Evaluation of a 14-day static renewal toxicity test withDaphnia magna Straus

Two replicate 14-day static renewal chronic toxicity tests were conducted with Daphnia magna Straus for each of three test chemicals (boric acid, aniline, and 2,4-dichlorophenol). These tests were conducted at 24 +/- 2 degrees C. The objective of this study was the comparison of the 14-day test results with chronic values derived for the same chemicals from 21-day studies (20 degrees C). It was hypothesized that the comparison of the chronic data resulting from the two test regimes would support the shortening of the standard 21-day exposure period and reduce the cost of these labor intensive studies. The results of this study are as follows: 1. The 14-day test met the 21-day chronic test acceptability criteria in terms of control data associated with the mean number of broods/adult, mean total young/adult, mean brood size and survival. 2. A comparison of the results shows the similarity of the chronic values generated from the 14 and 21-day tests. In all cases, the chemical specific chronic values were within a factor of 2. The chronic values for 2,4-dichlorophenol generated from the two test regimens were virtually identical (i.e., 14-day--1.1 and 1.2 mg/L; 21-day--1.1 mg/L). 3. The comparison of the chronic values resulting from the 14 and 21-day tests supports the use of the 14-day exposure period. A shorter exposure period will help reduce the cost of these labor intensive studies without compromising their scientific integrity.     

An Ecological Risk Assessment of the Exposure and Effects of 2,4-D Acid to Rainbow Trout (<Emphasis Type="Italic">Onchorhyncus mykiss</Emphasis>)

Numerous state and federal agencies are increasingly concerned with the rapid expansion of invasive, noxious weeds across the United States. Herbicides are frequently applied as weed control measures in forest and rangeland ecosystems that frequently overlap with critical habitats of threatened and endangered fish species. However, there is little published chronic toxicity data for herbicides and fish that can be used to assess ecological risk of herbicides in aquatic environments. We conducted 96-h flowthrough acute and 30-day chronic toxicity studies with swim-up larvae and juvenile rainbow trout (Onchorhyncus mykiss) exposed to the free acid form of 2,4-D. Juvenile rainbow trout were acutely sensitive to 2,4-D acid equivalent at 494 mg/L (95% confidence interval [CI] 334–668 mg/L; 96-h ALC₅₀). Accelerated life-testing procedures, used to estimate chronic mortality from acute data, predicted that a 30-day exposure of juvenile rainbow trout to 2,4-D would result in 1% and 10% mortality at 260 and 343 mg/L, respectively. Swim-up larvae were chronically more sensitive than juveniles using growth as the measurement end point. The 30-day lowest observable effect concentration (LOEC) of 2,4-D on growth of swim-up larvae was 108 mg/L, whereas the 30-day no observable effect concentration (NOEC) was 54 mg/L. The 30-day maximum acceptable toxicant concentration (MATC) of 2,4-D for rainbow trout, determined as the geometric mean of the NOEC and the LOEC, was 76 mg/L. The acute:chronic ratio was 6.5 (i.e., 494/76). We observed no chronic effects on growth of juvenile rainbow trout at the highest concentration tested (108 mg/L). Worst-case aquatic exposures to 2,4-D (4 mg/L) occur when the herbicide is directly applied to aquatic ecosystems for aquatic weed control and resulted in a 30-day safety factor of 19 based on the MATC for growth (i.e., 76/4). Highest nontarget aquatic exposures to 2,4-D applied following terrestrial use is calculated at 0.136 mg/L and resulted in a 30-day safety factor of 559 (e.g., 76/0.163). Assessment of the exposure and response data presented herein indicates that use of 2,4-D acid for invasive weed control in aquatic and terrestrial habitats poses no substantial risk to growth or survival of rainbow trout or other salmonids, including the threatened bull trout (Salvelinus confluentus).     

