California Medical Supervision Program

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Pesticides handling and spraying

The California Medical Supervision program 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.

Effective January 1, 2017, physicians that have contract(s) with one or more employers to provide medical supervision services are required to register with OEHHA.  Physicians can register here. You can view the current list of registered medical supervisors here.

In 2011, additional reporting 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
  • 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 Training for Physicians

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

Guidelines for Physicians-5th edition (July 2015)

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.

You can download the PDF version of the full Guidelines for Physicians  or a one-page summary of the Guidelines.

To obtain a printed version, contact OEHHA at or (510) 622-3170.

OEHHA is currently updating the online Medical Supervision training class, preparing an addendum to the 5th Edition of the Guidelines for Physicians, and revising the one-page summary of the Guidelines to reflect changes to Section 105206 of the Health and Safety Code that were recently enacted by the California legislature.

Medical Supervision Program Evaluation

In 2015, OEHHA and DPR, in consultation with CDPH, were jointly required to submit 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. The Report to the California Legislature is publicly available here.

In 1989, the Department of Health Services (now OEHHA) conducted a first evaluation of the California Medical Supervision Program since its inception in 1974. The results of the evaluation were published in a peer review journal (Ames et al., 1989).

Medical Supervision Survey

In 1999, OEHHA conducted a survey to determine the feasibility of certification for California medical supervisors.

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