THE ASSOCIATION BETWEEN WBGT AND DRY BULB TEMPERATURE ON HEAT EXPOSURE AND RISK ASSESSMENT AMONG OUTDOOR CULTIVATING FARMERS

Abstract

            Farmers exposed to sunlight induce health risk from heat exposure in outdoor work, but the risk assessment must be assessed by wet bulb globe thermometer (WBGT) which is expensive instrument. This cross-sectional analystic study aimed to assess relationship between air temperature and heat in outdoor farmers of the northeastern Thailand. Data was collected from 8 areas in 2 seasons between December 2020 to January 2021 and December 2021 to April 2022 for heat measurement (wet bulb globe temperature: WBGT) in the agricultural field. The results showed that most farmers had planted rice, sugarcane, and cassava. WBGT was 24.54 – 31.74 degree Celsius and dry temperature was 26.56 – 40.80 degree Celsius. The workload categories of farming activities was almost high workload (>350 kilocalories/hour), and average air velocity was 0.25 – 6.79 m/s and relative humidity was 31.60% – 80.00%. The relationship between dry bulb temperature and WBGT had a strong relationship by Pearson’s correlation, which was >0.80 (p-value < 0.05). The opportunity of heat exposure considering the matrix of workload level and air temperature or the WBGT showed the relationship of r=0.90. Therefore, dry bulb temperature could be useful, instead of WBGT measurement on heat exposure. This finding suggests that risk assessment on heat illness among outdoor farmers can use the air temperature information in order to prevent heat illness and decrease opportunity of heat exposure for surveillance program of heat-related illness among outdoor farmers.