Toxicity of 4-Chloroaniline in Early Life Stages of Zebrafish (Danio rerio): II. Cytopathology and Regeneration of Liver and Gills After Prolonged Exposure to Waterborne 4-Chloroaniline

Ultrastructural alterations in liver and gills of embryonic and larval zebrafish (Danio rerio) following prolonged exposure to waterborne 0.05, 0.5, and 5 mg/L 4-chloroaniline for up to 31 days as well as after a 14-day regeneration period were investigated by means of light and electron microscopy. Acute toxicity was also tested at 25 and 50 mg/L. Survival of zebrafish embryos and larvae was only impaired from 25 mg/L 4-chloroaniline, but—after a transient stimulation following exposure to 0.5 mg/L—4-chloroaniline hatching was retarded after exposure to ≥5 mg/L, and fish displayed increasing rates of abnormal development and pigmentation. In contrast, hepatocytes displayed a time- and dose-dependent response from 0.05 mg/L 4-chloroaniline, including changes in nuclei, mitochondria, peroxisomes, endoplasmic reticulum, Golgi fields, lysosomes, and hepatic glycogen and lipid stores, as well as invasion of macrophages. In gills, dose-dependent effects were evident from 0.5 mg/L 4-chloroaniline and included deformation of secondary lamellae due to vacuolization and desquamation of respiratory epithelial cells in conjunction with dilation of intercellular spaces. Respiratory epithelial cells displayed progressive mitochondrial changes, induction of cytoplasmic myelinated structures, augmentation of lysosomes, and modifications of Golgi fields. Erythrocytes were severely deformed. A 14-day regeneration period was sufficient for almost complete recovery of pathological symptoms in both liver and gills. Only minor volumetric changes in hepatocellular organelles and a limited number of myelinated bodies, lysosomes, and cytoplasmic vacuoles were reminiscent of prior 4-chloroaniline exposure. In both qualitative and quantitative terms, most effects in hepatocytes after exposure of embryonic and larval zebrafish to waterborne 4-chloroaniline are comparable to the reaction of hepatocytes in adult zebrafish liver after prolonged sublethal exposure as well as in larval zebrafish after microinjection. Morphological changes in erythrocytes indicate disturbance of respiration as an additional mode of action of 4-chloroaniline. Received: 8 July 1998/Accepted: 18 November 1998     

复合食品包装袋中二氨基甲苯的GC-MS测定方法研究

目的：建立二氨基甲苯残留的气相色谱一质谱检测方法。方法：沸水浸取样品中二氨基甲苯后，用甲苯进行液一液萃取，经三氟乙酸酐衍生化，再将衍生物进行GC—MS定性定量分析。结果：方法最低检出浓度为0．0002mg／L，相对标准偏差（RSD）为2．5％（n=6），样品加标回收率为98．11％～101．21％。结论：将GB／TS009．119—2003方法中的不足进行了一定的改良，用GC—MS方法检测复合食品包装袋是二氨基甲苯残留量，结果满意。     

Chronic Effects of the Herbicide Diuron on Freshwater Cladocerans, Amphipods, Midges, Minnows, Worms, and Snails

The chronic effects of the herbicide diuron on survival and reproduction of Daphnia pulex, and survival and growth of the amphipod Hyalella azteca, the midge Chironomus tentans, juvenile and embryo/larval fathead minnows, Pimephales promelas, annelid worms, Lumbriculus variegatus, and snails, Physa gyrina, were determined in laboratory static and static-renewal tests. D. pulex 96-h and 7-day LC50 values were 17.9 and 7.1 mg/L; 7-day LOAEL and NOAEL values based on mortality and reproduction were 7.7 and 4.0 mg/L. H. azteca 96-h and 10-day LC50 values were 19.4 and 18.4 mg/L; 10-day LOAEL and NOAEL values based on survival and reduced weight were 15.7 and 7.9 mg/L. C. tentans 10-day LC50 value was 3.3 mg/L; 10-day LOAEL and NOAEL values based on growth were 7.1 and 3.4 mg/L, and 3.4 and 1.9 mg/L based on mortality. Juvenile fathead minnows had a 10-day LC50 of 27.1 mg/L and 10-day LOAEL and NOAEL values based on growth of 3.4 and <3.4 mg/L. The fathead minnow embryo-larval test had a 7-day LC50 value of 11.7 mg/L and 7-day LOAEL and NOAEL values based on reduced growth of 8.3 and 4.2 mg/L. L. variegatus had 10-day LOAEL and NOAEL values based on reduced weight of 3.5 and 1.8 mg/L. P. gyrina had 10-day LOAEL and NOAEL values based on reduced weight of 22.8 and 13.4 mg/L. Laboratory effects concentrations were higher that those found in normal field application situations, except in areas of localized pooling after recent herbicide applications, indicating that there would probably be little harm to these fish and invertebrates from diuron exposure in the field. Received: 18 January 1998/Accepted: 28 March 1998     

Sister chromatid exchange induction by the herbicide 2,4-dichlorophenoxyacetic acid in chick embryos

