: the non-leaching alternative#

A contact-active polymer carries the antimicrobial function in its own backbone instead of releasing anything: quaternised polyethyleneimine built into thermoplastic polyurethane kills bacteria that touch the surface, and 2026 catheter research reports more than 99 % bactericidal activity against Staphylococcus aureus and Escherichia coli. That figure is a research result on a specific experimental material under the conditions of that study, not a property of any commercial grade. The appeal of the approach is that nothing migrates, so the depletion problem of the previous section does not arise and the migration questions that dominate food-contact and medical assessment change shape. An antimicrobial polymer is also a different entity from an antimicrobial additive: the additive is a separate substance compounded into a host polymer and regulated as an active substance, while an antimicrobial polymer is a macromolecule whose own chemistry is biocidal. Contact-active systems and natural biocides such as chitosan are not counted among the 6 commercial types, because the research record places them at bulk-chemistry and food-packaging research stage.

6 Types of Antimicrobial Additives for Plastics#

The 6 types of antimicrobial additives used in plastics are silver-based carriers, zinc and copper inorganics, zinc pyrithione, isothiazolinones, carbamate and benzimidazole fungicides, and the legacy actives that Europe has now closed off. The order runs from the class with the only current European polymer approval to the class that no longer has a European route at all, which is also, roughly, the order of where the volume is moving. The 6 types cover every substance documented on this site; contact-active polymers and natural biocides are described in the mechanism section above and are not counted here.

1. Silver-based carriers (zeolite, zirconium phosphate, phosphate glass)#

Silver-based antimicrobials are carriers rather than silver metal: a zeolite lattice, a zirconium phosphate ceramic or a soluble phosphate glass holds silver and exchanges it for sodium and hydrogen ions when moisture arrives, and in the European Union each carrier is approved or refused on its own, not as a class. Silver zinc zeolite (CAS 130328-20-0) is a zeolite LTA framework surface-modified with silver, zinc and ammonium ions, and it is the only member with a current approval: Implementing Regulation (EU) 2024/2635 approves it for product-types 2, 7 and 9 from 1 March 2026 to 29 February 2036. The approval carries conditions a compounder has to design around. Purity must be at least 990 g/kg on a dry-weight basis, arsenic and chromium are each capped at 40 mg/kg, non-textile polymer articles must not be in direct skin contact over more than 300 cm² for adults and children over 2 years or more than 200 cm² for toddlers and infants, product-type 7 use excludes outdoor-infrastructure paints, and the Article 58(3) treated-article label is mandatory.

The other carriers went the other way. Silver sodium hydrogen zirconium phosphate (CAS 265647-11-8), sold as AlphaSan by Milliken and Novaron by Toagosei, was not approved for product-types 2 and 7 by Implementing Decision (EU) 2019/1959 because efficacy was not demonstrated, and not approved for product-type 4 by Implementing Decision (EU) 2023/2052, which also found an unacceptable dietary risk from food in contact with treated polymers; product-type 9 remains in review. Silver zeolite and silver copper zeolite (CAS 130328-19-7) were refused for product-types 2 and 7 by Implementing Decisions (EU) 2019/1960 and 2019/1973, and the General Court upheld those refusals on 16 November 2022. Silver phosphate glass (CAS 308069-39-8), with the borophosphate and phosphoborate glasses, is still in the review programme for product-types 2, 7 and 9 with no decision as of 22 September 2026. Silver loading is a commercial variable rather than a regulatory one: the AlphaSan RC2000 grade contains 10 % silver, and a higher loading in the carrier allows a lower let-down.

Approval under the Biocidal Products Regulation attaches to a named carrier substance and a named product-type. No instrument approves "silver" for plastics.

2. Zinc and copper inorganics (zinc oxide, copper compounds, zinc zeolite)#

Zinc and copper inorganics act through metal-ion release and reactive oxygen species rather than ion exchange from a carrier, and zinc oxide is the one member of this group that is already authorised for European food-contact plastics, as FCM No 402 with a zinc limit of 5 mg/kg. Zinc oxide (CAS 1314-13-2) is the clearest case of a multifunctional additive in the whole family, since the same particle works as an antimicrobial through reactive oxygen species and Zn2+ release, as an ultraviolet absorber, as a vulcanisation activator and as a white pigment. Its nano forms are listed separately in Regulation (EU) No 10/2011 as FCM 1050 uncoated and FCM 1046 silane-coated, both restricted to unplasticised polymers, it is generally recognised as safe under 21 CFR 182.8991 in the United States, and it carries the harmonised aquatic classification H400 and H410 under CLP index 030-013-00-7.

