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PubMed2003

HQSAR and CoMFA approaches in predicting reactivity of halogenated compounds with hydroxyl radicals.

Two quantitative structure-activity relationship (QSAR) methods: hologram QSAR (HQSAR) and comparative molecular field analysis (CoMFa) were evaluated for predicting half-lives of the hydroxyl radicals reaction with substituted aromatic compounds. The HQSAR approach, which is topological in nature, results in a mathematical model which was more stable and has a greater predictive ability than the model derived on the 3-D CoMFA approach. Interpretations of the colour coded results of both methods are in good agreement with the proposed mechanism of the hydroxyl radical oxidation of halogenated aromatic compounds in the atmosphere.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2000

Chemical kinetic modelling of PCDD formation from chlorophenol catalysed by incinerator fly ash.

A kinetic model is developed for PCDD formation from chlorophenol catalysed by incinerator fly ash. The key step in the model is a Langmuir-Hinshelwood type elementary step for the coupling of two adsorbed chlorophenol species to PCDD. Kinetic expression is derived which can relate PCDD formation rates with process variables including temperature, precursor concentration, fly ash loading and number of active sites in fly ash. Calculated PCDD formation rates based on this kinetic model are in good agreement with laboratory measurements reported in the literature. When the model is applied to industrial incinerator conditions, at maximum a PCDD yield of 10(-3) microg/N m3 is calculated.

Air Pollution↗
PubMed2000

Estimating K(oc) for persistent organic pollutants: limitations of correlations with K(ow).

The n-octanol/water partition coefficient (K(ow)) is commonly used to predict the soil or aquatic particle water partition coefficient normalized to organic carbon (K(oc)). Many correlations are available covering several chemical classes and ranges of hydrophobicity. This work indicates the K(ow) may not be a strong predictor for persistent organic pollutants (POPs) which are defined here as chemicals with logK(ow) > 5.0. In addition, the correlation developed in this work for POPs will still result in a predicted value which is of by a factor of 15. Accordingly, care must be taken when applying K(oc) estimations using K(ow) for POPs until more suitable correlations are developed.

DDT↗
PubMed2002

Solar photocatalysis: a clean process for water detoxification.

The photocatalytic degradation of various toxic organic compounds has been proposed as a viable process to detoxify drinking water. Irradiating pulverulent semi-conductors like TiO2 in suspension or fixed to various supports in aqueous solutions containing organic pollutants, creates a redox environment able to destroy these pollutants. Solar photocatalytic mineralization of organic water pollutants has a strong potential in the industrial destruction of toxic organics in water as this has been widely demonstrated in recent years, and the applications and target compounds are numerous. The aim of this paper is to present the basic principle of the photocatalysis and especially to show the various applications of the solar photocatalysis in the field of the decontamination of wastewater.

Catalysis↗
PubMed2003

Developmental and subcellular effects of chronic exposure to sub-lethal concentrations of ammonia, PAH and PCP mixtures in brown trout (Salmo trutta f. fario L.) early life stages.

Brown trout (Salmo trutta f. fario L.) early life stages were studied for physiological effects caused by chronic exposure to sub-acute levels of unionised ammonia, a mixture of PCP and PAHs, and a combination of ammonia and the mixture of organics during the entire embryonic development. Nominal concentrations of tested compounds were based on field data. Accumulation data for PAHs and PCP in trout tissue reflected respective water concentrations of PCP and PAHs. Physiological responses were studied by early life stage tests (ELST) and by the analysis of the 70 kDa stress protein (hsp70). Endpoint responses in the ELST were: accelerated development, pre-hatching, and increased heart rates. For these endpoints, response levels were highest in the ammonia treatment, followed by the exposure to the PCP/PAH mixture. Weight was reduced in embryos treated with the PCP/PAH mixture, but not in the group treated with this mixture combined with ammonia. Induction of hsp70 by the test agents was found to be stage-specific with increased response levels at advanced developmental stages. In both the ELST and hsp70 analysis, response levels were lower in the combined ammonia/PCP/PAH treatment than in groups treated with either ammonia or the PCP/PAH mixture alone.

Ammonia↗
PubMed2000

Activation of the hsp70 promoter by environmental inorganic and organic chemicals: relationships with cytotoxicity and lipophilicity.

