Acute Toxicity Of Lead Research Articles

Combined Toxic Effects of Lead and Glyphosate on Apis cerana cerana.

Glyphosate (GY) is the most widely used herbicide in agriculture worldwide. Lead is a common heavy metal in the natural environment. Honeybees, as pollinators, are exposed to these pollutants. So far, few reports have evaluated the toxic effects of GY mixed with heavy metals on honeybees (Apis cerana cerana). This study found that the acute toxicity of lead (LC50 = 1083 mg/L) is much greater than that of GY (LC50 = 4764 mg/L) at 96 h. The acute toxicities of the mixed substances were as follows: LC50 = 621 mg/L of lead and LC50 = 946 mg/L of GY. The combination of lead and GY was more toxic than either of the individual substances alone. Compared to the individual toxicity, combined treatment significantly affected the bees' learning and cognitive abilities and changed the relative expression of genes related to immune defense and detoxification metabolism in A. c. cerana. The combination of lead and GY seriously affected the behavior and physiology of the studied honeybees. This study provides basic data for further research on the combined effects of GY and heavy metals on bee health. It also serves as a reference for effective colony protection.

Application and validation of a biotic ligand model for calculating acute toxicity of lead to Moina dubia in lakes of Hanoi, Vietnam.

It is increasingly being recognized that biotic ligand models (BLMs) can successfully predict the toxicity of divalent metals toward aquatic biota applied to temperate freshwater ecosystems. However, studies on the eutrophic lakes in tropical regions toward native tropical organisms, including Moina, are relatively limited. In this study, Moina dubia, the native organism of the Hanoi eutrophic urban lakes, were used in toxicological studies of lead (Pb); 24-h EC50 value of Pb was 523.19µg/L under optimal living conditions for M. dubia in the laboratory. The constant binding of Pb2+ on M. dubia surface sites (log KPbBL = 2.38) was significantly low. Other stability constants were obtained under experiments as logKCaBL = 2.48, logKMgBL = 2.80, logKNaBL = 2.35, logKKBL = 2.49, and logKHBL = 3.026. A BLM was developed to calculate the acute toxicity (EC50-24h) of lead on M. dubia based on the condition of the urban lakes of Hanoi. Validation with toxicity data in synthetic medium showed a coefficient determination of 79.16% and a mean absolute percentage error (MAPE) of 10.2%, while the validation with the toxicity data with natural water medium from 11 Hanoi lakes showed a coefficient determination of 73.7% and a MAPE of 13.66%. The BLM worked well with water at a pH of 7.0 to 8.0, but failed with water at a pH above 8.0. Eutrophic conditions proved to have a significant effect on the toxicity of lead on local zooplankton.

Development of regional water quality criteria of lead for protecting aquatic organism in Taihu Lake, China

Lead is a widely distributed priority controlled heavy metals in aquatic system, its toxicity to aquatic organisms affected by water quality parameters. This study investigated the acute toxicity of lead (Pb) to the aquatic organisms in Taihu Lake under various water hardness, corresponding regional water quality criteria were derived. The acute toxicity experimental results revealed that the toxicity of Pb to aquatic organisms increased with water hardness. The Pb toxicity has a highest toxicity at water hardness 50 mg/L (expressed as CaCO3), especially for Palaemon modestus where the 96 h LC50 value was 0.024 mg/L. The hazardous concentration for 5% of biological species (HC5) values were determined via species sensitivity distribution (SSD) method as 94.0 μg/L, 222.3 μg/L and 375.8 μg/L for Pb at water hardness 50, 150, and 250 mg/L, respectively. The assessment factor (AF) value was set at 2, followed by the current SSD framework where European commission recommend a fixed AF of 5–1. Thus, the predicted no effect concentration (PNEC) values was 47.0 μg/L, 111.2 μg/Land 187.9 μg/L at water hardness 50, 150, and 250 mg/L, respectively. Meanwhile, the short-term water quality criteria of Pb for Taihu lake aquatic organisms were derived as 111.2 μg/L at water hardness 150 mg CaCO3/L. The long-term water quality criteria were derived as 4.3 μg/L by using acute/chronic ratio 51.29. When the derived value was used for Taihu Lake, 2.7% of the sampling sites in Taihu Lake was exceeded this criterion. The results of this study can provide technical methods and basic information for deriving Pb regional water quality criteria for protecting native aquatic organisms, in China.

