Medical Surveillance Guidelines for Workers Who Were Exposed to Organophosphate and Carbamate Pesticides

Abstract

Organophosphate and carbamate pesticides are widely used in Thailand’s agricultural sector, posing significant both acute and chronic health risks to workers through inhibition of cholinesterase enzymes. Current medical surveillance in Thailand relies on the “cholinesterase test paper”, a qualitative method with limitations in accuracy that is not fully suitable for a roburst occupational health contexts. This study aims to review the toxicokinetics and toxicodynamics of these pesticide groups, as well as to examine literature on medical surveillance guidelines from four international organizations: the Office of Environmental Health Hazard Assessment (OEHHA, USA), the Health and Safety Executive (HSE, UK), Safe Work Australia, and the Department of Occupational Safety and Health (DOSH, Malaysia), in order to propose an appropriate guideline for Thailand. The literature review revealed all organizations recommend measuring blood cholinesterase activity (both acetylcholinesterase and butyrylcholinesterase) to establish a pre-placement baseline prior to exposure and to conduct regular follow-up testing. Clear occupational health action thresholds are specified when enzyme activity decreases to a defined level (e.g., a reduction to 80% of the baseline value), as well as criteria for return-to-work assessment. In summary, the authors propose a medical surveillance framework for Thai workers, adapted from international best practices and aligned with Thai legislation. This framework encompasses defined procedures for pre-placement health examinations, periodic health monitoring during employment, intervention measures upon detecting abnormalities, and return-to-work evaluations.