Farmworker Vulnerability to Heat Hazards: A Conceptual Framework

Now and in the future, global climate change will continue to be a persistent public health threat affecting all living spaces, including those where we live and work. Escalating trends in global warming place vulnerable worker populations at increased risk for heat-related illness (HRI; Lundgren, Kuklane, Chuansi, & Holmer, 2013; Roelofs & Wegman, 2014). HRI occurs when the body's innate compensatory mechanisms for combating heat stress are overpowered, leading to thermoregulatory imbalance. Agricultural workers are highly susceptible to heat stress and HRI, given routine occupational exposure to hot, humid, environments in which they have little opportunity to protect themselves. Every year agricultural workers continue to experience heat-related deaths. In 2016, Jean Francais Alcime of Immokalee, Florida, after exhibiting signs of HRI since earlier that day, died on the 2-hr return bus ride from the fields, the usual mode of transportation for crop workers for the farms in Collier County (Perez, 2016). During the years between 2000 and 2009, an examination of observed annual record high maximum and record low minimum daily temperatures across the United States indicated that there were nearly twice as many daily record high temperatures as daily record low temperatures, and temperature models predict increasing ratios of record highs to record lows (Meehl, Tebaldi, Walton, Easterling, & McDaniel, 2009).Several decades of research have examined physiologic responses to nonfatal heat strain in the general public (Schaffer, Muscatello, Broome, Corbett, & Smith, 2012; Semenza et al., 1996), athletes (Webborn, Price, Castle, & Goosey-Tolfrey, 2005), firefighters (McLellan & Selkirk, 2006), and military personnel (Sawka et al., 2001; Sawka, Young, Francesconi,Muza, & Pandolf, 1985; Sawka et al., 1992). Despite the history of research centered on other groups, heat stress remains an understudied but important occupational hazard for agricultural workers (Flocks et al., 2013). Recently work has begun to characterize HRI in farmworkers utilizing surveys (Bethel & Harger, 2014; Fleischer et al., 2013; Mirabelli et al., 2010; Spector, Krenz, & Blank, 2015), analyses of a longitudinal database of visit records from community and migrant health centers (C/MHCs; Cooper et al., 2014; Zhang, Arauz, Chen, & Cooper, 2016), and field-based continuous biomonitoring (Hertzberg et al., 2017; Mac et al., 2017). Research exploring the relationship between personal physiologic factors and outdoor work in agricultural settings has the potential to advance the state of the science for climate adaptation, specifically human physiologic responses to environmental heat.Given the complexity of the response of the human body to the exogenous factor of increasing environmental heat, models are needed to promote our understanding of the vulnerability and physiologic response. In this article, we propose a framework that can serve as a guide for nurses engaging in research, policy, and action in this vital area of public health. We first identify the inputs, mediators, and resulting outputs of this delicate system (Table 1), followed by an exploration of exemplars, and conclude with a discussion examining the dynamic functioning and application of this framework.Framework ComponentsA framework describing the factors surrounding heat stress in farmworkers needs to conceptualize the physiologic processes occurring internally via the body's attempt to maintain equilibrium in relation to heat stress sources and moderating factors. Romero-Lankao and Qin, building on others' earlier work (Ionescu, Klein, Hinkle, Kavi Kumar, & Klein, 2009, p. 4, fig. 1; McCarthy, Canziani, Leary, Dokken, & White, 2001), proposed a conceptual model relating climate change to the health of urban environments (Romero-Lankao & Qin, 2011, p. 143, fig. 1). Their framework proposed vulnerability to climate change in terms of relationships among five key concepts: "hazard," "exposure," "sensitivity," "adaptive capacity," and "response. …