Glen R. Shaw

Toxicology and Risk Assessment of Freshwater Cyanobacterial (Blue-Green Algal) Toxins in Water

The occurrence of cyanobacterial toxins affects aquatic organisms, terrestrial animals (both wild and domestic), and humans. Detrimental effects have been documented in the scientific literature during the past 50 years. Possible guideline values of some cyanobacterial toxins (microcystins, cylindrospermopsin, and anatoxin-a) are estimated, and they show that children and infants are more susceptible to cyanobacterial toxins than adults. Therefore, particular attention should be paid when cyanobacterial blooms occur, even at relatively low cell counts, to protect children and infants from possible risks. Based on these guideline values and the occurrence of the toxins, it can be concluded that chronic and subchronic exposure to cyanobacterial toxins does occur in some populations, particularly in developing countries where high proportions of the population consume untreated surface water directly, such as pond, ditch, river, or reservoir water. Because wildlife and domestic animals consume a large amount of untreated water daily, they are at higher risk than humans from cyanobacterial toxins. Calculated guideline values in Section X show that a relatively high risk posed by the toxins to these animals is likely to occur, even at low cell densities.

FIRST REPORT OF THE CYANOTOXINS CYLINDROSPERMOPSIN AND DEOXYCYLINDROSPERMOPSIN FROM RAPHIDIOPSIS CURVATA (CYANOBACTERIA)

A strain of Raphidiopsis (Cyanobacteria) isolated from a fish pond in Wuhan, P. R. China was examined for its taxonomy and production of the alkaloidal hepatotoxins cylindrospermopsin (CYN) and deoxy‐cylindrospermopsin (deoxy‐CYN). Strain HB1 was identified as R. curvata Fritsch et Rich based on morphological examination of the laboratory culture. HB1 produced mainly deoxy‐CYN at a concentration of 1.3 mg·g−1 (dry wt cells) by HPLC and HPLC‐MS/MS. CYN was also detected in trace amounts (0.56 μg·g−1). A mouse bioassay did not show lethal toxicity when tested at doses up to 1500 mg dry weight cells·kg−1 body weight within 96 h, demonstrating that production of primarily deoxy‐CYN does not lead to significant mouse toxicity by strain HB1. The presence of deoxy‐CYN and CYN in R. curvata suggests that Raphidiopsis belongs to the Nostocaceae, but this requires confirmation by molecular systematic studies. Production of these cyanotoxins by Raphidiopsis adds another genus, in addition to Cylindrospermopsis, Aphanizomenon, and Umezakia, now known to produce this group of hepatotoxic cyanotoxins. This is also the first report from China of a CYN and deoxy‐CYN producing cyanobacterium.

Stability of cylindrospermopsin, the toxin from the cyanobacterium, Cylindrospermopsis raciborskii: Effect of pH, temperature, and sunlight on decomposition

Cylindrospermopsin is a powerful hepatotoxin produced by the cyanobacterium Cylindrospermopsis raciborskii. It is considered a potential threat to livestock, wildlife, and humans, and is the suspected cause of an outbreak of hepatoenteritis on Palm Island, Queensland, Australia, and various stock poisoning incidents around Australia. In this study, the stability of cylindrospermopsin was investigated using different parameters, including visible and UV light, sunlight, temperature and pH. Cylindrospermopsin decomposes rapidly (half‐life of 1.5 h) when exposed to sunlight in an algal extract solution; however, no decomposition was recorded in pure cylindrospermopsin and Milli‐Q water solutions. Cylindrospermopsin decomposes slowly in temperatures ranging from 4 to 50°C at pH 7. After 10 weeks at 50°C, cylindrospermopsin had degraded to 57% of the original concentration. This degradation was accompanied by an increase in another compound which is believed to be structurally related to cylindrospermopsin. Boiling does not cause a significant degradation of cylindrospermopsin within 15 min. Initial investigations indicate that cylindrospermopsin is degraded slowly under artificial light ranging from 42, 29, and 9 μE m−1 s−1 and in darkness. Degradation of cylindrospermopsin was not affected by changes in pH. Experiments were performed in sterile conditions. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 155–161, 1999

