Office of Environmental Health Hazard Assessment


California Medical Supervision Program

The California Medical Supervisionprogram is designed to protect workers who regularly mix, load, or apply the highly toxic Category I and Category II organophosphate (OP) and N-methyl carbamate pesticides (CB).  The goal of the program is to identify and prevent excessive OP and CB exposure and resulting pesticide-related illness.  Exposure to OPs or CBs may lower the level of available cholinesterase (ChE) -- an enzyme essential to the proper functioning of the nervous system. Depression of cholinesterase levels can lead to symptoms ranging from blurred vision, diarrhea and tremors to seizures, loss of consciousness and even death. Monitoring plasma and red blood cell ChE levels allows detection of cholinesterase depression prior to the onset of illness.

Learn more about the program


Medical Supervision Training for Physicians

OEHHA offers a one-hour training class in Medical Supervision Training for Physicians that explains the California program for cholinesterase monitoring of agricultural pesticide mixer/loader/applicators. Continuing medical education credit is available to physicians and nurses upon completion of this module.

Guidelines for Physicians-4th edition (February 2002)

OEHHA publishes the Guidelines for Physicians - a booklet that describes the state program of ChE monitoring for agricultural pesticide mixers/loaders/applicators who regularly handle toxicity Category I and II OP or CB pesticides. Physicians who are medical supervisors are required to possess a copy of these Guidelines and be familiar with its content.

In 2011, additional requirements were added to the medical supervision program. Medical supervisors are now required to report in the test order the purpose of the test, including baseline or other periodic testing, and to ensure that the person tested receives a copy of the cholinesterase test results and any recommendations within 14 days of the medical supervisor receiving the results.

Medical Supervision Program Evaluation

In 1989, the Department of Health Services (former OEHHA) conducted a first evaluation of the California Medical Supervision Program since its inception in 1961. The results of the evaluation were published in a peer review journal (Ames et al., 1989). In 2011, additional requirements were added to the medical supervision program.  Laboratories performing cholinesterase testing are now required to report test results electronically to DPR, who shares the data with OEHHA.  Additionally, DPR is responsible for the collection and storage of data and OEHHA has been tasked with reviewing the test results and providing appropriate medical or toxicological consultation to the medical supervisor.  OEHHA and DPR, in consultation with CDPH, are jointly required to submit by the end of 2015 a report on the effectiveness of the medical supervision program and the utility of laboratory-based reporting, as well as any additional recommendations to the legislature.  Data collected since 2011 are being analyzed and will allow for the second evaluation of the program. The upcoming report will be publicly available on the website.

Medical Supervision Survey

In 1999, OEHHA conducted a survey to determine the feasibility of certification for California medical supervisors. A mail survey was sent to the 321 California physicians who were medical supervisors of record in 1995. Responses returned from 101 medical supervisors provided the basis for description of their practice, how they obtained information on the medical supervision program, and whether or not they would want or accept a state certification program (certification is not currently required).  Follow this link to download the PDF version of the full results of the survey: Medical Supervision Survey Results.

Additional Links:

U.S. EPA Publication Recognition and Management of Pesticide Poisonings:

Washington Cholinesterase Monitoring Program:

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