Aquatic pollution caused by mercury, lead, and cadmium affects cell growth and pigment content of marine microalga, Nannochloropsis oculata.

The present study investigated the acute (72h) and sub-acute (14days) toxicity of mercury, lead, and cadmium to the green microalga, Nannochloropsis oculata. The acute toxicity testing was conducted according to the modified OECD guideline (No. 201). The 72-h IC50 values of Hg, Pb, and Cd exposed to N. oculata were 0.87, 1.81, and 4.97mg/L, respectively. These results showed that mercury is about twice as toxic as lead and about 5.7 times more toxic than cadmium to this marine microalga. Lead is about 2.7 times more toxic than cadmium. The chlorophyll a content of the microalga decreased in the 10th and 14th days of the sub-acute toxicity test. Although the carotenoid content increased following exposure to the low levels of tested heavy metals (which may show the protective role of carotenoids against oxidative stress), with increased exposure time the total carotenoid reduced compared to control. A regular monitoring program to examine the level of metals in the aquatic ecosystem for protecting microalgae should be implemented.

Modulation of glutathione S-transferase and superoxide dismutase in response to heavy metals in brackish water flea Diaphanosoma celebensis

Superoxide dismutase (SOD) and glutathione S-transferase (GST) serve as biomarkers of oxidative stress in aquatic organisms. However, the modulatory effects of heavy metals on the expression of small crustaceans are yet unknown. The acute toxicity of inorganic arsenic (As), cadmium (Cd), and lead (Pb) to the brackish water flea Diaphanosoma celebensis (4 days old) was evaluated to determine their sublethal concentrations. Modulations in the activities and transcription of SODs (Cu/Zn-SOD and Mn-SOD) and GSTs (mu, kappa, theta, and sigma) in response to sublethal concentrations of heavy metals were investigated for 48 h. The 48-h median lethal concentration (LC50) was determined to be 2.62 mg/L, 2.60 mg/L, and 0.37 mg/L for Cd, As, and Pb, respectively, and the order of toxicity in this species was Pb > Cd = As. SOD and GST activities were induced after exposure to all metals; in particular, GST activity was sensitively enhanced upon As exposure. Real-time reverse-transcriptase polymerase chain reaction showed that GST mu and GST sigma were specific for As, and GST kappa and GST theta for Cd. Mn-SOD mRNA expression was more sensitive to As. These findings suggest that D. celebensis SOD and GST may be involved in the antioxidant defense mechanisms to heavy metals. These genes may serve as useful biomarkers for risk assessment of heavy metal pollution in aquatic ecosystems. This study may be helpful for the better understanding of the molecular mode of action of heavy metals in small crustaceans and provide preliminary data for future studies evaluating the combined effects of heavy metal mixture.

Acute toxicity of lead in fresh water bivalves Lamellidens jenkinsianus obesa and Parreysia (Parreysia) corrugata with evaluation of sublethal effects on acetylcholinesterase and catalase activity, lipid peroxidation, and behavior.

