Tetrachlorvinphos (TCVP)
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, emulsifiable concentrates, feed additives (solid and liquid), feed blocks, wettable powders, pellets and granular products.
TCVP, when used on pets to protect from fleas and ticks, can have associated pet health risks when not used according to label instructions. Learn more about safely protecting pets from fleas and ticks.
Using TCVP Products
In October 2022, EPA released a human health risk assessment finding that risk estimates for all pet collars found unacceptable risks for residential uses. Based on currently available data and taking into consideration currently registered residential uses for TCVP, EPA cannot determine that there are no unreasonable adverse effects to human health from residential exposure to TCVP in pet collars.
However, it is EPA’s understanding that the registrant is currently working on two studies related to the risks of TCVP from pet collars and plans to submit that data to EPA by the end of the year. Should the Agency receive data that impacts the current conclusions for TCVP pet collars, the Agency will review that data, make its review publicly available, update the TCVP risk assessment as appropriate, and make this information available for public comment.
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 and powder products out of reach of children, and
- washing hands thoroughly with soap and water after handling.
EPA Actions
TCVP was first registered as a pesticide in 1966. All crop uses of TCVP were voluntarily canceled in 1987. There are 18 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 of 2002, and in July of 2006 EPA issued the final TCVP RED following the completion of the organophosphate cumulative risk assessment. During the RED process, the 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 it is not an endocrine disruptor, and additional data were not needed.
EPA initiated the registration review process for TCVP in 2008.
In 2009, the 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. Risk to listed and non-listed mammals, birds, reptiles, and terrestrial-phase amphibians also are possible. EPA’s response to comment 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 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:
- EPA’s endocrine screening
- The application of the FQPA 10X Safety Factor for Organophosphates
- The occupational and residential exposure assessment
- The dietary assessment
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, 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 EPA’s 2020 denial of NRDC’s petition was not supported by substantial evidence as to the amount of TCVP released as dust (as opposed to liquid) by the pet collars; and the assumption that pet owners will trim the collars by at least 20% upon application, and directing the Agency to issue a new response by October 11, 2022.
On October 11, 2022, EPA released its response granting the petition for TCVP pet collars based on reevaluating 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. EPA granted NRDC’s petition for all remaining pet collars with TCVP. 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.
EPA is moving to draft a proposed Notice of Intent to Cancel (NOIC) for TCVP pet collars but is awaiting more data from the registrant that the registrant has informed EPA it is preparing. EPA intends to incorporate into the drafting of the NOIC any data received by the end of the year. Should the new data change the Agency’s conclusions, those conclusions will be captured in an updated risk assessment, as well as the Proposed Interim Decision (PID) for TCVP, which will be open for public comment. The Agency would not further pursue a NOIC if the data demonstrate that there is no longer a risk of concern for any TCVP pet collars.
The response to the Ninth Circuit U.S. Court of Appeals and all information related to the NRDC petition is available in docket EPA-HQ-OPP-2009-0308 at www.regulations.gov. The revised human health risk assessment is available in the TCVP registration review docket EPA-HQ-OPP-2008-0316 at www.regulations.gov.
The October 2022 revised human health risk assessment will not only be the basis for EPA’s response to NRDC’s petition on remand but will also be incorporated into the ongoing registration review of TCVP under section 3(g) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) (a separate process from the NRDC response). FIFRA section 3(g) requires EPA to review pesticides every 15 years to ensure that risk assessments reflect the best available science, and to ensure that registered products in the marketplace do not present unreasonable adverse effects to human health and the environment. EPA will take public comment on the revised human health risk assessment during the same 60-day public comment period that the Agency plans to open when it issues its PID in 2023. The PID, which is the next step in the FIFRA registration review process, will outline potential risk management options for this insecticide to address any potential risks of concern identified in the draft risk assessments.
Additional Information
- EPA's response to NRDC petition to cancel tetrachlorvinphos pet uses (pdf)
- Third Revision of Tetrachlorvinphos (TCVP) Human Health Draft Risk Assessment for Registration Review. (pdf)
- NRDC petition to cancel tetrachlorvinphos pet uses.
- Registration review docket for tetrachlorvinphos.
- Interim Tolerance Reassessment Decision and Reregistration Eligibility Decision Addendum (PDF). (184 pp, 551.98 K, About PDF)
- Use of human studies data in reviewing exposure to TCVP in pet collars.
- Tetrachlorvinphos tolerances.