Differences In Relative Toxicity Research Articles

Model of the Origin of a Ciguatoxic Grouper (Plectropomus leopardus)

Published data were used to model the transfer of ciguatoxins (CTX) across three trophic levels of a marine food chain on the Great Barrier Reef (GBR), Australia, to produce a mildly toxic common coral trout (Plectropomus leopardus), one of the most targeted food fishes on the GBR. Our model generated a 1.6 kg grouper with a flesh concentration of 0.1 µg/kg of Pacific-ciguatoxin-1 (P-CTX-1 = CTX1B) from 1.1 to 4.3 µg of P-CTX-1 equivalents (eq.) entering the food chain from 0.7 to 2.7 million benthic dinoflagellates (Gambierdiscus sp.) producing 1.6 pg/cell of the P-CTX-1 precursor, P-CTX-4B (CTX4B). We simulated the food chain transfer of ciguatoxins via surgeonfishes by modelling Ctenochaetus striatus feeding on turf algae. A C. striatus feeding on ≥1000 Gambierdiscus/cm2 of turf algae accumulates sufficient toxin in <2 days that when preyed on, produces a 1.6 kg common coral trout with a flesh concentration of 0.1 µg/kg P-CTX-1. Our model shows that even transient blooms of highly ciguatoxic Gambierdiscus can generate ciguateric fishes. In contrast, sparse cell densities of ≤10 Gambierdiscus/cm2 are unlikely to pose a significant risk, at least in areas where the P-CTX-1 family of ciguatoxins predominate. The ciguatera risk from intermediate Gambierdiscus densities (~100 cells/cm2) is more difficult to assess, as it requires feeding times for surgeonfish (~4-14 days) that overlap with turnover rates of turf algae that are grazed by herbivorous fishes, at least in regions such as the GBR, where stocks of herbivorous fishes are not impacted by fishing. We use our model to explore how the duration of ciguatoxic Gambierdiscus blooms, the type of ciguatoxins they produce, and fish feeding behaviours can produce differences in relative toxicities between trophic levels. Our simple model indicates thresholds for the design of risk and mitigation strategies for ciguatera and the variables that can be manipulated to explore alternate scenarios for the accumulation and transfer of P-CTX-1 analogues through marine food chains and, potentially, for other ciguatoxins in other regions, as more data become available.

Indoor PM2.5 from occupied residences in Sweden caused higher inflammation in mice compared to outdoor PM2.5.

We spend most of our time indoors; however, little is known about the effects of exposure to aerosol particles indoors. We aimed to determine differences in relative toxicity and physicochemical properties of PM2.5 collected simultaneously indoors (PM2.5 INDOOR ) and outdoors (PM2.5 OUTDOOR ) in 15 occupied homes in southern Sweden. Collected particles were extracted from filters, pooled (indoor and outdoor separately), and characterized for chemical composition and endotoxins before being tested for toxicity in mice via intratracheal instillation. Various endpoints including lung inflammation, genotoxicity, and acute-phase response in lung and liver were assessed 1, 3, and 28 days post-exposure. Chemical composition of particles used in toxicological assessment was compared to particles analyzed without extraction. Time-resolved particle mass and number concentrations were monitored. PM2.5 INDOOR showed higher relative concentrations (μg mg-1 ) of metals, PAHs, and endotoxins compared to PM2.5 OUTDOOR . These differences may be linked to PM2.5 INDOOR causing significantly higher lung inflammation and lung acute-phase response 1day post-exposure compared to PM2.5 OUTDOOR and vehicle controls, respectively. None of the tested materials caused genotoxicity. PM2.5 INDOOR displayed higher relative toxicity than PM2.5 OUTDOOR under the studied conditions, that is, wintertime with reduced air exchange rates, high influence of indoor sources, and relatively low outdoor concentrations of PM. Reducing PM2.5 INDOOR exposure requires reduction of both infiltration from outdoors and indoor-generated particles.

Effects of Bioavailable Heavy Metal Species, Arsenic, and Acid Drainage from Mine Tailings on a Microbial Community Sampled Along a Pollution Gradient in a Freshwater Ecosystem

