Abstract  Due to its geographical peculiarities, the Republic of Maldives represents a case study of great interest for the investigation of persistent organic pollutants, from both a socio-economic and an ecological perspective. Thus, we conducted a first survey to assess the current status of polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF) and dioxin-like polychlorinated biphenyl (DL-PCB) concentrations in Maldivian soils.

The range for PCDD/F and DL-PCB soil concentrations was 0.01-49.3 pg WHO2005-TEQ g(-1) and 0.01-3.69 pg WHO2005-TEQ g(-1) dw respectively. PCDD/F concentrations exceeding several international soil guidelines were found in samples from locations in the proximity of local waste combustion sources. DL-PCB concentrations were lower than PCDD/Fs and comparable to those in previous reports from background areas and in areas with developing industrial and agricultural activities. PCDD/F and DL-PCB levels (expressed as WHO2005-TEQ) in soils were strongly correlated (r = 0.89), which suggests that, in most of the sites, they are originated from the same emission sources. Results indicate that PCDD/F soil concentrations (expressed as WHO2005-TEQ) tend to decrease with the distance from the local pollution sources.

Principal component analysis (PCA) showed that PCDD/Fs in the most polluted locations are mainly generated by waste combustion. These findings highlight the need for immediate changes in waste management policies in the Archipelago, in order to reduce the release of Persistent Organic Pollutants (POPs) in the fragile local environment. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  In order to produce the black color for electrophoretic display (EPD) applications in dual-particle systems, a primary-like sized carbon black (PCB) surface modification method is developed and the electrophoretic properties of the resulting functionalized particles are reported. The PCB surface was chemically modified by hydroxylation and subsequent esterification. The final capping material of the PCB nanoparticle surface was a bulky fatty oleic acid, which was expected to improve dispersion stability and to produce electrostatic chargeability in a low dielectric medium. The zeta potential calculated from the measured electrophoretic mobility with a charge control agent was -31 mV. When the negatively chargeable oleic acid-capped PCB nanoparticles mixed with the positively chargeable polymer-coated white TiO2 nanoparticles, the PCB nanoparticles showed electrophoretic movement at an applied bias voltage of less than 5 V, which demonstrated potential application for very low voltage operation in EPDs. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  In this study, the concentrations of 10 organophosphorus flame retardants (PFRs) were determined in 89 human breast milk samples collected from Japan, the Philippines and Vietnam. Among the targeted PFRs, tris(2-chloroexyl) phosphate (TCEP) and triphenyl phosphate (TPHP) were the predominant compounds and were detected in more than 60% of samples in all three countries. The concentrations of PFRs in human breast milk were significantly higher (p < 0.05) in the Philippines (median 70 ng g(-1) lipid wt.) than those in Japan (median 22 ng g-1 lipid wt.) and Vietnam (median 10 ng g-1 lipid wt.). The present results suggest that the usage of products containing PFRs in the Philippines is higher than those of Japan and Vietnam. Comparing with a previous literature survey in Sweden, the levels of PERs in human breast milk from the Philippines were 1.5-2 times higher, whereas levels in Japan and Vietnam were 4-20 times lower, suggesting that these differences might be due to their variation in the usage of flame-retarded products utilized in each country. When daily intake of PFRs to infants via human breast milk was estimated, some individuals accumulated tris(2-butoxyethyl) phosphate (TBOEP) and TCEP were close to reference dose (RfD). This is the first report to identify PFRs in human breast milk samples from Asian countries. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract  In order to investigate the contamination levels of groundwater in the irrigation districts of the lower reaches of Yellow River, fifty-nine groundwater samples collected from the irrigation districts of Henan and Shandong provinces, were analyzed. Health risks associated with eleven metals (Ba, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se and Zn) were assessed using water pollution index and USEPA health risk assessment model. The average concentrations of Fe with 0.496 mg x L(-1) and Zn with 0.445 mg x L(-1) were higher than the concentrations of other heavy metals. Concentrations of Fe, Mn, Se and Zn exceeded the relevant standards and the over-standard rates by 27.12%, 27.12%, 15.25% and 5.09%, respectively. Inverse distance weighted method was applied to estimate the unobserved points and their distribution maps were obtained, which indicated that areas of over-standard heavy metals were Wucheng country, Fan country, Dong'e country, Yucheng city and Guan country. Health risks of ingestion of water for all non-carcinogenic metals are higher than those of dermal absorption, while health risks of ingestion of water for carcinogenic metals is lower than those of dermal absorption. Among the health risks caused by the carcinogenic metals in drinking water and dermal absorption, the highest risks associated with Cr, are seven times and twenty-eight times as that of Cd, respectively, but both were significantly lower than the maximum allowance levels recommended by ICRP (5 x 10(-5) a (-1)). The non-carcinogenic metal risks( Ba, Cu, Fe, Mn, Mo, Ni, Pb, Se and Zn), ranging from 1.73 x 10(-13) to 3.46 x 10(-10) a(-1) in dermal absorption and from 1.13 x 10(-9) to 6.06 x 10(-8) a(-1) in drinking water, were much lower than the maximum allowance levels.

