Active Ingredient: Chlorpyrifos
Human Health Risk Assessment and Mitigation
Documents and Activities

Risk Characterization Documents (RCDs) estimate the nature and likelihood of adverse health effects in humans who may be exposed to pesticides.

• Toxic Air Contaminant (TAC) Assessment
  • August 2018 - Director’s Proposed Determination Concerning Chlorpyrifos as a Toxic Air Contaminant (PDF)
  • August 2018 - Scientific Review Panel's Findings (PDF)
  • July 2018 - Executive Summary (PDF)
  • July 2018 - Final Toxic Air Contaminant Evaluation of Chlorpyrifos (Complete Document) (PDF)
  • July 2018 - Final Toxic Air Contaminant Evaluation of Chlorpyrifos (Evaluation Only) (PDF)
    • Appendix 1 – Summary of Toxicology for Chlorpyrifos (PDF)
    • Appendix 2 – Exposure Estimates and Margins of Exposure for Developmental Neurotoxicity (PDF)
    • Appendix 3 – Revised Margins of Exposure for Acetylcholinesterase Inhibition (PDF)
    • Appendix 4 – Andrews and Patterson, 2000 (PDF)
    • Appendix 5 – Mechanistic Studies of Chlorpyrifos Related Neurodevelopmental Effects (PDF)
    • Appendix 6 – December 2017 Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant (PDF)
  • June 2018 - Scientific Review Panel Meeting Presentation: Consideration of Addendum to Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant (PDF)
  • June 2018 - Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant (Addendum to December 2017 Draft Evaluation) (PDF)
    • June 2018 - Cover Letter to Scientific Review Panel (PDF)
  • December 2017 – Scientific Review Panel Meeting Presentation: Overview of Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant (PDF)
  • December 2017 – Office of Environmental Health Hazard Assessment Findings on the Health Effects of Chlorpyrifos as a Candidate Toxic Air Contaminant (PDF)
    • January 2018 – Responses to OEHHA Findings (PDF)
  • December 2017 – Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant for the Scientific Review Panel (PDF)
    • December 2017 – Cover Letter to Scientific Review Panel (PDF)
    • December 2017 – Charge Questions for the Scientific Review Panel (PDF)
  • August 2017 – Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant (PDF)
    • December 2017 – Responses to Technical Comments by the Public (PDF)
    • December 2017 – Responses to Comments by Dow AgroSciences LLC (PDF)

• December 2015 – Draft Risk Characterization Document (PDF)
  • August 2017 – Responses to Comments by the California Air Resources Board (PDF)
  • August 2017 – Responses to Comments by the Office of Environmental Health Hazard Assessment (PDF)
  • August 2017 – Responses to Comments on Toxicology by Dow AgroSciences LLC (PDF)
  • August 2017 – Responses to Comments on Exposure by Dow AgroSciences LLC (PDF)
• June 1993 – Exposure Assessment Document (PDF)
• May 1992 – Dietary Exposure Assessment Document (PDF)

