The California Medical Supervision Program is designed to protect agricultural workers from overexposure to Toxicity Category I and II organophosphate (OP) and carbamate (CB) pesticides by routinely monitoring their blood cholinesterase (ChE) activity levels. ChE testing is conducted at State-approved laboratories and electronically reported to the Department of Pesticide Regulation (DPR) and the Office of Environmental Health Hazard Assessment (OEHHA) for review. In 2015, OEHHA and DPR evaluated the effectiveness of the Program by analyzing ChE data from pesticide handlers performed between 2011 and 2013, which revealed issues with the data quality that hindered the evaluation process. Several interventions have been implemented since then to improve data quality and the overall function of the Program. A new evaluation was conducted in 2020 to 2021 using data from 2014 to 2019 to determine the effectiveness of the Program, Program compliance, and efficacy of the interventions. The analysis revealed similar data quality issues identified in the last evaluation, however, an improvement in data quality was observed. The number of individuals with ChE depression below the action level threshold have decreased in recent years, corresponding to the implementation of certain interventions, indicating that the effectiveness of the Program has improved. Spatial and temporal analysis showed the proportion of pre-exposure baseline tests inversely correlated with pesticide use data while routine follow-up ChE test results showed a positive correlation, indicating a high degree of Program compliance across the state. Major improvements in the data cleaning and analysis since the last evaluation have also improved the evaluation: pesticide handlers under the Program were able to be identified with more certainty and ChE depressions were able to be calculated with increased accuracy. However, further improvements to the data collection process could enhance future evaluations of the Program.

The California Medical Supervision program is designed to protect workers who regularly mix, load, or apply the highly toxic Category I and II organophosphates and carbamates from overexposure by monitoring cholinesterase (ChE) inhibition in plasma and red blood cells. Since January 2011, testing laboratories are required to report test results electronically to the California Department of Pesticide Regulation who shares it with the Office of Environmental Health Hazard Assessment for evaluation. The purpose of this study is to assess the utility of this reporting in evaluating the effectiveness of the Program for illness surveillance and prevention. From 2011 to 2013, we received more than 90 000 test results. Despite data gaps and data quality issues, we were able to perform spatial and temporal analyses and developed a screening tool to identify individuals potentially at risk of overexposure. The data analysis provided some evidence that the Program is effective in protecting agricultural workers handling the most toxic ChE-inhibiting pesticides even though it also identified some areas of potential concerns with individuals that appeared lacking corrective actions in the workplace in response to excessive ChE depressions and parts of the state with disproportionately at-risk individuals. However, changes to the electronic reporting are needed to more accurately identify tests related to the Program and therefore improve the utility of the data received. Moreover, data analysis also revealed that electronic reporting has its limitation in evaluating the Program.