Sediment and water samples representing a pollution gradient in a long, narrow lake polluted at one end by heavy metals, arsenic, and acid drainage from mine tailings, together with samples from an unpolluted reference lake, were analyzed to determine effects of pollutants on the microbial community of the polluted lake. Ribosomal ribonucleic acid, fatty acid, and phospholipid analyses, along with assays of CO2 production, denitrification, and enzyme activities, were performed to characterize the microflora; and environmental conditions were defined by various physicochemical analyses, including determination of bioavailable metal species. Mine waste pollution fostered the growth of Holophagal Acidobacteria, green sulphur bacteria, and α-Proteobacteria but inhibited numerous other types of microorganisms, reducing the overall productivity, biomass, and biodiversity of the microflora. The beneficial effects imply toleration of pollutants, suppression of competing or antagonistic species, and utilization of biogenic sulphide; and the toxic effects are attributable to bioavailable metals, arsenic, and sulphuric acid produced by oxidation of sulphides. The bioavailability and toxicity of sediment-bound metals were evidently increased by acidification, elevation of sediment Eh, and inhibition of metal-immobilizing bacteria by pollutants but were decreased by metal-scavenging oxyhydroxides, sulphide, and organic matter. Metal toxicity also depended on specific metal properties (e.g., electronegativity), providing a basis for inferring mechanisms of toxicity and oxidation states of metals and explaining differences in relative toxicity. The pollutants harmed the ecosystem as a whole by inhibiting microorganisms that performed crucial ecological functions, notably oxygen-releasing photosynthesis, decomposition and humification of organic matter, nutrient recycling, and control of metal availability.

Impact of Currently Used or Potentially Useful Insecticides for Canola Agroecosystems on &lt;I&gt;Bombus impatiens&lt;/I&gt; (Hymenoptera: Apidae), &lt;I&gt;Megachile rotundata&lt;/I&gt; (Hymentoptera: Megachilidae), and &lt;I&gt;Osmia lignaria&lt;/I&gt; (Hymenoptera: Megachilidae)

Pest management practices may be contributing to a decline in wild bee populations in or near canola (Brassica napus L.) agroecosystems. The objective of this study was to investigate the direct contact toxicity of five technical grade insecticides--imidacloprid, clothianidin, deltamethrin, spinosad, and novaluron--currently used, or with potential for use in canola integrated pest management on bees that may forage in canola: common eastern bumble bees [Bombus impatiens (Cresson); hereafter bumble bees], alfalfa leafcutting bees [Megachile rotundata (F.)], and Osmia lignaria Cresson. Clothianidin and to a lesser extent imidacloprid were highly toxic to all three species, deltamethrin and spinosad were intermediate in toxicity, and novaluron was nontoxic. Bumble bees were generally more tolerant to the direct contact applications > O. lignaria > leafcutting bees. However, differences in relative toxicities between the three species were not consistent, e.g., whereas clothianidin was only 4.9 and 1.3x more toxic, deltamethrin was 53 and 68x more toxic to leafcutting bees than to bumble bees and O. lignaria, respectively. Laboratory assessment of direct contact toxicity, although useful, is only one measure of potential impact, and mortality under field conditions may differ greatly depending on management practices. Research conducted using only honey bees as the indicator species may not adequately reflect the risk posed by insecticides to wild bees because of their unique biology and differential susceptibility. Research programs focused on determining nontarget impact on pollinators should be expanded to include not only the honey bee but also wild bee species representative of the agricultural system under investigation.

Comparison of Methyl Bromide LD50s of Codling Moth (Lepidoptera: Tortricidae) on Nectarine Cultivars as Related to Natural Variation

Responses of codling moth ( cydia pomonela L. ) fumigated with methyl bromide on 9 nectarine, prunuspersico (L.) Batsch variety nucipersico Schneid., cultivars indicated no significant differences in relative toxicity at LD50s based on response ratios and their respective 95% CL. Previous significant differences among the cultivars based on failure of 95%CLs of LD50s to overlap may reflect natural variation rather than differences in insect response among the cultivars. We conclude that, for quarantine purposes, varietal testing cannot provide definitive conclusions regarding differences in insect response on cultivars unless the influence of natural variation on test results is evaluated.

Chemical softness and acute metal toxicity in mice and Drosophila

Correlations reported by Jones and Vaughn (1978) between chemical softness parameters and LD50s for metal compounds in rodents have been confirmed and extended. In the present study 14-day LD50s for mice were determined under uniform experimental conditions for 24 metal salts injected ip. For certain ions the correlation between the LD50 and the Pearson and Mawby (1967) softness parameter, σ p is better than that obtained by Jones and Vaughn (1978) using data from diverse sources. Notably, however, we found no orrelation for the alkaline-earth metals either with σ p or with other softness parameters. In parallel experiments with the same metal compounds, we also found correlations between σ p and 4-day LC50s for Drosophila exposed to the salts in their food. For both the mouse and Drosophila, soft ions were generally found to be more toxic than hard ions such that their rankings are significantly correlated. Several differences in relative toxicities of the metal ions were found to occur between mice and Drosophila, and some interpretations of these findings are give. Correlations between toxicity and physicochemical parameters of toxic materials can offer insights into biochemical mechanisms of toxicity and may be useful in predicting toxicity.

Partition distribution of insecticides as a critical factor affecting their rates of absorption from water and relative toxicities to fish.

