Previous studies have employed collected MAWL (maximal acceptable weight of lift) data as criteria for designing manual handling tasks because MAWL relates to one's limitation of muscle strength. However, whether the Chinese MAWL can still be used for job design is questionable because the Chinese are relatively weaker than Western subjects in their upper extremities. To clarify this, in the present study 24 male Chinese subjects psychophysically determined their MAWL and MAWLo (maximal acceptable weight of lower) under task conditions of three lifting frequencies and two lifting ranges. The results indicated that subjects' MAWLo were significantly lower than their MAWL, especially when infrequent tasks were performed (including tasks of one time maximum and one lift (lower)/min, all p<.05). This could be attributed to a relatively disadvantageous position in the upper extremities at the beginning stage of these lowering tasks. This finding strongly implies that it is not enough to consider only Chinese MAWL when designing manual handling tasks; MAWLo data should not be ignored.
In this study the influences of microorganism species, relative humidity, and ozone dosage on ozone surface disinfection were evaluated. Bacterial and fungal cultures were spread on agar plates and exposed to ozone. The selected microorganisms included Escherichia coli, Bacillus subtilis, Candida famata, and Penicillium citrinum. Results showed that microorganism survival fraction and ozone dosage (ozone concentration times exposure time) have an exponential relationship. Results also indicated that E. coli was the most sensitive organism to ozone exposure. E. coli required only very low ozone doses of 2-2.5 and 3.5-4 mg to obtain 50 and 80% inactivation, respectively. In addition, P. citrinum was more resistant than E. coli and required ozone doses of 40-60 and 60-120 mg to obtain 50 and 80% inactivation. In addition, spores of B. subtilis were observed to be the most resistant organism, requiring ozone doses of 40-75 and 145-150 mg to obtain 50 and 80% inactivation. Yeast was less resistant than P. citrinum and B. subtilis, requiring ozone doses of 10 and 15-19 mg to obtain 50 and 80% inactivation. It was clearly indicated that the ozone dose differences for 80% microorganism inactivation could be as high as 40 times between B. subtilis and E. coli. Ozone surface germicidal efficiency increased as relative humidity increased, which could be related to more radicals generated from ozone reaction with more water vapor at higher relative humidity. It was concluded that ozone should be highly effective and provide a reliable safety factor in treating contaminated surface. In addition, workers might need to wear suitable respiratory protection at high ozone level operation.
The effect of building frame and moisture damage on microbial indoor air quality was characterized in 17 wooden and 15 concrete or brick school buildings. Technical investigations to detect visible moisture and mold damage were performed according to a standardized protocol. Viable airborne microbes were determined by using a six-stage impactor (Andersen 10-800). Mean concentrations of viable airborne fungi were significantly higher in wooden schools than in concrete schools, showing that the frame material was a determinant of concentrations of airborne fungi. Moisture damage of the building did not alter the fungal concentrations in wooden school buildings. In contrast, in concrete schools the effect of moisture damage was clearly seen as higher concentrations compared with the reference schools. Aspergillus versicolor, Stachybotrys, and Acremonium were detected only in samples from moisture damaged buildings, and can be considered marker fungi of such damage in school buildings. In addition, the presence of Oidiodendron as well as elevated concentrations of Cladosporium and actinobacteria were associated with moisture damage in concrete schools.
Dr. Peterson has written many articles, papers, and a textbook, Industrial Health. He is past president of the Yuma-Pacific Southwest Section of AIHA and past president of AAIH. Dr. Peterson is Visiting Professor in Environmental and Occupational Health Sciences at the University of Illinois and Clinical Professor of Preventive Medicine at the Medical College of Wisconsin. His consulting practice deals primarily with litigation.
Particle emissions from manual shielded metal arc welding of carbon steel were sampled in a typical industrial maintenance and metal fabrication workplace environment. Particle number measurements over the size range from 14 nm to 10 microm using a scanning mobility particle sizer and an optical particle counter showed that welding produced an approximately lognormal particle mode with a 120 nm count median and a geometric standard deviation of 2.07. This study produced welding particle number concentrations on the order of 2 x 10(5)/cm(3) in the building air 8.5 m away from the welding. Workplace exposure samples were below the current 8-hour American Conference of Governmental Industrial Hygienists mass concentration threshold limit value of 5 mg/m(3). Submicron particles comprised 80% of the total aerosol mass collected by a cascade impactor during welding. The concentration of larger particles was indistinguishable from indoor background. Microscopy showed that the welding emissions are dominated by clusters formed from <0.1 microm primary spheres. These data on the particles resulting from aerosol transformation by natural dilution inside an industrial building can be compared with laboratory-scale studies of welding particulate. The particle number characteristics observed in this study are significant because toxicological hypotheses suggest that number or surface area may be a better metric than mass when evaluating the health effects of fine particles.