Blooms of the cylindrospermopsin containing cyanobacterium, Aphanizomenon ovalisporum (Forti), in newly constructed lakes, Queensland, Australia

The cyanobacterium, Aphanizomenon ovalisporum (Forti) is reported herein for the first time in Australia. Its distribution appears to be restricted to an isolated subtropical region which has distinctive water quality parameters including ready availability of nutrients and relatively high chloride and hardness levels. Blooms of A. ovalisporum in Queensland, Australia, formed a thick brown surface scum from spring to autumn in newly constructed shallow lakes. During such blooms, the water and cellular material were both found to contain cylindrospermopsin, a water soluble toxin that produced fatty livers with hepatocyte necrosis in mice similar to the toxicity produced by Cylindrospermopsis raciborskii (Wolosz.). Toxin levels in freeze‐dried A. ovalisporum are approximately 25% of those present in freeze‐dried C. raciborskii. However, A. ovalisporum appears to release more of the produced toxin into the water body than does C. raciborskii.

Use of HPLC-MS/MS to monitor cylindrospermopsin, a blue–green algal toxin, for public health purposes

Increasing reports of blooms of the blue–green alga Cylindrospermopsis raciborskii (C. raciborskii), which contains the hepatotoxic alkaloid cylindrospermopsin (CYN), have led to public health concerns in Australia. The toxicology of CYN appears complex and is still being elucidated. We have utilized 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 monitoring low CYN concentrations in water samples. Intact algal cells in the water sample are lysed by a freeze–thaw cycle. After filtration (0.45 μm filter), 110 μL is injected. The HPLC uses an Altima C18 (250×4.6 mm, 5 μm) column at 40°C. Chromatography utilizes a linear gradient from 1 to 60% methanol over 5 min, with a final isocratic stage holding at 60% methanol for 1 min. The mobile phase is buffered to 5 mM with ammonium acetate. The transition from the M+H ion (416 m/z) to the 194 m/z fragment is monitored. Linearity of this assay is 1–600 μg/L [peak area=304×CYN (μg/L)−569; r2=1.000 (n=7)]. Using a single point standard curve, total coefficients of variation were 26.4, 10.5, 12.6, and 10.7% at 0.78, 5.2, 104, and 1040 μg/L. This assay is utilized in conjunction with algal cell counts and mouse bioassays to monitor water bodies for public health purposes. The rationale used in employing these methods is discussed. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 151–154, 1999

Deoxycylindrospermopsin, an analog of cylindrospermopsin from Cylindrospermopsis raciborskii

Cylindrospermopsin (CYN) is a hepatotoxic alkaloid found in the blue–green alga Cylindrospermopsis raciborskii (C. raciborskii). Data indicating CYN alone does not account for the toxicity of freeze dried cultures of C. raciborskii have been presented recently. In an attempt to explain these data, we have purified and characterized the structure of an analog of CYN, deoxycylindrospermopsin (deoxy‐CYN). Three mice dosed intraperitoneally (IP) with 0.8 mg/kg of deoxy‐CYN showed no toxicity after 5 days. Comparison with the toxicity of CYN (5 day median lethal dose approximately 0.2 mg/kg IP) and its relative abundance in C. raciborskii suggest deoxy‐CYN does not contribute significantly to the toxicity of C. raciborskii. The additional toxicity of freeze dried C. raciborskii over pure CYN, therefore, remains unexplained. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 163–165, 1999

Cylindrospermopsin, A cyanobacterial alkaloid: Evaluation of its toxicologic activity

This paper describes the natural occurrence of the toxin, cylindrospermopsin, in two species of cyanobacteria found in Australia. The structure and chemical properties of this compound are described along with a nontoxic analog of cylindrospermopsin. The results of both intraperitoneal (IP) and oral dosing of mice show that hepatotoxicity is the main effect of cylindrospermopsin in vivo, but that a thrombohemorrhagic phenomenon is observed in a proportion of dosed animals. It has been shown that the toxin can be metabolized in vivo and that a bound metabolite occurs in the liver. Cytotoxicity experiments using cell cultures show that cylindrospermopsin is more cytotoxic to isolated rat liver hepatocytes than to other cell types. Risk assessment calculations show that guideline values for cylindrospernopsin in drinking water should lie in the low microgram per liter range.