Abstract  Establishment of the dioxins emission inventory has been considered as a crucial step toward risk assessment and elimination of dioxins contaminations. Based on a total dioxin emission inventory in China from different emission categories in 2004, this study created a gridded emission inventory of 2,3,7,8-TCDD, the most toxic congener in dioxins, in China in 2009 with a 1/4 degrees longitude by 1/4 degrees latitude resolution. It was estimated that annually total 371 +/- 53 g (average +/- standard deviation) of 2,3,7,8-TCDD was released into the atmosphere in 2009 over China, increasing approximately by 37% compared with its emission in 2004. Differing from most developed countries where municipal waste incinerations were regarded as a major atmospheric emission source, in China ferrous and non-ferrous metal production made the largest contribution to 2,3,7,8-TCDD air emission (138 +/- 16 g), followed by waste incineration (109 +/- 12 g), power and heating generation (62 +/- 9 g), and production of mineral products (47 +/- 8 g). The rest of sources contributed approximately 3% to the total 2,3,7,8-TCDD emission in 2009. Iron and steel industries are mainly located in Beijing Tianjin Hebei (BTH) and Yangtze River Delta (YRD) regions, whereas waste incinerators are mainly located in Pearl River Delta (PRD) region. Higher 2,3,7,8-TCDD emissions were found in these three regions. While the BTH, YRD, and PRD accounted for only about 4% of total land area of China, they contributed approximately 14%, 15%, and 5% to the total 2,3,7,8-TCDD emission in 2009 in China, respectively. (C) 2015 Elsevier Ltd. All rights reserved.

Abstract  This paper presents an accurate analytical model to calculate the power loss of a high voltage Gallium Nitride high electron mobility transistor (GaN HEMT) in cascode configuration. The proposed model considers the package and PCB parasitic inductances, the nonlinearity of the junction capacitors and the transconductance of the cascode GaN transistor. The switching process is illustrated in detail, including the interaction of the low voltage Si MOSFET and high voltage GaN HEMT in cascode configuration. The switching loss is obtained by solving the equivalent circuits during the switching transition. The analytical results show that the turn on loss dominates in hard-switching conditions while the turn off loss is negligible, due to the intrinsic current source driving mechanism. The accuracy of the proposed model is validated by numerous experimental results. The results of both the analytical model and experiments suggest that soft-switching is critical for high voltage GaN in high frequency high efficiency applications.

