Degradation behavior of triclosan by co-exposure to chlorine dioxide and UV irradiation: influencing factors and toxicity changes.

This study investigated the transformation of triclosan (TCS) following co-exposure to UV irradiation and ClO2. Special attention was given to understand the influencing of water quality parameters and toxicity changes during the co-exposure process. The results show that the co-exposure process prompted TCS elimination quickly and effectively, with more than 99% of TCS degraded under the experimental conditions. The molar yield ratios of 2,4-dichlorophenol/TCS (2,4-DCP/TCS) were calculated to be 35.81-74.49%; however, the by-product of 2,8-dichlorodibenzop-dioxin (2,8-Cl2DD) was not detected. The TCS degradation was sensitive to ClO2 dosage, pH, H2O2, and natural organic matter (NOM), but not to the carbonate (CO32-) concentration. Neutral and slightly alkaline condition were favorable to TCS elimination. The TCS removal rate increased from 85.33 to 99.75% when the ClO2 concentration increased from 0.25 to 1.5 mg L-1. TCS degradation can be promoted at low NOM level (1, 3, and 5 mg L-1), whereas was inhibited at high NOM concentrations of 7 and 9 mg L-1. While adding H2O2, the degradation rate of TCS increased with increasing H2O2 concentration from 1 to 3 mg L-1; however, too low or overdosed H2O2 (0.5 and 5 mg L-1) hindered TCS degradation. Based on the results of a microtox bioassay, the toxicity did not change following the co-exposure process.

[Efficiency and Kinetics of Triclosan Degradation in Aqueous Solution by UV/Sodium Persulfate].

UV activated sodium persulfate was employed to remove triclosan (TCS) in aqueous solution. The effects of several factors such as UV wavelength,UV254 intensity,sodium persulfate dosage,pH value,and HA on TCS degradation were investigated. The second-order rate constants of free radicals (·OH, SO4·-) reacting with TCS and their contributions to TCS removal were determined,respectively. The dominant free radical was also identified. Furthermore, the TCS degradation efficiency in natural water by UV254/SPS and UV254/H2O2 was compared. Finally,the possible pathway and intermediate products of TCS degradation were analyzed with GC/MS. The results indicated that UV254 activated sodium persulfate could effectively remove TCS. The removal rate of TCS could reach 98.15% within 100s under the conditions of UV wavelength of 254 nm,UV intensity of 11.5µW·cm-2,sodium persulfate dosage of 1mmol·L-1,and TCS initial concentration of 275 µg·L-1. TCS degradation followed the pseudo-first-order kinetic model and the pseudo-first-order rate constant was determined to be 0.0392 s-1. Pseudo-first-order rate constant for TCS degradation increased with the increase of UV254 intensity(I)and sodium persulfate dosage within experiment ranges. The effect of UV wavelength on TCS removal was not notable. Neutral condition was detrimental to TCS degradation. TCS removal was inhibited in the presence of HA. The reaction rate constants for·OH and SO4·- reacting with TCS were 7.62×109 L·mol-1·s-1 and 9.86×109 L·mol-1·s-1,respectively. SO4·- was the dominant free radical and its contribution rate to TCS removal was 97.63% in UV254/SPS system. The K value of UV254/SPS was 4.13 times higher than that of UV254/H2O2 process,which demonstrated that UV254/SPS process could remove TCS more effectively than UV254/H2O2. The main intermediate products found were 2,4-DCP and phenol in the degradation process of TCS in Milli-Q water by UV254/SPS.

[Removal of triclosan with the method of UV/ClO2 and its degradation products].

The UV/ClO2 process for triclosan ( TCS) removal was studied. The influences of several factors such as the initial pH, dose of ClO2, initial concentration of TCS and humic acid( HA) on TCS degradation in the UV/ClO2 combined process were discussed. The results showed that the UV/ClO2 process could effectively remove TCS and had a synergistic effect. When the light intensity was 6.5 µW x Cm(-2), the dose of ClO2 was 0. 5 mg x L(-1) and the concentration of TCS was 300 µg x L(-1), when UV and ClO2 were applied alone, the TCS removal rates within 1 min were only 5.23% and 84.93% respectively. The removal rate reached up to 99.13% after 1 min degradation using the UV/ClO2 combined process. In test conditions ( pH 6-9), the removal rate increased from 99.4% to 99. 63% with the increase of pH. Increasing dose of CIO2 could promote TCS removal. When the dose of ClO2 was 0.5-1.5 mg x L(-1), the removal rate was increased from 98.1% to 99.89%. The initial concentration of TCS was negatively correlated with the removal rate. When the initial concentration increased from 100 - 500 µg x L(-1), the removal rate of TCS was decreased from 99.98% to 94.39%. Low concentration of humic acid was beneficial to the removal of TCS, and high concentration of it had the opposite effect. Degradation products of TCS were investigated by GC/MS. Degradation of TCS by the processes of UV, ClO2 and UV/ClO2 also indicated that the main degradation products of the TCS were 2, 4-dichlorophenol (2,4-DCP), 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD), etc.

