A Case-Crossover Study of Heat Exposure and Injury Risk in Outdoor Agricultural Workers

Abstract

BackgroundRecent research suggests that heat exposure may increase the risk of traumatic injuries. Published heat-related epidemiological studies have relied upon exposure data from individual weather stations.ObjectiveTo evaluate the association between heat exposure and traumatic injuries in outdoor agricultural workers exposed to ambient heat and internal heat generated by physical activity using modeled ambient exposure data.MethodsA case-crossover study using time-stratified referent selection among 12,213 outdoor agricultural workers with new Washington State Fund workers’ compensation traumatic injury claims between 2000 and 2012 was conducted. Maximum daily Humidex exposures, derived from modeled meteorological data, were assigned to latitudes and longitudes of injury locations on injury and referent dates. Conditional logistic regression was used to estimate odds ratios of injury for a priori daily maximum Humidex categories.ResultsThe mean of within-stratum (injury day and corresponding referent days) standard deviations of daily maximum Humidex was 4.8. The traumatic injury odds ratio was 1.14 (95% confidence interval 1.06, 1.22), 1.15 (95% confidence interval 1.06, 1.25), and 1.10 (95% confidence interval 1.01, 1.20) for daily maximum Humidex of 25–29, 30–33, and ≥34, respectively, compared to < 25, adjusted for self-reported duration of employment. Stronger associations were observed during cherry harvest duties in the June and July time period, compared to all duties over the entire study period.ConclusionsAgricultural workers laboring in warm conditions are at risk for heat-related traumatic injuries. Combined heat-related illness and injury prevention efforts should be considered in high-risk populations exposed to warm ambient conditions in the setting of physical exertion.

Heat related illness among workers in Washington State: A descriptive study using workers' compensation claims, 2006‐2017

“…With the increasing frequency of heat waves and hotter summers, we should expect to see more occupational injuries overall. Higher incidence of occupational injuries is associated with higher ambient temperatures for temperature sensitive industries such as Construction, Agriculture, Forestry, and Utility Servicing 8,9,40,41 …”

“…Temperature data were obtained from three weather data repositories: the Federal Aviation Administration, the National Oceanic and Atmospheric Administration, and AgWeatherNet 29–31 . Weather data were matched to geocoded addresses using a previously described method 9 . We prioritized the available address information on the claim to identify the nearest available weather station in relation to the (a) reported incident location, (b) employer's business location address, if matched to the treating provider's county, (c) treating provider's address, and (d) employer's business location address regardless of the treating providers address.…”

“…[29][30][31] Weather data were matched to geocoded addresses using a previously described method. 9 We prioritized the available address information on the retrieved were the maximum temperature on the date of illness, the temperature at the hour of illness, and the maximum temperature over the 3 days preceding the illness. Researchers chose to only use ambient temperature as a metric for heat because this is the same standard used by the WA heat rule and humidity measures were not consistently available across all temperature data points.…”

“…HRIs occur when a combination of exposure to environmental heat and the generation of heat from within the body due to physical exertion exceeds the capacity of the human body to dissipate heat. Exposure to higher ambient heat has also been linked to an increased risk of traumatic injuries among workers 8–10 …”

“…Exposure to higher ambient heat has also been linked to an increased risk of traumatic injuries among workers. [8][9][10] In occupational health, HRI has a broad impact occurring across many industrial sectors. A previous descriptive study in Washington State (WA) from 1995 to 2005 reported the highest rates of HRI in Agriculture, Forestry, Fishing and Hunting, Construction, and Public Administration industry sectors.…”