Stress proteins (heat shock proteins, HSPs) have been proposed as general markers of cellular aggression and their use for environmental monitoring is often suggested. The aim of this work was to study the potency of various environmentally relevant organic and inorganic chemicals to induce the expression of the HSP70 marker. For this purpose, we used an established HeLa cell line containing the chloramphenicol acetyl transferase (CAT) gene under the control of the hsp70 promoter. The screening of three metallic and 15 organic chemicals revealed differences in their capacities to induce the hsp70 promoter. The three metals tested (cadmium, zinc and mercury) were able to induce a stress response. Some organochlorine compounds (chlorophenol derivatives, tetrachlorohydroquinone, 3, 4-dichloroaniline, ethyl parathion and 1-chloro-2,4-dinitrobenzene) induced a response, whereas other common halogenated pesticides or aromatic hydrocarbons (e.g. benzo(a)pyrene, 2, 4-dichlorophenoxyacetic acid, endosulfan, diuron, 4-nonylphenol) did not. The potency to induce hsp70 was significantly correlated to the octanol-water partition coefficient (log K(ow)) of the inducing chemicals, except for 1-chloro-2,4-dinitrobenzene and ethyl parathion. Cytotoxicity assays run in parallel to the induction measurements revealed that the three metals were effective at non cytotoxic doses whereas all organic compounds, except tetrachlorohydroquinone and 1-chloro-2,4-dinitrobenzene, induced the promoter at cytotoxic doses. These results suggest that hsp70 is induced by different mechanisms of toxicity. We propose that this model can be used in mechanistic studies for the detection of toxic effects of certain pollutants.

Cadmium↗
PubMed2002

Metabolic disturbances in fish exposed to sodium pentachlorophenate (NaPCP) and 3,3',4,4',5-pentachlorobiphenyl (PCB126), individually or combined.

The Swan River Estuary is the recipient of multiple urban and agricultural contaminants which have the potential to induce liver detoxication enzymes as well as altering the metabolism of aquatic organisms. To test if altered liver metabolism would influence liver detoxication capacities, pink snapper (Pagrus auratus) were i.p. injected with peanut oil (controls), or pentachlorobiphenyl #126 (PCB126), with sodium pentachlorophenate (NaPCP), or PCB126+NaPCP. Relative to controls, ethoxyresorufin-O-deethylase (EROD) activity was induced in the PCB126 and PCB126+NaPCP fish, but not in the NaPCP group. In the liver, cytochrome c oxidase (CCO) activity was enhanced by the treatments while citrate synthase (CS) activity remained unchanged and lactate dehydrogenase (LDH) activity was increased in the NaPCP treatment only. The results suggest that liver CCO activity may be a suitable biomarker of effect following exposure to PCBs or phenolic compounds. In the white muscle, only the PCB126+NaPCP treatment enhanced CCO activity, with all other enzymatic activities remaining unchanged. It appears that the resilience to metabolic perturbations is greater for white muscle than for liver. Low serum sorbitol dehydrogenase (sSDH) activity and histopathology of the liver indicated no significant alteration of cellular structure, albeit the lipid droplet size was increased in the PCB126 and in the PCB126+NaPCP treatments. It is concluded that the hepatic metabolic changes correspond to histopathological observations, but an altered metabolic capacity do not influence the metabolism of xenobiotics by liver enzymes, as measured by EROD activity.

Animals↗
PubMed2003

Correlation of the structures of agricultural fungicides to gene expression in Saccharomyces cerevisiae upon exposure to toxic doses.

Correlations between the chemical structures of agricultural fungicides and mRNA expression levels following exposure of Saccharomyces cerevisiae to toxic doses of thiuram, zineb, maneb, TPN, and PCP were examined. Structurally, thiuram, zineb, and maneb are dithiocarbamate fungicides, whereas TPN and PCP are not. To characterize chemical toxicity, genes expression was classified according to the functional groups used by the MIPS database. However, no correlations between the classification scheme and chemical structures were found. Hierarchical clustering of gene expression profiles was performed to characterize the effects of the five chemicals. According to this analysis the similarity of gene expression profiles depended on the similarity of chemical structures. These results suggest that DNA microarray technology has potential for predicting the major chemicals which will cause environmental toxicity and will provide information on new biomonitoring methods.

Environmental Pollutants↗
PubMed2005

Concentrations of polybrominated diphenyl ethers, polychlonnated biphenyls, and polychlorobiphenylols in serum from pregnant Faroese women and their children 7 years later.

The objective of this study was to assess blood concentrations of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), and their polychlorobiphenylol (OH-PCB) metabolites in humans with a high seafood intake. Samples were obtained from pregnant women in the Faroe Islands in 1994-1995 and from their children at 7 years of age to examine maternal transfer of the compounds to their child, age-dependent metabolism, and temporal changes. Maternal serum was dominated by 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), while 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153) prevailed in the children's serum seven years later. DecaBDE was present in both mothers and children up to 3 and 6 ng/g lipid weight, respectively. The sigmaPCB concentration in the children averaged about 60% of the concentrations in their mothers, with median levels for both above 1 microg/g lipid weight and .with similar PCB congener patterns. sigmaOH-PCB serum concentrations from the mothers and their children showed ranges of 1.8-36 ng/g wet weight (ww) and 0.49-22 ng/g ww, respectively, with all OH-PCB congener concentrations being lower in the children, except for 2,3,3',4',5-pentachloro-4-biphenylol (4-OH-CB107). Children at 7 years of age are exposed to PCBs at levels only slightly below those of their mothers, and the increased 4-OH-CB107 concentrations in children could be due to age-related differences in PCB metabolism. The PBDE concentrations were similar in both mothers and their children. The main persistent organic pollutant concentrations in the children are most probably due to other environmental exposure than maternal transfer.

Child↗