Exhaled nitric oxide among pulpmill workers reporting gassing incidents involving ozone and chlorine dioxide. (1/131)

The aim of the study was to investigate whether measurement of nitric oxide in exhaled air could be used for assessing the effects of irritants on the respiratory system, in this case recurrent ozone gassing in an occupational setting. The study population comprised bleachery workers (n=56) from a Swedish pulpmill carrying out ozone-based pulp bleaching since 1992 and controls (n=39). Both groups were investigated by measuring NO in exhaled air, methacholine challenge test and answers to a questionnaire concerning history of respiratory symptoms and accidental exposure to ozone peaks. There was no significant difference in NO output between exposed subjects and controls (median 67.2 versus 55.0 nL x min(-1), p=0.64). However, among bleachery workers reporting ozone gassings, the median NO output was 90.0 nL x min(-1) compared to 58.8 nL x min(-1) among those not reporting such incidents (p=0.019). There was no relation between exhaled NO and the prevalence of respiratory symptoms or bronchial hyperresponsiveness. In a multiple regression model, only reported ozone gassings were associated (p=0.016) with NO output. The results indicate an association between previous response to ozone gassing and nitric oxide output. The increased nitric oxide output among the bleachery workers reporting peak ozone exposure may indicate that chronic airway inflammation is present. Further studies are needed to evaluate the extent to which nitric oxide can be used for biological monitoring of respiratory health effects, and to relate it to other markers of airway inflammation.  (+info)

Chlorine, chloramine, chlorine dioxide, and ozone susceptibility of Mycobacterium avium. (2/131)

Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.  (+info)

Identification of a serine hydrolase as a key determinant in the microbial degradation of polychlorinated biphenyls. (3/131)

The ability of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (HOPDA) hydrolase (BphD) of Burkholderia cepacia LB400 to hydrolyze polychlorinated biphenyl (PCB) metabolites was assessed by determining its specificity for monochlorinated HOPDAs. The relative specificities of BphD for HOPDAs bearing chlorine substituents on the phenyl moiety were 0.28, 0.38, and 1.1 for 8-Cl, 9-Cl, and 10-Cl HOPDA, respectively, versus HOPDA (100 mm phosphate, pH 7.5, 25 degrees C). In contrast, HOPDAs bearing chlorine substituents on the dienoate moiety were poor substrates for BphD, which hydrolyzed 3-Cl, 4-Cl, and 5-Cl HOPDA at relative maximal rates of 2.1 x 10(-3), 1.4 x 10(-4), and 0.36, respectively, versus HOPDA. The enzymatic transformation of 3-, 5-, 8-, 9-, and 10-Cl HOPDAs yielded stoichiometric quantities of the corresponding benzoate, indicating that BphD catalyzes the hydrolysis of these HOPDAs in the same manner as unchlorinated HOPDA. HOPDAs also underwent a nonenzymatic transformation to products that included acetophenone. In the case of 4-Cl HOPDA, this transformation proceeded via the formation of 4-OH HOPDA (t(12) = 2.8 h; 100 mm phosphate, pH 7.5, 25 degrees C). 3-Cl HOPDA (t(12) = 504 h) was almost 3 times more stable than 4-OH HOPDA. Finally, 3-Cl, 4-Cl and 4-OH HOPDAs competitively inhibited the BphD-catalyzed hydrolysis of HOPDA (K(ic) values of 0.57 +/- 0. 04, 3.6 +/- 0.2, and 0.95 +/- 0.04 microm, respectively). These results explain the accumulation of HOPDAs and chloroacetophenones in the microbial degradation of certain PCB congeners. More significantly, they indicate that in the degradation of PCB mixtures, BphD would be inhibited, thereby slowing the mineralization of all congeners. BphD is thus a key determinant in the aerobic microbial degradation of PCBs.  (+info)

Relation between stillbirth and specific chlorination by-products in public water supplies. (4/131)

During water treatment, chlorine reacts with naturally occurring organic matter in surface water to produce a number of by-products. Of the by-products formed, trihalomethanes (THMs) are among the highest in concentration. We conducted a retrospective cohort study to evaluate the relationship between the level of total THM and specific THMs in public water supplies and risk for stillbirth. The cohort was assembled from a population-based perinatal database in the Canadian province of Nova Scotia and consisted of almost 50,000 singleton deliveries between 1988 and 1995. Individual exposures were assigned by linking mother's residence at the time of delivery to the levels of specific THMs monitored in public water supplies. Analysis was conducted for all stillbirths and for cause-of-death categories based on the physiologic process responsible for the fetal death. Total THMs and the specific THMs were each associated with increased stillbirth risk. The strongest association was observed for bromodichloromethane exposure, where risk doubled for those exposed to a level of [greater and equal to] 20 microg/L compared to those exposed to a level < 5 microg/L (relative risk = 1. 98, 95% confidence interval, 1.23-3.49). Relative risk estimates associated with THM exposures were larger for asphyxia-related deaths than for unexplained deaths or for stillbirths overall. These findings suggest a need to consider specific chlorination by-products in relation to stillbirth risk, in particular bromodichloromethane and other by-product correlates. The finding of a stronger effect for asphyxia deaths requires confirmation and research into possible mechanisms.  (+info)

Foetal growth and duration of gestation relative to water chlorination. (5/131)