As genetic damage may result from exposure to agricultural chemicals, it seemed appropriate to assess the genotoxic potential of 2,4-dichlorophenoxyacetic acid (2,4-D), a widely used broad-leaf herbicide, using a test system that may provide some indications on the genetic risk to animal species in the wild. In the present study, sister chromatid exchange (SCE) induction and cell cycle kinetics alterations by 2,4-D in 4-day old chick embryos were evaluated. Both a commercial herbicide formulation containing 37% 2,4-D isooctyl ester as active ingredient and pure 2,4-D were tested. Chick embryos were treated with 0, 0.5, 1, 2, or 4 mg 2,4-D. Test solutions were applied to the inner shell membrane on day 0 of incubation. Either commercial formulation or pure 2,4-D induced a dose-related increase in SCE frequency over the concentration range from 0 to 4 mg/embryo. Significantly higher SCE frequency was seen for the 4-mg group of embryos treated with the commercial product. A slightly higher SCE value was observed for the vehicle group (acetone-treated embryos) compared with the negative controls (untreated embryos). Significant inhibition of cell cycle progression was evident in both experimental groups and was generally dose related. The extent of changes in cell kinetics was similar in both groups, although somewhat more marked in the group treated with pure 2,4-D. The present findings corroborate the positive results from recent in vivo rodent studies.     

Acute and Chronic Toxicity of Imidacloprid to the Aquatic Invertebrates <Emphasis Type="Italic">Chironomus tentans</Emphasis> and <Emphasis Type="Italic">Hyalella azteca</Emphasis> under Constant- and Pulse-Exposure Conditions

The toxicity of imidacloprid, a nicotinic mimic insecticide, to the aquatic invertebrates Chironomus tentans and Hyalella azteca, was first evaluated in static 96-hour tests using both technical material (99.2% pure) and Admire, a commercially available formulated product (240 g a.i. L(-1)). The 96-h lethal concentration (LC)50 values for technical imidacloprid and Admire were 65.43 and 17.44 microg/L, respectively, for H. azteca, and 5.75 and 5.40 microg/L, respectively, for C. tentans. Admire was subsequently used in 28-day chronic tests with both species. Exposure scenarios consisted of a constant- and a pulse-exposure regime. The pulse exposure lasted for four days, after which time the animals were transferred to clean water for the remaining 24 days of the study. Assessments were made on both day 10 and day 28. In the C. tentans under constant exposure, larval growth on day 10 was significantly reduced at 3.57 microg/L imidacloprid, the lowest-observed-effect concentration (LOEC). The no-observed-effect concentration (NOEC) and LOEC for the 28-day exposure duration (adult survival and emergence) were 1.14 and greater than 1.14 mug/L, respectively; the associated LC50 and LC25 were 0.91 and 0.59 microg/L, respectively. The LOEC for the pulse treatment was greater than 3.47 microg/L, but the day 10 LC25 was 3.03 microg/L. In the H. azteca tests, the day 10 and 28 constant exposure, as well as the day 28 pulse exposure, LOEC (survival) values were similar at 11.95, 11.46, and 11.93 microg/L, respectively. The day 10 and 28 constant exposure effective concentration (EC)25s (dry weight) were also similar, at 6.22 and 8.72 microg/L, respectively, but were higher than the pulse-exposure day 10 LOEC and EC25 (dry weight) values of 3.53 and 2.22 microg/L, respectively. Overall, C. tentans was more sensitive to acute and chronic imidacloprid exposure, but less sensitive to a single pulse, than H. azteca. Chronic, low-level exposure to imidacloprid may therefore reduce invertebrate survival and growth, but organisms are able to recover from short-term pulse exposure to similar imidacloprid concentrations if the stressor is removed after four days.     

The 2,4-D herbicide effects on acetylcholinesterase activity and metabolic parameters of piava freshwater fish (Leporinus obtusidens)

The effects of 2,4-D (1 or 10 mg/L) on acetylcholinesterase (AChE) and metabolic parameters were evaluated in piava (Leporinus obtusidens) after 96 h. AChE activity was significantly reduced in the brain at a concentration of 10 mg/L and in the muscle at both concentrations tested. Muscle glycogen and lactate were significantly reduced for both 2,4-D concentrations but no significant change was observed in liver glycogen. Muscle protein levels were enhanced after exposure at 10 mg/L, but no significant changes were observed in muscle and liver glucose. Liver lactate and protein were significantly reduced after exposure to this herbicide. 2,4-D exposure produced a decrease in blood glucose at both concentrations and enhanced lactate levels at 10mg/L. Plasma protein increased at both concentrations tested. In conclusion, the results obtained indicate that 2,4-D affects brain and muscle AChE activity and some blood and tissue metabolic parameters of L. obtusidens. The stress generated by 2,4-D is the probable cause of alterations observed and measured parameters can be used to monitor 2,4-D fish toxicity.     