Zinc oxide is not a BPR-approved biocidal active, and it belongs in this list for its mode of action and its food-contact standing rather than a biocidal approval. The loadings reported for this group run an order of magnitude above the silver systems and come from academic work rather than supplier data sheets: Bažant and co-workers reported an Ag-ZnO hybrid at up to 5 wt% in a TPO/PP blend in 2018, and Du and co-workers reported ZnO@Ag tetrapods at 10 wt% in polypropylene in 2021, giving 100 % activity against Escherichia coli and Staphylococcus aureus and a surface resistivity of 5.5 × 10^10 Ω. Zinc and copper each carry a specific migration limit of 5 mg/kg under Annex II to Regulation (EU) No 10/2011.

3. Zinc pyrithione#

Zinc pyrithione (CAS 13463-41-7) is the fungicide, bactericide and algaecide that replaced much of the arsenical volume in flexible PVC and polyurethane foam, and it is also the active in this family with the heaviest hazard classification. The identity is EC number 236-671-3, molecular formula C10H8N2O2S2Zn, molecular weight 317.7 g/mol, a metal pyrithione supplied as fine beige granules or powder. Its harmonised CLP classification under Delegated Regulation (EU) 2020/1182, applicable from 1 March 2022 under index 613-333-00-7, is Repr. 1B H360D, Acute Tox. 2 H330, Acute Tox. 3 H301, STOT RE 1 H372, Eye Dam. 1 H318, Aquatic Acute 1 with an M-factor of 1,000 and Aquatic Chronic 1 with an M-factor of 10. That reproductive-toxicity classification has a direct biocidal consequence, because Repr. 1B meets the exclusion criteria of the Biocidal Products Regulation, so a future approval is possible only by derogation. The substance remains an existing active in the review programme for product-types 2, 6, 7, 9 and 10 with no decision as of 22 September 2026, and the separate question of why it was prohibited in EU cosmetics is answered below the contextual border.

In the compound it goes where the plasticizer goes. Its hosts are flexible PVC flooring, roofing membranes and wallcoverings, polyurethane foams, wood-plastic composites and thermoplastic elastomer grips, and it is sold as Zinc Omadine and Omacide by Arxada, formerly Arch Chemicals, as Acticide PZ by Thor, as the zinc pyrithione and BBIT blend Vanquish SL-10, and as Sanitized PL 21-60 in a DINP carrier. In the United States it carries EPA Office of Pesticide Programs code 088002, and TSCA Chemical Data Reporting records 75,000 to under 100,000 lb in 2023 against 250,000 to under 400,000 lb in 2022. Decomposition at about 240 °C sets its melt-processing ceiling.

4. Isothiazolinones (OIT, DCOIT, BIT, BBIT)#

Isothiazolinones are the organic workhorses of plasticized PVC: OIT (CAS 26530-20-1) and DCOIT (CAS 64359-81-5) carry octyl chains that make them lipophilic enough to stay in the plasticized phase, which is exactly where the fungi feed. The 4 members named in our source library are listed below.

• OIT, octhilinone, CAS 26530-20-1. EC 247-761-7, C11H19NOS, molecular weight 213.34 g/mol, a clear dark amber liquid melting at 15 °C, water solubility 500 mg/L at 25 °C, log Pow 2.61. Approved for product-type 8 by Implementing Regulation (EU) 2017/1277, with product-types 6, 7, 9, 10, 11 and 13 in the review programme under France as rapporteur. Sold as Arch OIT 45, Micro-Chek and Preventol.
• DCOIT, CAS 64359-81-5. EC 264-843-8, C11H17Cl2NOS, molecular weight 282.2 g/mol, a solid melting at 40 to 46 °C with a water solubility of 14 ppm at 25 °C. Approved for product-type 8 by Directive 2011/66/EU and product-type 21 by Implementing Regulation (EU) No 437/2014, expiry dates postponed by Decisions (EU) 2023/471 and 2025/1811, with product-types 7, 9, 10 and 11 in review.
• BIT, CAS 2634-33-5. An in-can preservative for aqueous dispersions, paints and latex rather than a plastics additive, named here for its product-type 9 decision: Implementing Decision (EU) 2026/1420 did not approve it for product-type 9, since no participant supported the application.
• BBIT. Used in flexible foams, gaskets and insulation, and sold blended with zinc pyrithione as Vanquish SL-10 for soil-burial applications. No CAS number for BBIT is recorded in our source library, so none is printed.

