Chlorosilane Acute Inhalation Toxicity and Development of an LC50 Prediction Model

The acute inhalation toxicity of 10 chlorosilanes was investigated in Fischer 344 rats using a 1-h whole-body vapor inhalation exposure and a 14-day recovery period. The median lethal concentration (LC50₁) for each material was calculated from the nominal exposure concentrations and mortality. Experimentally derived LC50₁ values for monochlorosilanes (4257–4478 ppm) were greater than those for dichlorosilanes (1785–2092 ppm), which were greater than those for trichlorosilanes (1257–1611 ppm). Apparent was a strong structure-activity relationship (r² = .97) between chlorine content and LC50₁ value. Estimated LC50₁ values for mono-, di-, and trichlorosilanes were determined to be 3262, 1639, and 1066 ppm, respectively, utilizing this relationship and the lower limit of the 95% prediction interval. The LC50₁ values determined in this series of studies were greater than that reported for hydrogen chloride (3124 ppm), when expressed on a chlorine equivalence basis (3570–5248 ppm), demonstrating that the acute toxicity of these chlorosilanes is similar to or less than that for hydrogen chloride. The good correlation between chlorine content and LC50₁ provides a sound basis for estimation of LC50₁ for chlorosilanes not already evaluated. The use of structure–activity relationships is consistent with the chemical industry and federal agency initiatives to reduce, refine, and/or replace the use of animals in testing without compromising the quality of health and safety assessments.     

Estimation of toxicity to marine species with structure-activity models developed to estimate toxicity to freshwater fish

Structure-activity models which were developed to estimate toxicity of chemicals to freshwater fish were tested for use with an estuarine fish (Cyprinodon variegatus) and mysids (Mysidopsis bahia). Significant linear and polynomial relationships that correlated well existed between reported 96-h LC₅₀ values for each marine species and log P (log octanol/water partition coefficient). Good linear relationships were obtained when the 96-h LC₅₀ values for C. variegatus and M. bahia were regressed on water solubility (μmol/l). These models were compared to models developed for freshwater fish using log P and log S. Models using log P to estimate acute toxicity for two freshwater fish produced 96-h LC₅₀ values similar to those measured for C. variegatus and M. bahia, whereas, those models developed with water solubility produced 96-h LC₅₀ values similar to those for C. variegatus, but not for M. bahia. The data indicated that models developed with log P for freshwater fish can be used to estimate toxicity to C. variegatus for a minimum of 58% of the chemicals, whereas models using water solubility estimated toxicity to C. variegatus for a minimum of 77% of the chemicals within an order of magnitude for screening purposes. The calculated 96-h LC₅₀ values were compared to the measured values for each marine species and those measured for Pimephales promelas (fathead minnow) and Poecilia reticulata (guppy). Tests indicated generally that calculated 96-h LC₅₀ values were overestimates of the measured 96-h LC₅₀ values when models for freshwater fish were used to estimate toxicity to each marine species. More data are required for marine species to determine if highly significant relationships between marine and freshwater fish exist with comparisons using larger sample sizes.     

Acute toxicity tests using rotifers. III. Effects of temperature,strain, and exposure time on the sensitivity of Brachionus plicatilis

As part of the development of a standardized acute toxicity test, the effect of cyst age, strain, temperature, and exposure time on the toxicity of 21 chemicals to the estuarine rotifer Brachionus plicatilis was investigated. Toxicity was chemical specific, with LC₅₀s ranging from 0.061 mg · L^?1 for mecury to 598 mg · L^?1 for 2,4-dichlorophenoxyacetic acid. Intralaboratory coefficients of variation averaged 11%, at least three times lower than for other aquatic invertebrate acute tests. The age of rotifer cysts stored up to 27 months had no effect on the sensitivity of test animals, but significant differences in sensitivity were detected among rotifer strains. Test temperatures of 25, 30, and 35°C generally yielded lower LC₅₀s than at 20°C. LC₅₀s decreased by 80–90% for cadmium and pentachlorophenol when toxicant exposure time was increased from 24 to 72 h. Life table analysis of rotifer survival in the controls revealed that 72 h is the longest acute test possible without feeding. A comparison of the sensitivity of the rotifer test to that of sea urchin (Arabacia punctulata) early embryo, sea urchin sperm cell, Microtox®, and Mysidopsis bahia tests revealed comparability for several compounds. However, no species is consistently the most sensitive to all compounds.     