[Effect of carbon disulfide on mitochondrial respiratory chain in spermatogenic cells in male rats].

OBJECTIVE: To investigate the effect of carbon disulfide (CS(2)) on the mitochondrial respiratory chain in testicular spermatogenic cells in male rats and to explore the possible mechanism of reproductive system damage caused by CS(2) in male rats. METHODS: Twenty-four male Sprague-Dawley rats (clean grade) were randomly divided into four groups: three CS(2) exposure groups (CS(2) concentrations: 50, 250, and 1250 mg/m(3)) and a control group. The rats in CS(2) exposure groups were exposed to CS(2) by static inhalation for 10 weeks (2 h/d, 5 d/w), while the rats in control group were exposed to air. Then, all rats were sacrificed by decapitation; testicular tissues were collected, and mitochondrial protein in spermatogenic cells were extracted; the levels of mitochondrial respiratory chain enzyme complex I∼V were measured by enzyme-linked immunosorbent assay. RESULTS: Compared with the control group, all CS(2) exposure groups had significantly increased levels of mitochondrial respiratory chain enzyme complex I∼V in spermatogenic cells (P < 0.05). There were no significant differences in the levels of respiratory chain enzyme complex I∼IV between the CS(2) exposure groups (P < 0.05), but the level of respiratory chain enzyme complex V rose significantly as the concentration of CS(2) increased (P<0.05). CONCLUSION: Various levels of CS(2) exposure may increase the levels of mitochondrial respiratory chain enzyme complex in testicular spermatogenic cells among male rats, thus affecting the normal oxidative phosphorylation in mitochondria.

[Effect of carbon disulfide on mitochondrial apoptosis-related proteins in cytoplasm of testicular tissue among male rats].

OBJECTIVE: To investigate the role of mitochondrial pathway in the apoptosis of spermatogenic cells induced by inhalation of carbon disulfide in male rats. METHODS: Twenty-four male Sprague-Dawley rats (clean grade) were divided into four groups according to their body weights: three CS(2) exposure groups (CS(2) concentrations: 50, 250, and 1250 mg/m(3)) and a control group. The rats in CS(2) exposure groups were exposed to CS(2) by static inhalation for 10 weeks (2 h/d, 5 d/w), while the rats in control group were exposed to air. Then, all rats were sacrificed by decapitation; testicular tissues were collected, and cytoplasmic proteins were extracted; the levels of apoptosis-inducing factor (AIF), cytochrome c (cyto c), Bcl-2, Bax, procaspase-9, and procaspase-3 were measured by Western blot, and the activities of caspase-9 and caspase-3 were measured using a test kit. RESULTS: Compared with the control group, all CS(2) exposure groups had significantly increased levels of cyto c in the cytoplasm of testicular tissue (P<0.05); in the 250 mg/m(3) CS(2) exposure group, the Bax/Bcl-2 ratio and activities of caspase-9 and caspase-3 increased significantly (P<0.05), and the content of procaspase-9 and procaspase-3 decreased significantly (P<0.05); in the 1250 mg/m(3) CS(2) exposure group, the relative expression levels of Bax and AIF in cytoplasm increased significantly (P<0.05), and the expression level of Bcl-2 decreased significantly (P<0.05). CONCLUSION: Mitochondrial pathway plays an important role in the CS(2)-induced apoptosis of spermatogenic cells in testicular tissue among male rats.

[Effect of maternal BDE-209 exposure on sexual development in male offspring rats].

