Heat index trends and climate change implications for occupational heat exposure in Da Nang, Vietnam

Occupational extreme heat exposure can lead to a number of detrimental heat-health impacts on workers. Excessive night-time temperatures following hot days do not allow for workers to recover and can compound work heat-health impacts. A number of heat indices have been developed to estimate thermal comfort – how hot it feels – based on meteorological, physiological, and working conditions. We investigated potential changes in day and night-time ambient temperatures and heat indices for Da Nang, Vietnam over the period 2020–2049 when compared with 1970–1999 after downscaling daily minimum and maximum temperatures and humidity variables from six CMIP5 climate models. Two heat indices were employed, the U.S. National Weather Service Heat Index for day and the indoor Apparent Temperature for night. The Vietnam Ministry of Health (MOH) sets thermal comfort thresholds for particular workloads and rates. By 2050, daytime heat index values breach the average 32 °C MOH threshold for light work nearly continuously during the months of April to October. The number of nights per annum in which the heat index exceeds 28 °C is likely to range between 131 and 170 nights per year. Occupational heat exposure in Da Nang for outdoor workers or indoor workers without adequate ventilation, breaks or other cooling and heat precautionary and treatment measures will be exacerbated by climate change.