Acute lethal toxicity of hydrocarbons and chlorinated hydrocarbons to two planktonic crustaceans: The key role of organism-water partitioning

The acute toxicities of 38 hydrocarbons and chlorinated hydrocarbons were determined for two planktonic crustaceans, freshwater Daphnia magna and saltwater Artemia. In both cases median lethal concentrations (LC₅₀ values) at 48 h and 24 h, respectively, were strongly correlated with aqueous solubility, there being little direct dependence on chemical structure. In the case of solid chemicals, it is suggested that the appropriate correlating solubility is that of the subcooled liquid chemical, not that of the solid. Many solids constrained by low water solubility are thus unable to achieve dissolved concentrations sufficient to cause acute toxicity to the test organisms. It is hypothesised that acute toxicity is non-selective and is controlled by organism-water partitioning so that each hydrocarbon group may contribute equally to toxicity and no single group of hydrocarbons is the dominant toxicant.The partitioning characteristics are expressed in two mathematical models which relate the LC₅₀ to the chemical properties of solubility and molar volume.     

The effects of bayluscide and malathion on the mortality and infectivity of Schistosoma mansoni cercariae

Laboratory experiments were conducted to assess the effects of bayluscide and malathion on the mortality and infectivity of Schistosoma mansoni cercariae. Mortality of cercariae varied with time of exposure and concentration of tested chemicals. The LC₅, LC₅₀, and LC₉₅ for bayluscide were 0.04, 0.07, and 0.10 ppm after 2 h of exposure; 0.03, 0.04, and 0.06 ppm after 4 h of exposure; and 0.02, 0.03, and 0.05 ppm after 6 h of exposure, respectively. Malathion gave LC₅, LC₅₀, and LC₉₅ values of 59.16, 107.07, and 193.78 ppm after 2 h of exposure; and 39.79, 69.36, and 120.89 ppm after 4 h of exposure, respectively. Sublethal concentrations of bayluscide and malathion significantly reduced the rate of infection of laboratory mice by S. mansoni cercariae (p < 0.01). Approximately 1.50 and 0.00% of adult worms were recovered by autopsy of mice whose cercariae were preexposed for only 1 h to 0.04 ppm of bayluscide and 50.00 ppm of malathion, respectively. These results clearly show that bayluscide is much more toxic to cercariae than to snail intermediate hosts cited in the literature, and that malathion possesses some cercaricidal properties at concentrations expected to be achieved in the field.     

Acute inhalation toxicity of high concentrations of silane in male ICR mice

In order to examine the toxicity of silane, male ICR mice were exposed to silane for 30 min (n=8), 1 or 4 h (n=12) at concentrations of 2500, 5000, 7500 (30-min experiment only) or 10000 ppm. In the 1- and 4-h experiments, 12 mice were divided into two sub-groups: four for 2-day observation and eight for 2-week observation. The mortality was six deaths out of eight mice exposed to 10000 ppm for 4 h. No deaths occurred in any of the other experiments. In the mice sacrificed 2 days after the exposure, acute renal tubular necrosis was observed at 10000 ppm (1-h exposure) or at 2500 ppm or more (4-h exposure). Reduction in body weight, increase in relative kidney weight and blood urea nitrogen (BUN) level, and splenic atrophy and inflammatory changes of the nasal mucosa were also seen in the 10000 ppm-4 h exposure group. In the mice sacrificed 2 weeks after the exposure, tubulo-interstitial nephritis (TIN) developed at 7500 ppm or more (30-min exposure) or at 5000 ppm or more (1- and 4-h exposure). BUN increased in a dose-dependent manner, and BUN in TIN positive mice was significantly higher than that in TIN negative mice (1- and 4-h exposure). No histopathological changes were observed in the glomeruli. These results indicate that the LC₅₀ of silane in mice is between 5000 and 10000 ppm for 4-h exposure and is greater than 10000 ppm for 1-h or 30-min exposure. The target site of silane toxicity is the renal tubule, and the no-observed-effect levels of silane for acute inhalation exposure in mice are 1000 ppm for 4-h exposure (from the previous report of our research group), 2500 ppm for 1-h exposure and 5000 ppm for 30-min exposure.     

