Characterizing Heat-Related Illness in Florida Farmworkers: A Feasibility Study Open Access

Mac, Valerie (2016)

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Background: With increasing trends of rising temperatures and extreme weather events, agricultural worker populations are at an increased risk for heat-related illness (HRI). A few studies utilizing survey methods have examined the predictive factors of HRI development in farmworker populations, but studies to examine the feasibility of field-based biomonitoring of heat-related illness in farmworker populations are needed.

Purpose: The purpose of this dissertation was to develop a guiding framework conceptualizing farmworker vulnerability to heat, assess the feasibility of field-based biomonitoring of HRI in a sample of farmworkers and characterize the heat stress response.

Sample and Design: This was a feasibility study utilizing a repeated measures design guided by the Farmworker Vulnerability to Heat Hazards Framework. Forty-three male and female fernery workers participated in a biomonitoring protocol over 3 workdays following an initial baseline visit. The biomonitoring protocol included continuous core temperature, heart rate, actigraphy monitoring over the course of the workday as well as dehydration assessment before and after the workday. Self-reported HRI symptoms were also recorded, along with body composition measurements. Analyses included means, descriptive plots, and a logistic regression utilizing a generalized estimating equations approach to predict the key outcome variable of whether a participant's body core temperature (Tc) exceeded 38.0ºC (100.4ºF).

Results: Core temperature data was captured for two study days in nearly 90% of study participants. An improved protocol for core temperature monitoring was developed and best methods for future studies were identified. Participant Tc exceeded 38.0ºC on forty-nine (57%) of the workdays examined (n=86). On average, for those who met or exceeded 38.0ºC (100.4ºF), the duration of time was 79 minutes (SD=73, range=255). Energy expenditure was found to be a significant predictor (OR=1.08 [1.005,1.15]) for the key outcome variable and once adjusting for energy expenditure being female was also a significant predictor (OR=5.37, CI.95[1.03,18.30]).

Conclusion: The Farmworker Vulnerability to Heat Hazards Framework provides a base for designing studies regarding HRI in farmworkers. Field-based biomonitoring is indeed feasible and findings should be utilized to guide the design and implementation of future studies.

Table of Contents

Introduction 1

Statement of the Problem 1

Purpose 2

Specific Aims 3

Conceptual Framework 4

Relevance of the Study 6

Defining Heat-Related Illness 6

Fernery Operations 8

Heat-Related Illness in Farmworkers 8

Vulnerability of Farmworkers 13

Summary 14

References 15

Paper 1: Farmworker Vulnerability to Heat Hazards: A Conceptual Framework 21

Paper 2: Heat Exposure in Central Florida Fernery Workers: Results of a Feasibility Study 42

Paper 3: Elevated Core Temperature in Florida Fernery Workers: Results of a Pilot Study 68

Integrative Summary and Synthesis 86

Key Contributions 86

Conceptual Framework Synthesis 86

Hazard 87

Vulnerability Factors 87

Workplace Exposure 87

Sensitivity 88

Adaptive Capacity 87

Heat Stress Response 89

Feasibility and Best Methods 89

Recruitment, Population, and Setting 89

Environmental Temperature Monitoring 90

Core Temperature Monitoring 91

Energy Expenditure Monitoring 92

Dehydration Assessment 92

Body Composition Assessment 93

Heat Stress Response Assessment 93

Evidence of Heat Stress Response in Florida Fernery Workers 95

Future Directions 96

Protocol Improvements 96

Conclusion 97

References 98

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