Assessment of Organophosphate and Carbamate residues in vegetables marketed as pesticide-free in Pathum Thani Province

Abstract

Organic vegetables are widely regarded as safer and healthier alternatives to conventionally farmed produce. However, concerns persist regarding contamination from organophosphate and carbamate pesticide residues, especially in Thailand, where consumer demand for organic foods continues to grow. Despite certification standards, environmental exposure, post-harvest practices, and supply chain variability may compromise the safety of pesticide-free products. This study aimed to assess the prevalence of organophosphate and carbamate residues in six commonly consumed vegetables marketed as pesticide-free in Pathum Thani Province and to compare contamination levels between certified supermarkets and fresh markets.
A cross-sectional study was conducted using 48 vegetable samples—Napa cabbage, cabbage, bok choy, kale, water spinach, and garlic—collected through convenience sampling from four supermarkets and four fresh markets. Pesticide detection was performed using the MJPK test kit, a colorimetric cholinesterase inhibition assay with an 85% detection accuracy. Results were classified as Safe, Harmful, or Severely Harmful. Descriptive statistics were used to analyze residue prevalence by vegetable type and distribution source.

            Of the samples, 83.00% were classified as Safe, 2.08% as Harmful, and 12.50% as Severely Harmful. All leafy vegetables were 100% pesticide-free, while garlic showed the highest contamination, with 75.00% of samples classified as Severely Harmful. Contamination was found exclusively in supermarket-sourced vegetables; all fresh market samples were safe.

            Although most pesticide-free vegetables were safe for consumption, significant contamination in supermarket-sourced garlic highlights weaknesses in current monitoring and certification systems. Stricter regulatory oversight, enhanced residue testing, and improved consumer education are essential to ensure food safety and protect public health.