The median lethal concentrations (LC50) of Pb at 96 h were 8.84, 192.14, and 3.22 mg L-1 for pre-reproductive and reproductive individuals of Lamellidens jenkinsianus obesa and reproductive individuals of Parreysia (Parreysia) corrugata, respectively. Thus, young L. j. obesa were much more sensitive to Pb than its adults, while P. (P.) corrugata was the most sensitive. However, all the three values were much higher than the Pb levels commonly found in natural waters, and indicative of the tolerance of these mollusks to acute, short-term Pb exposure. In contrary to these findings, acetylcholinesterase (AChE) and catalase (CAT) activities were affected and lipid peroxidation (LPO) elevated in young L. j. obesa and P. (P.) corrugata in 21-day sublethal toxicity tests at 26-68 ppb Pb concentrations, which might be considered environmentally realistic. Some behavioral patterns such as number of movement (Mov) and durations of foot mobilization together with siphon extensions (FSE) were reduced, and the durations of valves remaining completely closed without any extension of foot and siphons (VC) increased significantly at 25-69 ppb Pb as well. Thus, the study revealed significant interspecific differences as well as that between life stages of the same species, suggesting that apparently hardy species could be impacted by low Pb concentrations in their young stages. Further, a multi-biomarker approach involving biological effects, anti-oxidative enzyme activity and easy-to-measure behavioral elements could comprise a valuable tool in assessment of Pb-induced stress in freshwater bivalves.

Lead toxicity at different life stages of the giant prawn (Macrobrachium rosenbergii, de Man): considerations of osmoregulatory capacity and histological changes in adult gills

This study evaluated the acute toxicity of lead in different life stages of the freshwater prawn Macrobrachium rosenbergii, determined the effect of sublethal Pb concentrations on osmoregulatory capacity (OC), measured the Pb level in gills, and investigated the effect of Pb on the structure of the gills of adult prawns. The 24-, 48-, and 96-h LC50 values for Pb to M. rosenbergii increased progressively with increasing life stage, from post-larvae (PL), juvenile to adult. The 24- and 48-h LC50 values for post-larvae ranged from 0.01- to 0.09-mg Pb/L. The 24-, 48-, and 96-h LC50 values for Pb were lower at 12 ppt than those at 0 ppt for either the juveniles or the adults. At 12 ppt, the 96-h LC50 values in PL11, juvenile and adult were 0.47-, 0.58-, and 2.03-mg Pb/L, respectively. Meanwhile, at 12 ppt, the 96-h LC50 values in PL11, juvenile and adult were 0.63-, 4.44-, and 7.98-mg Pb/L, respectively. In adults, the OC values of controls and prawns exposed to 2- and 4-mg Pb/L at 0 ppt were not significantly different. The OC of prawns exposed to and 2-mg Pb/L at 12 ppt increased by 72 and 109% from the OC of the control prawns. At media 12 ppt, the OC value of prawns exposed to 1-mg Pb/L was significantly different from that of prawns exposed to 2-mg Pb/L. The concentrations of Pb in gill tissues increased significantly in Pb exposed prawns both at 0 and 12 ppt. The level of Pb in gills of prawns exposed to 2-mg Pb/L at 12 ppt was not significantly different from those exposed at 0 ppt. The severe toxic actions of Pb were noted in gills of prawns exposed in media 12 ppt. Hyperplasia and necrosis were observed in gill lamellae, resulting in abnormal gill tips after Pb exposure at media 12 ppt. Since the effect of Pb is more pronounced in higher salinity (12 ppt) than in freshwater (0 ppt) it is clear that aquaculture of M. rosenbergii should be conducted in freshwater ponds.

Mortality assessment of Oreochromis niloticus fingerlings in varying salinity and influence of salinity changes on acute toxicity of lead