Effects of Tetrachloroethylene on the Viability and Development of Embryos of the Japanese Medaka, Oryzias latipes

We evaluated the acute toxicity of Tetrachloroethylene (C₂Cl₄), and investigated its sub-chronic effects on the embryonic development of Japanese medaka (Oryzias latipes). One-day-old eggs/embryos of this fish species were exposed, under static renewal conditions, to serial concentrations (0, 20, 40, 60, and 80 mg/L) of C₂Cl₄ for 96 h (acute) and 10 days (sub-chronic) time periods. The toxic endpoints evaluated included: egg/embryo viability, hatchability, and morphological/developmental abnormalities. The acute toxicity test resulted in a 96 h-LC₅₀ of 27.0 (19.5–32.9) mg/L for egg viability. Exposure of eggs to sub-chronic concentrations (0, 1.5, 3, 6, 12, and 25 mg/L) of C₂Cl₄ significantly reduced hatchability and larval survival, in a concentration dependent manner. At the highest tested concentration (25 mg/L) of the sub-lethal exposure, larval survival was greatly reduced to within three days post-hatch. The lowest tested concentration (1.5 mg/L) produced a significant number of developmental effects to the Japanese medaka, including abnormal development of the circulatory system, yolk-sac edema, pericardial edema, scoliosis, hemorrhaging, blood pooling, and defects in heart morphology. The severity of these abnormalities was concentration-dependent. It can be concluded from these results that tetrachloroethylene is teratogenic to the Japanese medaka. Received: 20 February 2001/Accepted: 21 December 2001     

Strain difference in sensitivity to 3,4-dichloroaniline and insect growth regulator, fenoxycarb, in Daphnia magna

Acute and reproductive toxicity tests were conducted on seven strains of Daphnia magna from six laboratories in five countries. 3,4-Dichloroaniline (DCA) and fenoxycarb were used as test chemicals. Acute toxicity tests revealed that estimated EC(50) (50% effective concentration) values for DCA varied by a factor of 2.1 among strains (310-640 microg/L), whereas the EC(50) values for fenoxycarb varied by a factor of 4 (210-860 microg/L). EC(50) values for reproductive toxicity tests with DCA ranged from 5.9 to 38 microg/L among strains. Fenoxycarb exposure induced the production of male neonates in all the strains used in the present study. Estimated EC(50) values for the induction of male offspring were highly variable among strains: sensitivity to fenoxycarb differed by a factor of approximately 23 overall (0.45-10 microg/L). The present pre-validation tests suggest that induction of male sex in neonates by a juvenile hormone analog is universal among genetically different strains. Decreased total numbers of neonates at increased concentrations of fenoxycarb as well as other juvenoids may, however, obscure the incidence of male neonates production in the 21-day reproduction tests due to the low statistical power.     

Toxicities of butoxyethanol ester and propylene glycol butyl ether ester formulations of 2,4-dichlorophenoxy acetic acid (2,4-D) to juvenile salmonids

Continuous-flow toxicity tests were conducted to determine acute toxic effects of butoxy-ethanol ester (BOEE) and propylene glycol butyl ether ester (PGBEE) formulations of 2,4-D on juvenile chinook salmon (Oncorhynchus tshawytscha) and steelhead-rainbow trout (Salmo gairdneri). A chronic toxicity test with chinook salmon egg-to-fry was conducted to determine effects of BOEE on survival and growth. The hydrolysis in water of 2,4-D esters to 2,4-D acid was influenced by the presence of fish. Median lethal concentrations (96-hr LC50 values) indicated that PGBEE (170 to 355 g/L) was slightly more toxic (37 to 57%) than BOEE (303 to 525 g/L). The LC50 values also indicated that chinook salmon were generally more sensitive than steelhead-rainbow trout and that fry and smolts were equally sensitive to the 2,4-D esters. Static tests substantially underestimated BOEE toxicity when compared to dynamic tests. Based on reduced survival and growth of chinook salmon alevins and fry, the estimated maximum safe chronic exposure concentration under these test conditions is 40 g/L BOEE.     

