Probable Aerosol Transmission of SARS-CoV-2 through Floors and Walls of Quarantine Hotel, Taiwan, 2021.

We investigated a cluster of SARS-CoV-2 infections in a quarantine hotel in Taiwan in December 2021. The cluster involved 3 case patients who lived in nonadjacent rooms on different floors. They had no direct contact during their stay. By direct exploration of the space above the room ceilings, we found residual tunnels, wall defects, and truncated pipes between their rooms. We conducted a simplified tracer-gas experiment to assess the interconnection between rooms. Aerosol transmission through structural defects in floors and walls in this poorly ventilated hotel was the most likely route of virus transmission. This event demonstrates the high transmissibility of Omicron variants, even across rooms and floors, through structural defects. Our findings emphasize the importance of ventilation and integrity of building structure in quarantine facilities.

Combined effects of noise, vibration, and low temperature on the physiological parameters of labor employees.

Noise, vibration, and low temperature render specific occupational hazards to labor employees. The purpose of this research was to investigate the combined effects of these three physical hazards on employees' physiological parameters. The Taguchi experimental method was used to simulate different exposure conditions caused by noise, vibration, and low temperature, and their effects on the physiological parameters of the test takers were measured. The data were then analyzed using statistical methods to evaluate the combined effects of these three factors on human health. Results showed that the factor that influenced the finger skin temperature, manual dexterity, and mean artery pressure (MAP) most was air temperature, and exposure time was the second most influential factor. Noise was found to be the major factor responsible for hearing loss; in this case, hand-arm vibration and temperature had no effect at all. During the study, the temperature was confined in the 5-25°C range (which was not sufficient to study the effects at extremely high- and low-temperature working conditions) because the combined effects of even two factors were very complicated. For example, the combined effects of hand-arm vibration and low temperature might lead to occupational hazards such as vibration-induced white finger syndrome in working labors. Further studies concerning the occupational damage caused by the combined effects of hazardous factors need to be conducted in the future.

Developing a semi-quantitative occupational risk prediction model for chemical exposures and its application to a national chemical exposure databank.

In this study, a semi-quantitative occupational chemical exposure risk prediction model, based on the calculation of exposure hazard indexes, was proposed, corrected, and applied to a national chemical exposure databank. The model comprises one factor used to describe toxicity (i.e., the toxicity index), and two factors used to reflect the exposure potential (i.e., the exposure index and protection deficiency index) of workers exposed to chemicals. An expert system was used to correct the above proposed model. By applying the corrected model to data obtained from a national occupational chemical hazard survey program, chemical exposure risks of various manufacturing industries were determined and a national control strategy for the abatement of occupational chemical exposures was proposed. The results of the present study would provide useful information for governmental agencies to allocate their limited resources effectively for reducing chemical exposures of workers.

Size distributions and exposure concentrations of nanoparticles associated with the emissions of oil mists from fastener manufacturing processes.

The aims of the present study were set out to measure size distributions and estimate workers' exposure concentrations of oil mist nanoparticles in three selected workplaces of the forming, threading, and heat treating areas in a fastener manufacturing plant by using a modified electrical aerosol detector (MEAD). The results were further compared with those simultaneously obtained from a nanoparticle surface area monitor (NSAM) and a scanning mobility particle sizer (SMPS) for the validation purpose. Results show that oil mist nanoparticles in the three selected process areas were formed mainly through the evaporation and condensation processes. The measured size distributions of nanoparticles were consistently in the form of uni-modal. The estimated fraction of nanoparticles deposited on the alveolar (AV) region was consistently much higher than that on the head airway (HD) and tracheobronchial (TB) regions in both number and surface area concentration bases. However, a significant difference was found in the estimated fraction of nanoparticles deposited on each individual region while different exposure metrics were used. Comparable results were found between results obtained from both NSAM and MEAD. After normalization, no significant difference can be found between the results obtained from SMPS and MEAD. It is concluded that the obtained MEAD results are suitable for assessing oil mist nanoparticle exposures.

Establishing aerosol exposure predictive models based on noise measurements--using concrete drilling as an example.

This study used a full scale mockup of a concrete drilling simulator to simulate drilling processes in an exposure chamber. Six drilling conditions were selected with rotating speeds and drill bit sizes varied from 265 to 587 rpm and 16 to 32 mm, respectively. For each drilling condition, the emitted noise power spectrums were measured and dust exposure concentrations of the fractions of the total (C(tot)), inhalable (C(inh)), thoracic (C(tho)), and respirable (C(res)) were estimated. We find that neither the resultant dust exposure levels nor the noise levels can be explained simply by the involved drilling mechanical energy. By dividing the emitted noise power spectrums into the high and low frequency noise (i.e., W(H) and W(L)), we find that 86.3%, 85.6%, 81.5%, and 77.6% variations of C(tot), C(inh), C(tho), and C(res) could be explained by the combination of W(H) and W(L), respectively. We also find that the emissions of coarse particles and W(L) were possibly contributed by two mechanisms of the impact wear and brittle fracture wear, whereas fine particles and W(H) could be contributed by the mechanism of abrasive wear. Although the predictive models obtained from this study could not be directly used in other dust emission sources, the developed methodology would be beneficial to industries in the future for aerosol exposure assessment, particularly when conducting conventional personal aerosol samplings is not possible in the field.

