Use of whole-body and subcellular Cu residues of Lumbriculus variegatus to predict waterborne Cu toxicity to both L. variegatus and Chironomus riparius in fresh water

We tested the use of whole-body and subcellular Cu residues (biologically-active (BAM) and inactive compartments (BIM)), of the oligochaete Lumbriculus variegatus to predict Cu toxicity in fresh water. The critical whole-body residue associated with 50% mortality (CBR₅₀) was constant (38.2-55.6 μg g⁻¹ fresh wt.) across water hardness (38-117 mg L⁻¹ as CaCO₃) and exposure times during the chronic exposure. The critical subcellular residue (CSR₅₀) in metal-rich granules (part of BIM) associated with 50% mortality was approximately 5 μg g⁻¹ fresh wt., indicating that Cu bioavailability is correlated with toxicity:subcellular residue is a better predictor of Cu toxicity than whole-body residue. There was a strong correlation between the whole-body residue of L. variegatus (biomonitor) and survival of Chironomus riparius (relatively sensitive species) in a hard water Cu co-exposure. The CBR₅₀ in L. variegatus for predicting mortality of C. riparius was 29.1-45.7 μg g⁻¹ fresh wt., which was consistent within the experimental period; therefore use of Cu residue in an accumulator species to predict bioavailability of Cu to a sensitive species is a promising approach.     

Enantioselectivity of racemic metolachlor and S-metolachlor in maize seedlings

Chiral herbicides may have enantioselective effects on plants. In this study, we assessed and compared the enantioselectivity of the chiral herbicides rac-metolachlor and S-metolachlor to maize seedlings. The superoxide dismutase activity (SOD) activity of roots and stem leaves treated by rac-metolachlor was 1.38 and 1.99 times that of roots and stem leaves treated by S-metolachlor. The peroxidase activity (POD) activity of roots and stem leaves was 1.48 and 2.79 times that of roots and stem leaves treated by S-metolachlor, respectively, while the catalase activity (CAT) activity was 4.77 and 8.37 times greater, respectively. The Hill reaction activity of leaves treated by rac-metolachlor were 1.45, 1.33, and 1.14 times those treated by S-metolachlor with treatments of 18.6, 37.2, and 74.4 μM. The differences observed between treatments of rac- and S-metolachlor were significant. Significant differences in maize seedling morphology were also observed between rac- and S-metolachlor treatments. The degradation rate of S-metolachlor in roots was greater than that of rac-metolachlor. The half-lives of rac- and S-metolachlor were 80.6 and 60.3 h at 18.6 μM; 119.5 and 90 h at 37.2 μM; and 169 and 164.8 h at 74.4 μM, respectively. Using the liquid chromatography-mass spectrometry method, hydroxymetolachlor, deschlorometolachlor and deschlorometolachlor propanol were considered to be possible metabolites. We determined the enantioselective toxicity of rac- and S-metolachlor to maize and speculated on the proposed metabolic pathway of metolachlor in maize roots. These results will help to develop an understanding of the proper application of rac- and S-metolachlor in crops, and give some information for environmental safety evaluation of rac- and S-metolachlor.     

An overview of the latest development of microencapsulation for agricultural products

Abstract

For the production of controlled‐release agricultural formulations microencapsulation technologies are now the most used. Over the past two decades enormous progress has been made in order to develop the technologies which allow us to produce formulations tailor made to reach the target and fitting our toxicological requirements. This lecture is devoted to the definition of the criteria for selection of an active ingredient for microencapsulation and to a detailed review of the various techniques used today in commerçai microencapsulated formulations.

Resources are increasingly allocated into microencapsulation research & development by many agrochemical companies. Therefore the next 20 years should continue to yield innovative ideas including significant improvement of the physico‐chemical and toxicological properties of the actual formulations on the market. Some of this new ideas are applied by our company in order to modify or improve those properties playing the key role in the intent for targeted activity:

√ Recombination during production or upon storage.

New protective colloides

Dermal toxicity (LD 50) ‐ secondary protective colloides.

√ Release rate parameters.

Modification by the change of mobility of the active ingredient from the core (solvent or fluid type) affecting transit time and therefore LD 50 values.

√ Oral toxicity (LD 50).

Graft copolymers irreversibly adsorbed to the capsule surface.     

