Reregistration Eligibility Decision and Risk Assessment for the Pesticidal Uses of Triclosan

Current as of October 2008

EPA has completed its reregistration eligibility decision (RED) for the pesticide uses of triclosan. The RED is available on EPA’s website. A Federal Register Notice will announce the availability of the RED and associated risk assessment documents at the end of October 2008. At that time, the Agency will place the RED, revised risk assessments and Response to Comments document in the federal docket at: http://www.regulations.gov in docket number EPA-HQ-OPP-2007-0513. There will be a 60-day public comment period on the RED.

Sources of triclosan

Triclosan is regulated by both EPA and the U.S. Food and Drug Administration (FDA). EPA regulates the antimicrobial uses of triclosan when used as a bacteriostat, fungistat, mildewistat, and deodorizer. The FDA-registered uses include hand soaps, toothpaste, deodorants, laundry detergent, fabric softeners, facial tissues, antiseptics for wound care, and medical devices. Although these uses are not regulated under pesticide law, EPA considered these exposures in the aggregate risk assessment. EPA used population-based biological monitoring data to assess the co-occurrence of uses to develop an aggregate exposure assessment.

Use profile for triclosan when used as an antimicrobial pesticide

Triclosan (2,4,4’ –trichloro-2’-hydroxydiphenyl ether) is a chlorinated aromatic compound that has functional groups representative of both phenols and ethers and is used as a synthetic broad-spectrum antimicrobial agent. EPA first registered triclosan in 1969. Currently there are 20 antimicrobial registrations. Triclosan uses include:

Summary of the findings of preliminary risk assessment

commercial, institutional, and industrial premises and equipment;
residential and public access premises; and
as a materials preservative.

The use of triclosan as a registered pesticide represents a small portion of the overall use of this chemical.

Commercial, institutional, and industrial premises and equipment uses include conveyor belts, fire hoses, dye bath vats, and ice-making equipment. As a material preservative, triclosan is used in many products including adhesives, fabrics, vinyl, plastics (toys, toothbrushes), polyethylene, polyurethane, polypropylene, floor wax emulsions, textiles (footwear, clothing), caulking compounds, sealants, rubber, and latex paints (the paint use has recently been requested to be voluntarily cancelled by the registrants).

There are many residential and public access premises uses including direct application to HVAC coils (commercial use only). It also is used as a materials preservative in carpets, toys, mattresses, clothing, brooms, mulch, floors, shower curtains, awnings, tents, toilet bowls, urinals, garbage cans, refuse container liners, insulation, concrete mixtures, grouts, and upholstery fabrics.

Summary of the findings of the risk assessments

Human Health

EPA conducted a human health risk assessment for triclosan to support the reregistration eligibility decision. EPA evaluated the submitted toxicology, product and residue chemistry, and occupational/residential exposure studies as well as available open literature and determined that the data are adequate to support the RED. EPA conducted these assessments using available animal studies.

EPA conducted an aggregate assessment to evaluate the potential for co-occurrence of uses, including the uses that are regulated by the FDA (hand soaps, toothpaste, deodorants, laundry detergent, fabric softeners, facial tissues, antiseptics for wound care, and medical devices). These exposures were considered in the aggregate risk assessment using National Health and Nutrition Surveys (NHANES) biological monitoring monitoring data to assess the co-occurrence of uses. The Agency believes the NHANES data are a more accurate predictor of aggregate exposure because the data are triclosan-specific, and are based on actual consumer use of the various triclosan products as they co-occur through normal use.

Residential and occupational risks were not of concern except for paint uses. However, the registrants have requested voluntary cancellation of the paint use. Once the action to terminate the paint use is completed, any risks associated with triclosan-treated paint will be eliminated. In addition, for the occupational use of triclosan as a materials preservative in pulp and paper manufacturing, the use of a closed delivery system will be required.

However, because there are many uses of triclosan under the regulation of the FDA, for the aggregate assessment the Agency used the most protective assumptions from the NHANES data. This assessment indicates that there are no concerns for uses that are anticipated to co-occur.

Environmental Fate and Ecological Risks

Based on available data, triclosan is expected to be immobile in soil and is not expected to volatilize from soil (moist or dry) or water surfaces. In aquatic environments, triclosan is expected to adsorb to (attach to the surface of) suspended solids and sediments and may bioaccumulate, potentially posing a concern for aquatic organisms. There is also a low-to-moderate potential for bioconcentration in aquatic organisms. The majority of published studies on the occurrence of triclosan in waste water treatment plants, treatment plant efficiency, and open water measurements of triclosan suggest that aerobic biodegradation is one of the major and most efficient biodegradation pathways.

Based on monitoring data, triclosan was found in approximately 36 U.S. streams where effluent from activated sludge waste water treatment plants, trickle-down filtration, and sewage overflow appear to contribute to the occurrence of triclosan in open water.

EPA performed a qualitative environmental risk assessment using levels of triclosan found through monitoring data in waterways and toxicity values to develop risk quotients (RQs) and compare them to levels of concern (LOCs) for triclosan. LOCs were not exceeded for fish but were exceeded for aquatic plants.

In addition, the Agency performed consumer environmental modeling for triclosan. The consumer environmental modeling assumed that all triclosan used in the manufacture of the antimicrobial uses is released into surface waters. After adjustments, these models concluded that estimated concentrations of triclosan in surface water do not exceed concentrations of concern for acute risk presumptions for any of the aquatic organisms and plants (vascular and non-vascular).

Considering the low probability of triclosan being released into household wastewater and surface waters from the antimicrobial uses, the Agency also concluded that chronic aquatic risks are unlikely from consumer uses of triclosan-treated plastic and textile items. Therefore, the Agency can reasonably conclude that the antimicrobial uses of triclosan (e.g., triclosan-treated plastic and textile items in households) are unlikely to contribute significant quantities of triclosan into household wastewater and eventually to surface water.

Because it is unknown how much triclosan is released from industrial sites (where triclosan is incorporated into plastic and textile items) into the environment the Agency is requiring the technical registrants to perform environmental modeling and surface water monitoring. Depending upon the results of this modeling and monitoring effort, additional ecological effects data may be required. In addition, four studies to address bioaccumulation potential will also be required as well as one environmental fate study.

Next Steps

The Agency recognizes that there is a considerable amount of research being conducted on triclosan. The Agency will track the progress of these studies and, as new scientific data becomes available, will review these data. The Agency will then determine what, if any, changes to the risk assessment and risk management decision are necessary.
The Agency will also continue to participate in the Interagency Task Force on Antimicrobial Resistance and evaluate information that results from that activity.
Further, given the rapidly developing scientific database for triclosan, the Agency intends to accelerate the schedule for the registration review process for this chemical. Currently, the Agency intends to begin that process in 2013, ten years earlier than originally planned.

Related Information

EPA’s public docket: www.regulations.gov EPA-HQ-OPP-2007-0513

Public Health Action Plan to Combat Antimicrobial Resistance (PDF) (46 pp, 114k about PDF)

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