Hazard classification is where DCOIT differs most from the rest of the class. Its harmonised entry under CLP index 613-335-00-8 covers Acute Tox. 2 H330, Skin Corr. 1 H314 and Skin Sens. 1A H317 with a specific concentration limit of 0.0015 %, plus Aquatic Acute 1 and Aquatic Chronic 1 at an M-factor of 100, which is why a masterbatch containing it reaches a classification threshold at a low active content. TSCA Chemical Data Reporting records 38,801 lb of DCOIT in 2023 under EPA pesticide code 128101, and under 50,000 lb of OIT under code 099901. DCOIT also has better ultraviolet resistance than OBPA, the practical reason it took over outdoor flexible PVC after the arsenical route closed.

5. Carbamate and benzimidazole fungicides (IPBC, thiabendazole)#

IPBC (CAS 55406-53-6) and thiabendazole (CAS 148-79-8) are the fungicides that widen the spectrum of a biocide package beyond what an isothiazolinone alone covers, and both are sold for plastics as ready-made formulations rather than as neat actives. IPBC, 3-iodo-2-propynyl butylcarbamate, is EC 259-627-5, C8H12INO2, molecular weight 281.09 g/mol, an off-white solid with a pungent odour melting at 66 °C. It works in polyolefins, styrenics and flexible PVC, and reaches the compounder as Polyphase and Micropel 612 for polyolefins and styrenics, as the non-metallic liquid Micropel A285 for flexible PVC, both from Troy, now Arxada, and as Acticide PI from Thor. Its European approvals are product-type 6 under Regulation (EU) No 1037/2013 with the expiry postponed by Decision (EU) 2025/450, product-type 8 under Directive 2008/79/EC with the latest postponement in Decision (EU) 2026/1129, and product-type 13 under Regulation (EU) 2015/1728; product-types 7, 9 and 10 remain in review. US formulations run from 0.05 to 97 % active ingredient, and TSCA Chemical Data Reporting records under 75,000 lb in 2023.

Thiabendazole is the benzimidazole partner and the highest-melting organic active in the family. It is EC 205-725-8, C10H7N3S, molecular weight 201.25 g/mol, a white to cream odourless powder melting at about 300 to 305 °C, which is why it appears in blends intended for higher-temperature processing; that melting point is a physical property from the substance record and not a processing recommendation, because our source library holds no processing window for it. It is approved for product-type 8 by Directive 2008/85/EC with product-types 7, 9 and 10 in review, carries EPA pesticide code 060101, and reaches plastics biocide blends as Metasol TK-100 and Mertect. The full organic set is compared on organic biocides and fungicides for plastics.

6. Legacy and restricted actives (OBPA, triclosan, organotins)#

OBPA (CAS 58-36-6) was the largest single plastics biocide by volume in 2005, holding more than a third of formulated biocide consumption, and it is now closed off in Europe for a procedural reason rather than a new toxicological one: it is not in the Biocidal Products Regulation review programme, so it cannot be an active substance in a treated article placed on the EU market. 10,10'-oxybisphenoxarsine is EC 200-377-3, C24H16As2O3, molecular weight 502.2 g/mol, an organoarsenic broad-spectrum fungicide and bactericide melting at about 184 to 185 °C and supplied as a solution in plasticizer carriers such as DIDP, DIHP and DINP. Its historical trade names were Vinyzene BP-5 from Rohm and Haas, Micropel from Troy and Intercide from Akzo Nobel, and its historical applications read like a catalogue of flexible PVC: shower curtains, floor and wall coverings, coated fabrics, marine upholstery, vinyl mouldings, awnings, weather stripping and pool liners.

Triclosan reached the same commercial end by a different path. CAS 3380-34-5, EC 222-182-2, C12H7Cl3O2, molecular weight 289.5 g/mol, melting at 55 to 57 °C, it was not approved for product-type 1 by Implementing Decision (EU) 2016/110 and does not appear in the 2022 review list for product-types 2, 7 or 9, so there is no route to a European treated article. It was removed from the EU plastics food-contact additive list by Commission Decision 2010/169/EU after Ciba withdrew the application on 21 April 2009, with existing articles marketable until 1 November 2011. The FDA rule at 21 CFR 310.545 is frequently misread here: it is a 2016 final rule on over-the-counter consumer antiseptic washes, a drug rule rather than a plastics rule, while the EPA continues to regulate triclosan as a pesticide in materials. Historical plastics uses were cutting boards, food containers and toys. Organotins such as tributyltin complete the legacy group and no longer have a European route; our source library holds no approval instrument for them, so none is cited here.