Loaches, Misgurnus anguillicaudatus (Cantor), a common fish in Taiwan, were treated with DDT, dieldrin, and monocrotophos by continuous exposure in aqueous solutions (or suspensions) and by injection. DDT and dieldrin were 150 and 220 times more toxic, respectively, than monocrotophos, to the fish exposed in aqueous solutions (24-hr LC50), but only 1/9 and 1/4 as toxic as monocrotophos by injection (24-hr LD50). Results of GLC analyses indicate that, at the end of 24-hr exposure, 96.5% of DDT, 92.7% of dieldrin, and 14.3% of monocrotophos were absorbed by loaches from aqueous solutions. The initial rates of absorption for DDT and dieldrin were about 10 to 20 times faster than that for monocrotophos. The large differences in relative toxicity may be due to partition distribution which in turn caused differences in absorption, as DDT and dieldrin are lipophilic and monocrotophos is hydrophilic. Statistical analysis of the relationship between fish toxicities and partition coefficients supports the present finding. The coefficient of correlation is 0.70 between parition coefficients (benzene/water) and toxicities to fish (rainbow trout) of 12 organophosphorus insecticides, 0.74 between coefficients and corrected fish toxicities, and 0.96 between partition coefficients and corrected fish toxicities for organophosphates only. Results of analyses are significant at less than 1% probability level. Similar correlation was also obtained between partition coefficients for hexane/water and toxicities of 8 organophosphorus and 5 organochlorine insecticides to rainbow trout.

Relative Toxicity of Three Homologous Series of Nonionic Surfactants in the Planarian

An investigation on the toxicity of three homologous series of nonionic surfactants was carried out using planarian Dugesia lugubris (O. Schmidt). The surfactants used in this study were polyoxyethylene stearic acid esters, polyoxyethylene sorbitan fatty acid partial esters, and polyoxyethylene alkyl ethers. The effect of surfactant concentration (C) on time of death (T) of planarian can be described by a regression equation, where 1/T is linearly related to C. Analysis of variance of 1/T showed that each regression was highly significant and that deviations from linearity were not significant. The behavior of the polyoxyethylene stearic acid esters and polysorbates was in good agreement with the Levy-Gucinski theory, which describes the effect of toxic agents on goldfish. No agreement with the same theory was shown by surfactants of the polyoxyethylene alkyl ethers, whose regression lines, in the C range 0.05-1.0%, failed to intersect the origin. Statistical differences in relative toxicity between the members of each series were assessed. In the polyoxyethylene stearic acid esters, a linear relationship between the length of the polyoxyethylene chain and lethal time was detected. Relative toxicity in the polysorbates decreases in the order of the 20, 40, 60, and 80 esters, thereby depending on the nature of the esterifying acid (lauric, palmitic, stearic, and oleic, respectively). No clear-cut pattern was found with the polyoxyethylene alkyl ethers; differences in relative toxicity between the ethers of the series were not statistically significant. The present study is indicative of the utility of the planarian in biopharmaceutical research.

THE INSECTICIDAL ACTIVITY OF SUBSTANCES RELATED TO THE PYRETHRINS

The toxicity as contact insecticides of the esters of (±)‐3‐methyl‐2‐allyl‐cycfopent‐3‐en‐4‐ol‐i‐one with the natural (+)‐trans and with synthetic (±)‐cis‐trans‐chrysaii‐themum monocarboxylic acids has been compared with that of the natural pyrethrins. The comparison was carried out on five species of test‐insects.It was found that the figure for both the absolute and the relative toxicities of these compounds varied with the species used as test‐subject.The factors involved in this variation are discussed. The extremes of variation of relative toxicity for the compounds with the natural acid were from about one‐eighth as toxic as the pyrethrum standard when the aphid Macrosiphum solanifolii was used as test subject to nearly four times as toxic as the standard with the larvae of the moth Plutella maculipennis. The fully synthetic material varied from about one‐sixteenth as toxic as the standard to Macrosiphum solanifolii to nearly twice as toxic to the larvae of Plutella maculipennis. The compound with the natural acid was approximately twice as toxic as the fully synthetic material to three of the insect species, but the fully synthetic material was considerably more than half as toxic as the partially synthetic to the fourth test‐species. It is pointed out that while it is widely recognized that large differences in relative toxicity may occur when the effect of chemicals of widely different structure and mechanism of action are compared on a number of different test‐species, the fact that these differences may also occur with related chemicals with, presumably, a similar mechanism of action, has not been clearly stated.Even when the differences in relative toxicity are taken into account, the two synthetic pyrethrin‐like esters still show high insecticidal activity.It seems reasonable to suppose from the results that economic commercial synthesis of pyrethrin‐like insecticides is not impossible.