OBJECTIVE: To investigate the effect of maternal decabromodiphenyl ether (BDE-209) exposure on the sexual development in male offspring rats. METHODS: Twenty-four pregnant Sprague-Dawley rats were randomly divided into three BDE-209 exposure groups and one control group. The three BDE-209 exposure groups were given BDE-209 (100, 300, and 900 mg/kg) by gavage on gestational days 12∼18, and the control group was given corn oil. The body weight and body length of each newborn male rat was measured at postnatal days 4, 10, 16, and 21. Twelve newborn male rats were randomly selected from each group; anogenital distance was measured at postnatal day 21, serum testosterone was measured, and the organ coefficient of testis was calculated. RESULTS: The newborn male rats in all exposure groups showed declining trends in body weight and body length compared with those in the control group, and the 900 mg/kg BDE-209 exposure group had significantly lower body weight and body length than the control group at postnatal days 4, 10,16, and 21 (P < 0.01). At postnatal day 21, the 100, 300, and 900 mg/kg BDE-209 exposure groups had anogenital distances of 17.82±2.35 mm, 16.32±1.66 mm, and 15.80±1.34 mm, respectively, demonstrating a significant decrease with increased exposure dose (P < 0.05), but no significant difference was found when comparing these values with that of the control group (16.64±2.38 mm) (P > 0.05). There were no significant differences in serum testosterone and organ coefficients of testis and epididymis between the control group and BDE-209 exposure groups (P > 0.05). CONCLUSION: Maternal exposure to BDE-209 has adverse effect on the growth of male offspring rats, but it leads to no significant changes in sexual development.

The effects of carbon disulfide on male sexual function and semen quality.

A cross-sectional study was initiated to clarify whether the current level of exposure to carbon disulphide (CS(2)) is low enough to prevent occurrence of subclinical health impairments. This paper describes the effects of exposure to CS(2) on male sexual function and semen quality in a baseline observation. The effects of CS(2) on male sexual function were evaluated, including number of sexual encounters and length of sexual encounters related to solvents in 80 male workers exposed to CS(2) and 49 reference workers from the filature and cotton pulp departments of a fabric factory in China. And the semen samples were obtained from 43 of the exposed and 35 of the control. Adjustment was made for potential confounding factors such as age or alcohol drinking. Exposure to CS(2) was dichotomized by job type. The rate of sexual dysfunction was higher, number of sexual encounters was lower, and length of sexual encounters was shorter compared with the control (p < 0.001). It was indicated that exposed workers had fewer semen quantity, longer liquefaction time, lower acrosomal membrane integrity rate, vitality and density, and more deformity of semen than the control (p < 0.01). The age and type of work played the most important roles in sexual dysfunction by the multinomial logistic regression analysis (p < 0.01).The duration of exposure had the effect on sexual function and semen quality but no statistical significance (p > 0.05). Clinical effects on the male sexual function and semen quality were found in the workers exposed to CS(2).

Diversity and abundance of ammonia-oxidizing bacteria in eutrophic and oligotrophic basins of a shallow Chinese lake (Lake Donghu).

Classical cultivation and molecular methods based on the ammonia monooxygenase gene (amoA) were used to study the abundance and diversity of beta-proteobacterial ammonia-oxidizing bacteria (AOB) in lake sediments. The eutrophic and oligotrophic basins of a Chinese shallow lake (Lake Donghu), in terms of ammonium (NH(+)(4)) concentrations, were sampled. The AOB number was significantly lower in the oligotrophic basin, but significantly higher in the eutrophic basin. In addition, using restriction fragment length polymorphism targeting the amoA, ten restriction patterns including six unique ones were found in the eutrophic basin, while five patterns were observed in the oligotrophic basin with only one unique restriction group. Phylogenetic analysis for AOB revealed that Nitrosomonas oligotropha- and Nitrosomonas ureae-related AOB and Nitrosospira-affiliated AOB were ubiquitous; the former dominated in the eutrophic basin (87.2%), while the latter dominated in the oligotrophic basin (65.5%). Furthermore, Nitrosomonas communis-related AOB was only detected in the eutrophic basin, at a small proportion (3.2%). These results indicate significant selection and adaptation of sediment AOB in lakes with differing trophic status.

Effects of carbon disulfide on the expression and activity of nitric oxide synthase in rat hippocampus.