The setting of safe limits for lead (Pb) into the lagoon and protection of fishes such as Oreochromis niloticus has been based on its toxicity ignoring the influence of salinity, an important parameter in the lagoon. The study therefore investigates the salinity tolerance and relative acute toxicity of lead nitrate [Pb(NO3)2] under fresh water and varying salinity against O. niloticus fingerlings. A total of 280 fingerlings were used as test animals and Pb(NO3)2 as test chemical. Concentrations were 1, 2, 4, 6, 8, 10, 30, 40, 50, 60, 80, 120, 160 and 180mg/l at salinity levels of 2, 12, 18, 22, 32, 35 parts per thousand (ppt) and fresh water. Dose response data were analyzed by Probit. Mortality assessment showed that the fingerlings could not survive at salinities of 22, 32 and 35 ppt within 24 h but survived well in 2 ppt. The 96 h LC50 was 130.094 mg/l at 12 ppt but below 12 ppt there was a steady increase in toxicity (3.255 and 6.243 mg/l) in fresh water and 2 ppt respectively. Similarly, the toxicity also increased with an increase in salinity from 12.1 to 18 ppt (113.191 mg/l). The significance of this study shows the need for inclusion of varying salinity in setting of safe limits to confer protection on the delicate biotic components of the rich lagoon biodiversity. Key words: Lead nitrate, Oreochromis niloticus, salinity.

Acute toxicity of lead, cadmium and arsenic mixture in sprague dawley rats

Acute toxicity of lead, cadmium and arsenic mixture in sprague dawley rats

Acute toxicity of lead, cadmium and arsenic mixture in sprague dawley rats

Acute toxicity of lead, cadmium and arsenic mixture in sprague dawley rats

The influence of hydroxyl-functionalized multi-walled carbon nanotubes and pH levels on the toxicity of lead to Daphnia magna

The acute toxicity of lead was examined for Daphnia magna in waters with different pH values (5.0, 6.0, 7.0, 8.0 and 9.0) and different concentrations (0.01, 0.10, 0.50 and 1.00mg/L) of hydroxyl-functionalized multi-walled carbon nanotubes (OH-MWCNTs). The results indicated that pH values could affect the toxicity of lead. With pH values increasing from 5.0 to 9.0, the 24h-LC50 of Pb(II) increased from 0.784 to 9.473mg/L, suggesting that the toxicity of Pb(II) was dramatically decreased. Although OH-MWCNTs almost caused no lethal effect to D. magna at the studied four concentrations, the combination of OH-MWCNTs and Pb(II) could cause more serious toxic effects to D. magna than Pb(II) alone. This study indicated that the synergistic effect caused by CNTs and lead could not be neglected.

Acute toxicity of copper, lead, cadmium, and zinc to early life stages of white sturgeon (Acipenser transmontanus) in laboratory and Columbia River water.

Populations of white sturgeon (Acipenser transmontanus) are in decline in North America. This is attributed, primarily, to poor recruitment, and white sturgeon are listed as threatened or endangered in several parts of British Columbia, Canada, and the United States. In the Columbia River, effects of metals have been hypothesized as possible contributing factors. Previous work has demonstrated that early life stage white sturgeon are particularly sensitive to certain metals, and concerns over the level of protectiveness of water quality standards are justified. Here we report results from acute (96-h) toxicity tests for copper (Cu), cadmium (Cd), zinc (Zn), and lead (Pb) from parallel studies that were conducted in laboratory water and in the field with Columbia River water. Water effect ratios (WERs) and sensitivity parameters (i.e., median lethal accumulations, or LA50s) were calculated to assess relative bioavailability of these metals in Columbia River water compared to laboratory water, and to elucidate possible differences in sensitivity of early life stage white sturgeon to the same concentrations of metals when tested in the different water sources. For Cu and Pb, white sturgeon toxicity tests were initiated at two life stages, 8 and 40 days post-hatch (dph), and median lethal concentrations (LC50s) ranged between 9-25 μg Cu/L and 177-1,556 μg Pb/L. LC50s for 8 dph white sturgeon exposed to Cd in laboratory water and river water were 14.5 and 72 μg/L, respectively. Exposure of 8 dph white sturgeon to Zn in laboratory and river water resulted in LC50s of 150 and 625 μg/L, respectively. Threshold concentrations were consistently less in laboratory water compared with river water, and as a result, WERs were greater than 1 in all cases. In addition, LA50s were consistently greater in river water exposures compared with laboratory exposures in all paired tests. These results, in combination with results from the biotic ligand model, suggest that the observed differences in toxicity between river water exposures and laboratory water exposures were not entirely due to differences in water quality and metal bioavailability but rather in combination with differences in fish sensitivity. It is hypothesized that differences in concentrations of calcium in the different water sources might have resulted in differences in acquired sensitivity of sturgeon to metals. Canadian water quality guidelines, US national criteria for the protection of aquatic life, and water quality criteria for the state of Washington were less than LC50 values for all metals and life stages tested in laboratory and Columbia River water. With the exception, however, that 40 dph white sturgeon exposed to Cu in laboratory water resulted in threshold values that bordered US national criteria and criteria for the state of Washington.

