The Combined Effects Of High-temperature And Noise On Hearing Of Steel Factory Workers

Objective: To investigate the combined effects of noise and heat onthe occupational groups permanent hearing loss.Method: A steel plant workers who exposure to noise and heat wereselected as the object of this study, and two-factor factorial statisticaldesign was used in this study. The noise was divided into three levels: lessthan85dB group,85to91dB group and greater than or equal to91dBgroup, high temperature was also divided into three levels: the lowtemperature group, medium temperature group and high temperature group,a total of nine groups. The workers were assigned to appropriate groupsbased on the degree of noise and heat exposure. Each group contains30cases, a total of270cases was selected in this study. Hearing test resultsfrom2008to2011of the270cases were obtained for statistical analysis.Results:1. The change of speech frequency hearing threshold: thethree years cumulative effect of high temperature did not show ofsynergistically enhanced effect of noise on speech frequency hearing threshold. At the same time, there was no obvious speech frequencyhearing threshold difference among the three temperature groups andamong noise groups respectively when the cumulative effect reached oneyear. Significant speech frequency hearing threshold differences wereshowed among noise groups when the cumulative effect reached two years.The difference among the three temperature groups and among noisegroups showed significant in speech frequency hearing threshold whencumulative effect reached three years.2. The change of high-frequencyhearing threshold: When the cumulative effect reached two years, hightemperature showed of synergistically enhanced effect of noise onhigh-frequency hearing threshold. At the same time, significanthigh-frequency hearing threshold differences were showed among noisegroups when the cumulative effect reached one year. When the cumulativeeffect reached two years and three years, not only among the threetemperature groups but also among the noise groups showed significanthigh-frequency hearing threshold differences.3. The change of annualhearing threshold loss rate: High temperature did not show ofsynergistically enhanced effect of noise on annual speech frequencyhearing threshold loss rate but on annual high-frequency hearing thresholdloss rate. Meanwhile, both among the three temperature groups and amongthe noise groups showed significant differences in annual speech frequencyhearing threshold loss rate and annual high-frequency hearing threshold loss rate.Conclusion: The exposure reached a certain level and a certainnumber of years, the high temperature will have a negative impact onhearing in a certain extent. Compared with speech frequency hearingthreshold, high-frequency hearing threshold is more sensitive totemperature. Compared with high temperature, noise have greater impacton hearing, especially on high-frequency hearing threshold. The hightemperature exhibit synergistically enhanced effect of noise on thehigh-frequency hearing threshold, but not on speech frequency hearingthreshold. High temperature alone will not have a significant impact onhearing, the impact of high temperature on hearing establish on the basis ofa certain extent noise exposure.