Which Plastics and Applications Use Antimicrobial Additives?#

Antimicrobial additives go first into flexible PVC, which consumed about two thirds of plastics biocide volume in 2005, because the plasticizer that makes the PVC flexible is also the nutrient the fungi feed on, then into polyolefins at about 20 % and polyurethane foam at under 10 %. Those shares come from the Townsend Polymer Services survey of 2005 published in Plastics Additives and Compounding, and no more recent public split by polymer exists in our sources. The pattern behind them still holds, because it follows the chemistry: where a compound contains a large organic fraction that micro-organisms can metabolise, the biocide is there for material protection, and where the polymer is clean and hydrophobic, the biocide is usually there for a surface claim instead.

Where the application is a food-contact or drinking-water part, the European route is BPR product-type 4, in which every silver carrier assessed so far has been refused.

Two application notes cut across the table. Rohm and Haas launched Vinyzene DCOIT grades specifically for wood-plastic composites, which is the clearest case of an active being reformulated for a new host rather than a new host adopting an existing grade. And the refusals of silver carriers for product-type 4 block the food-contact hygiene claim in Europe for every silver system assessed so far, which pushes appliance and kitchenware work back toward material protection wording. The rest of the soft-PVC package, from the plasticizer to the heat stabiliser, is on additives for PVC.

How Much Antimicrobial Additive Does a Plastic Need?#

Antimicrobial additives are used at the lowest levels of any functional additive family: biocides make up 0.001 to 1 wt% of finished plastic products, and the silver systems with published data work at 80 to 160 ppm of silver in polypropylene. The 0.001 to 1 wt% range is the composition of finished articles rather than a recommended addition level, and it comes from the survey of plastic-product composition by Hahladakis and co-workers in 2018, as compiled by Chea and co-workers in 2025. Everything else with a number attached to it is either a measured research level from an academic study or the active content of a formulated product sold to compounders, and the table below keeps those three categories strictly apart.

None of these values is a supplier-recommended dosage. Ask the supplier for the let-down ratio of the specific grade in the specific polymer.

One conversion is worth doing before any of these numbers reaches a recipe. A masterbatch percentage and an active level in the finished part are different quantities, and mixing them up is the most common error in antimicrobial specification, so convert the concentrate percentage into an active level with the let-down ratio calculator before comparing any two quotations.

What the published dosage evidence actually shows#

No supplier-published let-down range for antimicrobial masterbatch in a named polymer survived our source check, so this page prints the measured research levels and the finished-product composition range instead of a recommended dosage. The supplier technical data sheets that would carry such a range, from Microban, Sanitized, BioCote, Milliken AlphaSan and Addmaster, were not reachable during the research pass, and no primary source on file gives a typical commercial level for OBPA in flexible PVC, for silver glass in polypropylene or ABS, or for zinc pyrithione in PVC or polyurethane. Publishing an estimate in their place would be inventing a number that formulators would then quote back.

Ask the supplier for 4 things instead, in writing: the active substance and its CAS number, the active content of the grade, the recommended let-down ratio in your specific polymer, and the test method and pass criterion the recommendation is based on. A recommendation without a method behind it is not a dosage.

Masterbatch, carriers and how biocides are dosed#

Antimicrobial additives reach the compound in one of 3 forms: a masterbatch concentrate at 1 to 20 % active, a liquid dissolved in a plasticizer carrier, or a powder dosed directly into the dry blend. The 3 dosing routes are set out below.

• Masterbatch concentrate. Most antimicrobials for plastics are sold as concentrates at 1 to 20 % active substance, which is why almost every antimicrobial is dosed as an additive masterbatch rather than as a neat active.
• Liquid in a plasticizer carrier. Liquid biocides for PVC arrive dissolved in DINP, DIDP or DIHP, so the carrier counts toward the plasticizer level of the recipe and has to be deducted from the plasticizer budget rather than added on top of it. IPBC illustrates the split cleanly, since it is sold as a solid grade for polyolefins and styrenics and as a non-metallic liquid grade for flexible PVC.
• Powder into the dry blend. A powder active can be dosed directly, which puts the whole thermal load of the process on the active itself: silver carriers survive melt processing, while an organic active has to be checked against the melt temperature, and zinc pyrithione decomposes at about 240 °C.