Abstract  When reporting circulating levels of persistent organic pollutants (POPs), usually lipid-normalized values are given. However, animal experiments and some human data indicate that exposure to POPs may change lipid values. The aim of the present study is to investigate if POP levels can predict future changes in levels of circulating lipids. In the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, lipids were measured at age 70 and at age 75 in 598 subjects without lipid-lowering medication. Twenty-three different POPs, including 16 polychlorinated biphenyls (PCBs), five organochlorine pesticides, one dioxin (OCDD) and one flame retardant brominated compound (BDE47) were analyzed by high-resolution chromatography coupled to high-resolution mass spectrometry (HRGC/HRMS) at age 70. Strong relationships were seen among the baseline levels of the non-dioxin-like PCBs 194, 206 and 209 and the degree of increase in total serum cholesterol and LDL-cholesterol during the 5 year follow-up. These relationships were generally stronger when lipid-normalized levels were used compared to wet-weight based levels. On the contrary, for two of the pesticides, hexachlorobenzene and trans-nonachlordane, levels were inversely related to the change in LDL-cholesterol, with strongest associations found using wet-weight based levels. PCBs 194, 206 and 209 were inversely related to the change in HDL-cholesterol, in particular for wet-weight based levels. However, these relationships were only significant for wet-weight PCB 194 following adjustment for multiple testing. None of the POPs was related to the change in serum triglycerides. When investigating the association between the change in total serum cholesterol and LDL-cholesterol across different categories of change in BMI, we noted robust results especially in the group with stable BMI, suggesting that the observed relationships were not due to fluctuations in BMI over time. In conclusion, POPs are related to the change in lipids over time, especially LDL-cholesterol. This may explain why POP exposure previously has been linked to atherosclerosis and cardiovascular disease.

Abstract  Persulfate-based in situ chemical oxidation (ISCO) is a promising technique for the remediation of organic compounds contaminated soils. Electrokinetics (EK) provides an alternative method to deliver oxidants into the target zones especially in low permeable-soil. In this study, the flexibility of delivering persulfate by EK to remediate polychlorinated biphenyls (PCBs) polluted soil was investigated. 20% (w/w) of persulfate was injected at the anode, cathode and both electrodes to examine its transport behaviors under electrical field, and the effect of field inversion process was also evaluated. The results showed that high dosage of persulfate could be delivered into S4 section (near cathode) by electroosmosis when persulfate was injected from anode, 30.8% of PCBs was removed from the soil, and the formed hydroxyl precipitation near the cathode during EK process impeded the transportation of persulfate. In contrast, only 18.9% of PCBs was removed with the injection of persulfate from cathode, although the breakthrough of persulfate into the anode reservoir was observed. These results indicated that the electroosmotic flow is more effective for the transportation of persulfate into soil. The addition of persulfate from both electrodes did not significantly facilitate the PCBs oxidation as well as the treatment of electrical field reversion, the reinforced negative depolarization function occurring in the cathode at high current consumed most of the oxidant. Furthermore, it was found that strong acid condition near the anode favored the oxidation of PCBs by persulfate and the degradation of PCBs was in consistent with the oxidation of Soil TOC in EK/persulfate system. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract  In the complex electromagnetic environment, the cable is one of the paths through which the energy of electromagnetic interference (EMI) may couple into the electronic component and circuit in the shielding enclosure. A modified field-circuit method which combing the 2-port network theory and the mixed potential integral equation and the method of moments (MPIE-MOM) is presented to analyze the electromagnetic radiation effects of an enclosure with a cable under any form of electromagnetic interference. Taking the Gaussian pulse as an example, the electromagnetic radiation effect of the PCB in the enclosure is analyzed with the field-circuit method. The model presented in the paper is a theoretical reference for the design of the electronic equipment which working in the complex electromagnetic environment.