Pentachlorotoluene and pentabromotoluene: Results of a subacute and a subchronic toxicity study in the rat

Abstract

Pentachlorotoluene (PCT) and pentabromotoiuene (PBT) are environmental contaminants detected in the Great Lakes ecosystem. In view of the paucity of toxicity data and the potential for human exposure, a subacute (28 day) and a subchronic (91 day) study were conducted in the rat. In the subacute study, groups of 10 male and 10 female rats were fed the diet containing PCT or PBT at 0, 0.5, 5.0, 50 or 500 ppm for 28‐days. In the subchronic study, the group size was increased to 15, the dose levels were 0, 0.05, 0.5, 5.0, 50 and 500 ppm in the diet and the exposure period was 91 days. Growth rate and food consumption were not affected by exposure to either chemical in the subacute and subchronic study. Clinical observations revealed no abnormalities. Decreased hemoglobin was observed in female rats fed 5.0 ppm PCT and higher levels in the subacute (28 day) study. In the same study the hematocrit value and erythrocyte numbers of females fed 5.0 or 500 ppm PCT diets were significantly lower than the control. In both subacute and subchronic studies mild dose‐dependent histopathological changes were observed in the thyroid, liver and kidney of rats fed PCT and PBT diets. In general male rats were more susceptible than females to the treatment of PCT and PBT. Based on these data, it was concluded that the no observable adverse effect level for PCT was 50 ppm in the diet (3.5 mg/kg b.w./day) and that of PBT was 5.0 ppm (0.35 mg/kg b.w./day).     

Oxidative stress and genotoxicity of 1-methyl-3-octylimidazolium chloride on loach (Misgurnus anguillicaudatus)

This study was a preliminary step to evaluate the acute toxicity of 1-methyl-3-octylimidazolium chloride ([C₈mim]Cl) on loach (Misgurnus anguillicaudatus) by determining the effects on hepatic antioxidant enzyme activities and by the comet assay. The results showed that [C₈mim]Cl had acute toxicity at concentrations above 20 mg L^?1, inducing oxidative stress and genotoxicity on fish liver cells. In respect to enzyme activities, [C₈mim]Cl induced changes in the activities of superoxide dismutase, catalase, and glutathione content the livers of fish exposed at 20–80 mg L^?1. [C₈mim]Cl at the same exposure level caused a remarkable increase in malondialdehyde level. The comet assay indicated that [C₈mim]Cl at 20–80 mg L^?1 induced genotoxicity in liver cells. With increased exposure concentration and time, the two comet parameters trailing rate and tail moment were significantly increased, with significant differences (P < 0.05) observed between control group and each treatment group. The present study shows that ionic liquids can be a threat to the health of aquatic organism when accidentally released to aquatic ecosystems.     

Predicting molybdenum toxicity to higher plants: Estimation of toxicity threshold values

Four plant species (oilseed rape, Brassica napus L.; red clover, Trifolium pratense L.; ryegrass, Lolium perenne L.; and tomato, Lycopersicon esculentum L.) were tested on ten soils varying widely in soil properties to assess molybdenum (Mo) toxicity. A larger range (66-fold-609-fold) of added Mo concentrations resulting in 50% inhibition of yield (ED₅₀) was found among soils than among plant species (2-fold-38-fold), which illustrated that the soils differed widely in the expression of Mo toxicity. Toxicity thresholds based on soil solution Mo narrowed the variation among soils compared to thresholds based on added Mo concentrations. We conclude that plant bioavailability of Mo in soil depends on Mo solubility, but this alone did not decrease the variability in observed toxicity enough to be used in risk assessment and that other soil properties influencing Mo toxicity to plants need to be considered.     

采油用油田化学剂对鱼类的急性毒性实验研究

以白鲢鱼为实验生物,采用半静态实验方法,研究了几种油田化学剂的半致死浓度和安全浓度。研究表明:防膨剂、杀菌剂K、杀菌剂L、清蜡剂、四氟硼酸、酸化缓蚀剂、阻垢剂、阻垢缓蚀剂、缓蚀阻垢剂和破乳剂的96h半致死浓度LC50值分别为0.68、1.6、9.3、25、123、510、620、3240、4570、7410mg/L。根据化学物质对鱼类毒性物质分级标准,防膨剂属于剧毒物质;杀菌剂K、杀菌剂L和清蜡剂属于高毒物质;四氟硼酸、酸化缓蚀剂和阻垢剂属于中毒物质;阻垢缓蚀剂、缓蚀阻垢剂和破乳剂属于低毒物质。这几种油田化学剂的安全浓度为0.068～741mg/L。此研究可为评价油田化学剂对水生生物的影响,制定废水排放浓度标准提供依据。     

