Photocatalytic degradation of the cyanotoxin cylindrospermopsin, using titanium dioxide and UV irradiation

Cylindrospermopsis raciborskii produces the cyanotoxin cylindrospermopsin, which is commonly found in SouthEast Queensland water reservoirs, and has been responsible for the closure of these reservoirs as a source of drinking water in recent times. Thus, alternative more effective treatment methods need to be investigated for the removal of toxins such as cylindrospermopsin. This study examined the effectiveness of two brands of titanium dioxide under UV photolysis for the degradation of cylindrospermopsin. Results indicate that titanium dioxide is an efficient photocatalyst for cylindrospermopsin degradation. The titanium dioxide (TiO2), brand Degussa P-25 was found to be more efficient than the alternate brand Hombikat UV-100. There was an influence from solution pH (4, 7, and 9) with both brands of titanium dioxide, with high pH resulting in the best degradation rate. Importantly, there was no adsorption of cylindrospermopsin to titanium dioxide particles as seen with other cyanotoxins, which would adversely influence the degradation rate. Degradation rates were not influenced by temperature (19-34 degreesC) when P-25 was the source of TiO2, some temperature influence was observed with UV-100. Dissolved organic carbon concentration will reduce the efficiency of titanium dioxide for cylindrospermopsin degradation, however the presence of other inorganic matter in natural waters greatly assists the photocatalytic process. With minimal potentially toxic by-product formation expected with this treatment, and the effective degradation of cylindrospermopsin, titanium dioxide UV photolysis is a promising speculative alternative water treatment method. (C) 2001 Elsevier Science Ltd. All rights reserved.

A sensitive and specific assay for glutathione with potential application to glutathione disulphide, using high-performance liquid chromatography-tandem mass spectrometry

We have utilised the combination of sensitivity and specificity afforded by coupling high-performance liquid chromatography (HPLC) to a tandem mass spectrometer (MS-MS) to produce an assay which is suitable for assaying glutathione (GSH) concentrations in liver tissue. The sensitivity suggests it may also be suitable for extrahepatic tissues, The method has been validated for GSH using mouse liver samples and also allows the assay of GSSG. The stability of GSH under conditions relevant to the assay has been determined. A 20-mul amount of a diluted methanol extract of tissue is injected with detection limits of 0.2 pmol for GSH and 2 pmol for GSSG. The HPLC uses an Altima C-18 (150X4.6 mm, 5 mum) column at 35 degreesC. Chromatography utilises a linear gradient from 0 to 10% methanol in 0.1% formic acid over 5 min, with a final isocratic stage holding at 10% methanol for 5 min. Total flow rate is 0.8 ml/min. The transition from the M+H ion (308.1 m/z for GSH, and 613.3 m/z for GSSG) to the 162.0 m/z (GSH) and 355.3 m/z (GSSG) fragments are monitored. (C) 2001 Elsevier Science B.V. All rights reserved.

Human Fatalities from Cyanobacteria: Chemical and Biological Evidence for Cyanotoxins

An outbreak of acute liver failure occurred at a dialysis center in Caruaru, Brazil (8 degrees 17 'S, 35 degrees 58 'W), 134 km from Recife, the state capital of Pernambuco. At the clinic, 116 (89%) of 131 patients experienced visual disturbances, nausea, and vomiting after routine hemodialysis treatment on 13-20 February 1996. Subsequently, 100 patients developed acute liver failure, and of these 76 died. As of December 1996, 52 of the deaths could be attributed to a common syndrome now called Caruaru syndrome. Examination of phytoplankton from the dialysis clinic's water source, analyses of the clinic's water treatment system, plus serum and liver tissue of clinic patients led to the identification of two groups of cyanobacterial toxins, the hepatotoxic cyclic peptide microcystins and the hepatotoxic alkaloid cylindrospermopsin. Comparison of victims' symptoms and pathology using animal studies of these two cyanotoxins leads us to conclude that the major contributing factor to death of the dialyses patients was intravenous exposure to microcystins, specifically microcystin-YR, -LR, and -AR. From liver concentrations and exposure volumes, it was estimated that 19.5 mug/L microcystin was in the water used for dialysis treatments. This is 19.5 times the level set as a guideline for safe drinking water supplies by the World. Health Organization.