Other Documents

• August 2017 – Revised: Estimation of Chlorpyrifos Horizontal Deposition and Air Concentrations for California Use Scenarios (PDF)
• August 2017 – Report for Pesticide Application Air Monitoring for Chlorpyrifos and Chlorpyrifos-Oxon in San Joaquin County in July 2015
• August 2017 - Cases Reported to the Pesticide Illness Surveillance Program and Evaluated as Associated with Exposure to Chlorpyrifos, Alone or in Combination with Other Products, 2004-2014 (PDF)
• December 2016 – Report for Pesticide Application Site Monitoring for Chlorpyrifos and Chlorpyrifos-Oxon in Imperial County in October 2014
• December 2015 – Estimation of Chlorpyrifos Horizontal Deposition and Air Concentrations for California Use Scenarios (PDF)
• March 2013 – Lompoc Monitoring Report
• August 2011 – Comments On U.S. EPA's Preliminary Risk Assessment For Chlorpyrifos: With A Focus On Exposure Assessment (PDF)
• May 2010 – Comparison of Initial Deposition and Residue Dissipation of Chlorpyrifos Using Conventional Flat Fan Nozzles vs. Hypro® TwinCap™ Nozzles Fitted with Ultra-Lo Drift Spray Tips (PDF)
• September 2007 – Results from Sample Collection in Tulare County for A Suspected Organophosphate Exposure Event (PDF)
• September 2007 – Project 0706 - Worker Health and Safety's Involvement In: Chlorpyrifos Drift Investigation In Fresno County (PDF)
• September 2007 – Project 0704 - WHS Involvement In Priority Investigation 41-Tul-07: Chlorpyrifos Drift Investigation, Tulare County (PDF)
• September 2007 – Project 0703 - Tulare County Chlorpyrifos Restricted Entry Interval Violation in Oranges (PDF)
• February 2005 – Chlorpyrifos Field Spike Degradation Study, Project #0403 (PDF)
• April 2004 – Forensic Review and Sampling of PPE/Respiratory Protective Equipment Associated with Priority Investigation 3-RIV-04 (PDF)
• March 2004 – Forensic Review and Sampling of PPE/Respiratory Protective Equipment Associated with Priority Investigation 3-RIV-04 (PDF)
• October 2002 – Response to Comments from Dow AgroSciences LLC on the Draft Chlorpyrifos Risk Characterization Document by the California Department of Pesticide Regulation (Exposure Assessment Section) (PDF)
• October 2001 – WH&S Branch Activities and Results of Analyses Related to the Investigation of Priority Illness Episode 45-TUL-00 (Project 0002) (PDF)
• October 2001 – WH&S Branch Activities and Results of Analyses Related to the Investigation of 22-TUL-00 (Project 0001) (PDF)
• WH&S Branch Activities and Results of Analyses Related to the Investigation of 43-FRE-99 (Project 9903) (PDF)
• July 1999 – Chlorpyrifos Odor Provoking the Onset of Clinical Symptoms (PDF)
• January 1999 – Oral and Dermal Absorption of Chlorpyrifos: A Human Volunteer Study (PDF)
• April 1998 – Report for the Application and Ambient Air monitoring of Chlorpyrifos in Tulare County During Spring/Summer, 1996
  • Appendices
• February 1998 – Contact Dermatitis in California Nursery Workers: Part II. Pilot Field Study (PDF)
• February 1993 – Aerial Movement and Deposition of Diazinon, Chlorpyrifos, and Ethyl Parathion (PDF)
  • Executive Summary
• December 1991 – 1989 Probe Study to Determine the Exposure of Aerial Application Flaggers to Organophosphate Pesticides Via Urinary Metabolite Monitoring (PDF)
• August 1991 – Determination of Dermal Absorption of Chlorpyrifos in Humans (PDF)
• April 1991 – Structural Chemical Exposure Studies Provide Human Metabolism and Urine Clearance Data for Chlorpyrifos, Dimethoate and Malathion (PDF)
• March 1991 – Situational Chemical Exposure Studies Provide Human Metabolism and Urine Clearance Data for Chlorpyrifos, Dimethoate, and Malathion (PDF)
• March 1991 – Measuring Potential Dermal Transfer of Surface Pesticide Residue Generated from Indoor Fogger Use: Using the CDFA Roller Method, Interim Report II (PDF)
• May 1990 – Measuring Potential Dermal Transfer of Surface Pesticide Residue Generated from Indoor Fogger Use: An Interim Report (Chemosphere 20, (3/4), 349-360, 1990) (PDF)
• January 1990 – Human Illnesses/Injuries Reported by Physicians in California Involving Indoor Exposure to Pesticides Containing Chlorpyrifos, DDVP and/or Propoxur 1983-1986 (PDF)
• July 1986 – Dissipation of Dislodgeable Foliar Residue for Chlorpyrifos and Dichlorvos Treated Lawn: Implication for Safe Reentry (Bull Environ Contam & Toxicol 37, 33-40, 1986) (PDF)
• December 1985 – Monterey County Residential Air Monitoring
• November 1984 – Dissipation of Dislodgeable Residue of Chlorpyrifos and DDVP on Turf (PDF)
• July 1984 – Degradation of Dislodgeable Residues of Chlorpyrifos and Diazinon on Turf - A Preliminary Survey (PDF)

