Health Impact Assessment of Heat Exposure among Agricultural Workers in Mueang District, Nakhon Ratchasima Province

Abstract

This cross-sectional descriptive study aimed to: (1) assess heat index and workload among outdoor farmers; (2) evaluate chronic kidney disease (CKD) risk; (3) compare physiological parameter differences; and (4) identify physiological factors associated with dehydration among farmers in Mueang District, Nakhon Ratchasima Province. Field data were collected from May to June (08:30–17:30) using a Wet Bulb Globe Temperature (WBGT) heat stress monitor per ISO 7243, alongside physiological assessments including body temperature, blood pressure, digital body weight scales, urine dipstick tests, and microalbumin cassette kits. A structured interview covering personal information, occupational factors, and physiological changes was also administered. The sample comprised 130 outdoor agricultural workers (57 males, 73 females; mean age 47.84±12.8 years). Friedman test, Wilcoxon signed-rank test, Cochran Q Test. McNemar Test and multiple binary logistic regression were adopted for data analysis. Results revealed a maximum outdoor WBGT (WBGT_out) of 33.2°C, with 100% of outdoor agricultural workers exceeding ACGIH threshold limit values. Applying the clothing adjustment factor, the maximum effective WBGT reached 37.1°C. Dehydration prevalence was 73.8%, with abnormal urinary protein and leukocytes found in 12.3% and 16.2%, respectively. Approximately 16.3% showed risk for CKD of unknown etiology. Significant differences in body weight, core body temperature, and heart rate were observed before, during, and after work (p-value<0.05). Male outdoor agricultural workers had 2.86 times greater dehydration risk than females (95% CI=1.036–7.874; p-value=0.043), while BMI and age showed no significant association. These findings highlight the urgent need for heat management interventions and adequate hydration promotion among outdoor agricultural workers in tropical regions.