Common Mechanism Groups; Cumulative Exposure and Risk Assessment
Common mechanism of toxicity pertains to two or more pesticide chemicals or other substances that cause a common toxic effect(s) by the same, or essentially the same, sequence of major biochemical events (i.e., interpreted as mode of action).
On this page:
- Dichlorvos (DDVP)
Organophosphates (OPs) are a group of closely related pesticides used in agriculture and non-agricultural sites that affect functioning of the nervous system. They are among the Agency's first priority group of pesticides to be reviewed under the Food Quality Protection Act.
OP Cumulative Assessments
A key step in the process of reassessing tolerances for the organophosphate pesticides was the assessment of cumulative exposure and risk to human health from these pesticides. In December 2001, EPA released a preliminary version of the OP cumulative assessment. A revised version of the assessment was released in June 2002. In August 2006, EPA issued the 2006 Update to the OP Cumulative Assessment. The Agency concluded that with the adoption of risk mitigation measures for over 40 individual OPs from risk management decisions completed during the previous several years, the cumulative risks associated with the OP pesticides do not exceed the Agency's level of concern.
- OP Cumulative Risk Assessment – 2006 Update. Documents related to the Agency’s 2006 Update to the OP Cumulative Assessment are available on this web page. These documents are also available in the docket (EPA-HQ-OPP-2006-0618), accessible online at Regulations.gov.
- For more information, please contact Susan Lewis (email@example.com), 703-308-8009.
- Memorandum: Finalization of Interim Reregistration Eligibility Decisions (IREDs) and Interim Tolerance Reassessment and Risk Management Decisions (TREDs) for the Organophosphate Pesticides, and Completion of the Tolerance Reassessment and Reregistration Eligibility Process for the Organophosphate Pesticides (PDF) (3 pp, 47 KB, About PDF)
- Response to Public Comments on the Organophosphate Cumulative Risk Assessment, December 20, 2007 (28 pp, 1.86 MB, About PDF)
- Organophosphate Cumulative Risk Assessment; Notice of Availability (Federal Register Notice; August 2, 2006)
OP Cumulative Risk Assessment (June 10, 2002) Documents related to the Agency's
revised OP assessment are available on this web page.
- Preliminary OP Cumulative Risk Assessment (December 3, 2001) Documents related to the Agency's preliminary OP assessment are available
on this web page.
OP Pesticides Review Status
EPA has also assessed uses and risks associated with each individual organophosphate pesticide. Decisions were captured in Interim Reregistration Eligibility Decision (IRED) or Tolerance Reassessment Decision (TRED) documents for these pesticides, as reflected in the OP status table. In completing the cumulative risk assessment for the OPs, EPA concluded that, with the mitigation measures encompassed in the individual Interim REDs and TREDs, the cumulative risks associated with the OPs are below the Agency’s level of concern. Based on the results of the OP cumulative assessment, the Interim REDs and TREDs for the OP pesticides are now considered final, and the associated tolerance reassessment and reregistration eligibility decisions are considered complete.
Revised OP Cumulative Risk Program -- The OP Cumulative Risk ("OPCumRisk") Program was developed by EPA's Office of Research and Development (ORD) National Health and Environmental Effects Laboratory (NHEERL) to facilitate the data analysis for the July 2001 OP dose-response assessment. To execute this program,
1) install and run the companion file, "tcl832.exe"
2) install and run the OPCumRisk Program
Note: If you are using a screen reader and cannot execute this modeling program or wish to obtain the results in accessible format, please contact Bill Wooge (firstname.lastname@example.org), 703-308-8794 in EPA's Office of Pesticide Programs.
The N-methyl carbamates are a group of closely related pesticides used in homes, gardens and agriculture that may affect the functioning of the nervous system. In 2004, EPA described its reasoning and identified the N-methyl carbamate pesticides designated as a common mechanism group for the purposes of its cumulative risk assessment. The cumulative risk assessment, along with individual risk assessments was the basis for completing tolerance reassessment for the N-methyl carbamate pesticides.