Toxicity of selenate and selenite to the potworm <Emphasis Type="Italic">Enchytraeus albidus</Emphasis> (Annelida: Enchytraeidae): a laboratory test

Little information is available about the toxicity of inorganic selenium forms in soil animals. Therefore, the effects of selenate and selenite on the mortality and reproduction of Enchytraeus albidus were examined in standard laboratory tests with chronic exposure. Total and available amount of selenate and selenite were tested in a calcareous loamy chernozem soil. The LC₅₀ of selenate was 5.69 (2.7–8.12) mg kg^-1 dry wt. for total Se and 4.74 (2.14–6.98) mg kg^-1 dry wt. for available Se. Selenite LC₅₀ was as high as 22.5 (19.6–25.7) mg kg^-1 dry wt. for total Se and 8.10 (6.8–9.6) mg kg^-1 dry wt. for available Se. The EC₅₀ of selenate was 0.41 (0.35–0.48) mg kg^-1 dry wt. for total Se and 0.28 (0.24–0.34) mg kg^-1 dry wt. for available Se. Selenite EC₅₀ was as high as 7.3 (6.2–8.5) mg kg^-1 dry wt. for total Se and 2.46 (2.05–2.91) mg kg^-1 dry wt. for available Se. The response in reproduction was more sensitive to Se toxicity than the response in mortality. Selenate proved to be more toxic than selenite. Available data show that E. albidus may function as a biological indicator for some inorganic selenium forms in the soil.     

The toxicity of the three antifouling biocides DCOIT,TPBP and medetomidine to the marine pelagic copepod <Emphasis Type="Italic">Acartia tonsa</Emphasis>

Copepods, the largest group of pelagic grazers, are at risk from exposure to antifouling biocides. This study investigated the toxicity of the antifouling biocides 4,5-dichloro-2-octyl-1,2-thiazol-3(2H)-one (DCOIT), triphenylborane pyridine (TPBP) and 4-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole (medetomidine) to the copepod Acartia tonsa, using mortality and egg production as endpoints. The toxicity ranking for mortality was as follows: DCOIT (LC₅₀ 57 nmol l^?1) = TPBP (LC₅₀ 56 nmol l^?1) > medetomidine (LC₅₀ 241 nmol l^?1). Egg production was more sensitive than mortality to TPBP (EC₅₀ 3.2 nmol l^?1), while DCOIT and medetomidine inhibited egg production at roughly the same concentrations (72 and 186 nmol l^?1 respectively). Furthermore, TPBP seems to affect egg hatching directly which was not the case for DCOIT and medetomidine. DCOIT and medetomidine might pose an environmental risk as they have been reported to occur in different exposure scenarios or analytical surveys at concentrations only 2–3 times lower than the respective EC₁₀. Reported environmental concentrations of TPBP are few but clearly lower than the EC₁₀ values reported here, suggesting current risk of TPBP to copepods to be moderate.     

Hazard/Risk Assessment of Pyridaben: II. Outdoor Aquatic Toxicity Studies and the Water-Effect Ratio

Outdoor acute aquatic toxicity studies with pyridaben and bluegill sunfish (Lepomis macrochirus) and mysid (Mysidopsis bahia) showed that the 96-h LC50s in site-specific water were significantly greater than in classical laboratory studies. In addition, outdoor acute studies showed that pyridaben degrades rapidly in water, in hours, which supports other laboratory and field studies on the fate of pyridaben in aquatic systems. Chronic toxicity to aquatic organisms is not an issue after application in the field because exposures will be brief. The water-effect ratio (WER) of site-specific to laboratory-water 96-h LC50s for L. macrochirus and M. bahia were 18.5 and 24.5, respectively. The lowest WER was used as an application factor with the laboratory LC50 values of several other aquatic organisms to develop adjusted site-specific LC50 values. Comparison of the distribution of adjusted LC50 values with a distribution of potential environmental exposure concentrations for pyridaben in water indicates minimal acute risk to aquatic organisms. When only acute laboratory data are available, the WER approach is a relevant and realistic means for determining an application factor and for estimating the aquatic hazard/risk assessment of non-persistent pesticides, because it considers a host of factors that affect bioavailability and subsequent toxicity.     