How Do You Select an Antimicrobial Additive? 7 Steps#

Select an antimicrobial additive in 7 steps: decide whether you are protecting the plastic or making a hygiene claim, name the target organisms, check the product-type approval in every market, match the chemistry to the polymer, check the thermal limit against your melt temperature, check the rest of the formulation, then fix the test method and the label wording before you compound. The 7 steps are ordered so that the decisions that cannot be reversed come first.

1. Decide whether the job is material protection or a surface-hygiene claim. This sets the product-type and the whole compliance route, and it should be settled before any chemistry is discussed.
2. Name the target organisms. Bacteria, mould, algae and yeast are controlled by different actives, and a fungicide is not a bactericide.
3. Check that the active is approved for that product-type in every market you sell into, and read the conditions attached to the approval, not only the approval itself.
4. Match the active to the polymer. A plasticized system needs a lipophilic organic; a dry, hydrophobic polyolefin surface needs an inorganic carrier, and its low water uptake still limits ion release.
5. Check the thermal limit of the active against your melt temperature. Zinc pyrithione decomposes at about 240 °C, and silver carriers pass through melt processing unchanged.
6. Check the rest of the formulation for antagonism and for hazard-classification consequences at the loading you plan, because M-factors and specific concentration limits classify a masterbatch at a low active content.
7. Fix the test method and the pass criterion before compounding, and write the treated-article label wording at the same time, since under Article 58(3) a biocidal property may be stated only where it is substantiated.

Steps 3 and 7 should be signed off by someone who is not the formulator, because both are legal rather than technical decisions and both are far cheaper to fix before the first trial than after the first shipment. The general framework is on how to select plastic additives.

How Do Antimicrobials Interact with Other Additives?#

An antimicrobial additive is never independent of the rest of the formulation: the plasticizer is the food source, the UV package decides how long an organic active survives outdoors, and the carrier the biocide arrives in counts as part of the recipe. Three of those interactions are documented in our sources and two are not, and the table below marks which is which rather than filling the gaps with plausible chemistry. Our source library contains no measured antagonism data for this family, which means the only honest recommendation for an untested combination is to test the full package rather than the biocide alone.

The one interaction that is legal rather than chemical deserves its own line. Because Annex V places odour prevention by antagonising microbial settlement inside product-type 9, an odour claim on a compound that contains a biocide is a biocidal claim, whatever the marketing department intended. The dispersion and feeding questions that decide whether a low-level active is evenly distributed at all belong to plastic compounding.

How Is Antimicrobial Performance Tested? ISO 22196, JIS Z 2801 and ISO 7581#

Antimicrobial activity in plastics is reported as the value R, the log10 reduction in viable count on a treated specimen against an untreated control, and the standard that defines it, ISO 22196, runs the test wet for 24 hours at 35 °C and above 90 % relative humidity. ISO 22196:2011 and its Japanese predecessor JIS Z 2801 use a sandwich arrangement: the inoculum is held under a 40 × 40 mm cover film of 1,600 mm², incubated for 24 hours at 35 ± 1 °C at a relative humidity of at least 90 %, and counted where the plates fall between 30 and 300 CFU. Those conditions are also the method's main criticism. The 2024 comparison of wet and dry methods published in Frontiers in Microbiology identifies 4 critical factors that move the result, namely incubation time, starting inoculum, the physiological state of the organism and nutrient concentration, and concludes that wet conditions overestimate activity relative to a real dry surface.

A wet-method result and a dry-method result are not interchangeable. The wet method overestimates activity relative to a real dry surface.

ISO 7581:2023 was written to close that gap. It is a dry test for non-porous antimicrobial surfaces in which a 1 µL inoculum is spread and dried, held at 20 ± 1 °C and 30 to 65 % relative humidity, with a contact time of 1 hour and an optional 24-hour reading, and counts taken between 14 and 330 CFU. The same 2024 comparison found it more realistic than the wet method but less reproducible, which is the trade-off a specifier has to make consciously. Never quote a log reduction or a 99.9 % figure as a property of a material without naming the method, the organism and the contact conditions. The full method comparison, with the pass criteria, is on antimicrobial plastics testing.

