Tetrachlorvinphos (TCVP)

• Basic information
• Using TCVP products safely
• EPA actions and regulatory history
• Additional information

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Basic Information

Tetrachlorvinphos (TCVP) is an organophosphate (OP) insecticide used to control fleas, ticks, various flies, lice, and insect larvae on livestock and pets and their premises. TCVP is also applied as a perimeter treatment for livestock premises and livestock facilities. TCVP is formulated into dusts, pet collars, sprays, emulsifiable concentrates, feed additives (solid and liquid), feed blocks, wettable powders, pellets and granular products.

As described below, TCVP, when used on pets to protect from fleas and ticks, can have associated pet health risks if not used according to label instructions. Learn more about safely protecting pets from fleas and ticks.

Using TCVP Products Safely

FIFRA requires that pesticides be used according to the approved label. Always follow the directions on the product label. EPA advises consumers to take certain precautions when handling TCVP products in residential areas. These precautions are listed on TCVP product labels, including:

• not allowing children to play with TCVP pet collar products,
• keeping TCVP spray products out of reach of children, and
• washing hands thoroughly with soap and water after handling the collar.

TCVP pet collars also include restrictions for age and weight of pets that may wear collars and notes to physicians and veterinarians.

EPA encourages pet owners to discuss with their veterinarian when flea and tick control is needed for their pets and which type of control product they should use. Pet owners should read the entire label before using the recommended product and follow all directions carefully, as well as monitor the pet after treatment.

EPA Actions and Regulatory History

TCVP was first registered as a pesticide in 1966. All crop uses of TCVP were voluntarily canceled by 1987. There are 16 tolerances (maximum residue limits) listed under 40 CFR § 180.252 (all are for animal products).

TCVP reregistration was initially completed via the September 1995 Reregistration Eligibility Decision (RED). Later, EPA completed an interim tolerance reassessment eligibility decision in July 2002, and in July 2006 EPA issued the final TCVP RED following the completion of the organophosphate cumulative risk assessment. During the RED process, EPA required registrants to update end-use product labeling to reduce potential risk associated with the use of TCVP products.

TCVP was one of the initial pesticide cases to be screened under the Endocrine Disruptor Screening Program. Based on this screening, EPA determined that no additional data were needed to evaluate the potential for TCVP to disrupt the estrogen, androgen or thyroid pathways.

EPA initiated the registration review process for TCVP in 2008.

In 2009, EPA received a petition from the Natural Resources Defense Council (NRDC) to cancel all TCVP pet uses.

In January 2016, EPA released preliminary human health and ecological risk assessments for public comment. The ecological risk assessment found that TCVP is very highly toxic to freshwater aquatic invertebrates, including a potential for acute and chronic risk to federally listed threatened and endangered (referred to as “listed”) and non-listed species of freshwater aquatic invertebrates for all of the registered uses of TCVP. Risks to listed and non-listed mammals, birds, reptiles, and terrestrial-phase amphibians are also possible. EPA’s response to comments received on the ecological risk assessment can be found in the docket.

In December 2016, EPA completed a revised human health risk assessment for TCVP. The human health risk assessment found risks of concern for people, including children, in residential settings exposed to dusts/powder products and pet collars; and exposure to workers applying TCVP.

In May 2017, EPA published an addendum to the human health risk assessment, as well as four responses to stakeholder comments on the human health risk assessment concerning:

• The application of the FQPA 10X Safety Factor for Organophosphates
• The occupational and residential exposure assessment
• The dietary assessment
• EPA’s endocrine screening

In July 2020, EPA denied NRDC’s 2009 petition to cancel all TCVP pet uses. As part of the Agency’s response to the petition, EPA released the Tetrachlorvinphos: Revised Residential Exposure Assessment for the Registered Pet Product Uses and Tetrachlorvinphos: Addendum to the Revised Residential Exposure Assessment for the Registered Pet Product Uses. Based on EPA’s assessment of the 2019 mechanical torsion study submitted in support of the pet collar uses and an assumption of collar trimming after application to pets, the revised risk assessment found no risks of concern from the pet collar products, and the Agency denied NRDC’s petition. The 2020 revised risk assessment also indicated that there were no risks of concern from liquid spray products. Risk estimates for use of dust/powder products on cats and dogs exceeded EPA’s level of concern. Therefore, the Hartz Mountain Corporation (Hartz) voluntarily canceled all dust/powder formulations registered for use on pets and Chem-Tech LTD removed use of dusts/powders on cats and dogs. Hartz also canceled one pet collar registration and modified the dimensions of remaining pet collars by manufacturing thinner collars which release less TCVP over time.

In April 2022, the Ninth Circuit issued a decision finding that EPA’s 2020 denial of NRDC’s petition was not supported by substantial evidence regarding the amount of TCVP released as dust (as opposed to liquid) by the pet collars, as well as the assumption that pet owners will trim the collars by at least 20% upon application, and directed the Agency to issue a new response by October 11, 2022.