Abstract  Compound-specific carbon isotope ratio analysis is a promising tool to assess the origins and fates of organic contaminants in many fields. The present study aims to investigate the isotope effects of dichloro-diphenyl-trichloroethane (DDT) and its degradates in carrots during digestion processes simulating the human gastrointestinal tract. To accurately interpret isotopic data obtained for unreleased DDTs (p,p-DDT, p,p-DDD and p,p-DDE) from carrots during digestion, spiked carrots with known delta(13)C values of DDTs were incubated in simulated gastric and intestinal solutions using a static in vitro model of the human gut. The delta(13)C values and concentrations of DDTs remaining in the carrot and in the digestive solutions were measured. The difference in the delta(13)C values of the added DDTs and the matrix-bound DDTs after digestion was always <0.50 parts per thousand, which is within the technical specification of the analytical system, although the released DDTs increased or decreased under the digestion conditions. The study demonstrated that there were no significant carbon isotopic fractionations during digestion. To our knowledge, this is the first report demonstrating the isotope effect of organic compounds during stomach and small intestine digestion, and the first reported isotope analyses of DDTs. Copyright (C) 2008 John Wiley & Sons, Ltd.

Abstract  Thirty-five surface sediment samples collected from Beibu Gulf and its tributary rivers, China were analyzed for DDTs, HCHs and chlordanes. Total concentrations of DDTs, HCHs and chlordanes in sediments ranged from 0.59 to 126 ng g(-1), ND to 2.65 ng g(-1) and 0.27 to 3.41 ng g(-1) based on dry weight (dw), respectively. Concentrations of DDTs were higher than those reported in the sediments from other regions of the world, while concentrations of HCHs and chlordanes were relatively low. High concentrations of DDTs were observed in the harbor region and aquaculture bases and high concentrations of HCHs were found in the Qin River Estuary. The ratios of (DDE + DDD)/DDTs reflected a mixed input of weathered and fresh DDTs. The predominant beta-HCH indicated that HCHs in the study area mainly originated from the historical usage of technical HCH. The residues of DDTs would pose adverse biological effects on the study area. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  A focus on the studies of the Antarctic environment that have been performed by mass spectrometry is presented herein; our aim is to give evidence of the essential role of this instrumental technique in the framework of the scientific research in Antarctica, with a comprehensive review on the main literature of the last two decades. Due to the wideness of the topic, the present review is limited to the determination of organic pollutants, natural molecules and biomarkers in Antarctica, thus excluding elemental analysis and studies on inorganic species. The work has been divided into five sections, on the basis of the considered environmental compartment: air; ice and snow; seawater, pack ice and lakes; soil and sediments; and organisms and biomarkers. Copyright © 2014 John Wiley & Sons, Ltd.

Abstract  Mountains are observed to preferentially accumulate persistent organic pollutants (POPs) at higher altitude due to the cold condensation effect. Forest soils characterized by high organic carbon are important for terrestrial storage of POPs. To investigate the dominant factor controlling the altitudinal distribution of POPs in mountainous areas, we measured concentrations of polychlorinated biphenyls (PCBs) in different environmental matrices (soil, moss, and air) from nine elevations on the eastern slope of Mt. Gongga, the highest mountain in Sichuan Province on the Tibetan Plateau. The concentrations of 24 measured PCBs ranged from 41 to 510 pg/g dry weight (dw) (mean: 260 pg/g dw) in the O-horizon soil, 280 to 1200 pg/g dw (mean: 740 pg/g dw) in moss, and 33 to 60 pg/m(3) (mean: 47 pg/m(3)) in air. Soil organic carbon was a key determinant explaining 75% of the variation in concentration along the altitudinal gradient. Across all of the sampling sites, the average contribution of the forest filter effect (FFE) was greater than that of the mountain cold trapping effect based on principal components analysis and multiple linear regression. Our results deviate from the thermodynamic theory involving cold condensation at high altitudes of mountain areas and highlight the importance of the FFE.

