Kristina Blank

Project title: Relationship between Payment Schemes and Heat-Related Illness in Washington Agricultural Workers

Degree: MPH | Program: Environmental and Occupational Health (EOH) | Project type: Thesis/Dissertation
Completed in: 2014 | Faculty advisor: June T. Spector


Aim: Previous studies in various sectors have indicated that piece rate payment is associated with increased rates of occupational injuries, compared to hourly pay. The relationship between payment type and heat-related illness (HRI) has not previously been studied. We aimed to examine the relationship between payment type and HRI in agricultural workers. We hypothesized that workers paid piece rates, compared to hourly workers, have increased risk of engaging in behaviors that enhance their risk of HRI, and of developing HRI symptoms, and that this effect is more pronounced in hotter and more humid work environments.

Methods: A cross-sectional survey was administered to 100 agricultural workers in south central Washington using an audio computer-assisted self-interview instrument during the summer of 2013. Mean daily maximum heat indices over the week (HImax) preceding each participant’s survey were computed from hourly temperature and relative humidity data obtained from nearby Washington State University AgWeather Net weather stations. Associations between piece rate pay and workers’ self-reported work exertion (hard/very hard versus light/medium), frequency of hydration (less frequently than every 30 min. versus every 30 min. or more frequently), and specific HRI symptoms (heavy sweating and light headedness versus no specific symptoms), adjusted for potential confounders, were examined using logistic regression.

Key Findings: The maximum HI ranged from 82˚F to 93˚F (median 85˚F). The odds of greater work exertion was higher in piece rate compared to hourly workers (adjusted OR=4.08; 95% CI: 1.20, 13.80), and the odds of drinking water infrequently was lower in piece rate compared to hourly workers (adjusted OR=0.31; 95% CI: 0.12, 0.79). The odds of experiencing specific HRI symptoms were higher in piece rate compared to hourly workers (adjusted OR= 3.93; 95% CI: 1.32, 11.67). We did not observe significant effect modification by HImax.

Conclusion: In this cross-sectional study, piece rate workers had greater risk of self-reported HRI symptoms compared to hourly workers, and this increased risk may have been mediated in part by increased exertion at work. Results should be confirmed in larger, longitudinal studies that better address potential confounding by elements of work task and incorporate objective measures of hydration and heat health effects.