Embryonic and developmental toxicity of the ionic liquid 1‐methyl‐3‐octylimidazolium bromide on goldfish

The embryonic developmental toxicity of the ionic liquid (IL) 1‐methyl‐3‐octylimidazolium bromide ([C₈mim]Br) on the goldfish Carassius auratus was evaluated in this study. First, the 72 h 50% lethal concentrations (72 h‐LC₅₀) for [C₈mim]Br in goldfish embryos at the stages of cleavage, early gastrula, closure of blastopore, and heart beating were determined by preliminary acute toxicity tests. After that, fish embryos in different developmental stages (cleavage, early gastrula, closure of blastopore, and heart beating) were exposed to 10.4, 20.8, 41.6, and 104 mg/L of [C₈mim]Br until their hatching stage. The results of the acute toxicity tests showed that 72 h‐LC₅₀ values at the early cleavage, early gastrula, closure of blastopore, and heart beating stages of development were 208.96, 187.1, 245.03, and 298.33 mg/L, respectively. In the subchronic tests, [C₈mim]Br exposure prolonged the duration of embryo dechorionation and decreased the hatching rates of the treated embryos compared to control embryos. In addition, [C₈mim]Br treatment also caused remarkable increases of embryonic malformation and mortality ratio in most treatment groups. Finally, we also found that the embryonic and developmental toxicity of [C₈mim]Br on fish embryos was dose‐response and developmental stage‐specific. These results indicate that [C₈mim]Br has toxic effects on the early embryonic development of goldfish, and the risk to aquatic ecosystem by ILs leaking into the water body must be evaluated in the future. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

INHALATION TOXICITY STUDIES OF AQUEOUS DISPERSION RESIN

Aqueous dispersion resin (ADR) is a water-based acrylate copolymer designed to allow a range of ethanol concentrations for hair-spray formulations. A series of inhalation (whole-body) aerosol toxicity studies, including acute, 9-day, and 90-day exposures, was conducted to determine any toxicological effects for ADR. An acute study of ADR was conducted for 4 h with a 14-day observation period. The maximum ADR aerosol concentration was 1.07 (+/- 0.04) mg/L with a mass medium aerodynamic diameter (MMAD) value of 1.46 mu m and a geometric mean (sigma_g) of 1.42. No deaths or exposure-related lesions were observed. Thus, the LC50 value was greater than 1.07 mg/L. For the 9-day study, each group contained 10 animals/sex and was exposed for 2 h/day. The mean exposure concentrations (+/- standard deviation) were 244 (+/- 39.6), 543 (+/- 71.9), and 843 (+/- 186.2) mg/m³ for the 250-, 500-, and 1000-mg/m³ groups, respectively. The mean MMADs were 2.83, 2.90, and 4.09 mu m for the 250-, 500-, and 1000-mg/m³ groups, respectively, with sigma g values ranging from 3.15 to 6.22. Unkempt fur and alopecia in the males and females from the 1000-mg/m³ group at sacrifice were the only exposure-related clinical signs observed. Increased lung weights in the 500- and 1000-mg/m³ exposure groups were found. Histopathological effects, such as alveolar histiocytosis and interstitial pneumonitis, were also noted in these two exposure groups. For the 90-day study, 10 animals per sex were included in each group with a 6-wk recovery group of 5 female rats/group. Exposures were conducted for 2 h/day. The mean exposure concentrations were 30.4 (+/- 2.3), 102 (+/- 11.6), and 308 (+/- 19.3) mg/m³ with mean MMADs of 3.09, 2.64, and 2.67 mu m and sigma_g values ranging from 3.54 to 3.90 for exposure concentrations of 30, 100, and 300 mg/m³, respectively. The only findings at the 90-day sacrifice were increased lung weights for the males and females in the 300-mg/m³ group and males in the 100-mg/m³ group. For the 6- wk recovery sacrifice of the females, the lung weights for the 300- and 100-mg/m³ groups were increased. Histopathological effects at the 90-day sacrifice included alveolar histiocytosis and lymphadenitis in the mediastinal lymph nodes in the 100- and 300-mg/m³ exposure groups for males and females, while alveolar histiocytosis, intraalveolar cellular debris, lymphadenitis in the mediastinal lymph nodes, and/or interstitial pneumonitis were noted in these 2 exposure groups of the females after the 6-wk recovery period. Animals exposed for 90 days to 100 and 300 mg/m³ for 2 h had increased lung weights. However, no effects were observed in the 30-mg/m³ exposure group. Thus, under the conditions of the present 90-day study, a no-observable-effect level (NOEL) was found to be 30 mg/m³.     