Efeitos do Chumbo no metabolismo do camarão branco (Litopenaeus schmitti) em relação à salinidade

Penaeid shrimps are important resources for worldwide fisheries and aquaculture. In Brazil, Litopenaeus schmitti is animportant commercially exploited species, and the ideal animal for studying the impairment caused by the effects ofheavy metals often detected in coastal areas. The main purpose of the present study was to detect the acute toxicity of lead(Pb) in L. schmitti and to investigate its effect on oxygen consumption and ammonia excretion for different salinities. Thishas not been studied in this species before. Lead was significantly more toxic at salinity 8 than at 20 and 33. The oxygenconsumption and ammonia excretion were estimated through experiments performed on each of the fifteen possiblecombinations of three salinities (33, 20 and 8), at the temperature of 21 °C. Cadmium showed a significant improvementin oxygen consumption at salinity 8, and results show that the oxygen consumption increases with respect to the leadconcentration. At the highest lead concentration employed (2.12 10-2 mg/L), the salinity 8 and the temperature at 21 °C,oxygen consumption increases 131% in relation to the control. In addition, after separate exposure to lead, elevation inammonia excretion was obtained, which was 88.2% higher than the control. The results show that lead is more toxic to L.schmitti at lower salinities.

Effect of Lead on Survival, Osmoregulation, and Histological Changes of the Gills of the White Shrimp, Litopenaeus vannamei, Boone, 1931

AbstractThe purpose of this study was to evaluate the acute toxicity of lead for different life stages of shrimp, Litopenaeus vannamei, and to determine the effect of its sublethal concentrations on osmoregulatory capacity (OC) as well as the possible histological alteration in the gills of juvenile shrimp. The 24‐, 48‐, and 96‐h LC50 values for lead to L. vannamei increased progressively with increasing life stage, from nauplii < zoeae < mysis < postlarvae < juvenile. After 15‐d exposure to 3.25, 6.50, and 9.75 mg Pb/L, the OC values of exposed shrimp were reduced by 39, 73, and 157%, respectively compared to control animals. Compared to controls, the lead concentrations in gill tissues increased significantly by 127,500, 137,500, and 141,000% in shrimps exposed to 3.25, 6.50, and 9.75 mg Pb/L, respectively. After lead exposure, hemocytic congestion in efferent vessels and multiple hyperplasia were observed in gill filaments, resulting in narrowed hemolymphatic lacuna. The histopathological effects increased with increasing Pb concentration.

Acute and chronic toxic effect of lead (Pb) and zinc (Zn) on biomarker response in post larvae of Penaeus monodon (Fabricus, 1798)

Metal pollution produces damage to marine organisms at the cellular level possibly leading to ecological imbalance. The present investigation focused on the acute and chronic toxicity of lead (Pb) and zinc (Zn) by examining the effects of biomarker enzymes in post-larvae of Penaeus monodon (Tiger prawn). Antioxidant biomarker responses such as lipid peroxidation (LPO) and catalase (CAT) activity for Pb and Zn were determined following chronic exposure. Acute Lethal Concentration 50 (LC50) values observed in the study at 96 h for Pb and Zn at 5.77 ± 0.32 mg L−1 and 3.02 ± 0.82 mg L−1, respectively. The estimated No Observed Effect Concentration and Lowest Observed Effect Concentration values for Pb were 0.014 and 0.029 mg L−1 and that recorded for Zn was 0.011 and 0.022 mg L−1, respectively. Among the two metals studied, toxicity of Zn was found to be greater to P. monodon than Pb. The activities of antioxidant defense enzymes and total protein content differed significantly from control following exposure to both metals. Overall, the biomarker studies demonstrated that alterations in antioxidant enzymes and induction of LPO reflect the consequences of heavy metal exposure in P. monodon.

