Wet bulb globe temperatures and risk of acute kidney injury among Central American workers

Abstract

Background/Aim: There is an epidemic in Central America of chronic kidney disease of unknown etiology (CKDu), also referred to as Mesoamerican Nephropathy (MeN). MeN prevalence is high among agricultural workers and other occupations involving physical labor in hot working environments, such as brickmaking. Chronic heat stress and volume depletion are hypothesized to be important risk factors. Methods: The MesoAmerican Nephropathy Occupational Study (MANOS) is a prospective cohort study of 569 Salvadoran and Nicaraguan workers designed to investigate environmental and occupational risk factors for MeN. MANOS participants represent five industries: sugarcane, corn, plantain, brick manufacturing, and construction. At baseline, workers were monitored for three consecutive work days. Wet bulb globe temperature (WBGT) was collected every minute during these work shifts using wet bulb globe thermometers. Participants provided serum samples pre- and post-shift on the third day of baseline monitoring. Results: At baseline, the mean estimated glomerular filtration rate (eGFR) of MANOS participants was 106.7 mL/min/1.73 m2. Fifty three (9.3%) had an eGFR < 60 mL/min/1.73 m2. Fourteen participants met serum creatinine-based criteria for cross-shift acute kidney injury (AKI) during baseline monitoring. The mean percent increase in serum creatinine across work shifts was 5.3%. In El Salvador, WBGT was measured on forty-six separate days of workplace monitoring. On these days, an average of 54.7% of the work shift temperatures monitored after 6am were above 28°C, the American Conference of Governmental Industrial Hygienists Threshold Limit Value for moderate work at a continuous work rate. In unadjusted analyses, mean WBGT temperature on the third day of monitoring was positively associated with percent increase in serum creatinine (1.3% increase per 1°C) among Salvadoran workers. Conclusions: MANOS participants experience workplace temperatures that regularly exceed health-protective guidelines. Exposures to these high temperatures may increase the risk of AKI among these workers.