Heat-Related Illness in Midwestern Hispanic Farmworkers: A Descriptive Analysis of Hydration Status and Reported Symptoms

Over the last 20 years, global warming has resulted in increased risk for heat-related illness (HRI), yet very few changes in personal protective strategies exist for minority agricultural workers who must deal with rising temperatures and humid conditions (Park, Hannaford-Turner, & Lee, 2009). Hispanic farmworkers (HF) tend to seek employment on more labor-intensive and time-sensitive crop production tasks than non-Hispanic farmers who have machinery-assisted crop production that requires hiring fewer workers (Goldstein & Kopin, 2007). In the Midwest, climate change from elevated carbon emissions compared to 50 years ago has increased spring and summer temperature levels as a result of combined earlier snowmelt and higher mid-July temperatures with more humidity (Foufoula-Georgiou et al., 2016). For farmers in the Midwest, this has translated into more hazardous working conditions due to an increase in the number of humid days over 95°F in the summer (Pryor et al., 2014).

Little is known about the physiological burden of crop production work performed in hot weather conditions, and even less is known about HRI in the Midwest as most studies are based in the southern states such as Arizona (Harlan et al., 2014), North Carolina (Beck, Balanay, & Johnson, 2018; Moyce et al., 2017), Texas (Zhang, Chen, & Begley, 2015), California, and Alabama (Singleton et al., 2016; Stoecklin, Bigham, Bennett, Tancredi, & Schenker, 2015). Also, there are few safety inspections for heat-related prevention/management strategies on U.S. farms except for the states of California (Arcury et al., 2015) and Washington (Reid & Schenker, 2016).

Despite decades of HRI research on military populations (Reynolds, Schumaker, & Feighery, 1998; Rickards, Ryan, Cooke, Romero, & Convertino, 2008), athletes (Lopez, Cleary, Jones, & Zuri, 2008; Maughan & Shirreffs, 2004), and other industrial workers (Nag & Nag, 2001; Singh, Bhardwaj, & Deepak, 2010), the physiological impact of HRI in agriculture on minority workers while they perform crop production tasks is relatively unknown (Lam et al., 2013). Symptoms and physiological data in farmworkers related to HRI and climate change only exacerbate the need to study this problem (Kjellstrom et al., 2016; Luber & Lemery, 2015).

The threat of HRI is largely physiological and at its worst may result in heat stroke (Kearney, Xu, Balanay, & Becker, 2014). Many minority farmworkers performing outdoor work tasks may not be consuming adequate fluids to replace the volume lost from excessive sweating and heavy exertion and are at risk (Kearney, Hu, Xu, Hall, & Balanay, 2016). Symptoms of HRI include headache, tachycardia, muscle cramps, fever, nausea, difficulty breathing, and dizziness; the incidence of these in farmworkers varies according to climate conditions, type of work performed, and pre-existing health conditions (Crowe, Nilsson, Kjellstrom, & Wesseling, 2015). According to the Centers for Disease Control and Prevention (CDC), heat-related fatalities for all agricultural workers was 0.39 per 100,000 FTE workers compared to 0.02 for all U.S. civilian workers over a 15-year period (Luginbuhl, Jackson, Castillo, & Loringer, 2008) according to the Centers for Disease Control and Prevention.

HRI in the general population also results in excess emergency room visits and hospitalizations (Knowlton et al., 2009), but many minority workers in agriculture do not have adequate access to health care (Arcury et al., 2015). Also, most of these providers who do see farmworkers are volunteers, or in private practice, they lack occupational and environmental health training.

Given the unique caveats of the minority workforce in agriculture, the sparseness of Midwest samples in existing farm-related HRI research and the minority farmworker susceptibility characteristics of low income, limited educational opportunities, and language barriers (Culp, Tonelli, Ramey, Donham, & Fuortes, 2011), we elected to conduct a descriptive study of this symptom cluster.

The purpose of this research was to use a mixed-methods approach in examining HRI signs and symptoms in Midwestern migrant and seasonal farmworkers with HRI symptoms consisting of a cross-sectional survey (CS) and an intensive surveillance (IS) on a smaller group of workers consisting of field trials while the workers actually performed crop production tasks. We sought to measure workers’ physiological response to different climate conditions while they performed crop production tasks.

Hispanic farmworkers are typically contracted to work in the months of June and July to perform tasks such as manual de-tasseling of corn and picking of melons. In the Midwest, these workers are extremely transient, and the composition of these farm communities are quickly formed and dispersed.

