RESUMEN
The thermal environment and the workers' physiological response to heat were monitored throughout the casting process in two foundries. Of the 86 thermal observations in the iron foundry, 25 (29%) exceeded the heat stress index set by Occupational Safety and Health Administration (OSHA) advisory committee in 1974. In the steel foundry during a steel casting the environmental thermal measurements remained above the standard. The workers' physiological indices of heat strain as measured by pulse rate and body temperature rarely showed excursions above limits recommended by World Health Organization (WHO) in 1969. The environmental noise levels exceeded the standard in certain foundry operations. A significant hearing threshold shift was observed at 4 kHz among the foundry workers when compared with non-exposed controls. The illuminance in both foundries was below values recommended by the illuminating Engineering Society, in 1977. The prevalence of lens and corneal opacities among workers in the iron foundry was 32.5% and 30.0% respectively, which was significantly higher than that of the workers in the steel foundry and non-exposed controls.