Leptospiral antibodies in Flying Foxes in Australia

The sera of 271 pteropid bats (or flying foxes) collected from Queensland, New South Wales, Western Australia, and the Northern Territory were screened against it reference panel of 21 Leptospira spp. using the microscopic agglutination test (MAT). Sera were collected from December 1997 through August 1999. The MAT panel represented those serovars previously isolated in Australia. as well as exotic serovar found in neighboring countries. Leptospiral antibodies were detected in 75 (28%) of the sera and represented seven serovars, one of which. L. interrogans serovar cynopteri has been regarded as exotic to Australia. Sixty sera were reactive to one serovar, 12 sera were reactive to two serovars, and three sera were reactive to three serovars. The L. kirschneri serovar australis was most frequently identified (60.2%). The findings suggest a previously unrecognized role of pteropid bats in the natural history of leptospirosis. The potential exists for establishment of infection in new host species, the transmission of new serovars to known host species, and for changes in virulence of leptospires as a result of passage through these species.

Eating 'Green': Motivations behind organic food consumption in Australia

Central to the development of green lifestyles is the consumption of foods that by dint of their status as chemical-free, locally produced and/or free of genetically modified ingredients, reduce the environmental impact of food provision. Yet there are many other factors, such as health concerns, that may also encourage the consumption of 'green' foods. This paper explores the ways in which Australian consumers construct organic food-a sector of the food industry that is currently growing at between 20 and 50 percent per annum but is struggling to keep up with rising consumer demand. In order to examine the significance of 'green' signifiers in the consumption practices of Australian consumers a series of focus group interviews and a national consumer survey were conducted. These examined both those characteristics of food that were valued in general, and those meanings that were associated with organic food in particular. In very general terms, analysis reveals that while consumers believed organic foods to be healthy and environmentally sound-both of which were considered desirable-these characteristics were subsumed by an overarching concern with convenience. This does not mean that consumers did not hold genuinely positive environmental attitudes. Rather, it reflects a range of contradictory beliefs and practices that appeared to derive from the discursive conflict between conventional and organic food industries over environmental, health and safety claims. The paper concludes by identifying the barriers and opportunities for expanding the organic industry in Australia in the context of the ways organics is constructed by consumers.

New type of dual-channel PAM chlorophyll fluorometer for highly sensitive water toxicity biotests

A new type of dual-channel PAM chlorophyll fluorometer has been developed, which is specialised in the detection of extremely small differences in photosynthetic activity in algae or thylakoids suspensions. In conjunction with standardised algae cultures or isolated thylakoids, the new device provides an ultrasensitive biotest system for detection of toxic substances in water samples. In this report, major features of the new device are outlined and examples of its performance are presented using suspensions of Phaeodactylum tricornutum (diatoms) and of freeze-dried thylakoids of Lactuca sativa (salad). Investigated and reference samples are exposed to the same actinic intensity of pulse-modulated measuring light. The quantum yields are assessed by the saturation pulse method. Clock-triggered repetitive measurements of quantum yield typically display a standard deviation of 0.1%, corresponding to the inhibition induced by 0.02 mug diuron l(-1). Hence, for diuron or compounds with similar toxicity, the detection limit is well below the 0.1 mug l(-1) defined as the limit for the presence of a single toxic substance in water by the European Commission drinking water regulation. The amounts of water and biotest material required for analysis are very small, as a single assay involves two 1 ml samples, each containing ca. 0.5 mug chlorophyll. Both with Phaeodactylum and thylakoids the relationship between inhibition and diuron concentration is strictly linear up to 10% inhibition, with very similar slopes. Apparent inhibition depends on the actinic effect of the measuring light, showing optima at 6 and 4 mumol quanta m(-2) s(-1) with Phaeodactylum and thylakoids, respectively.

Trace organic compounds in the marine environment

Trace organic chemicals include a range of compounds which, due to a combination of their physico-chemical properties and toxicological implications, have been described as a serious threat to the biotic environment. A global treaty to regulate the manufacture and release of some of the most persistent trace chemicals has been promulgated and signed. The marine environment is an important sink for many trace chemicals, some of which accumulate in the marine food chain and in particular in marine mammals. With respect to the global distribution of trace organic chemicals, the levels of organohalogen compounds in the Southern Hemisphere are comparatively lower for a given environmental compartment and latitude compared to the Northern Hemisphere. A debate is currently evolving about the toxicity of alternative halogen substitutions such as bromine instead of chlorine and also of mixed halogen substitution. Recently a series of potentially natural bioaccumulative and persistent organohalogen chemicals have been found in marine mammals and turtles at levels in excess of those of anthropogenic trace organochlorines including PCBs and DDE. Little is known about the sources, behaviour and effects of natural trace organic chemicals. This manuscript presents an overview on the occurrence of trace organic chemicals in different compartments of the aquatic environment. Important knowledge gaps with regards to trace chemicals in the marine environment are presented. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.