Large-scale risk assessment of polycyclic aromatic hydrocarbons in shoreline sediments from Saudi Arabia: Environmental legacy after twelve years of the Gulf war oil spill

A large-scale assessment of polycyclic aromatic hydrocarbons (PAHs) from the 1991 Gulf War oil spill was performed for 2002-2003 sediment samples (n = 1679) collected from habitats along the shoreline of Saudi Arabia. Benthic sediment toxicity was characterized using the Equilibrium Partitioning Sediment Benchmark Toxic Unit approach for 43 PAHs (ESBTU_FCV,43). Samples were assigned to risk categories according to ESBTU_FCV,43 values: no-risk (≤1), low (>1-≤2), low-medium (>2-≤3), medium (>3-≤5) and high-risk (>5). Sixty seven percent of samples had ESBTU_FCV,43 > 1 indicating potential adverse ecological effects. Sediments from the 0-30 cm layer from tidal flats, and the >30-<60 cm layer from heavily oiled halophytes and mangroves had high frequency of high-risk samples. No-risk samples were characterized by chrysene enrichment and depletion of lighter molecular weight PAHs, while high-risk samples showed little oil weathering and PAH patterns similar to 1993 samples. North of Safaniya sediments were not likely to pose adverse ecological effects contrary to sediments south of Tanaqib. Landscape and geomorphology has played a role on the distribution and persistence in sediments of oil from the Gulf War.     

Comparative Toxicities of Polar and Non-Polar Organic Fractions From Sediments Affected By the Exxon Valdez Oil Spill in Prince William Sound,Alaska

Abstract

Standardized tests were applied to aromatic and polar fractions of sediment extracts to determine whether polar constituents or oxidative degradation products contributed significantly to the toxicity of sediments oiled by the Exxon Valdez spill. Intertidal sediment and pore-water samples were collected in September 1990 from two heavily oiled sites and an unoiled site in Prince William Sound (PWS). Methylene chloride extracts from these samples were fractionated by liquid chromatography into aliphatic, aromatic and polar fractions, and the aromatic and polar fractions were tested for toxicity using the Microtox^R test, bivalve larval mortality and development (Mytilus); several measures of genotoxicity in Mytilus, including SOS Chromotest^R, anaphase aberrations and sister chromatid exchange; and survival, anaphase aberrations and teratogenicity in coho salmon (Onchorhynchus kisutch). Microtox^R and SOS Chromotest^R protocols were applied in a screening mode to all samples, whereas other tests were applied only to selected fractions from two sites. Samples from Bay of Isles (oiled) were consistently more toxic (usually only 2 to 5-fold) than the Mooselips Bay (unoiled) samples, which gave very low responses in all tests. for both sites, however, responses to polar and aromatic fractions were about the same in most tests, suggesting that while the overall toxicity of the oil was low in these samples, at least part of that toxicity was derived from polar constituents. Compared to the parent hydrocarbons, polar oxidation products partition preferentially into pore-water and are more rapidly diluted and dispersed in the water column. These results suggest that polar oxidation products of petroleum hydrocarbons pose little risk to marine organisms, except possibly for infauna continuously exposed to pore-water in heavily oiled sediments. Independent surveys showed that sediment toxicity in PWS declined during 1989–1991 to near background levels, in accord with previous understanding of oil weathering and toxicity.     

Acute toxicity and ecotoxicological risk assessment of rice pesticides to Lithobates catesbeianus tadpoles

The objective of this study was to determine the acute toxicity of some pesticides used in irrigated rice farming to Lithobates catesbeianus tadpoles. The LC_50-96h for commercial formulations containing bentazon, penoxsulam, vegetable oil, permethrin and carbofuran, separately and their mixtures, were determined at the proportions commonly used in the field. The limits of risk concentrations of these products for the studied species were also established. The LC_50-96h for tadpoles was 4,530 mg L^?1 for bentazon; 7.52 mg L^?1 for penoxsulam + 145.66 mg L^?1 of vegetable oil; 81.57 mg L^?1 for vegetable oil; 0.10 mg L^?1 for permethrin; 29.90 mg L^?1 for carbofuran (active ingredients), and 38.79 times the dose used in the field for the mixture of these products. The environmental risk was determined only for permethrin, and care should be taken when using the vegetable oil.