The oral toxicity for mice of the tropical cyanobacterium Cylindrospermopsis raciborskii (Woloszynska)

Exposure of humans and domestic animals to Cylindrospermopsis raciborskii and its associated toxin cylindrospermopsin in their drinking water will normally be by ingestion. Studies of the cyanobacterium to date have involved dosing mice by the intraperitoneal route, which excludes the possible influence on its toxicity of the alimentary tract barrier. In the present study, outbred MF1 male mice were fasted overnight and then given a single oral dose suspended in normal saline of freeze‐dried C. raciborskii culture containing 0.2% cylindrospermopsin. The median lethal dose was in the range 4.4–6.9 mg/kg alkaloid equivalent. Death occurred from 2 to 6 days after dosing, and pathological changes included marked fatty liver, often with periacinar coagulative necrosis, acute renal tubular necrosis, atrophy of the thymic cortex and the lymphoid follicles in the spleen, subepicardial and myocardial hemorrhages, and multiple ulcerations of the esophageal part of the gastric mucosa. The syndrome was consistent with that already reported for cylindrospermopsin dosed parenterally. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 135–142, 1999

Persistent Lipophilic Contaminants and Other Chemical Residues in the Southern Hemisphere

Data on the levels of persistent lipophilic contaminants and other chemicals have been reviewed and the dominant persistent lipophilic contaminants in the Southern Hemisphere found to be the chlorohydrocarbons commonly described as the DDTs, HCHs, and the PCBs. The distribution patterns suggest that long-range transport, probably by global distillation, occurred with these substances. Endosulfan residues appear significant in areas of usage but the data are limited. The data are in accord with a reduction in usage of chlorohydrocarbons in developed countries, but an increase in usage in many tropical countries. A systematic comparison of data on the northern and southern hemispheres indicates that the northern hemisphere is generally more contaminated than the southern hemisphere. It also suggests that the process of equilibration between the two hemispheres is relatively slow. In addition, with the HCBs there is an equatorial to polar gradation in concentration probably as a result of global distillation...

Pesticides in Sediments From Queensland Irrigation Channels and Drains

Abstract Pesticide concentration in sediment from irrigation areas can provide information required to assess exposure and fate of these chemicals in freshwater ecosystems and their likely impacts to the marine environment. In this study, 103 sediment samples collected from irrigation channels and drains in 11 agricultural areas of Queensland were analysed for a series of past and presently used pesticides including various organochlorines, synthetic pyrethroids, benzoyl ureas, triazines and organophosphates. The most often detected compounds were endosulphans (α, β and/or endosulphan sulphate) which were detectable in 78 of the 103 samples and levels ranged from below the limit of quantification (0.1 ng g−1 dw) up to 840 ng g−1 dw. DDT and its metabolites were the second most often detected pesticide investigated (74 of the 103 samples) with concentrations up to 240 ng g−1 dw of ∑DDTs. Mean ∑endosulphan and ∑DDT concentrations were 1–2 orders of magnitude higher in sediments from the irrigation areas which are dominated by cotton cultivation compared to those which are dominated by sugarcane cultivation. In contrast to these insecticides, the herbicides diuron, atrazine and ametryn were the compounds which were most often detected in sediments from irrigation drains in sugarcane areas with maximum concentrations in areas of 120, 70 and 130 ng g−1 dw, respectively. In particular during flood events, when light is limiting, transport of these photosynthesis inhibiting herbicides from the sugarcane cultivation areas to the marine environment may result in additional stress of marine plants.