Abstract  Chlorophenols are an important class of persistent environmental contaminants and have been implicated in a range of adverse health effects, including cancer. They are readily conjugated and excreted as the corresponding glucuronides and sulfates in the urine of humans and other species. Here we report the synthesis and characterization of a series of ten chlorophenol sulfates by sulfation of the corresponding chlorophenols with 2,2,2-trichloroethyl (TCE) chlorosulfate using N,N-dimethylaminopyridine (DMAP) as base. Deprotection of the chlorophenol diesters with zinc powder/ammonium formate yielded the respective chlorophenol sulfate ammonium salts in good yield. The molecular structure of three TCE-protected chlorophenol sulfate diesters and one chlorophenol sulfate monoester were confirmed by X-ray crystal structure analysis. The chlorophenol sulfates were stable for several months if stored at -20 degrees C and, thus, are useful for future toxicological, environmental and human biomonitoring studies. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  A method for simultaneous determination of polychlorinated dibenzo-p-dioxins/furan (PCDD/Fs), polybrominated dibenzo-p-dioxins/furans (PBDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) was established by using elution curve and fraction cut technology to eliminate the PCB and PBDE blank of interference and optimize the pre-treatment. The technology was developed using AutoSoxtec, acid silica gel column, multi-layered silica gel column and active carbon column. The sample recovery of sampling standards was in the range of 63%-100% and the recovery of internal standards was in the range of 52%-132%. The detection limits was between 6x10(-4)-1x10(-2) pg/m(3), dicabromodiphenyl ether (BDE-209) was 0.3 pg/m(3), which reached the US Environmental Protection Agency (EPA) standards. Air sample toxic equivalent quantity (TEQ) (PCDD/Fs, dl-PCBs) was between 0.216-0.949 pg/L WHO-TEQ, TEQ(PBDD/Fs) was 0.0181-0.0462 pg/L WHO-TEQ, and PBDEs content was 105-132 pg/m(3).

Abstract  Final technical rept. 1 Oct 1998-31 Mar 2002.

Abstract  Twenty laboratories worldwide participated in a collaborative trial sponsored by the International Programme on Chemical Safety on the mutagenicity of complex mixtures as expressed in the Salmonella/ microsome assay. The U.S. National Institute of Standards and Technology provided homogeneous reference samples of urban air and diesel particles and a coal tar solution to each participating laboratory, along with samples of benzo[a]pyrene and 1-nitropyrene which served as positive controls. Mutagenic potency was characterized by the slope of the initial linear component of the dose-response curve. Analysis of variance revealed significant interlaboratory variation in mutagenic potency, which accounted for 57–96% of the total variance on a logarithmic scale, depending on the sample, strain and activation conditions. Variation among replicate bioassays within the same laboratory was (required for the air and diesel particles) and among replicate bioassays within the same laboratory was also appreciable. The average potencies for air and diesel particles in laboratories using Soxhlet extracts were not significantly different from those in laboratories using sonication, although there was larger interlaboratory variation for the Sohlet method. Repeatability (which approximates the coefficient of variation within laboratories) ranged from 18 to 40% for air and diesel particles extracted using sonication, depending on the strain and activation conditions. Repeatability of Soxhlet-extracted air and diesel particles, however, ranged from about 37 to 89% including outliers and from about 11 to 31% excluding outliers. Repeatability of the coal tar sample and the 2 positive controls was in the range 18–34%. Reproducibility (which approximates the coefficient of variation between laboratories) was generally at least twice repeatability, and exceeded 100% for Soxhlet-extracted air and diesel particles, as well as 1-nitropyrene. Reanalysis of the data omitting observations of more than 1500 revertants/plate generally had little effect on these results. Elimination of outlying observations had limited impact, with the exception of Soxhlet-extracted air and diesel particles. In this case, reproducibility of bioassay results was notably improved, due largely to the omission of results for replicate extractions which varied more than 5-fold within one laboratory. Normalization of the log potency slopes for the mixtures by the corresponding slopes for benzo[a]pyrene tended to reduce this variation, although variation was increased after normalization by 1-nitropyrene. Adjustment for the percentage of organic matter extracted from the air and diesel particulate samples had little effect on variation for sonication-extracted particles, whereas variation was reduced for diesel particles and increased for air particles for Soxhlet.