• Consultation on Proposed Cancellation of Chlorpyrifos Products
  • August 2019 – Response to Comments Received from the California Agricultural Commissioners and Sealers Association for Proposed Cancellation
  • August 2019 – Response to Comments Received from the California Department of Food and Agriculture for Proposed Cancellation
  • July 2019 – California Agricultural Commissioners and Sealers Association Comments on Proposed Cancellation
  • July 2019 – California Department of Food and Agriculture Comments on Proposed Cancellation
• May 2019 -- Risk Management Directive for Chlorpyrifos, PDF
  • June 2019 – Response to Comments Received for Proposed Risk Management Directive
  • April 2019 – Office of Environmental Health Hazard Assessment Comments on Proposed Risk Management Directive
  • April 2019 – California Air Resources Board Comments on Proposed Risk Management Directive
  • May 2019 – California Air Pollution Control Officers Association Comments on Proposed Risk Management Directive
  • April 2019 – California Department of Food & Agriculture Comments on Proposed Risk Management Directive
• November 2018 - Revised Interim Permit Conditions (PDF)
• October 2017 - Revised Interim Permit Conditions (PDF)
• October 2017 - Evaluation and Options for Interim Mitigation Measures to Reduce Acute Chlorpyrifos Exposure to Bystanders (PDF)
• August 2017 – Directive for Interim Mitigation Measures to Address Health Risk from Chlorpyrifos (PDF)
• July 2015 – Interim Permit Conditions (PDF)
• July 2015 – Designating Chlorpyrifos as a Restricted Material

Enforcement Letters

• November 2018 - ENF 2018-22 – Updates to Volume 3, Restricted Materials and Permitting, Pesticide Use Enforcement Program Standards Compendium, Appendix O-Chlorpyrifos Interim Recommended Permit Conditions
• October 2017 - ENF 2017-23 - Updates to Volume 3, Restricted Materials and Permitting, Pesticide Use Enforcement Program Standards Compendium, Appendix O: Chlorpyrifos Interim Recommended Permit Conditions
• July 2015 – ENF 2015-09 - Interim Recommended Permit Conditions for Chlorpyrifos used to Produce and Agricultural Commodity: Addition to Compendium Volume 3, Restricted Material and Permitting
• February 2005 – ENF 2005-008 - Chlorpyrifos Phase Out Questions and Answers

• September 2017 - Pesticide Registration and Evaluation Committee Agenda (PDF)
  • California's Toxic Air Contaminant Program for Pesticides (PDF)
  • Draft Evaluation of Chlorpyrifos as a Toxic Air Contaminant (PDF)
  • Directive for Interim Mitigation Measures to Address Health Risks from Chlorpyrifos (PDF)
• March 2015 - Agricultural Pest Control Advisory Committee Meeting Agenda (PDF)
  • Chlorpyrifos Update
  • Agricultural Pest Control Advisory Committee Meeting Minutes (PDF)
• November 2014 - Pest Management Advisory Committee Meeting Agenda (PDF)
  • Proposed Regulation to Designate Chlorpyrifos a Restricted Material (PDF)
• October 2014 - Critical Uses of Chlorpyrifos
• September 2014 - Agricultural Pest Control Advisory Committee Meeting Agenda (PDF)
  • Chlorpyrifos Update (PDF)
• August 2014 - Pesticide Registration and Evaluation Committee Agenda (PDF)
  • Chlorpyrifos Update (PDF)
  • Pesticide Registration and Evaluation Committee Meeting Minutes (PDF)
• January 2009 - Pesticide Registration and Evaluation Committee Agenda (PDF)
  • Status of Chlorpyrifos and Diazinon Reevaluations (PDF)
  • Pesticide Registration and Evaluation Committee Meeting Minutes (PDF)
• May 2007 - Pest Management Advisory Committee Meeting Agenda (PDF)

• Pesticide Product Database
• Human Health Assessment Branch Memos
• Human Health Assessment Branch Publications, Posters/Abstracts and Presentations
• Worker Health and Safety Reports and Memos
• Environmental Monitoring Branch Publications
  • Environmental Fate Reviews
• Air Monitoring Network
• Pesticide Use Reporting (PUR)
• California Pesticide Illness Query (CalPIQ)
• Environmental Justice (EJ)
• OEHHA Proposition 65 Information
• U.S. EPA Pesticide Chemical Search
• PubChem-Chemical Information