Heat strain while wearing pesticide protective clothing in hot environments: Effects of textile physical properties and ambient humidity

The purpose of this study was to investigate heat strain while wearing pesticide protective clothing (PPC) with different physical properties in hot environments. Eight young males participated in the following three PPC conditions [polyester/cotton work clothing (IT = 1.26 clo, Ret = 42.0 m2·PaW−1), Tyvek coverall (1.16 clo, 47.5 m2·PaW−1), and commonly used nylon suit with a microporous membrane (1.42 clo, 54.1 m2·PaW−1)] and in two environmental conditions (32 °C with 50% RH and 32 °C with 80% RH). All physiological variables (rectal and mean skin temperature, heart rate, and physiological strain index) and most subjective perceptions showed greater values in the 80% RH than in the 50% RH environment (all p < 0.05). Physiological burden was greater in the commonly used nylon suit condition than in the polyester/cotton work clothing condition (all p < 0.05), but in many variables there were no statistical differences between the Tyvek and nylon suit condition, especially in the 80% RH environment. There were no differences in humidity sensation during exercise among the PPC conditions, whereas, during recovery, subjects felt more humid in the Tyvek or nylon suit than in the polyester/cotton work clothing condition (p < 0.05). These results indicate that the 30%-higher humidity induced a greater physiological burden. However, physiological or subjective burden would not always be proportional or inversely proportional to the physical property level of PPC but was affected more by heat exchange modes between the human body and ambient environments.