Five further standards appear in the trade literature for this family, and this page names them without parameters because they were not verified during the research pass behind it. Every method used across the additive families is indexed under testing plastic additives.

How Are Antimicrobial Plastics Regulated?#

An antimicrobial plastic is regulated in 4 layers: the biocidal-active layer (approval per product-type under the EU Biocidal Products Regulation, registration under FIFRA in the United States), the article layer (treated-article rules and labelling), the chemical layer (REACH and CLP), and, where the part touches food or drinking water, the food-contact layer. Those layers are independent of each other, which is the point most often missed: an active can be approved as a biocide and still be absent from the food-contact positive list, and an article can be perfectly legal to sell and still be illegal to advertise the way its maker would like. All four layers and the instruments behind them are summarised in plastic additive regulations.

This page covers the European Union and the United States. The Chinese schemes GB 21551 and QB/T 2591, the Japanese SIAA mark and the Korean biocides regime under K-REACH are named in our research but are not covered on this version of the page.

EU: the Biocidal Products Regulation and the treated-article rules#

In the European Union any plastic that intentionally incorporates a biocidal product is a treated article, and Regulation (EU) No 528/2012 allows it on the market only if every active substance in it is approved for the relevant product-type and use, with all attached conditions met. Article 3(1)(l) defines the treated article as any substance, mixture or article which has been treated with, or intentionally incorporates, one or more biocidal products, and Article 58(2) sets the market-access condition. An article whose primary function is biocidal is not a treated article at all: it is a biocidal product needing authorisation in its own right.

Article 58(3) then sets out what has to be on the label. The 5 required elements are listed below.

• A statement that the article incorporates biocidal products.
• The biocidal property attributed to the article, where that property is substantiated.
• The names of all active substances contained in the biocidal products.
• The name of any nanomaterial, followed by the word "(nano)" in brackets.
• Instructions for use and any precautions to be taken.

Two further duties complete the regime. Article 58(5) gives any consumer the right to ask for information on the biocidal treatment of an article and requires the supplier to provide it free of charge within 45 days, and Article 58(6) requires the labelling to be visible, legible and durable rather than buried in a technical file. A transitional rule under Article 94 kept articles already on the market on 1 September 2013 saleable where an application for the active substance was submitted by 1 September 2016, which is why several actives without an approval are still legally present in European supply chains while their review continues. The labelling and documentation duties for treated articles are set out in full there.

Which actives are approved, refused or still in review#

Only one antimicrobial active in commercial plastics use holds a current EU approval for the polymer product-type: silver zinc zeolite, approved for product-types 2, 7 and 9 from 1 March 2026 to 29 February 2036. Every other active in the family sits in one of three other states, and the difference between them is commercially decisive. Approved for a different product-type means the active is legal for wood or for antifouling and not for polymerised materials, which is the position of OIT, DCOIT, IPBC and thiabendazole. In review means the review programme under Regulation (EU) No 1062/2014 has reached no decision, which is a transitional status and not a permission. Not approved means a named Commission instrument closed the route, usually because efficacy was not demonstrated. The matrix below gives the position of every active on this page against the four product-types that matter to plastics, with the instrument in the last column; a blank is written as "in review" and never as "allowed".

"In review" means the active is in the Biocidal Products Regulation review programme with no decision as of 22 September 2026, which is a transitional status, not an approval.

One chemical-layer consequence follows from this matrix and is worth stating explicitly, because it confuses buyers who check registration status before they check approval status. Article 15(2) means biocidal active substances are regarded as registered under REACH for their biocidal use, so the absence of a separate registration dossier for an approved or in-review biocidal active says nothing at all about its legal standing.

US: the FIFRA treated-article exemption#

In the United States a plastic that contains a biocide to protect itself is covered by the treated-article exemption of 40 CFR 152.25(a), provided that the pesticide is registered for that use and the claim stays limited to protecting the article. The exemption covers an article treated with, or containing, a pesticide to protect the article or substance itself, and the wording of the claim is the boundary condition. "Protects the product from microbial deterioration" sits inside the exemption; "protects you from germs" is a public-health claim that takes the article out of the exemption and requires full FIFRA registration of the article itself. The US system therefore polices claims where the European system polices product-types, and the same compound can be legal in both markets with two different labels.

This site never writes "EPA approved" or "FDA approved". The correct formulation is that a pesticide is registered under FIFRA for a named use.

Production volumes are the closest thing to a current market signal for this family in the United States, because no current market-size figure is published for plastics antimicrobials. Read them with care, since Chemical Data Reporting covers all uses of a substance and not only its plastics use.