The CS survey group (N = 148) and IS participants are described in Table 2. There were no significant differences between the groups although the self-reported chronic health conditions for diabetes and hypertension differed slightly.

The rationale for the mixed-method approach was warranted as workers in general may have under-reported HRI symptoms. Asking workers about HRI symptoms in a larger sample was needed to estimate ORs, but we also needed to directly observe their physiological responses to crop production tasks under different climate conditions with the IS approach. The field trials, as described in our protocols, were not experimental, and participants were subject to random climate conditions and work demands by their farm employers. The research team did not report WGBT or other climate measures to the farm manager as we wanted to observe when farm crew leaders made decisions. Many times, there were congruent decisions on the part of the farm manager with our physiological and climate data. In general, we found field trials shorter when climate conditions were uncomfortable, and we also found shorter work periods when indicated by our WGBT readings. During field trials, when WGBT readings were ≥27^oC, farm crew leaders determined more rest breaks were needed and water was made available, but we did not see very good tracking of individual fluid intake by farm supervisors nor any reminders to consume a given quantity.

As for physiological measures, elevated blood pressure and tachycardia were occasionally issues for the farmworkers. Research team members informed the participant privately of their vulnerability before proceeding with a field trial, but we did not notify the employer. Specifically, two IS participants had acute hypertension before working the start of crop production when the climate condition was potentially unsafe at WGBT > 27^oC. We recommended that the impacted individuals seek permission from their supervisor to rest, but they refused. Three individuals experienced mean HRs >115 per minute wearing the MPMWS device during particularly undesirable field conditions (i.e., hilly terrain) so the PI assigned a research assistant to “tag along” and to call “911” in case of worker collapse and to provide emergency first aid for heat exhaustion.

In the CS group, the frequency between those self-reporting HRI symptoms and the actual number seeking medical treatment suggests self-management (e.g., resting in the field, seeking shade, and/or increasing fluid intake). In the CS group, the peak number of clinical visits was during the first week of field work, with a decrease in later weeks most likely due to heat acclimatization (Stoecklin-Marois, Hennessy-Burt, Mitchell, & Schenker, 2013). While the majority in our CS data indicated they were consuming water for fluid replacement, the use of sodas and sports drinks was quite alarming. We also noted the use of salt tablets among younger workers that we have previously documented (Culp et al., 2011). Our finding that workers in the CS group were consuming beverages high in caffeine and sugar is consistent with others (Bethel, Spector, & Krenz, 2017). One study of HFs found that the consumption of caffeinated drinks may be related to a desire to stay alert and that the consumption of soft drinks may have been related to on-site water quality (Lam et al., 2013). No workers reported alcohol consumption while working in our CS group, but others have reported heavy episodic drinking while away from home in migrant farm camps; one study reported 48.5% in the previous 3 months among Hispanic farmers (Arcury et al., 2016).

IS participants occasionally posed some ethically challenging events in this investigation. In general, farm supervisors used good judgment in keeping workers out of harm’s way when climate conditions were not optimal for crop production. Although there was no direct influence by the research team on working conditions, we did see that the “uncomfortable” climate conditions resulted in declining productivity as HR and BR increased. On these field trials, farm managers offered more frequent rest periods or dismissed workers earlier in the afternoon than originally scheduled. This was also confirmed in our observations when field trials were classified by the physical intensity score PI > 4 (exhausting and uncomfortable) where field trials were ended by supervisors at 129 minutes versus 154 minutes when workers PI scores were < 2.5 (mildly challenging). We noted that in field trials with PI > 4, the mean body temp was higher (100.05°F) than PI < 2.5 trials where mean body temp was 99.56°F. These field trials also resulted in more symptom reporting including extreme thirst, muscle cramping, and confusion. Indeed, about one third of our IS group workers were obese. These higher BMI participants often had higher body temperatures Obesity in young HFs has been reported previously (Qenani, MacDougall, & Roy, 2016), but the physiological stress posed by the environment was concretely measured in this study where others may not have implemented the level of surveillance we conducted here. One possible reason that some obese Latino farmworkers enroll in crop production work is because they see the strenuous activity and excessive sweating as an opportunity to lose weight (Lam et al., 2013).

We also observed older workers (>35 years) tolerating the field trials and hotter climate conditions remarkably well with stable blood pressure and HRs in the IS group. Physiologic susceptibility such as higher intake of caffeinated drinks and sodas and poor cardiorespiratory, renal, or endocrine health have been known to increase HRI symptoms, and these behaviors are more common in young people (Gronlund, 2014). There are also possible ethnic differences in younger workers compared to nonminority youth. According to one study, many American teens employed in agricultural jobs worked fewer hours per week than Hispanic workers and less time in the fields (Bonauto, Keifer, Rivara, & Alexander, 2003).