N-methyl Carbamate Revised Cumulative Risk Assessment
EPA issued the N-methyl carbamate revised cumulative risk assessment for comment on September 26, 2007. The Agency concluded that, with the adoption of the risk mitigation measures required in the individual N-methyl carbamate pesticide risk management decisions, the cumulative risks associated with the N-methyl carbamate pesticides do not exceed the Agency's level of concern.
- N-methyl Carbamate Revised Cumulative Risk Assessment; Notice of Availability, [September 26, 2007], comments accepted through November 26, 2007.
- To comment on the N-methyl Carbamate Revised Cumulative Risk Assessment, go to Regulations.gov, in Document ID Number EPA-HQ-OPP-2007-0935-0001.
- Additional information is also available at Regulations.gov in Docket Number EPA-HQ-OPP-2007-0935.
- N-methyl Carbamate Revised Cumulative Risk Assessment Decision Fact Sheets
- N-methyl Carbamate Revised Cumulative Risk Assessment Available for Public Comment
- Background and Summary of N-methyl Carbamate Revised Cumulative Risk Assessment
- Risk Management Decisions for Individual N-methyl Carbamate Pesticides
- N-methyl Carbamate Revised Cumulative Risk Assessment (PDF) (277 pp, 3.2 MB, About PDF) This document does not contain the appendicies. The appendicies may be found in Regulations.gov in Docket Number EPA-HQ-OPP-2007-0935.
- Completion of the Tolerance Reassessment and Final Reregistration Eligibility Decisions for the N-methyl Carbamate Pesticides
- If you have questions, contact Tracy Perry (email@example.com), 703-308-0128.
N-methyl Carbamate Pesticides Review Status
EPA also has assessed uses and risks associated with each individual N-methyl carbamate pesticide (that is, for aldicarb, carbaryl, carbofuran, formetanate hydrochloride, methiocarb, methomyl, oxamyl, pirimicarb, propoxur, and thiodicarb). Decisions are captured in reregistration eligibility and tolerance reassessment decision documents for these pesticides, as reflected in the carbamates status table.
Preliminary N-methyl Carbamate Cumulative Risk Assessment
- Reassessment of Commodity Tolerances that are Insignificant Contributors to the N-methyl Carbamate Cumulative Risk
- Preliminary N-Methyl Carbamate Cumulative Risk Assessment: Fact Sheet - August 2005
- Preliminary N-methyl Carbamate Cumulative Risk Assessment - August 2005
- Computer Risk Model Input Files used in the Preliminary Cumulative Risk Assessment of N-Methyl Carbamate Pesticides
The triazine pesticides and their metabolites are a group of closely related herbicides used widely in agriculture and non-agricultural sites. After taking public comment, EPA concluded in 2002 that the triazine-containing pesticides atrazine, simazine, and propazine and their three chlorinated degradates should be included in a common mechanism group and considered through a cumulative risk assessment. In laboratory animal studies, the triazines share a common neuroendocrine mechanism of toxicity which results in both developmental and reproductive effects. Propazine was not included in the cumulative assessment because no dietary, drinking water, or residential human exposure to propazine is anticipated from any of the currently registered uses. The triazines have been given a high priority in EPA's review of older pesticides and associated tolerances.
Triazine Cumulative Assessment
EPA issued the triazine cumulative risk assessment for comment on June 21, 2006. The Agency concluded that, with mitigation measures for atrazine and simazine, the cumulative risks associated with the triazines are below the Agency's level of concern.
- Triazine Cumulative Risk Assessment; Notice of Availability, [June 21, 2006], (comment period closed on August 21, 2006).