Using accelerated life testing procedures to compare the relative sensitivity of rainbow trout and the federally listed threatened bull trout to three commonly used rangeland herbicides (picloram, 2,4-D, and clopyralid)

We conducted 96-h static acute toxicity studies to evaluate the relative sensitivity of juveniles of the threatened bull trout (Salvelinus confluentus) and the standard cold-water surrogate rainbow trout (Onchorhyncus mykiss) to three rangeland herbicides commonly used for controlling invasive weeds in the northwestern United States. Relative species sensitivity was compared using three procedures: standard acute toxicity testing, fractional estimates of lethal concentrations, and accelerated life testing chronic estimation procedures. The acutely lethal concentrations (ALC) resulting in 50% mortality at 96 h (96-h ALC50s) were determined using linear regression and indicated that the three herbicides were toxic in the order of picloram acid > 2,4-D acid > clopyralid acid. The 96-h ALC50 values for rainbow trout were as follows: picloram, 41 mg/L; 2.4-D, 707 mg/L; and clopyralid, 700 mg/L. The 96-h ALC50 values for bull trout were as follows: picloram, 24 mg/L; 2.4-D, 398 mg/L; and clopyralid, 802 mg/L. Fractional estimates of safe concentrations, based on 5% of the 96-h ALC50, were conservative (overestimated toxicity) of regression-derived 96-h ALC5 values by an order of magnitude. Accelerated life testing procedures were used to estimate chronic lethal concentrations (CLC) resulting in 1% mortality at 30 d (30-d CLC1) for the three herbicides: picloram (1 mg/L rainbow trout, 5 mg/L bull trout), 2,4-D (56 mg/L rainbow trout, 84 mg/L bull trout), and clopyralid (477 mg/L rainbow trout; 552 mg/L bull trout). Collectively, the results indicated that the standard surrogate rainbow trout is similar in sensitivity to bull trout. Accelerated life testing procedures provided cost-effective, statistically defensible methods for estimating safe chronic concentrations (30-d CLC1s) of herbicides from acute toxicity data because they use statistical models based on the entire mortality:concentration:time data matrix.     

Acute toxicity of selenium dioxide to freshwater fishes.

Acute toxicity tests of selenium dioxide were conducted for 96 to 336 hr in intermittent-flow bioassay systems using six species of freshwater fish. The decreasing order of species sensitivity was: fathead minnow, flagfish, brook trout, channel catfish, goldfish, and bluegil. Curves relating median lethal concentration to exposure time for each species exposed for more than 168 hr were sigmoid in shape and were characterized by a change in slope indicating a more rapid mortality rate after 96 to 168 hr toxicant exposure. The 96-hr LC50 estimates ranged from 2.9 mg/L SeO2 for fathead minnow fry to 40.0 mg/L for bluegill juveniles. Effects of brief toxicant exposure (24 hr) on fathead minnow and flagfish juveniles included limited delayed mortality and no effects on growth over a 28-day period.     

Comparative toxicity of two glyphosate formulations (original formulation of Roundup® and Roundup WeatherMAX®) to six North American larval anurans

The toxicity of two glyphosate formulations (the original formulation of Roundup? and Roundup WeatherMAX?) to six species of North American larval anurans was evaluated by using 96-h static, nonrenewal aqueous exposures. The 96-h median lethal concentration values (LC50) ranged from 1.80 to 4.22 mg acid equivalent (ae)/L and 1.96 to 3.26 mg ae/L for the original formulation of Roundup and Roundup WeatherMAX, respectively. Judged by LC50 values, four species were more sensitive to Roundup WeatherMAX exposures, and two species were more sensitive to the original formulation. Two of six species, Bufo fowleri (p < 0.05, F = 14.89, degrees of freedom [df] = 1) and Rana clamitans (p < 0.05, F = 18.46, df = 1), had significantly different responses to the two formulations tested. Increased sensitivity to Roundup WeatherMAX likely was due to differences in the surfactants or relative amounts of the surfactants in the two formulations. Potency slopes for exposures of the original formulation ranged from 24.3 to 92.5% mortality/mg ae/L. Thresholds ranged from 1.31 to 3.68 mg ae/L, showing an approximately three times difference in the initiation of response among species tested. For exposures of Roundup WeatherMAX, slopes ranged from 49.3 to 84.2% mortality/mg ae/L. Thresholds ranged from 0.83 to 2.68 mg ae/L. Margins of safety derived from a simulated direct overspray were above 1, except for one species in exposures of Roundup WeatherMAX. Laboratory data based on aqueous exposures are conservative because of the lack of environmental ligands; however, these tests provide information regarding the relative toxicity between these two Roundup formulations.     

