Investigating the relationship between heat stress and workers’ blood parameters in a foundry

Background and Aim: Heat stress is one of the physical hazardous agents in the workplace with many adverse health effects. This study aimed to investigate the relationship between heat stress and workers' blood parameters in a foundry. Methods: This case-control study was conducted in July 2018 on 55 male subjects employed in Saipa Malleable foundry located in Tehran, Iran. The selected individuals included 35 subjects working in the Foundry Hall (exposed group) and 20 subjects working in the CNC workshop (Control group) of a foundry plant. First, demographic information, medical records and occupational data of all subjects were collected using a self-regulated questionnaire. Blood samples (5 ccs) were taken from the subjects during the work to determine the blood components (including WBC, RBC, HCT, HGB, MCH, MCHC, MCV, PLT, RDW, PDW, MPV). Samples were analyzed by Automated Blood Cell Counting. The time-weighted average value of WBGT was determined for studied job tasks in the exposure group and two job tasks in the control group. Sound pressure levels and light intensities were also measured.  Results: The average WBGT index was 32.97 ° C for the exposed group and 22.5 ° C for the control group. Laboratory findings showed that the number of white blood cells was less in the exposed group. The hemoglobin concentration, hematocrit, mean corpuscular volume (MCV) and platelet count in the exposed group were higher than the control group (P<0.05). No significant relationship was found between the WBGT index and other blood Parameters (P>0.05). The t-test results did not show a significant difference between sound pressure level and light intensity in both exposure and control groups (P>0.05). Spearman's results did not show a significant correlation between sound pressure level and light intensity with blood Parameters, but significant correlation was observed between the average WBGT index and the number of white blood cells, hemoglobin concentration, and hematocrit. Conclusion: The average number of white blood cells in the exposed group was lower than the control group. Also, the mean concentration of hemoglobin, hematocrit, mean corpuscular volume (MCV) and platelet count was higher than the control group. Exposure to chronic heat stress can increase blood concentrations with increased hematologic factors and increase vascular resistance and reduce oxygen supply to tissues.