Heat exposure and cardiovascular risk factors among migrant and seasonal farmworkers in the United States: data from the National Agricultural Workers Survey (1999–2020)

BACKGROUND: The United States (U.S.) currently lacks a Federal occupational heat standard and hot weather threatens the safety and health of farmworkers who often work under extreme heat conditions. Chronic disease and related risk factors can enhance worker susceptibility, yet prior studies on heat vulnerability in farmworkers used small samples over short time periods, leaving knowledge gaps about the scope of the problem. OBJECTIVE: To describe temperature exposures and characteristics, including cardiovascular disease (CVD) and risk factors (diabetes, high blood pressure, elevated cholesterol), of a U.S. national sample of farmworkers over a 21-year period. METHODS: We obtained demographic and health data on farmworkers from the U.S. National Agricultural Workers Survey (NAWS) and publicly available temperature data from 1999 to 2020. We aggregated temperature datasets to six NAWS regions and calculated average daily mean temperature days above four absolute thresholds of 32.2-40.6 Celsius (°C) and seasonal average summertime temperatures to represent potential exposure of the survey population. We used joinpoint regression to describe temporal patterns in temperatures and the prevalence of CVD outcomes within the repeated cross-sectional NAWS data. Multivariate logistic regression analysis was used to explore patterns in CVD outcomes across farmworker characteristics. RESULTS: Farmworkers (n = 44,388) were predominantly Hispanic (81%) and male (73%) with 33% below the poverty level and 40% receiving benefits from needs-based government programs. Seasonal temperatures experienced overall increasing trends, and all regions experienced days over heat thresholds. Prevalence of diabetes, high blood pressure, and CVD generally increased over the study period, with some diminishing trends for diabetes and high blood pressure after 2017. SIGNIFICANCE: Increasing prevalence of CVD and related risk factors, combined with the aging workforce and other social vulnerabilities, support targeted actions to mitigate heat-related health risks and ensure safety and health provisions for this essential workforce. IMPACT STATEMENT: Elevated temperatures pose a risk of morbidity and mortality for farmworkers and outdoor workers in general. We present evidence from a nationwide survey that U.S. farmworkers, while generally younger and healthier than the population as a whole, experience potential vulnerability to heat as their prevalence of cardiovascular disease, average age and risk factors have risen nationally over 21 years. These results highlight the need to pass and implement heat standards and policies to ensure the safety and health of this essential workforce, in light of the absence of such standards in all but five states.