BACKGROUND: Carbon disulfide (CS(2)) is a commonly used organic solvent. Many epidemiological investigations and animal experiments have indicated that learning and memory ability can be affected to different degrees after long-term exposure to CS(2), but the mechanisms are still unclear. The aim of this study was to explore the possible mechanisms of CS(2)-related impairment of the learning and memory ability of rats, by investigating the effects of CS(2) on nitric oxide synthase (NOS) activity and NOS mRNA expression in rat hippocampus. METHODS: Rat models of toxicity were generated by inhalation of various doses of CS(2). After two months of inhaling intoxication, the activities of constitutive NOS (cNOS) and induced NOS (iNOS) in the hippocampus were measured. The levels of neuronal NOS (nNOS) mRNA and iNOS mRNA were measured by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS: cNOS activity was significantly decreased compared with controls, while iNOS activity was changed only slightly. CS(2) treatment significantly decreased nNOS mRNA levels. iNOS mRNA levels were significantly increased only at higher doses of CS(2). CONCLUSION: The effect of CS2 on learning and memory ability in rats is related to the activity of NOS and the expression of nNOS in the hippocampus.

[Antagonism of vitamin E on lipid peroxidation in testis of male rats with carbon disulfide].

OBJECTIVE: To study the antagonistic joint action of vitamin E (VE) lipid peroxidation of testis in the male rats with carbon disulfide (CS2). METHODS: 36 wistar male rats were randomly dicided into six groups. It took 10-week for the rats to breath CS2 in different concentrations (0, 50, 250 and 1250 mg/m3), respectively, CS2 (1250 mg/m3) with VE (250 mg/kg diet) and VE (250 mg/kg diet) group. After 10-week treatment, rats were killed and the following parameters of lipid peroxidation in testis were determined:SOD, MDA, GST, GSH, GSH-px, NO, NOS and iNOS. RESULTS: Compare with the control group, SOD, GST, GSH-px, NOS and iNOS activity were decreased (P < 0.05 or P < 0.01), GSH, NO content decreased also, MDA content was increased (P < 0.01). After the antioxidant VE treatmented, the parameters were significantly increased (the amount of MDA was decreased). CONCLUSION: The antioxidant VE significantly protects against on lipid peroxidation in testes of male rats with CS2.

[Apoptosis and gene FasL expression induced by carbon disulfide in rat sertoli cells].

OBJECTIVE: To study apoptosis and gene FasL expression induced by carbon disulfide in sertoli cells of male rats. METHODS: Sertoli cells were exposed to different concentrations of CS(2) (0, 0.36, 0.72, 1.44 micromol/ml) for 24 hours. Survival rate, apoptosis rate, expression level of gene FasL were measured using MTT, FCM, and RT-PCR methods respectively. RESULTS: Sertoli cell survival rate decreased as the concentration of CS(2) increased. The survival rate (73.34% +/- 1.39%) was significantly lower than the control group (99.98% +/- 5.48%) when the concentration of CS(2) > or = 1.44 micromol/ml (P < 0.05). Apoptosis rate increased as the CS(2) concentration increased. Apoptosis rate (7.93% +/- 0.43%) was significantly higher when the concentration of CS(2) > or = 1.44 micromol/ml (P < 0.05). Expression level of the FasL significantly increased as the concentrations of CS(2) (P < 0.05). CONCLUSION: CS(2) is cytotoxic to sertoli cells. It could cause apoptosis of sertoli cells.

[Study on the reproductive effects of carbon disulfide in male rats and their subgeneration].

OBJECTIVE: To study reproductive toxicity of carbon disulfide and the effects of their subgeneration. METHODS: 40 male rats were randomly divided into four groups. It took ten weeks for the rats to breath CS2 in different densities (0, 50, 250, 1250 mg/m3). Five rats were randomly chosen from the controlling group, high and low dosage group, put them together with female rats for copulation in the ninth week. We observed the pregnant rates, miscarry counts, resorption counts, the numbers and body weight of their subgeneration, weight of the placenta, length of the body, length of the tail, length of the belly, the distance from the rectum to the genital, the effects of the sketetion and the purtenunce. In the eleventh weeks, we measured testide coefficient and testide horizontal of male rats, epididymal weight, sperm count, sperm motility and its classification, the ratio of sperm deformity, etc. RESULTS: The pregnant rats of the dosage groups were all lower than the control group, but the differences were not statistically significant. The data of the high dosage group was obviously lower than the control group (P < 0.05 or P < 0.01). The body weight and the organ coefficient were all lower than the control group, but only brain coefficient of the high group between the control group were statistically significant (P < 0.05). Teside coefficient of the high dosage group obvioulsly decreased than the control group (P < 0.05). Epididymal weight, sperm count, sperm molitity and incidence rate of ospermia of middle and high dosage group obviously decreased than control group. CONCLUSION: The effects of CS2 in distortion rate and abnormal data of growth are possibly related to the decrease in sperm quality and quantity.