This study was performed in a climatic chamber to evaluate the combined effects of noise intensity, heat stress, workload, and exposure duration on both noise-induced temporary threshold shift (TTS) and the recovery time by adopting Taguch's method. Fourteen subjects without previous significant noise exposure and smoking history were recruited to participate in this study. All hearing threshold levels at eight different frequencies (250 to 8,000 Hz) of better ear were measured in an audiometric booth by using the ascending method in 2 dB steps before each exposure condition. The test was also carried out after exposure to evaluate TTS at various times. The TTS recovery time was assessed using an audiometric test on all subjects at post-exposure times of 2, 20, 40, 60, 80 and 120 min, respectively. It was found that TTS depended mainly on the exposed noise dose and was enhanced by workload and heat stress. The TTS recovery time is dependent upon the magnitude of the initial hearing loss. In conclusion, TTS driven by noise exposure is enhanced by heat and workload. Further studies are required to evaluate the effects of workload with extreme temperature in a workplace environment.

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The purpose of this study is to evaluate the non-ionizing radiation (NIR) exposure, especially optical radiation levels, and potential health hazard from aluminum arc welding processes based on the American Conference of Governmental Industrial Hygienists (ACGIH) method. The irradiance from the optical radiation emissions can be calculated with various biological effective parameters [i.e., S(lambda), B(lambda), R(lambda)] for NIR hazard assessments. The aluminum arc welding processing scatters bright light with NIR emission including ultraviolet radiation (UVR), visible, and infrared spectra. The UVR effective irradiance (Eeff) has a mean value of 1,100 microW cm at 100 cm distance from the arc spot. The maximum allowance time (tmax) is 2.79 s according to the ACGIH guideline. Blue-light hazard effective irradiance (EBlue) has a mean value of 1840 microW cm (300-700 nm) at 100 cm with a tmax of 5.45 s exposure allowance. Retinal thermal hazard effective calculation shows mean values of 320 mW cm(-2) sr(-1) and 25.4 mW (cm-2) (380-875 nm) for LRetina (spectral radiance) and ERetina (spectral irradiance), respectively. From this study, the NIR measurement from welding optical radiation emissions has been established to evaluate separate types of hazards to the eye and skin simultaneously. The NIR exposure assessment can be applied to other optical emissions from industrial sources. The data from welding assessment strongly suggest employees involved in aluminum welding processing must be fitted with appropriate personal protection devices such as masks and gloves to prevent serious injuries of the skin and eyes upon intense optical exposure.

low thermal impact condition, the exposure chamber studied can still be regarded as a feasible one for assessing workers' thermal hazard. (J Occup Health 2003; 45: 153-159) K e y w o r d s : T h e r m a l e x p o s u r e c h a m b e r, Environmental factors, Uniformity, Monte Carlo simulation, Sensitivity analysisThe four environmental factors, air temperature (T a ), air velocity (V a ), relative humidity (RH) and globe temperature (T g ), together with workers' workload and clothing, were known to be the main factors affecting the extent of the thermal hazard for workers in thermal environments. Based on this concept, the ISO 7933 Standard entitled Analytical Determination and Interpretation of Thermal Stress Using Calculation of Required Sweat Rate proposed a physiologically-based approach in 1989 for estimating the allowable exposure times (AETs) for workers in various thermal environments 1) . In principle, the use of the above approach for determining workers' AETs requires no direct measurement of workers' physiological responses (such as the worker's sweat rate, metabolic rate and skin temperature etc.) in the field. Instead, it allows us to estimate workers' physiological responses by incorporating the on-site measured environmental factors into the empirical equations proposed in ISO 7933. Indeed, the above approach has been criticized by many researchers [2][3][4][5][6] . Nevertheless, recently the American Conference of Governmental Industrial Hygienists (ACGIH) has incorporated it into its work/rest-time regimen determination process 7) . But because the physiological responses could not be directly measured in the field, it can be expected that the above approach might have some inherent uncertainties, which warrants the need for establishing a thermal exposure chamber that can accurately simulate various thermal environments. Abstract: Evaluating the Efficacy of a ThermalExposure Chamber Designed for Assessing Workers' Thermal Hazard: Perng-Jy TSAI, et al. Department of Environmental and OccupationalHealth, Medical College, National Cheng Kung University, Taiwan-This study was conducted on a thermal exposure chamber designed for assessing workers' thermal hazard. In order to assess the efficacy of the studied chamber, three environmental conditions were selected to simulate high, middle and low thermal impact situations, with air temperatures (T a ) of 43.12, 36.23 and 25.77°C, globe temperatures (T g ) of 44.41, 41.07 and 29.24°C, relative humidity (RH) of 77, 59 and 39 %, and air flow velocities (V a ) of 1.70, 0.91 and 0.25 m/s, respectively. For the three specified thermal impact conditions, results show that the coefficients of variation (CVs) for T a , T g , RH and V a measured in the chamber studied were consistently less than 10%, except for V a under the low thermal impact condition (=50%). For each specified thermal impact condition, we generated 1,000 environmental combinations by using the Monte Carlo simulation approach according to the variations obtained from the four environmental ...