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Preliminary Risk Assessment for Zinc Pyrithione

Current as of June 29, 2004

EPA is announcing the availability of its preliminary risk assessment on zinc pyrithione and the opening of a 60-day public comment period beginning June 30, 2004, and ending August 30, 2004. The data reviewed included acute and sub-chronic toxicology, and exposure information. Environmental fate and ecological risk data were also analyzed.

By allowing access and opportunity for comment on the preliminary risk assessment, EPA is seeking to strengthen stakeholder involvement and help ensure that our decisions under FQPA are transparent and based on the best available information. After carefully considering the comments received, EPA may make changes before issuing revised or final risk assessments. If, at any point during the process, unreasonable risks of concern are identified, EPA may take action to protect public health and the environment.

The full preliminary assessment is available for public inspection in EPA's Docket (by Docket Number OPP-2004-0147). The Federal Register Notice can be found at

What is zinc pyrithione?

Zinc pyrithione (also known as Zinc Omadine® or Zinc 2-pyridinethiol-1-oxide) is used to prevent microbial degradation and deterioration of manufacturing starting materials such as plastics, polymers, and latexes, and in a wide range of finished articles made from these starting materials. The chemical acts to prevent the growth of bacteria, fungi, mildew, and algae that can cause various types of deterioration such as discoloration, staining, odors, etc.

What are the major uses of zinc pyrithione?

Zinc pyrithione is used to preserve a wide variety of food/drinking water contact, and non-food contact articles such as: adhesives; carpet fibers; carpet backings; rubber or rubber-backed bath mats; foam underlay for carpets; synthetic, non-leather materials; foam stuffing for cushions and mattresses; wire and cable insulation; vinyl, linoleum, tile and other synthetic floor coverings; wall coverings; plastic furniture; athletic flooring and mats; mattress liners, covers or ticking; molding; mats; gaskets; weather stripping; coated fabrics for furniture cushions, boat covers, tents; tarpaulins and awnings; rubber gloves (non-surgical); garbage bags, cans, and other refuse containers; bathtub appliques; garden hose; pipe (non-potable water); ductwork; air filters; air filtration components and media for industrial, hospital, residential, and commercial heating and cooling; conveyor belts; shower curtains; sponge or fiber mops; household use sponges; toilet brush receptacles; toothbrush receptacles (non-bristle contact); scrub brushes (non-medical); sink mats and drain boards; storage containers; soap dish holders; towel bars; components of uppers in footwear.

Zinc pyrithione is also registered for incorporation into antifoulant boat paints to control the growth of slime, algae, and marine fouling organisms (e.g., barnacles, tubeworms, etc.) below the water line on recreational and commercial boat hulls.

The largest use for zinc pyrithione is non-pesticidal (i.e., control of dandruff, seborrheic dermatitis, and psoriasis), and is regulated by the Food and Drug Administration. It is the active ingredient in many anti-dandruff shampoo.

How is zinc pyrithione formulated and incorporated?

Zinc pyrithione is incorporated into various polymers and plastics as a liquid, powder, or aqueous dispersion, during the manufacturing process of these materials, and during the manufacture of finished articles from these materials. Zinc pyrithione is added usually by metering pump if it is a liquid, and by open pouring if it is the powder form. It is added at a point where thorough mixing will take place.

What are the risks associated with zinc pyrithione?

Areas of concern include potential dermal and inhalation exposure risks during residential application of antifoulant boat paints and application of house paints which contain zinc pyrithione as an in-can preservative. Another concern involves potential occupational dermal and inhalation exposure risks to those who regularly work with the chemical.

Since this risk assessment is in the public review and comment phase, however, its findings are preliminary in nature and are subject to additional analysis. Based on such input through this public comment period, EPA will develop a revised risk assessment and will be able to determine whether or not risk mitigation measures are needed.

What is the reregistration process for zinc pyrithione?

The reregistration of zinc pyrithione is part of EPA's ongoing effort to reevaluate pesticides and ensure that they meet current scientific standards for health, safety, and environmental protection. The reregistration process involves the publication of a Federal Register Notice, the posting of the Preliminary Risk Assessment in the public docket, and a 60-day comment period. After comments are received and reviewed, and any mitigation measures are discussed with stakeholders, the final registration eligibility decision (RED) is issued. The estimated reregistration eligibility determination date is September 30, 2004.

Where can I get further information?

You can obtain further information by visiting EPA's Web site at, or you may call the Antimicrobials Hotline at 703-308-0127.


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