OBJECTIVE: To assess the effect of exposure to chlorination byproducts during pregnancy on foetal growth and duration of pregnancy. METHODS: A population based study was conducted of 137,145 Norwegian children born alive in 1993--5. Information was obtained from the Norwegian medical birth registry, waterwork registry, and social science data service. The outcomes of interest were birth weight, low birth weight (<2500 g), small for gestational age, and preterm delivery (gestational age <37 weeks). The exposure assessment was based on quality of drinking water in the municipality where the mother lived during pregnancy. Municipal exposure was calculated with information on chlorination and the amount of natural organic matter in raw water measured as colour in mg precipitate/l. The main exposure category was high colour and chlorination, which was contrasted with the reference category of low colour and no chlorination. RESULTS: In logistic regression analysis adjusting for confounding, the risks of low birth weight (odds ratio (OR) 0.97, 95% confidence interval (95% CI) 0.89 to 1.06) and small for gestational age (OR 1.00, 95% CI 0.91 to 1.10) were not related to exposure. Contrary to the hypothesis, the risk of preterm delivery was slightly lower among the exposed than the reference category (OR 0.91, 95% CI 0.84 to 0.99). The risks of the studied outcomes were similar in newborn infants exposed to high colour drinking water without chlorination and chlorinated drinking water with low colour compared with the reference category. CONCLUSIONS: The present study did not provide evidence that prenatal exposure to chlorination byproducts at the relatively low concentrations encountered in Norwegian drinking water increases the risk of the studied outcomes.  (+info)

Chlorine dioxide inactivation of Cryptosporidium parvum oocysts and bacterial spore indicators. (6/131)

Cryptosporidium parvum, which is resistant to chlorine concentrations typically used in water treatment, is recognized as a significant waterborne pathogen. Recent studies have demonstrated that chlorine dioxide is a more efficient disinfectant than free chlorine against Cryptosporidium oocysts. It is not known, however, if oocysts from different suppliers are equally sensitive to chlorine dioxide. This study used both a most-probable-number-cell culture infectivity assay and in vitro excystation to evaluate chlorine dioxide inactivation kinetics in laboratory water at pH 8 and 21 degrees C. The two viability methods produced significantly different results (P < 0.05). Products of disinfectant concentration and contact time (Ct values) of 1,000 mg. min/liter were needed to inactivate approximately 0.5 log(10) and 2.0 log(10) units (99% inactivation) of C. parvum as measured by in vitro excystation and cell infectivity, respectively, suggesting that excystation is not an adequate viability assay. Purified oocysts originating from three different suppliers were evaluated and showed marked differences with respect to their resistance to inactivation when using chlorine dioxide. Ct values of 75, 550, and 1,000 mg. min/liter were required to achieve approximately 2.0 log(10) units of inactivation with oocysts from different sources. Finally, the study compared the relationship between easily measured indicators, including Bacillus subtilis (aerobic) spores and Clostridium sporogenes (anaerobic) spores, and C. parvum oocysts. The bacterial spores were found to be more sensitive to chlorine dioxide than C. parvum oocysts and therefore could not be used as direct indicators of C. parvum inactivation for this disinfectant. In conclusion, it is suggested that future studies address issues such as oocyst purification protocols and the genetic diversity of C. parvum, since these factors might affect oocyst disinfection sensitivity.  (+info)

Selective oxidation in vitro by myeloperoxidase of the N-terminal amine in apolipoprotein B-100. (7/131)

In contrast to the multiple low abundance 2,4-dinitrophenylhydrazine-reactive tryptic peptides formed by oxidation of LDL with reagent HOCl in vitro, myeloperoxidase-catalyzed oxidation produces a dominant product in considerably greater yield and selectivity. This modified peptide had a single amino-terminal sequence corresponding to amino acids 53-66 of apolipoprotein B-100 (apoB-100), but its mass spectra indicated a significantly higher mass than could be reconciled with simple modifications of this peptide. Subsequent studies indicate that this product appears to result from N-chlorination of the N-terminal amino group of apoB-100 and dehydrohalogenation to the corresponding imine, which may form the hydrazone derivative directly, or after hydrolysis to the ketone. The methionine residue is oxidized to the corresponding sulfoxide, and the primary sequence peptide (residues 1-14 of apoB-100) is linked by the intramolecular disulfide bond between C-12 and C-61 to the peptide composed of residues 53-66, as we have observed previously (Yang, C-Y., T. W. Kim, S. A. Weng, B. Lee, M. Yang, and A. M. Gotto, Jr. 1990. Proc. Natl. Acad. Sci. USA. 87: 5523-5527) in unmodified LDL. The selective oxidation by myeloperoxidase of the N-terminal amine suggests strong steric effects in the approach of substrate to the enzyme catalytic site, an effect that may apply to other macromolecules and to cell surface molecules.  (+info)

Water disinfection for international and wilderness travelers. (8/131)

Acquisition of waterborne disease is a substantial risk for international travelers to countries with inadequate sanitation facilities. It also poses smaller but still significant risks for wilderness travelers who rely on surface water in developed countries with low rates of diarrheal illness, such as the United States. This article reviews the etiology and risks associated with waterborne disease that might be encountered by both types of travelers. It also summarizes--and makes recommendations for--the various water-treatment methods available to travelers for reducing their risk of contracting waterborne disease.  (+info)