High kidney stone risk in men working in steel industry at hot temperatures

To study the incidence of urinary lithiasis and metabolic alterations among male employees from a steel industry who were exposed to high temperatures in the work environment.

A retrospective cross-sectional study was performed and consisted of two stages. First, the incidence of urolithiasis among the industry's 10,326 employees was assessed. These employees were divided into two group's: group 1 (n = 1289) consisted of the hot-area workers (temperature greater than 45 degrees C) and group 2 (n = 9037) consisted of those working in areas at room temperature. In the second stage, 59 workers without urolithiasis who underwent a metabolic evaluation were divided into two group's: group 3 (n = 34) consisted of hot-area workers and group 4 (n = 25) consisted of those working in areas at room temperature. Evaluations were made of calcium, creatinine, and uric acid in serum; in the 24-hour urine samples, we assessed the volume, calcium, uric acid, citrate, and oxalate.

Of the 10,326 workers, 181 (1.75%) had presented with at least one episode of urinary stones. Of these, 103 were among the hot-area workers (8.0%) and 78 among the room-temperature workers (0.9%; P <0.001). The metabolic evaluation showed that the hot-area group (group 3), compared with the room-temperature group (group 4), presented more frequently with hypocitraturia (55.8% versus 28%, P = 0.03) and low urinary volume (79.4% versus 48%, P = 0.01).

Workers exposed to high temperatures presented with a ninefold risk of lithiasis. Hypocitraturia and low urine volumes were the metabolic alterations observed.