Exposure assessment of aluminum arc welding radiation.

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.

Evaluation of auditory fatigue in combined noise, heat and workload exposure.

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.

Development of a Taiwanese head model for studying occupational particle exposure.

This study reports a method for constructing a head model with a continuous airway passage beginning from the nostrils and continuing through the second generation of bronchi, using computerized tomographic (CT) images of facial features and airway passages from a healthy Taiwanese male adult. When combined with a manikin torso and connected to a cyclic breathing machine, the Taiwanese head model can simulate human breathing movement. This model enables investigation of important parameters of deposition efficiency without the inter- and intrasubject variability that often occurs in human studies. Being an assembly of numerous polymethyl methacrylate (PMMA) plastic slabs, the head model can be applied to study particle deposition at specified respiratory regions. The nasal geometry obtained in this study was compared with those obtained in other studies, which demonstrated this head model to be 36% smaller in nostril cross-sectional area than for European Americans. Additionally, this Taiwanese head model was found to be shorter in nasal cavity length, and the minimum cross-sectional area was only 50% compared to that of European Americans. This study also measured the nasal inhalation efficiency and deposition for particles ranging from 1.5 to 15 microm under various ventilation levels to test the feasibility of this head model. Future particle deposition studies using this Taiwanese head model can be compared with the currently available data, which are primarily based on Caucasian cast models or human subjects.

Speciation and quantification of vapor phases in soy biodiesel and waste cooking oil biodiesel.

This study characterizes the compositions of two biodiesel vapors, soy biodiesel and waste cooking oil biodiesel, to provide a comprehensive understanding of biodiesels. Vapor phases were sampled by purging oil vapors through thermal desorption tubes which were then analyzed by the thermal desorption/GC/MS system. The results show that the compounds of biodiesel vapors can be divided into four groups. They include methyl esters (the main biodiesel components), oxygenated chemicals, alkanes and alkenes, and aromatics. The first two chemical groups are only found in biodiesel vapors, not in the diesel vapor emissions. The percentages of mean concentrations for methyl esters, oxygenated chemicals, alkanes and alkenes, and aromatics are 66.1%, 22.8%, 4.8% and 6.4%, respectively for soy biodiesel, and 35.8%, 35.9%, 27.9% and 0.3%, respectively for waste cooking oil biodiesel at a temperature of 25+/-2 degrees C. These results show that biodiesels have fewer chemicals and lower concentrations in vapor phase than petroleum diesel, and the total emission rates are between one-sixteenth and one-sixth of that of diesel emission, corresponding to fuel evaporative emissions of loading losses of between 106 microg l(-1) and 283 microg l(-1). Although diesels generate more vapor phase emissions, biodiesels still generate considerable amount of vapor emissions, particularly the emissions from methyl esters and oxygenated chemicals. These two chemical groups are more reactive than alkanes and aromatics. Therefore, speciation and quantification of biodiesel vapor phases are important.

Characteristics and health impacts of volatile organic compounds in photocopy centers.

This study investigates the indoor air quality of typical photocopy centers in Taiwan to evaluate the human health risk following inhalation exposure. Both personal and area samplings were conducted at seven photocopy centers in the Tainan area from July 2002 to March 2003, which covered both summer and winter seasons in Taiwan. The benzene, toluene, ethylbenzene, xylenes, and styrene (BTEXS) measurements indicated no difference between personal and area samplings (P>0.05) and found that air conditioning improves indoor air quality. The additive factor at each photocopy center was significantly below 1.0, based on the current BTEXS permissible exposure limits in Taiwan. However, the mean benzene and styrene levels in the current study were 138 and 18 times, respectively, higher than those in another study conducted in the United States. Comparison of mass ratios of BTEXS with those of several chamber studies revealed that the photocopier is not the only volatile organic compound (VOC) source in photocopy centers. The lifetime cancer and noncancer risks for workers exposed to VOCs were also assessed. Results show that all seven centers in this study had a lifetime cancer risk exceeding 1x10(-6) (ranging from 2.5x10(-3) to 8.5x10(-5)). Regarding noncancer risk, levels of toluene, ethylbenzene, xylenes, and styrene were below the reference levels in all photocopy centers; however, the hazard indices for all still exceeded 1.0 (range 26.2-1.8) because of the high level of benzene in the photocopy centers.