An interpretation of toxicity response of bobwhite quail with respect to duration of exposure

Avian dietary toxicity tests were conducted with seven pesticides, two age groups (2 and 16 weeks old) of northern bobwhite (Colinus virginianus) and two durations (5 and 28 days) of exposure. Results were analyzed with an emphasis placed upon comparing mortalities on similar test conditions. An analysis that used the entire dose-time-response results led to the calculation of a common measure (asymptotic rate e) of temporal development of the response surface and served as a basis of comparison of diverse test results. The asymptotic median lethal concentrations were designated by ALC50 and the median lethal concentrations at the end of a test period by LC50.It was found that: (1) Young birds in 5- and 28-day tests were more sensitive to incremental increases in the duration of exposure than adults. (2) Young birds were less sensitive to incremental increases of dietary concentration than adults only in the 5-day test and displayed delayed response patterns in six of seven chemicals in those tests. (3) LC50 values of 5-day tests of young birds were greater than LC50 values of 28-day tests, but the corresponding ALC50s were smaller in 5-day tests than 28-day tests. (4) ALC50s for 28-day tests were lower for young birds than for adults.The analysis based on the whole response surface can be used in the design of experiments, in utilizing less than optimum test results due to difficulties encountered during the test in selecting optimum dietary concentration, in linking results of short term exposure with long-term exposure, and in interpreting results of variable exposure tests on a common basis.     

Effects of sediment-bound zinc contamination on early life stages of the mummichog (Fundulus heteroclitus L.) in the Christina watershed, Delaware, U.S.A

During the last century, the Christina River, the major estuarine river system in New Castle County (DE, USA), has received loadings of organic and inorganic chemicals, primarily from manufacturing facilities. Among the most abundant chemicals is zinc, which has accumulated in sediments at concentrations as high as 5,440 mg/kg. We studied the possible effects of zinc on early life stages of the mummichog (Fundulus heteroclitus), a resident species in the river and watershed. We conducted three different types of exposures. The first was a 96-h median lethal concentration (LC50) test with larvae exposed to waterborne zinc. The second was a larval exposure with zinc-spiked sediments (obtained from the relatively uncontaminated Magothy River in Anne Arundel County, MD, USA). The third was an embryo-larval exposure with Christina River sediments having a gradient of zinc concentrations. The average 96-h LC50 with newly hatched yolk sac larvae was 970 lig/L. In the larval tests, the average 7- and 21-d LC50s were 1154 and 1012 mg/kg, respectively. In the embryo-larval test, no significant difference was found in survival at concentrations between 38.8 and 1098 mg/kg. However, significant reductions were observed in condition factor at concentrations of 582, 799, and 1098 mg/kg. We calculated an average no-observed-effects concentration of 579 mg/kg and an average lowest-observed-effects concentration of 849 mg/kg for larval survival. Based on these results, we suggest that zinc in the Christina River may be affecting early life stages of the mummichog.     

Effect of release herbicide on mortality, avoidance response, and growth of amphibian larvae in two forest wetlands

Effects of Release herbicide (triclopyr butoxyethyl ester, [TBEE]) on mortality, avoidance response, and growth of larval amphibians (Rana clamitans, Rana pipiens) were investigated using in situ enclosures deployed in two forest wetlands in northern Ontario, Canada. Release was applied at nominal concentrations ranging from 0.26 to 7.68 mg TBEE acid equivalents (AE)/L. No significant deleterious effects of this herbicide on larval growth were detected. However, concentration-dependent mortality and abnormal avoidance response were observed. Most mortality occurred within 96 h following treatment. Median lethal concentration (LC50) values for each species and experimental site ranged from 2.79 to 3.29 mg AE/L, while median effective concentration (EC50) values (abnormal avoidance response) ranged from 1.67 to 3.84 mg AE/L. The LC10 and EC10 endpoints approximated aqueous concentrations (0.59 mg AE/L) expected under direct aerial overspray scenarios, indicating a potential risk of impacts for a small proportion of native amphibian larvae. However, given the low frequency and limited use of this herbicide formulation in Canadian forestry, these risks are considered negligible. Changes in usage patterns would require concurrent chemical and biological monitoring of operational spray programs to accurately quantify the probability and magnitude of real-world exposures and to relate these exposure levels to concentration-response relationships including those described in this study.     