On October 6, 2022, EPA issued its response granting the petition regarding TCVP pet collars based on reevaluation of the methodology used in the 2019 mechanical torsion study and determining that the study did not adequately assess the form of TCVP that is released from the collars. Therefore, EPA returned to the 2016 human health risk approach for assessing pet collars which found that risk estimates for all pet collars exceeded EPA’s level of concern for residential uses. Risk estimates for liquid spray products did not result in risks of concern. EPA, therefore, denied the NRDC petition for liquid pump/trigger spray products which remain active. Regarding the pet collars, EPA explained: “EPA is moving to draft a proposed [Notice of Intent to Cancel (NOIC)]... Hartz is working on two studies and plans to submit the data for EPA review. EPA intends to incorporate into the drafting of the NOIC review of any data received in a timeframe that allows for such incorporation. Should the new data result in a change to the Agency’s conclusions, those conclusions will be captured in an updated risk assessment as well as the PID, which will be open for public comment. The Agency would not further pursue an NOIC if the data demonstrates that there is no longer a risk concern for any TCVP pet collars.” See Document Number EPA-HQ-OPP-2009-0308-0028 at 44, available at regulations.gov.

After EPA granted the petition for TCVP pet collars, the registrant conducted additional studies related to the pet collar uses: a new dust torsion study, and on-animal fur clipping studies. These studies have been reviewed, deemed acceptable for risk assessment and were incorporated into EPA’s September 2023 revised human health risk assessment. Using the available chemical-specific data and residential non-cancer handler inhalation, EPA did not find residential risks of concern for adults or children. Residential handler and post-application cancer risks estimated for TCVP pet collars, using chemical-specific data, were also not of concern. Based on these new data, the Agency issued a Determination Not to Further Pursue Cancellation of TCVP Pet Collars in September 2023, which is available in docket EPA-HQ-OPP-2009-0308 at www.regulations.gov.

In September 2023, EPA also released the Proposed Interim Decision (PID) for TCVP and the updated human health risk assessment. EPA took public comments on the PID and revised human health risk assessment for 60 days. The Agency did not receive any additional comments regarding TCVP pet products. The PID, 2023 revised human health risk assessment, and additional supporting documentation are available in the TCVP registration review docket EPA-HQ-OPP-2008-0316 at www.regulations.gov.

In June 2024, EPA released the Interim Decision (ID) for TCVP. EPA is moving forward with measures that were proposed in the PID to require updates to terms and conditions of registration for pet collars. Pet product registrants will be required to submit annual enhanced reports and annual sales information. EPA is also requiring risk mitigation for applications to livestock and poultry and their premises. The ID is available in the TCVP registration review docket EPA-HQ-OPP-2008-0316 at www.regulations.gov

Additional Information

• Agency Determination Not to Further Pursue Cancellation of Tetrachlorvinphos (TCVP) Pet Collars (September 19, 2023)
• Tetrachlorvinphos (TCVP) Proposed Interim Registration Review Decision
• Tetrachlorvinphos (TCVP). Fourth Revision: Human Health Draft Risk Assessment for Registration Review (September 7, 2023)
• Tetrachlorvinphos (TCVP): Third Revision - Occupational and Residential Exposure Assessment for Registration Review (September 7, 2023)
• Tetrachlorvinphos (TCVP): Revised Data Evaluation Record for the Study “On
  Animal Collar Release over Time” (September 7, 2023)
• Tetrachlorvinphos Data Evaluation Records (DERs) (September 5, 2023)
• Tetrachlorvinphos (TCVP): Tier I Updated Review of Domestic Animal Incidents for the Proposed Interim Decision (PID) (May 2, 2023)
• Approach for Evaluating Developmental Neurotoxicity Potential for the Organophosphate Pesticides
• Tetrachlorvinphos (TCVP): Revised Occupational and Residential Exposure Assessment for Registration Review (January 26, 2022)
• Tetrachlorvinphos (TCVP): Revised Acute, Steady State, and Cancer Aggregate Dietary (Food and Drinking Water) Exposure and Risk Assessments for the Registration Review Human Health Risk Assessment (January 26, 2022)
• Tetrachlorvinphos (TCVP): Tier I Update Review of Human Incidents and Epidemiology for Draft Risk Assessment (July 27, 2021)
• Tetrachlorvinphos (TCVP): Addendum to Tier I Update Review of Human Incidents and Epidemiology for Draft Risk Assessment (DP Barcode: D462910) (September 9, 2021)
• Tetrachlorvinphos (TCVP): Summary of the Joint Hazard and Science Policy Council (HASPOC) and Cancer Assessment Review Committee (CARC) (October 4, 2022)
• Tetrachlorvinphos (TCVP) (083701) Use in Animal Production: Percent of Animals Treated Data (April 14, 2021)
• Tetrachlorvinphos (TCVP) Drinking Water Assessment for Registration Review (November 6, 2014)
• Assessment of the Use, Usage, and Benefits of Tetrachlorvinphos (TCVP) (PC #083701) and Impacts of Potential Mitigation Measures Related to Poultry and Livestock Production (August 16, 2023)
• Tetrachlorvinphos (TCVP) Revisit of Mutagenicity Studies (May 1, 2020)
• Tetrachlorvinphos Data Evaluation Records (DERs) (September 2023)
• EPA's response to NRDC petition to cancel tetrachlorvinphos pet uses (pdf) (705.4 KB, 10/11/2022)
• NRDC petition to cancel tetrachlorvinphos pet uses.
• Registration review docket for tetrachlorvinphos.
• Interim Tolerance Reassessment Decision and Reregistration Eligibility Decision Addendum (PDF).
• Use of human studies data in reviewing exposure to TCVP in pet collars.
• Tetrachlorvinphos tolerances.