Acute aquatic toxicity of tire and road wear particles to alga,daphnid, and fish

Previous studies have indicated that tire tread particles are toxic to aquatic species, but few studies have evaluated the toxicity of such particles using sediment, the likely reservoir of tire wear particles in the environment. In this study, the acute toxicity of tire and road wear particles (TRWP) was assessed in Pseudokirchneriella subcapita, Daphnia magna, and Pimephales promelas using a sediment elutriate (100, 500, 1000 or 10000 mg/l TRWP). Under standard test temperature conditions, no concentration response was observed and EC/LC₅₀ values were greater than 10,000 mg/l. Additional tests using D. magna were performed both with and without sediment in elutriates collected under heated conditions designed to promote the release of chemicals from the rubber matrix to understand what environmental factors may influence the toxicity of TRWP. Toxicity was only observed for elutriates generated from TRWP leached under high-temperature conditions and the lowest EC/LC₅₀ value was 5,000 mg/l. In an effort to identify potential toxic chemical constituent(s) in the heated leachates, toxicity identification evaluation (TIE) studies and chemical analysis of the leachate were conducted. The TIE coupled with chemical analysis (liquid chromatography/mass spectrometry/mass spectrometry [LC/MS/MS] and inductively coupled plasma/mass spectrometry [ICP/MS]) of the leachate identified zinc and aniline as candidate toxicants. However, based on the high EC/LC₅₀ values and the limited conditions under which toxicity was observed, TRWP should be considered a low risk to aquatic ecosystems under acute exposure scenarios.     

Assessment of the acute toxic effects of the fungicide Ridomil plus 72 on aquatic organisms and soil micro‐organisms

The acute toxic effects of Ridomil plus 72 (Ridomil), used as a fungicide in agriculture, were studied under laboratory conditions. These effects on freshwater cladoceran (Chydorus eurynotus) and freshwater fish (Oreochromis niloticus) were determined using standard bioassay procedures. The 4 h LC₅₀ for Chydorus eurynotus was 6.9 mg/L and the 96 h LC₅₀ for Oreochromis niloticus was 1.1 mg/L. The toxicity of Ridomil to a mixed population of soil micro‐organisms was measured using oxygen uptake and growth as measured by turbidity. At short‐term exposure (48 min), Ridomil was moderately toxic to the culture at 5000 mg/L and above, based on an activity quotient (AQ) of 0.50–0.70. For longer exposure periods (up to 6 h), Ridomil was slightly toxic to the culture at 200 to 500 mg/L. At 1000 mg/L, Ridomil was moderately toxic and at 3000 mg/L and above, Ridomil was extremely toxic to soil microorganisms. The toxicity of metalaxyl (one of the two active ingredients of Ridomil) to these micro‐organisms was measured using growth as measured by the turbidity change. The average toxic endpoint (16 h IC₅₀) was 1100 mg/L. The acute toxic values of Ridomil found in these studies were much below the expected environmental concentrations resulting from normal applications of the chemical on a cocoa tree as a fungicide. ©2000 John Wiley & Sons, Inc. Environ Toxicol 15: 65–70, 2000     