Food contact, drinking water and medical devices#

No silver-based, pyrithione, isothiazolinone or triclosan antimicrobial appears on the Union list of Regulation (EU) No 10/2011 in the consolidation of 14 July 2026, and every silver carrier assessed under product-type 4, the food and feed area, has been refused. The Union list and the Annex II metal limits are explained on EU 10/2011, and the metal limits are where the one usable route runs: zinc oxide is authorised as FCM No 402 under the Annex II zinc limit of 5 mg/kg, with the nano forms FCM 1050 uncoated and FCM 1046 silane-coated restricted to unplasticised polymers. Triclosan was removed from the plastics food-contact list by Commission Decision 2010/169/EU, and the product-type 4 refusal for silver sodium hydrogen zirconium phosphate under Decision (EU) 2023/2052 cited both a failure to demonstrate efficacy in food-contact materials and an unacceptable dietary risk from food in contact with treated polymers.

The practical conclusion for a European food-contact part is blunt. A food-contact antimicrobial claim currently has no approved silver route in the European Union, and substituting one carrier for another changes nothing, because all four assessed carriers were refused for product-type 4. The US route runs through the notification system explained on FDA food contact rules, and this site publishes no Food Contact Notification number for any antimicrobial substance, because none is recorded in our sources.

Water-contact parts add a third set of requirements on top of the biocidal and food-contact layers. Water coolers, whirlpool piping and similar components fall under drinking-water contact rules in both the European positive-list system and the US certification schemes, and those rules apply to the whole formulation rather than to the biocide alone.

Medical parts add a fourth. Device components carry the requirements on plastic additives in medical devices alongside everything above, which is why silver carriers and contact-active thermoplastic polyurethane appear in device research far more often than in device products.

Who Makes Antimicrobial Additives? Suppliers and Trade Names#

Global consumption of formulated biocides for plastics was 15.4 million kg in 2005, about a third of it in Europe and a third in North America, and no more recent public figure for the plastics segment survived our source check. That figure, together with the annual average growth rate of 3 to 4 % for Europe and North America and the note that China then held under 10 % of the market while growing at about 15 %, comes from the Townsend Polymer Services survey published by John Markarian in 2006. No current market-size estimate for plastics antimicrobials is published in any primary source we could verify, so none is printed here. The full buyer directory is antimicrobial additive suppliers.

Trade-name attributions from the 2006 trade survey are marked with their date. Several of these businesses have since changed owner or name, and grade-level attributions marked unverified must not be published as fact.

Two structural facts about this supplier list matter more than any individual name. The active-substance producers and the formulators are different businesses, so the company whose brand appears on a masterbatch is often not the company that holds the biocidal active dossier, and it is the dossier holder whose approval status decides whether the compound may be sold in Europe. Company profiles are in the directory of plastic additive manufacturers and suppliers.

Complete List of Antimicrobial Substances (10 Pages)#

The 10 antimicrobial substances documented on this site are listed below with their CAS number, chemical class, target organisms, EU biocidal status and the polymers they are used in.

Zinc oxide (CAS 1314-13-2) has an antimicrobial mode of action but is filed on this site under acid scavengers, because that is its main function in plastics. BIT and BBIT are covered on the isothiazolinone page and have no substance page.

Five of these 10 substances hold a current approval for at least one product-type, and only one of those approvals covers polymerised materials. Every substance record carries its full regulatory matrix, its physical data and its suppliers per grade, and all of them sit in the plastic additives database.

What Are the Health and Environmental Questions Around Antimicrobial Plastics?#

Three questions follow antimicrobial plastics out of the technical literature and into public debate: what the actives do in the environment, why one of them was prohibited in cosmetics, and whether antimicrobial surfaces contribute to resistance. All three are answered below with instruments and classifications rather than with reassurance, because that is the only evidence our source library holds. The neighbouring family that also acts on living organisms is anti-rodent and anti-termite additives, regulated as product-type 19 rather than product-type 9.

The opposite design goal also exists, and it uses a related vocabulary. Where an antimicrobial additive stops micro-organisms from consuming the polymer, a pro-degradant is added so that they can, and the evidence on that route is weighed on biodegradation additives.