Chronic toxicity of copper and ammonia to juvenile freshwater mussels (Unionidae)

The objectives of the present study were to develop methods for conducting chronic toxicity tests with juvenile mussels under flow-through conditions and to determine the chronic toxicity of copper and ammonia to juvenile mussels using these methods. In two feeding tests, two-month-old fatmucket (Lampsilis siliquoidea) and rainbow mussel (Villosa iris) were fed various live algae or nonviable algal mixture for 28 d. The algal mixture was the best food resulting in high survival (>or=90%) and growth. Multiple copper and ammonia toxicity tests were conducted for 28 d starting with two-month-old mussels. Six toxicity tests using the algal mixture were successfully completed with a control survival of 88 to 100%. Among copper tests with rainbow mussel, fatmucket, and oyster mussel (Epioblasma capsaeformis), chronic value ([ChV], geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) ranged from 8.5 to 9.8 microg Cu/L for survival and from 4.6 to 8.5 microg Cu/L for growth. Among ammonia tests with rainbow mussel, fatmucket, and wavy-rayed lampmussel (L. fasciola), the ChV ranged from 0.37 to 1.2 mg total ammonia N/L for survival and from 0.37 to 0.67 mg N/L for growth. These ChVs were below the U.S. Environmental Protection Agency 1996 chronic water quality criterion (WQC) for copper (15 microg/L; hardness 170 mg/L) and 1999 WQC for total ammonia (1.26 mg N/L; pH 8.2 and 20 degrees C). Results indicate that toxicity tests with two-month-old mussels can be conducted for 28 d with >80% control survival; growth was frequently a more sensitive endpoint compared to survival; and the 1996 chronic WQC for copper and the 1999 chronic WQC for total ammonia might not be adequately protective of the mussel species tested. However, a recently revised 2007 chronic WQC for copper based on the biotic ligand model may be more protective in the water tested.     

Uptake of 2,4-D in higher plants from artificial rain

Sinapis alba L., Lapsana communis L., Achillea millefolium L., Brassica napus L., Lactuca sativa L., and Lycopersicum esculentum L. were exposed to 2,4-dichlorophenoxy [2-14C]acetic acid (2,4-D) at 10 micrograms liter-1 in artificial rain, pH 6.5 and 3.3. The 2,4-D was absorbed in all species tested. Concentrations of parent 2,4-D appeared at the highest level in Achillea (0.1 mg kg-1 dry wt), and at zero level in Lycopersicum. Twenty-one daily treatments at pH 6.5 for 30-min periods increased dry-matter concentrations (P less than or equal to 0.05) in the leaves of Achillea and decreased those in Brassica. No change in dry-matter concentration was observed in the leaves of Brassica by seven daily treatments for 30-min periods at pH 3.3.     

Toxicity of cadmium to early life stages of brown trout (Salmo trutta) at multiple water hardnesses

Toxicity of cadmium to early life stages of brown trout (Salmo trutta) was determined at multiple water hardnesses. Increasing water hardness decreased cadmium toxicity. Postswimup fry were much more sensitive than embryos and larvae. Chronic values from early life stage tests initiated with eyed embryos were 3.52, 6.36, and 13.6 microg Cd/L at water hardnesses of 30.6, 71.3, and 149 mg/L, respectively. In tests initiated with 30-d postswimup fry, chronic values were 1.02, 1.83, and 6.54 microg Cd/L at water hardnesses of 29.2, 67.6, and 151 mg/L, respectively. Higher chronic values from the early life stage tests compared to tests initiated with swimup fry likely are caused by acclimation during cadmium-tolerant embryo and larval stages. Growth was not affected by cadmium in the early life stage tests but was negatively affected in tests initiated with fry at water hardnesses of 29.2 and 67.6 mg/L. Concentrations of cadmium that reduced growth were higher than those that increased mortality. Median lethal concentrations for swimup fry after 96 h were 1.23, 3.90, and 10.1 microg Cd/L at water hardnesses of 29.2, 67.6, and 151 mg/L, respectively. Test results enable prediction of acute mortality of brown trout swimup fry based on cadmium concentration and water hardness.