Environmental safety level of lead (Pb) pertaining to toxic effects on grey mullet (Mugil cephalus) and Tiger perch (Terapon jarbua)

Acute and chronic bioassay toxicity test of Lead (Pb) in Grey Mullet (Mugil cephalus), and Tiger perch (Terapon jarbua) was conducted. LC₅₀ values (Lethal Concentration) from acute tests and chronic values were calculated by the geometric mean of the No‐Observed‐Effect Concentration (NOEC) and the Lowest‐Observed‐Effect Concentration (LOEC) in a study period of 30 days. This research was conducted to evaluate the quantitative relationship between toxicity test statistics and correlation between toxicant and the organisms exposed. Three test average LC₅₀ was analyzed for 24, 48, 72, and 96 h and the 96 h average LC₅₀ of M. cephalus and T. jarbua is 2.57 ± 0.47 and 2.99 ± 0.23 mg/L of Pb, respectively. Significant correlation is observed with the increased time duration and exposure concentration. The NOEC and LOEC values were calculated based on survival of test organisms for M. cephalus and T. jarbua and the values are 0.014 and 0.029 and 0.011 and 0.022 mg/L, respectively. The chronic value is found to be 0.011 mg/L for M. cephalus and 0.021 mg/L for T. jarbua. The intensity of biochemical and histological alterations increased gradually with increased Pb concentration and the exposure time. Toxicity testing is the primary step to determine the water quality safe limit on marine organisms. The outcome of the study indicates that the sensitivity of juvenile organisms to Pb, persistence of toxic effects and biomarkers as a tool capable of revealing the toxic effects of heavy metals on the environment and aquatic biota. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 24–43, 2016.     

Effects of selected PAHs on reproduction and survival of the calanoid copepod <Emphasis Type="Italic">Acartia tonsa</Emphasis>

The effects of selected polycyclic aromatic hydrocarbons on the marine calanoid copepod Acartia tonsa were tested in laboratory short-term toxicity tests in order to facilitate risk assessment of those compounds to the marine pelagic environment. Photo-induced toxicity of pyrene was also investigated under naturally relevant UV light regimes. Lethal and sublethal effects on egg production rate, hatching and potential recruitment rate were evaluated after 48 h exposure to fluoranthene, phenanthrene and pyrene. The 48 h-median lethal concentrations (LC₅₀) reducing survival by 50% were 594, 2,366 and >640 nM for fluoranthene, phenanthrene and pyrene, respectively, whilst lower concentrations induced different sublethal effects. Median effective concentrations (EC₅₀) affecting the egg production rate and the recruitment rate were 433 and 385 (fluoranthene), 1,245 and 1,012 (phenanthrene) and 306 and 295 nM (pyrene), respectively. An increase in toxicity of pyrene was detected after incubation under UV light, resulting in LC₅₀ values of 201 nM (24 h) and 138 nM (48 h) and EC₅₀ values of 79 nM (egg production rate) and 41 nM (recruitment rate). Finally, a comparison between effective concentrations and worst-case environmental concentrations reported in literature indicated that pyrene may pose a threat to A. tonsa from exposure in the field, and that the risk of adverse effects is high for fluoranthene.     

Cyst-based toxicity tests. VII. Evaluation of the 1-h enzymatic inhibition test (fluotox) with Artemia nauplii