Silver in the environment: the CLP M-factors#

From 1 May 2026 the European Union classifies silver by particle size, and the multiplying factor of 1,000 for nanoparticles of 1 to 100 nm means a masterbatch that contains nano-silver reaches an environmental hazard classification at a far lower concentration than the silver content alone suggests. Delegated Regulation (EU) 2024/2564, the 22nd adaptation to technical progress of the CLP Regulation, classifies silver in massive form at 1 mm and above as Repr. 2 H361f and STOT RE 2 H373 for the nervous system; silver powder above 100 nm and below 1 mm carries those entries plus Aquatic Acute 1 and Aquatic Chronic 1 with an M-factor of 10; and silver nanoparticles of 1 to 100 nm carry an M-factor of 1,000.

An M-factor is a multiplier in the mixture calculation: the concentration of the classified component is multiplied by M before it is compared against the classification threshold, so an M-factor of 1,000 brings a mixture over the environmental threshold at one thousandth of the concentration that would otherwise be needed. Two other actives in this family carry large M-factors as well. Zinc pyrithione is classified Aquatic Acute 1 with M = 1,000 and Aquatic Chronic 1 with M = 10, and DCOIT carries Aquatic Acute 1 and Aquatic Chronic 1 with M = 100. The mixture rules behind the M-factor are on CLP classification.

Why zinc pyrithione was banned in EU cosmetics#

Zinc pyrithione was prohibited in EU cosmetics from 1 March 2022 by Regulation (EU) 2021/1902, which added it to Annex II after it was classified as toxic for reproduction category 1B, and the same classification is why its future as a plastics biocide in Europe now depends on a derogation. The cosmetics prohibition and the plastics question share one cause and nothing else. The cause is the harmonised classification Repr. 1B H360D introduced by Delegated Regulation (EU) 2020/1182 and applicable from the same date, 1 March 2022.

In plastics the consequence is different in kind. A CMR category 1B classification meets the exclusion criteria of Article 5 of the Biocidal Products Regulation, which does not prohibit the substance outright but means that approval as a biocidal active is possible only by derogation. Zinc pyrithione therefore remains an existing active in the review programme for product-types 2, 6, 7, 9 and 10, with no decision as of 22 September 2026, and it remains legally usable in treated articles under the Article 94 transitional regime while that review continues. The high-volume consumer search around this substance concerns anti-dandruff shampoo, a use governed in the United States by 21 CFR 358.710, and has no bearing on its status in a PVC flooring compound.

Antimicrobial additives and the resistance debate#

The European decisions that removed several silver actives from the market turned on efficacy rather than on resistance: the regulator asked whether the treated article itself does what is claimed, and in the Sciessent judgment of 16 November 2022 the General Court confirmed that it may ask that question. In joined cases T-122/20 and T-123/20 the Court upheld the non-approval of silver zeolite and silver copper zeolite and confirmed that where an active substance is intended for use in treated articles, the Commission may assess the efficacy of those treated articles themselves rather than only the intrinsic activity of the substance.

Our source library holds no data on antimicrobial resistance caused by additives in plastics, so this page neither asserts a resistance risk nor denies one. What the record does show is a pattern of decisions grounded in demonstrated efficacy: Implementing Decisions (EU) 2019/1959, 2019/1960 and 2019/1973 all cite a failure to demonstrate efficacy, and Decision (EU) 2023/2052 adds a dietary-risk finding on top of it. The legal architecture reinforces the same point, because the separation between protecting an article and claiming hygiene exists precisely so that the second claim has to be substantiated before it may be made.

Is an antimicrobial plastic additive the same as an antimicrobial paint additive or coating?#

No: an antimicrobial additive for plastics is compounded into the polymer and acts from within the article, while a paint or coating additive protects a film on a surface, and in the European Union the two even sit under different product-types, 9 and 7. Product-type 9 covers fibre, leather, rubber and polymerised materials preservatives, and product-type 7 covers film preservatives, which are separate approvals held by separate applicants, so an active approved for one says nothing about the other.

Do antimicrobial plastics prevent infections?#

That is a public-health claim, and both regulators treat it as one: in the United States it takes the article out of the treated-article exemption and requires full registration, and in the European Union it may appear on the label only where the biocidal property is substantiated. Article 58(3) of Regulation (EU) No 528/2012 permits a statement of the biocidal property attributed to a treated article only where that property is substantiated, and 40 CFR 152.25(a) limits an exempt claim to protecting the article itself. Several actives in this family were refused approval precisely because efficacy was not demonstrated, which is the strongest available indication of how much evidence such a claim requires.