Effect Of Heat Stress In Deep Mine On Physiological And Biochemical Indexes Of Miners

Heat stress increases with mine depth because of the geothermal gradient and auto-compression. Deep underground mines are hot and humid for several reasons: the surface air temperature and humidity may be high, especially in tropical regions. Virgin rock temperature increases with depth (geothermal gradient). Air temperature also increases with depth due to increasing air pressure (auto compression). Groundwater and mine water transfer heat to the air by evaporation and increase the humidity. Most of the energy consumed by mining machinery and equipment, be it electrical, compressed air, or diesel, is liberated as heat. Less important sources of heat underground include human metabolism, oxidation processes, explosive blasting, rock movement, and pipelines. This study was to explore the effect of heat stress in deep mine on the incidence of heat illness and physiological and serum biochemical indexes of miners.Part I Survey of occupational hazards in deep mine and heat illness in minersIn this part, we enrolled 50 miners (the exposed group) and 15 non-miners (the control group) from a tine mine factory in Guangxi, and used a questionnaires to survey the information of workers about general information, labor organization, work load and the incidence of heat illnesses in both groups. At the same time, we determined the temperature, relative humidity, air pressure, wind speed, noise and dust concentration in workplace. We found that the heat stroke incidence of miners group was higher than that of the control group, but the difference was not statistically significant (P >0.05). The incidence of chronic heat illnesses in miners group was significant higher than the control group. Compared with subjects who did not exposed to heat in underground pit in the control group, the risk ratio was 3.90 (95% confidence interval 1.05 to 14.56, P <0.05) in miners. These results suggested that the chronic heat illness is the primary impact on the health of miners in deep mine. The heat and humidity working environment is one of the most important factors of chronic heat illnesses.Part II Study on physiological and biochemical changes for miners exposed to heat in deep mineIn this part, we determined the physiological indicators such as blood pressure and oral temperature and the serum concentrations of biochemical indexes, including the lactic acid, lactate dehydrogenase, creatinine, urea, sodium and potassium in controls and miners before and after work. The results showed that the systolic and diastolic blood pressure of both groups between before and after work were not differences (P> 0.05), but the oral temperature of workers in both groups after work were higher than those before work, and these differences were statistically significant (P<0.05). In mine worker group, the serum concentrations of lactic acid, lactate dehydrogenase, creatinine and urea in workers after work were higher than those before work with statistical significance (P<0.05). On the contrary, the concentrations of serum sodium and serum potassium after work were lower than those before work with statistical significance (P<0.05). In the control group, the serum concentrations of lactic acid and lactate dehydrogenase in the serum of workers after work were higher than those before work ,while the serum concentrations of creatinine ,urea, sodium and potassium in workers after work were lower than those before work, however ,these differences were not statistically significant (P>0.05). This indicated that the impact of heat harm in deep mine is obvious to the health of miners, and appropriate protective measures should be taken.