The newly developed 1-h enzymatic inhibition bioassay (Fluotox) was applied to toxicity testing with the larvae of the brine shrimp Artemia. The method consists of visual observation of in vivo inhibition of an enzymatic process using a fluorigenic enzyme substrate. The 1-h Fluotox test and the conventional 24- and 48-h LC₅₀ toxicity tests were conducted in parallel on 8 different organic and inorganic chemicals. A good correlation was found between the 1-h EC₅₀ and the 24- and 48-h LC₅₀ data with r² s of 0.94 and 0.93 for each respective regression. Addition of the enzyme substrate did not influence the toxicity of the chemicals in the 24- and 48-h tests. The repeatability of the Fluotox test compares favorably with that of the conventional 24-h acute test; coefficients of variation (CV) ranged from 8 to 34% and from 1 to 39%, respectively. Investigations on the applicability of the Fluotox procedure for testing in brackish waters revealed that lowering the salinity from 35 to 15 ppt did not affect the fluorescence and mortality responses in the controls. The same decrease in salinity had no significant influence on the 1-h EC₅₀s except for NaLS and acetic acid. The ratio between the 1-h EC₅₀s at 35 and 15 ppt varied from 0.46 to 2.18 depending on the chemical. However, the same decrease in salinity significantly influenced (p < 0.05) the 24-h LC₅₀s (except NaPCP) and the 48-h LC₅₀ (except formaldehyde). In general, the ratio of the LC₅₀ values obtained at 35 and 15 ppt varied from 0.30 to 2.21 and from 0.48 to 2.53 for the 24- and 48-h exposures, respectively. In view of several inherent advantages such as rapidity, experimental simplicity, low cost of performance, and the use of dry cysts as biological starting material (which eliminates the maintenance of live stock culture) the 1-h Artemia Fluotox test offers promising potential for numerous ecotoxicological applications. © by John Wiley & Sons, Inc.     

Acute toxicity assessment of industrial effluents with a microplate-based Hydra attenuata assay

The acute toxicity potential of ten industrial plants located in Toyama Prefecture (Japan) was appraised with a microplate-based assay developed with the freshwater cnidarian Hydra attenuata. Three measurement end points (LC₅₀, EC₅₀, and TC or “threshold concentration”) were determined based on specific morphological changes displayed by Hydra under conditions of progressive intoxication. Four effluents were shown to be lethal toward Hydra while eight induced sublethal toxicity responses, LC₅₀s varied from 18.8 to > 100% v/v, while EC₅₀s ranged from 15 to > 100% v/v. Similarly, lethal and sublethal TCs ranged from 17.7 to > 100% v/v and from 8.8 to > 100% v/v, respectively. Statistical analyses performed on all toxicity data for the ten effluents confirmed that the sublethal end points (EC₅₀s and sublethal TCs), previously unreported to assess complex wastewaters, proved to be more sensitive than the lethal end points (LC₅₀s and lethal TCs). This was also reflected by lethality to sublethality ratios, which ranged from 1 to 2.6 (LC₅₀/EC₅₀ comparisons) and from 1.1 to 5.4 (LC₅₀/TC comparisons) within a 96 h exposure period. Similar statistical analyses undertaken on 24, 48, 72, and 96 h toxicity data failed to show any significant time-related differences, thereby suggesting that an exposure time as short as 24 h would not diminish test sensitivity. Since Hydra displayed an apparent increase in sensitivity toward a few effluents with time of exposure, however, we would nevertheless recommend a 96 h time frame for this microtest. A correlation was also observed between conductivity and Hydra responses, highlighting a possible link to the presence of toxic metal ions. Based on our study, this simple and cost-effective microassay appears valuable as a (sub)lethal toxicity screening tool for effluents. Additional studies are planned with chemicals and other environmental matrices to better circumscribe its scope of usefulness. © 1997 by John Wiley & Sons, Inc. Environ Toxicol Water Qual 12: 53–60, 1997     

Acute inhalation toxicity testing: considerations of technical and regulatory aspects

