M.S.

No description available.

M.S.

M. S.

There is much debate on the carcinogenic potential of disinfection by-products (DBP) in chlorinated water supplies. Until recently, epidemiological studies have been limited in their ability to examine accurately the risk of cancer with exposure to environmental carcinogens. This has largely been due to the long latency periods associated with cancer development, and the difficulties in accurately estimating chronic exposure. Although there is evidence, from predominantly case-control studies, of increased bladder cancer with exposure to chlorinated water supplies, the evidence is inconclusive. ¶ In an attempt to determine the carcinogenic potential of trihalomethanes (THMs) in chlorinated water, this study utilises DNA damage to bladder cells, evident as micronuclei, as a pre-clinical outcome measure. Using a pre-clinical marker helps overcome some of the limitations associated with long latency periods. The study improves on previous studies by estimating exposure to DBP at an individual level, and takes into consideration ingestion, inhalation and dermal exposure. ¶ A cohort study was undertaken in three Australian communities. The Bungendore (NSW) water supply was not chlorinated thereby providing a community unexposed to DBPs from chlorinated water. Canberra (ACT) and Adelaide (SA) had intermediate and relatively higher (but still within NHMRC guideline levels) of DBPs in the reticulation system. Trihalomethane levels in reticulated water (external dose) and in urine (internal dose) were used as exposure indices. As well, intake dose was computed by adjusting external dose for individual variations in ingestion and bathing. The primary outcome measure was the prevalence of micronuclei in bladder epithelial cells. A DNA index derived from flow cytometry was also used to estimate DNA damage in bladder cells. Associations between exposure and outcome were estimated using Poisson regression models, having identified and adjusted for interaction effects and confounders. ¶ A total of 529 participants were eligible to participate, of which 348 (65.8%) completed all aspects of the study. Analysis was limited to the 228 participants (65.53% of those who completed the study) who had slides suitable for micronuclei scoring. One hundred and forty three (63%) of the 228 participants were from the exposed communities, while 85 (37%) were from the unexposed community. This sample exceeded the estimated 50 per group required to detect a relative risk of 1.4, with a significance level of 0.05 and 80% power. ¶ External dose for total THM for the two chlorinated (exposed) communities ranged from 37.75 to 157.25 mg/l. Intake dose estimated by fluid intake diary ranged from 2.9 to 469.5 mg/l, while a retrospective questionnaire estimated intake dose to range from 0 to 409.4 mg/l. Internal dose (urine levels) of total THM for the same two communities ranged from 0 to 6.82 mg/l. Adjusted risk estimate for DNA damage to bladder cells (using the micronuclei assay) when total THM was assessed by available dose was 1.0002 (0.997 to 1.003), by intake dose estimated by fluid intake diary was 1.0001 (0.998 to 1.002), by intake dose estimated by questionnaire was 1.001 (0.999 to 1.003), and by internal dose was 1.05 (0.89 to 1.24). Using DNA index from flow cytometry as the outcome measure also did not identify significant associations, except when exposure was assessed as available dose of total THM (RR=1.0042; 1.0003 to 1.0081). ¶ The results suggest that THM levels are not significantly associated with DNA damage to bladder cell. This supports suggestions of THMs being non-genotoxic. Further work is required to assess the relationship between THM and the more mutagenic compounds, and to assess the carcinogenicity of the more mutagenic compounds at concentrations occurring in drinking water.

<p>Chlorine is an essential building block in the environment and can be found in most places. Chlorine participates in a complex biogeochemical cycle and has been discussed for many years and it is well documented that natural chlorination of organic compound takes place in many parts of the ecosystem. Chlorine can be inorganic (Clin) and organically bound (Clorg). Previous studies have shown that the transformation of Clin to Clorg is connected with the amount of organic matter and the microbial activity in the soil. So far, studies have been focused on forest soil and there is a need for analysing the natural chlorination in other soil types. The aim of this study was to provide chlorination rates in agricultural soil which does not weem to have been done previously. Three common agricultural soils experiencing different agricultural practice and different cropping systems were incubated with Na36Cl at 20o C in a 56 days radiotracer experiment. The results show that a chlorination of 36Clin to 36Clorg in agricultural soil occurred and the Clorg levels increased over time. The chlorination rates ranged from 0,040 to 0,063 μg Cl g dry weight soil-1 d1. This was 10-fold lower than rates previously measured in coniferous forest soil. However, when expressed as μg Cl g dry weight organic carbon-1 d-1, rates in the agricultural soil was only slightly (at the most 2-fold) lower than in coniferous forest. This study contributes with new knowledge of natural chlorination rates in agricultural soil and gives further evidence that the natural chlorination can be connected to the amount of organic matter in the soil.</p>

The regioselectivity in Pd(0)-catalyzed direct arylation of pyrrole, thiophene, and indole can be improved by blocking some of the reactive sites with a chloride group, leading to increased yields of the desired regioisomers. Competition experiments and computational studies show that the blocking group also activates the substrates toward arylation. Due to the activated nature of chlorinated heteroaromatics, rare and sought after regioisomers, such as 3-arylthiophenes, can be obtained under mild conditions in good yields. Chlorine-bearing thiophenes arylated at C3 and C4 have the potential to undergo controlled regioregular polymerization under conditions developed in the field of polythiophene chemistry. Mechanistic studies support the hypothesis that the arylation of the substrates under investigation likely proceeds via the CMD transition state.

The regioselectivity in Pd(0)-catalyzed direct arylation of pyrrole, thiophene, and indole can be improved by blocking some of the reactive sites with a chloride group, leading to increased yields of the desired regioisomers. Competition experiments and computational studies show that the blocking group also activates the substrates toward arylation. Due to the activated nature of chlorinated heteroaromatics, rare and sought after regioisomers, such as 3-arylthiophenes, can be obtained under mild conditions in good yields. Chlorine-bearing thiophenes arylated at C3 and C4 have the potential to undergo controlled regioregular polymerization under conditions developed in the field of polythiophene chemistry. Mechanistic studies support the hypothesis that the arylation of the substrates under investigation likely proceeds via the CMD transition state.

No description available.

The regioselectivity in Pd(0)-catalyzed direct arylation of pyrrole, thiophene, and indole can be improved by blocking some of the reactive sites with a chloride group, leading to increased yields of the desired regioisomers. Competition experiments and computational studies show that the blocking group also activates the substrates toward arylation. Due to the activated nature of chlorinated heteroaromatics, rare and sought after regioisomers, such as 3-arylthiophenes, can be obtained under mild conditions in good yields. Chlorine-bearing thiophenes arylated at C3 and C4 have the potential to undergo controlled regioregular polymerization under conditions developed in the field of polythiophene chemistry. Mechanistic studies support the hypothesis that the arylation of the substrates under investigation likely proceeds via the CMD transition state.