Evaluation of acute toxicity of zinc, lead and cadmium to zooplanktonic community in upper Berach river system, Rajasthan, India

Current study investigated through static bioassay, the acute toxicity of Zinc,Lead and Cadmium to fresh water zooplankters in the upper Berach riversystem which is a part of Gangetic river system. The river basin stretchesfrom Madar tank to Sarjana tank with a total length of 46 Km, including ninewater bodies i.e. Bada madar tank (73‹36f0ffE and 24‹38f0hN ), Chhotamadar tank, Fateh sagar lake, Udaisagar lake, Up]stream pond (Bichhdi]I),Down]stream pond(Bichhdi]II), Gadwa, Daroli and Sarjana tank (73‹ 57f10hEand 24‹14f30h N). Whole zooplanktonic communities were exposed to different heavy metal stresses. Exposed zooplanktonic community included nine planktonic forms i.e. Heliodiaptomus viduus, Mesocyclops hyalinus, Heterocypris, Daphnia lumholtzi, Moina, Brachionus, Monostyla, Filinia. Cadmium was found to be most toxic and Zinc was least toxic to zooplankton. Ostracods and Cyclops were resistant forms and rotifers were sensitive forms in relation to metallic exposure. Sensitivity pattern observed during laboratory experiments was found to be in accordance with biodiversity variation of zooplankton in different ponds of Berach river system.

Multi-linear regression models predict the effects of water chemistry on acute lead toxicity to Ceriodaphnia dubia and Pimephales promelas

The current study examined the acute toxicity of lead (Pb) to Ceriodaphnia dubia and Pimephales promelas in a variety of natural waters. The natural waters were selected to range in pertinent water chemistry parameters such as calcium, pH, total CO2 and dissolved organic carbon (DOC). Acute toxicity was determined for C. dubia and P. promelas using standard 48h and 96h protocols, respectively. For both organisms acute toxicity varied markedly according to water chemistry, with C. dubia LC50s ranging from 29 to 180μg/L and P. promelas LC50s ranging from 41 to 3598μg/L. Additionally, no Pb toxicity was observed for P. promelas in three alkaline natural waters. With respect to water chemistry parameters, DOC had the strongest protective impact for both organisms. A multi-linear regression (MLR) approach combining previous lab data and the current data was used to identify the relative importance of individual water chemistry components in predicting acute Pb toxicity for both species. As anticipated, the P. promelas best-fit MLR model combined DOC, calcium and pH. Unexpectedly, in the C. dubiaMLR model the importance of pH, TCO2 and calcium was minimal while DOC and ionic strength were the controlling water quality variables. Adjusted R2 values of 0.82 and 0.64 for the P. promelas and C. dubia models, respectively, are comparable to previously developed biotic ligand models for other metals.

Influences of water chemistry on the acute toxicity of lead to Pimephales promelas and Ceriodaphnia dubia