Asbtract The EU regulatory statute for the acute hazard identification of chemicals requires selection of the two most appropriate routes of administration. Testing employing the oral route is mandatory, whereas selection of the dermal or inhalation route requires expert judgement, i.e. considerations of structural alerts with regard to the inherent acute inhalation toxicity as well as the likelihood of dermal and inhalation exposure, respectively. Currently, testing of chemicals requires acute inhalation exposure of 4-h and 1-h durations according to EU classification and labelling and UN Transport Guidelines, respectively. The analysis made revealed that 1-h exposures appear to add little knowledge in addition to existing 4-h LC₅₀ values and a default value of 4 should be used for conversion of 4-h to 1-h LC₅₀ values, independently of the physical state of the chemical. Therefore, also the unit of concentration of exposure atmospheres should be independent of nominal features of the test substance. Hence, the preferred dose metric is mass (mg/litre air) rather than volume (ppm). Taking into account the overall variability of acute toxicity data the recommendations given are classification into the following groups of 4-h LC₅₀ values: ?0.05, >0.05–0.2, >0.2–1, >1−5 and >5.0 mg/l. No distinction should be made concerning vapours and aerosols with regard to units and conversion factors from 4-h to 1-h LC₅₀ values and the default factor of 4 appears to be most suitable. Further differentiation of classification is not indicated due to technical variability of acute inhalation testing and resolution of the acute bioassay. Received: 23 January 1996/Accepted: 10 May 1996     

Fluoride sensitivity in freshwater snail,Bellamya bengalensis (Lamarck, 1882): An integrative biomarker response assessment of behavioral indices,oxygen consumption,haemocyte and tissue protein levels under environmentally relevant exposure concentrations

There is limited information on fluoride toxicity and risk overview on ecotoxicological risks to aquatic invertebrate populations particularly molluscan taxa. This necessitated the assessment of toxicity responses in the freshwater snail, Bellamya bengalensis exposed to environmentally relevant concentrations of sodium fluoride. Under lethal exposures (150, 200, 250, 300, 400 and 450 mg/l), the median lethal concentrations (LC₅₀) were determined to be 422.36, 347.10, 333.33 and 273.24 mg/l for B. bengalensis at 24, 48, 72 and 96 h respectively. The rate of mortality of the snails was increased significantly with elevated concentrations of the toxicant. The magnitude of toxicity i.e., toxicity factor at different time scale was also higher with increased exposure duration. Altered behavioural changes i.e., crawling movement, tentacle movement, clumping tendency, touch reflex and mucous secretion in exposed snail with elevated concentrations and exposure duration. Similarly, oxygen consumption rate of the treated snail also lowered significantly during 72 and 96 h of exposure. Under 30-day chronic exposures (Control-0.00 mg/L; T1–27.324 mg/L; T2–54.648 mg/L), protein concentrations in gonad and hepatopancreas of exposure groups was significantly lowered. Chronic exposures also revealed lowered haemocytes counts in exposure groups. The potential for loss of coordination, respiratory distress and physiological disruption in organisms exposed to environmentally relevant concentrations of fluoride was demonstrated by this study. The estimation and magnitude of toxicity responses are necessary for a more accurate estimation of ecological risks to molluscan taxa and invertebrate populations under acute and chronic fluoride exposures in the wild.     

Short-term inhalation toxicity studies with peroxyacetyl nitrate in rats

The inhalation toxicity of peroxyacetyl nitrate (PAN) was examined in acute (single exposure), sub-acute (4-week repeated exposure) and subchronic (13-week repeated exposure) studies in rats. The 4-h LC₅₀ was found to be 95 ppm.In the 4-week study rats were exposed to 0, 0.9, 4.1 or 11.8 ppm PAN vapour for 6 h/day, 5 days/week. Exposure to 11.8 ppm caused abnormal behaviour, growth retardation, mortality, elevated haemoglobin contents, haematocrit values and erythrocyte counts, increased lung weights and severe inflammatory changes and epithelial hyper- and metaplasia in the respiratory tract. At 4.1 ppm minimal behavioral disturbance, transient growth depression, slightly increased lung weights and mild histopathological changes in the respiratory tract were found. At 0.9 ppm no treatment-related alterations were detected.In the 13-week study rats were exposed to 0, 0.2, 1.0 or 4.6 ppm PAN vapour for 6.5 h/day, 5 days.week. Exposure to 4.6 ppm resulted in changes similar to those found at 11.8 ppm in the 4-week experiment, but no mortality occurred. At 1.0 ppm minimal irritation of the mucous membranes in the nasal cavity was the only PAN-related effect observed. No treatment- related changes were seen at 0.2 ppm. It was concluded that the no-toxic- effect level is between 0.2 and 1.0 ppm, and very probably close to the upper value.