Abstract  Final rept.

Abstract  Pseudomonas putida OU83 is a soil organism capable of degrading 3-nitrotoluene (3-NT), 2,4-dinitrotoluene (DNT), 2,6-DNT, and mono and polychlorinated biphenyls. An investigation of the nitro group dependent biotransformation of nitrotoluenes in P. putida revealed accumulation of two metabolic products, a and b from each of the three tested NT isomers (2-, 3-, and 4-NT). Gas chromatography-mass spectrophotometer (GC-MS) analysis of the accumulated metabolite a showed that it had a major fragmentation pattern (107, 88, 76, and 65 amu) similar to the pattern of pure aminotoluene (AT). Evidently metabolite a resulted from the reduction of the nitro group to an amino group. The metabolite b produced from 3-NT was identical to the MS pattern of 3-nitrophenol (3-NP) (139 amu). However, the metabolite b formed from 2- and 4-NT showed fragmentation patterns (153, 136, 108, 77, and 65 amu) similar to authentic 6-hydroxy-2-nitrotoluene (6H2NT). The identity of the bacterial metabolites was confirmed by the H-1 NMR spectral analysis. The H-1 NMR results showed transformation of 2-NT to 2-AT and 6H2NT, 4-NT to 4-AT and 2H4NT, and 3-NT to 3-AT and 3-NP. Oxygen consumption in the NT-induced cell suspension of strain OU83 was increased when 2-, 3-, and 4-NT, 6H2NT, 3-nitrobenzyl alcohol, 3-nitrobenzoic acid, and 3-nitrophenol were used as substrate. In summary, the nitro group at 2-, 3-, and 4-position was reduced to an amino group, the methyl group of 3-NT was oxidized, and the benzene ring is hydroxylated at the 2 and 6 position of and 2-NT, respectively. These results show that the degradation of nitrotoluene in P. putida was influenced by the position of the nitro group on the benzene ring. (C) 2003 Elsevier Inc. All rights reserved.

Abstract  There is a growing need for short-term assays which can assess the mechanisms and efficacy of cancer chemopreventive agents. In the present study we have employed a microsome-mediated test system concomitantly with DNA adduct detection to assess the efficacy of five chemopreventive agents, N-acetylcysteine, butylated hydroxytoluene (BHT), curcumin, oltipraz, and ellagic acid. 32P-Postlabeling analysis of DNA incubated with benzo[a]pyrene (BP) in the presence of Aroclor 1254-induced microsomes produced two major adducts: one derived from the interaction of benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) with deoxyguanosine (dG) and the other from further activation of 9-OH-BP (309 and 34 adducts/10(7) nucleotides, respectively). With the exception of N-acetylcysteine, all test agents significantly altered BP-DNA adduct levels: Intervention with ellagic acid and oltipraz substantially (64-94%) inhibited both BPDE-dG and 9-OH-BP adducts, while intervention with curcumin and BHT inhibited the BPDE-dG adduct (57% and 38%, respectively) and enhanced the 9-OH-BP adduct (230% and 650%, respectively). Furthermore, ellagic acid was the only test agent observed to inhibit the anti BPDE-dG adduct in the absence of microsomal enzymes, which is consistent with the known conjugation of ellagic acid with BPDE. These results suggest that oltipraz may be acting as an inhibitor of P4501A1, the isozyme involved in activation of BP to BPDE, or by conjugation of the electrophilic species by a metabolite of oltipraz. A plausible mechanism for inhibition of the BPDE-dG adduct and enhancement of the 9-OH-BP adduct by curcumin and BHT includes inhibition of epoxide hydrolase. Our results also indicate that N-acetylcysteine does not act as an electrophilic trapping agent of BP metabolites but may exert its protective effect in vivo by various other means, including modulation of detoxification enzymes and altering DNA repair processes. These data suggest that this cell-free system in conjunction with the sensitive 32P-postlabeling DNA adduct analysis may prove a viable test system for assessing the mechanisms and efficacy of chemopreventive agents.