- Pesticide News Story: Triazine Cumulative Risk Assessment Decisions Comments Requested on Cumulative Decision, Simazine RED, and Propazine TRED
Cumulative Risk Assessment and Decisions for Atrazine, Simazine, and
Propazine; Fact Sheet
Cumulative Risk Assessment (PDF) (67 pp, 611.1 KB, About PDF)
- The Grouping of a Series of Triazine Pesticides Based on a Common Mechanism of Toxicity
- Triazine cumulative risk assessment: EPA-HQ-OPP-2005-0481
- Atrazine IREDs and RED: EPA-HQ-OPP-2003-0367
- Propazine TRED: EPA-HQ-OPP-2005-0496
- Simazine RED: EPA-HQ-OPP-2005-0151
Triazine Pesticides Review Status
EPA also has assessed uses and risks associated with each individual triazine pesticide (that is, for atrazine, simazine, propazine, and their three chlorinated degradates). Decisions are captured in reregistration eligibility and tolerance reassessment decision documents for these pesticides, as reflected in the triazine status table.
The chloroacetanilides are a group of closely related herbicides used in agriculture for general weed control in food and feed crops. After taking public comment in 2001, EPA grouped together three of the choloracetanilides - acetochlor, alachlor, and butachlor - for cumulative assessment based on their ability to cause nasal tumors. Because butachlor no longer has active product registrations or tolerances, only acetochlor and alachlor were considered in the chloroacetanilide cumulative assessment, released in March 2006.
Chloroacetanilide Cumulative Assessment
EPA issued the completed chloroacetanilide cumulative risk assessment for comment on March 29, 2006. The Agency concluded that the cumulative risk associated with the chloroacetanilide pesticides is below the Agency's level of concern.
Cumulative Risk Assessment; Notice of Availability, [March 29, 2006],
(comment period closed on May 30, 2006).
- To comment on the Chloroacetanilide Cumulative Risk Assessment, go to Regulations.gov, in Document ID Number EPA-HQ-OPP-2006-0202-0002.
- Additional information is also available at Regulations.gov in Docket Number EPA-HQ-OPP-2006-0202.
New Story: EPA Releases Cumulative Assessment on a Group of Closely
Cumulative Risk Assessment (PDF) (74 pp, 1.5 MB, About PDF)
- Implementation of the Determinations of a Common Mechanism of Toxicity for N-methyl Carbamate Pesticides and for Certain Chloroacetanilide Pesticides
Chloroacetanilide Pesticides Review Status
EPA also has assessed uses and risks associated with both of the individual chloroacetanilide pesticides (that is, for acetochlor and alachlor). Decisions are captured in RED and TRED documents for these pesticides, as reflected in the chloroacetanilide status table.
Pyrethroids are a class of synthetic insecticides which are structurally based on the pyrethrins, botanical insecticides extracted from Chrysanthemum cinerariaefolium. In conducting the screening-level cumulative risk assessment, EPA considered all registered uses of pyrethrins/pyrethroids and exposure from food, drinking water, and residential use through oral, dermal, and inhalation routes of exposure.
Pyrethrins/Pyrethroid Cumulative Risk Assessment
EPA completed the Pyrethrins/Pyrethroid Cumulative Risk Assessment on October 4, 2011. This screening-level cumulative risk assessment is highly conservative, overestimating actual risk. That is, the assessment assumes that people are exposed to the highest levels of residues in food, water, and in their homes, all on the same day. Even with these conservative and protective assumptions, the assessment shows that cumulative risks for both children and adults are not of concern for the currently registered uses of pyrethrins/pyrethroid pesticides. Further, the assessment shows that there is sufficient room in the pyrethroid cumulative risk cup to support consideration of additional individual pyrethroid pesticide uses.
- Pyrethrins/Pyrethroid Cumulative Risk Assessment, October 4, 2011
- Pyrethrins/Pyrethroid Cumulative Risk Assessment; Extension of Comment Period (FR notice published 12-30-11; extended comment period closes 2-8-12)
- Pyrethrins/Pyrethroid Cumulative Risk Assessment; Notice of Availability (FR Notice published 11-9-11; comment period closes 1-9-12)
- Pyrethrins/Pyrethroid Docket EPA-HQ-OPP-2011-0746
Pyrethrins/Pyrethroid Pesticides Review Status
The Agency will update individual pyrethrins/pyrethroid pesticide risk assessments as these pesticides come up for review.