Personal protective equipment and clothing influences heat dissipation and is physiologically related to HRI symptom frequency (Choi, Kim, & Lee, 2008). Shirts made with a heavy material or higher insulation value fabric is known to cause heat intolerance (Bakkevig & Nielsen, 1994). In our study, long sleeve shirts were commonly observed in the IS group. This is consistent with the National Agricultural Worker Survey where 77% of workers reported wearing a long-sleeve shirt, but this practice was slightly higher (83%) in “unauthorized” workers (Gabbard, Nakamoto, & Daniel Carroll, 2015). In our study, the long-sleeved shirts protected the upper extremities and decreased exposure to pollen and other irritants from the corn plants. In addition, long sleeves provided some protection from solar radiation and sunburns.

We did not see large numbers of farmworkers in the on-site clinic for HRI symptoms in the CS participants based on our post-season medical record audit. Delay in seeking medical assistance in minority farmworkers has been previously reported (Thierry & Snipes, 2015). Hispanic farmworkers have a history of not complaining due to a fear of losing their employment or not being hired the following work season (Liebman, Juarez-Carrillo, Reyes, & Keifer, 2016). Indeed, migrant and seasonal farmworkers may be influenced in many ways by their peers in symptom reporting; for this reason, we decided to use a small folded piece of paper to report symptoms discretely to the research team after each field trial. In general, farm housing units for seasonal workers are over-crowded and not climate-controlled (Arcury, Trejo, Suerken, Ip, & Quandt, 2017). Air-conditioned (AC) housing or air conditioned rest locations are rare in farm work areas (Quandt, Wiggins, Chen, Bischoff, & Arcury, 2013). The housing units on the two farms sampled here were not closely inspected by the research team, but no AC units were known to be present. Shade tents or canopies were used in the fields in the IS group, this has been reported by others and also a humanitarian gesture by benevolent employers (Kearney et al., 2016).

Our IS group physiological findings support PI of crop production labor . Kilocalories per hour and mean body temperature was higher when the PI scores in field trials were >4.0 or extremely challenging in terms of physical exertion. This finding is consistent with a study of sugarcane workers (Crowe et al., 2015), where 6.8 kcal/min was found at 26°C WBGT, which was reached by 7:30 a.m. on most days. This kcal rate was not sustained for long periods of time but is more challenging than the production tasks of corn de-tasslers here. Indeed, sugarcane workers had more upper extremity effort as they were cutting plants manually fluctuated with the surgarcane density in the fields.

Occupational health professionals (OHPs) must develop strategies for preventing HRI in non-English-speaking minorities and developing workplace educational interventions that take into account a number of complexities that include climate conditions PI of the work being performed. This includes health literacy, poor safety precautions, language barriers, piece-rate pay, undocumented worker status, and geographical isolation as many are young people who are far away from home for the first time (Liebman & Augustave, 2010). This is very different from the industrial work environment, and OHPs may need to rethink the actual control they have over the pace of crop production tasks, the climate conditions, and the behavior of workers in consuming fluids. Calories consumed at meal times may need to be increased when adverse climate conditions are present.

There are few Occupational Safety and Health Administration (OSHA) inspections on farming operations during peak crop production times, and sometimes, safety-related activities like HRI precautions are overlooked in an effort to meet harvest objectives in a timely manner (Gadomski, Vargha, Tallman, Scribani, & Kelsey, 2016). Workers may not be aware of sun-safety risks, and most state-OSHA offices do not track HRI-related training (Lin & Chan, 2009). The OSHA recently developed a smartphone application for determining unsafe work environments based on live data-feeds and a heat-stress index with risk appraisal (available at www.osha.gov), but few farmer managers in our experience knew about it. This OSHA app helps farm owners who do not have adequate equipment for measuring environmental conditions. Workers need to have adequate fluid replacement, rest breaks, and monitoring for HRI symptoms while working in the fields.

Identifying culturally sensitive ways to screen Hispanic workers for field work is challenging, particularly for fitness and their ability to acclimate to changing climate conditions (Buchanan et al., 2010; Menzel & Gutierrez, 2010; Peak, Gast, & Ahlstrom, 2010). Screening for health problems is often left to labor contractors for minority farmworkers (Gonzalez, 2017). This means that no professional occupational health assessment is conducted, and at-risk workers are placed in work that is often physiologically demanding in remote areas where emergency medical services may be required.