RESEARCH WATCH BIODEGRADATION Nitrophenol toxicity Nitrophenols are among the most important organic industrial compounds and are listed as priority pollutants by EPA. V. Uberoi and S. K. Bhattacharya studied the toxic effects and biodegradability of 2-nitrophenol, 4-nitrophenol, and 2,4dinitrophenol in anaerobic methanogenic acetate and propionate enrichment systems. Results indicated that 2,4-dinitrophenol was the most toxic. Higher biomass decreased the impact of nitrophenol toxicity; there was 95% degradation of 20 mg/L of 2-nitrophenol and 4-nitrophenol. All three nitrophenols degraded in the absence of a primary carbon source Propionate in enrichment cultures enhanced removal rates The authors describe conditions in which nitrophenols can be degraded under anaerobic conditions (Water Environ Res 1997 69 146-56)
How the atmosphere removes dioxins Uncertainty exists over the environmental fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) produced in combustion processes. Relative amounts of PCDD/F in environmental sinks differ from amounts present in the original combustion sources. W. W. Brubaker, Jr., and R. A. Hites identified the gas-phase reaction of PCDD/F with the hydroxyl radical as an important removal mechanism. The authors used structure-activity rate constants for PCDD/F homologues and residence times for PCDD/Fladen particles to model atmospheric removal processes The model indicated that atmospheric removal involves gas-phase procpcepe for lower chlorinatpH dioxins and furans anri particle-phacp pro coccoc for
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GREEN CHEMISTRY Bioassimilable polymers Little information is available about the degradation mechanisms of a whole class of biodegradable plastics based on poly(lactic acid). A. Torres and co-workers reported the results of biodegradation studies of racemic lactic acid polymer (PLA50) buried in the soil and also in controlled conditions. PLA50 plates were placed in mixed microbial cultures of Fusarium moniliforme and Pseudomonas putida. After 32 weeks, the plates appeared to have completely disintegrated. PLA50 plates were also buried in the soil for eight weeks then recovered and examined after an additional eight weeks of controlled degradation The authors found that racemic lactic acid Dolymers are bioassimilable Hydrolvsis occurs in the first stage of degradation producing
byproducts that then are assimilated by microorganisms. (/. Appl. Polym. Sci. 1996, 62, 2295-2302)
HEALTH Airborne latex particles Latex allergy from natural rubber products is a problem that affects health care personnel and patients, and recent studies suggest that the general population may also be at risk. A. G. Miguel and colleagues investigated the presence of latex allergens in particulate tire tread debris and airborne particulate matter in the Los Angeles area. Allergens were found in all tire dust and particulate samples. Estimated exposure levels, however, were substantially lower
0013-936X/97/0931-259A$14.00/0 © 1997 American Chemical Society
Ozone threshold effect Recent health effects studies suggest the existence of a threshold level for ozone, with respiratory effects reduced below a certain concentration. In searching for the threshold, D. M. Stieb and colleagues examined eight years' worth of Canadian data. Mean daily 1-h maximum ozone concentration during the study was 41.6 ppb. Canada's National Ambient Air Quality Objective for ozone (80 ppb) was exceeded on only 3.7% of study days. Ozone levels were above the U.S. standard (120 ppb) on only 0.4% of study days. Despite the low ozone levels, significant associations were observed between o z o n e flnrf hospital emercrenov r o o m
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than those reported for incidents of occupational latex allergy. The authors suggest that airborne latex particles may be important factors in producing latex allergy and asthma symptoms associated with airborne particle exposure. {Environ. Health Perspect. .996, ,04, 1180-86)
visits for asthma. Statistical models suggested that ozone effects reduced or absent below concentrations of 75 DDb (Environ Health Perr spect 1996 104 1354-60)
Smog components Although many studies have linked ambient air pollution with increased hospital emergency room visits, there is uncertainty about the relative toxicity of specific air pollutants, especially ozone and various particulates. R. J. Delfino and colleagues compared the levels of ozone, PM10, PM2 5, aerosol sulfate, and aerosol acidity in Montreal with the number of emergency room visits by people with respiratory disease. Increases in n7nne
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