Trends in Occupational Heat-Health Research in Low-and Middle-Income Countries: A Mapping Review

Extreme heat is increasingly threatening the health of workers worldwide and disproportionately impacting workers in low- and middle-income countries (LMICs). This mapping review was conducted to characterize the existing literature and to identify key gaps in field assessments of heat stress impacts on workers in LMICs. A total of 210 reports were included in the analysis. Almost two-thirds of included articles reported on studies conducted in lower-middle income countries (65%), with most reports from the South-East Asia Region (40%) and from India (30%), Iran (16%), and China (9%). At-risk populations were underrepresented, with 39% of reports not including any female participants and only 10% specifying migrant status, with wide variation in reporting of additional demographic, occupational, and workplace characteristics. Manufacturing and agriculture were by far the occupations most studied (36% and 33%, respectively). The most common index of heat stress was the wet bulb globe temperature (WBGT), with a report-level average ranging from 17.1 to 38.5 °C, with peaks as high as 54.4 °C. The most commonly reported outcomes were cardiovascular responses (50%) such as heart rate and blood pressure, body temperatures (43%), and self-reported symptoms of heat illness or heat strain (35%). Among all reports, only 9% included some form of intervention to protect workers. This review identifies the key trends and gaps in populations, occupations, and regions evaluated in heat-health research. As emerging technologies facilitate research expansion, this mapping review can guide future efforts to promote comparability of studies, overcome gaps, and protect worker health.