Abstract

Background International migrant workers, representing 170 million people globally, often face hazardous working conditions, including extreme heat exposure. These increase their risk of occupational heat strain, exacerbated by poor and exploitative working conditions. This systematic review aims to identify the health risks associated with occupational heat exposure among international migrant workers and document protective interventions and measures being used globally, to inform policies that protect this vulnerable population. Methods We searched four electronic databases (Medline, Embase, Ovid Global Health and PsychINFO) for primary research studies (January 2014–April 2024) on international migrant workers experiencing adverse health outcomes alongside high working temperatures. Records were screened, and data were extracted by two independent reviewers. Assessment of study quality was done using Joanna-Briggs Institute checklists. Results were synthesised narratively and reported following PRISMA 2020 guidelines. Results Of the 646 records screened, 19 studies involving 2293 migrant workers across six countries were included in the analysis, most of which were conducted in high-income countries (n = 14, 74%), mainly the United States of America (USA). At-risk workers, with ages ranging 10-90 years, were employed in construction (48%) and agriculture (42%), and originated from 14 countries, predominantly India, Mexico, and Nepal. Studies reported workers affected by heat-related illnesses (n = 12 studies), dehydration (n = 5), kidney disease (n = 2), and poor skin health (n = 2). Workers most commonly suffered from symptoms of headaches (n = 83 workers), muscle cramps (n = 53), and heavy sweating (n = 44), with other issues including poor mental health, infertility, and risk to pregnancy interventions focused on water, rest, shade, skin protection, and education, but evaluations were limited and some measures failed to address heat exposure effectively. Conclusions Occupational heat exposure poses significant health risks for international migrant workers. Where interventions exist, barriers to effectiveness remain, with little evidence from low- and middle- income countries. Amid rising global temperatures, a greater focus is needed on improved worker education, worker-tailored and co-designed interventions, updated guidelines, and increased healthcare accessibility. Systematic review registration PROSPERO CRD42024519547.