A review of animal models for the study of arsenic carcinogenesis

As inorganic arsenic is a proven human carcinogen, significant effort has been made in recent decades in an attempt to understand arsenic carcinogenesis using animal models, including rodents (rats and mice) and larger mammals such as beagles and monkeys. Transgenic animals were also used to test the carcinogenic effect of arsenicals, but until recently all models had failed to mimic satisfactorily the actual mechanism of arsenic carcinogenicity. However, within the past decade successful animal models have been developed using the most common strains of mice or rats. Thus dimethylarsinic acid (DMA), an organic arsenic compound which is the major metabolite of inorganic arsenicals in mammals, has been proven to be tumorigenic in such animals. Reports of successful cancer induction in animals by inorganic arsenic (arsenite and arsenate) have been rare, and most carcinogenetic studies have used organic arsenicals such as DMA combined with other tumor initiators. Although such experiments used high concentrations. of arsenicals for the promotion of tumors, animal models using doses of arsenicals species closed to the exposure level of humans in endemic areas are obviously the most significant. Almost all researchers have used drinking water or food as the pathway for the development of animal model test systems in order to mimic chronic arsenic poisoning in humans; such pathways seem more likely to achieve desirable results. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

HPLC measurement of harderoporphyrin in the harderian glands of rodents as a biomarker for sub-lethal or chronic arsenic exposure

An improved HPLC method has been established for the measurement of harderoporphyrin (HP) in the harderian gland of rats and mice. Groups of female Wistar rats were given a single oral dose of sodium arsenite at 0, 0.5 or 5.0 mg As(III)/kg body weight, or a slurry of arsenic-contaminated soil at equivalent dose rates and the animals were sacrificed 96 h after dosing. A group of C57BL/6J female mice were chronically exposed to drinking water containing 500 mug As(V)/I of sodium arsenate ad libitum for over 2 years. Porphyrins were measured in the harderian glands of rats and mice. Our results suggest that HP and the alteration of the porphyrin profile in the harderian glands of rodents is a highly sensitive biomarker for both single sub-lethal and chronic arsenic exposure. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments from Hong Kong

Concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in 14 sediment samples collected from four sites in the Mai Po Marshes Nature Reserve (within a RAMSAR Site) and from another six sites in Victoria Harbour and along the Hong Kong coastline. Elevated levels of PCDDs, and particularly OCDD, were detectable in all samples collected from the Mai Po Marshes and five of the six sites. In contrast to PCDDs, PCDFs were mainly found in sediment samples collected from industrial areas (Kwun Tong and To Kwa Wan) in Victoria Harbour. PCDD/F levels and congener profiles in the samples from the Mai Po Marshes Nature Reserve in particular show strong similarities to those reported in studies which have attributed similar elevated PCDD concentrations to nonanthropogenic PCDD sources. (C) 2002 Elsevier Science Ltd. All rights reserved.

Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant

A new cloud-point extraction and preconcentration method, using a cationic, surfactant, Aliquat-336 (tricaprylyl-methy;ammonium chloride), his-been developed for the determination of cyanobacterial toxins, microcystins, in natural waters. Sodium sulfate was used to induce phase separation at 25 degreesC. The phase behavior of Aliquat-336 with respect to concentration of Na2SO4 was studied. The cloud-point system revealed a very high phase volume ratio compared to other established systems of nonionic, anionic, and cationic surfactants: At pH 6-7, it showed an outstanding selectivity in ahalyte extraction for anionic species. Only MC-LR and MC-YR, which are known to be predominantly anionic, were extracted (with averaged recoveries of 113.9 +/- 9% and 87.1 +/- 7%, respectively). MC-RR, which is likely to be amphoteric at the above pH range, was. not cle tectable in.the extract. Coupled to HPLC/UV separation and detection, the cloud-point extraction method (with 2.5 mM Aliquat-336 and 75 mM Na2SO4 at 25 degreesC) offered detection limits of 150 +/- 7 and 470 +/- 72 pg/mL for MC-LR and MC-YR, respectively, in 25 mL of deionized water. Repeatability of the method was 7.6% for MC-LR and 7.3% for MC-YR: The cloud-point extraction process can be. completed within 10-15 min with no cleanup steps required. Applicability of the new method to the determination of microcystins in real samples was demonstrated using natural surface waters, collected from a local river and a local duck pond spiked with realistic. concentrations of microcystins. Effects of salinity and organic matter (TOC) content in the water sample on the extraction efficiency were also studied.