Abstract  HEEP COPYRIGHT: BIOL ABS. Six kinds of chlorinated 4-nitrobiphenyl ethers (4-nitrobiphenyl ether, p-NO2; 2'-, 3'- and 4'-chloro-4-nitrobiphenyl ethers, 2-, 3- and 4-CNO2; 2',4'-dichloro-4-nitrobiphenyl ether, 2,4-DCNO2; 2',4',6'-trichloro-4-nitrobiphenyl ether, 2,4,6-TCNO2) and their nitroso- and amino-derivatives were tested for mutagenicity using Salmonella typhimurium strains (TA98 and TA100) in the presence and the absence of rat, mouse and guinea pig liver homogenates, which were stimulated with Kaneclor-500. All the chlorinated 4 nitrobiphenyl ethers except for 2,4,6-TCNO2 induced mutations in TA100 strain without metabolic activation although their mutagenic activities were weak compared with the nitroso (| S-9) and amino (+S-9) derivatives. The mono-chloro-compounds were more effective in inducing mutations than those with multiple chlorines and their mutagenic activities were closely related to the rate of reduction of the nitro-moiety by tester strains. After metabolic activation the mutagenicity of these compounds was enhanced. All the nitroso derivatives (except for 2,4,6-TCNO which was inactive with TA98), without metabolic activation, induced mutations in both TA98 and TA100 strains. At high concentrations they showed antimicrobial activity. At low concentrations, the nitroso compounds having fewer chlorine atoms were more effective in inducing mutations and their mutagenic activities were closely related to their rate of reduction by tester strains. After metabolic activation with S-9, their antimicrobial activities at high concentrations were markedly decreased and their mutagenic activities were greatly enhanced. The amino derivatives all induced mutations in both TA98 and TA100 strains but only after metabolic activation. Here too, the amino-compounds having fewer chlorine atoms were more effective in inducing mutations than those having multiple chlorines. After addition of S-9, the mutagenic activity of the nitro compounds was lower than that of the analogous nitroso and amino compounds which showed almost the same mutagenic activity. S-9 fraction from guinea pig liver was the most active in conversion of these chemicals to mutagens, whereas S-9 fractions from rat and mouse livers were about equal in potency. (This study may be applicable to carcinogenesis.)

Abstract  Persistent Organic Pollutants (POPs) are man-made chemicals that have an intrinsic resistance to natural degradation processes, and are therefore environmentally persistent. Introduction of POPs into the environment from anthropogenic activities has resulted in their widespread dispersal and accumulation in soils and water bodies, as well as human and ecological food chains where they are known to induce toxic effects. Due to their ubiquity in the environment and lipophilic properties, there is mounting concern over the potential risks of human exposure to these POPs via the ingestion and inhalation pathways. This has led to the establishment of a worldwide research program to determine prevailing levels of POPs in the population and investigate the health risks associated with background exposure. This paper reviews the state of knowledge regarding residual levels of POPs in human adipose tissue worldwide, and provides preliminary data on the levels of key POPs in female adipose tissues collected in Singapore. Organochlorine pesticides (OCPs) were found to have a comparable level to levels reportednfor Poland in 2001, with a mean of 0.98 ug/g and 0.84 ug/g on a lipid weight basis respectively. For total polychlorinated biphenyl (PCB) congeners, the mean concentration of 34 ng/g (lipid weight basis) is lower than values reported from Japan in 1980 and Belgium in 2000. Polybrominated diphenyl ethers (PBDEs) are present at similar levels to Belgium in 2000, at 3.7 and 4.7 ng/g (lipid weight basis) respectively.