There are many U.S. health-related standards for ozone that aim to limit exposure to ozone. The potential for ozone emission from electrically connected air cleaners is well- known and has led to standards and regulations for portable indoor air cleaning devices, which emit ozone at measured rates of 0.056 – 13.4 mg/hr. However, there is evidence that some in-duct air cleaners may actually emit more ozone than portable air cleaners, despite being exempt from most regulations due to the lack of a suitable test method for measuring ozone generation. To explore if in-duct cleaners actually do emit ozone, I investigated seven commercially available residential in-duct air cleaning devices. These devices used one of two broad technologies as means of air cleaning: UV light or electrical corona. The lowest measured emission rates came from two air cleaners that utilized UV light technology and were 0.309 ± 1.7 mg/hr, which was likely below the detection limit of the apparatus and method, and 4.29± 1.5 mg/hr. Three of the air cleaners tested, also with UV lamps, were of the same brand and model yet exhibited differing emission rates, ranging from 7.44± 1.6 mg/hr to 15.8± 2.6 mg/hr. These three air cleaners were classified as medium emitters and also utilized UV light technology. The high median measured emission rates were measured from both an air cleaner utilizing electrical corona technology, 30.2 ± 4.0 mg/hr, and UV light technology, 29.4 ± 3.9 mg/hr. These experimental results confirm that some in-duct air cleaners are able to generate more ozone than some portable air cleaners and also suggest potential health risks to the indoor environment. / text

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The effects of a newly mapped DNA repair-defective mutant, uvsI, on mutagen sensitivities and mutation were investigated. Results showed that uvsI differs for most of the investigated properties from other uvs mutants of A. nidulans which are known to belong to three different epistatic groups, "UvsF", "UvsC", and "UvsB". Most of these mutants are sterile and many of them alter mitotic recombination frequencies, while uvsI exhibits normal levels of meiotic and mitotic recombination. In addition, uvsI strains are not more sensitive than wild type to MMS (methyl methanesulfonate) to which all other uvs strains are sensitive. However, the uvsI mutant was found to be very sensitive to the killing effects of UV light and the chemical mutagen, 4-NQO (4-nitro-quinoline-N-oxide). In line with the distinct phenotype of uvsI, no epistatic interactions were found for this mutant with any members of the established three epistatic groups. The effects of uvsI on mutagenesis are highly specific and dependent on the mutational test systems. In the uvsI mutant, two types of forward mutation were not affected, but spontaneous and UV-induced reversion frequencies of choA1 and pabaA1 were significantly reduced. Specific effects were further demonstrated in reversion tests of various sC alleles originally isolated as selenate resistant mutants by treatment with EMS (ethyl methanesulfonate), which leads mainly to G:C to A:T transitions. After EMS treatment uvsI mutants showed highly reduced reversion frequencies for all these sC alleles (except one) compared to $uvs sp+$ strains. These results suggest that the uvsI mutation may be defective in AT to GC transition mutagenesis, while increasing transversion(s) from A:T base pairs. In contrast, uvsI affected the frequencies of spontaneous and UV-induced reversions for these sC alleles in a variety of ways. Thus, uvsI may well represent a fourth functional and epistatic group of DNA repair and possibly be involved in a minor mutagenic DN

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Wastewater microbial flocs can protect microorganisms from inactivation by UV light. This effect is detected as tailing at high UV doses in the UV dose response curve. A double-layer structure composed of an inner compact core surrounded by a loose outer layer was proposed by earlier studies to describe UV resistance of microbial flocs. Due to limited oxygen diffusion into the compact cores, the UV inactivation of compact cores and microbial flocs under anaerobic conditions needed to be addressed. The UV disinfection kinetics under anaerobic culturing condition was nearly identical to that of the aerobic study. Moreover, the role of iron concentration on the differences in the UV inactivation kinetics of flocs and cores was assessed. The increase in UV absorbance of floc material due to iron addition could dominate the UV disinfection kinetics of flocs and cores such that they exhibited similar UV disinfection kinetics.

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No description available.

Wastewater microbial flocs can protect microorganisms from inactivation by UV light. This effect is detected as tailing at high UV doses in the UV dose response curve. A double-layer structure composed of an inner compact core surrounded by a loose outer layer was proposed by earlier studies to describe UV resistance of microbial flocs. Due to limited oxygen diffusion into the compact cores, the UV inactivation of compact cores and microbial flocs under anaerobic conditions needed to be addressed. The UV disinfection kinetics under anaerobic culturing condition was nearly identical to that of the aerobic study. Moreover, the role of iron concentration on the differences in the UV inactivation kinetics of flocs and cores was assessed. The increase in UV absorbance of floc material due to iron addition could dominate the UV disinfection kinetics of flocs and cores such that they exhibited similar UV disinfection kinetics.

No description available.