Association between Urinary Metabolites of Organophosphate Insecticides and Malondialdehyde Oxidative Stress Biomarker Among Adults in a Rural Area of Chiang Mai, Thailand: A Follow-Up Study in Two Post-Harvest Seasons

The upper northern Thailand is well-known as abundant of variety of crop production, including several vegetables, longans, lychees, and mangoes, as well as paddy rice. In Thailand, village health volunteers (VHVs) are an essential component of the primary healthcare system. This study aims to determine the concentration of urinary dialkylphosphates (DAPs), the common organophosphate (OP) insecticide metabolites, and the relationship between DAPs and malondialdehyde (MDA), an oxidative stress biomarker among VHVs in two post-harvest seasons. The urinary DAPs and MDA were determined in two post-harvest seasons in 2021 and 2022. The results revealed the total DAPs and MDA concentrations were significantly higher in 2021 than in 2022, may cause by locked down during the COVID-19 pandemic in 2022, this made VHVs less faming activity. In 2021, the post-harvest season showed a significant association between total DMPs, with total DAPs and MDA (β = 1.53 and 1.59, respectively). While in the 2022 post-harvest season, there was a significant relationship between the total DEPs and MDA, with β = 1.44 and border line reached in total DAPs with β = 1.43. This study suggested that OP exposure in post-harvest season depends on insecticides used in each crop production. In addition, OP exposure can cause oxidative stress in the human body via urinary DAPs and MDA expressions among farmers. Hence the protection of insecticides exposure using personal protective equipment (PPE) is crucial.