The acute toxicity of lead (Pb) was examined for fathead minnows ( Pimephales promelas; 96-h) and daphnids ( Ceriodaphnia dubia; 48-h) in waters modified for hardness (as CaSO 4), dissolved organic carbon (DOC; as Aldrich humic acid) and alkalinity (as NaHCO 3) for parameterization of an acute freshwater biotic ligand model (BLM). Additionally, acute (96-h) and chronic (30-d) bioassays were performed for P. promelas to more clearly define the influence of pH (5.5–8.3) on Pb toxicity as modified by addition of HCl or NaOH using an automated titration system. Results indicate that Ca 2+ is protective against acute Pb toxicity to P. promelas but not C. dubia. Strong protection was afforded by DOC and NaHCO 3 against acute Pb toxicity to P. promelas, whereas milder protection was observed for C. dubia with both parameters. Dissolved Pb LC50s from the P. promelas pH bioassays revealed a complex effect of pH on Pb toxicity, likely explained in part by Pb speciation and the competitive interaction of H + with ionic Pb 2+. Chronic pH bioassays also demonstrated that 30-d growth is not impaired in fathead minnows at relevant Pb concentrations. The findings reported herein suggest that development of separate BLMs for P. promelas and C. dubia should be considered.

Sensitivity of early life stages of freshwater mussels (Unionidae) to acute and chronic toxicity of lead, cadmium, and zinc in water

Toxicity of lead, cadmium, or zinc to early life stages of freshwater mussels (fatmucket, Lampsilis siliquoidea; Neosho mucket, L. rafinesqueana) was evaluated in 48-h exposures with mussel larvae (glochidia), in 96-h exposures with newly transformed (5-d-old) and two- or six-month-old juvenile mussels, or in 28-d exposures with two- or four-month-old mussels in reconstituted soft water. The 24-h median effect concentrations (EC50s) for fatmucket glochidia (>299 microg Pb/L, >227 microg Cd/L, 2,685 microg Zn/L) and 96-h EC50s for two- or six-month-old fatmucket (>426 microg Pb/L, 199 microg Cd/L, 1,700 microg Zn/L) were much higher than 96-h EC50s for newly transformed fatmucket (142 and 298 microg Pb/L, 16 microg Cd/L, 151 and 175 microg Zn/L) and Neosho mucket (188 microg Pb/L, 20 microg Cd/L, 145 microg Zn/L). Chronic values for fatmucket were 10 microg Pb/L, 6.0 microg Cd/L, and 63 and 68 microg Zn/L. When mussel data from the present study and the literature were included in updated databases for deriving U.S. Environmental Protection Agency water quality criteria, mussel genus mean acute values were in the lower percentiles of the sensitivity distribution of all freshwater species for Pb (the 26th percentile), Cd (the 15th to 29th percentile), or Zn (the 12th to 21st percentile). The mussel (Lampsilis) genus mean chronic value was the lowest value ever reported for Pb (the 9th percentile) but was near the middle of the sensitivity distribution for Cd (the 61st percentile) or Zn (the 44th percentile). These results indicate that mussels were relatively sensitive to the acute toxicity of these three metals and to the chronic toxicity of Pb, but were moderately sensitive to the chronic toxicity of Cd or Zn compared to other freshwater species.

Acute and chronic toxicity of lead in water and diet to the amphipod Hyalella azteca

We evaluated the influence of waterborne and dietary lead (Pb) exposure on the acute and chronic toxicity of Pb to the amphipod Hyalella azteca. Test solutions were generated by a modified diluter with an extended (24-h) equilibration period. Acute (96-h) toxicity of Pb varied with water hardness in the range of 71 to 275 mg/L as CaCO3, despite similar dissolved Pb concentrations. Acute toxicity was greatest in soft test water, with less than 50% survival at the lowest dissolved Pb concentration (151 microg/L). Survival also was significantly reduced in medium-hardness water but not in hard test water. In chronic (42-d) studies, amphipods were exposed to waterborne Pb and fed either a control diet or a diet equilibrated with waterborne Pb levels. For animals fed the control diet, the median lethal concentration (LC50) for Pb was 24 degrees g/L (as dissolved Pb), and significant reductions in survival occurred at 16 microg/L. Exposure to Pb-treated diets significantly increased toxicity across a wide range of dissolved Pb concentrations, with a LC50 of 16 microg/L and significant reductions in growth and reproduction at 3.5 microg/L. Significant effects on growth and reproduction occurred at dissolved Pb concentrations close to the current U.S. chronic water-quality criterion. Our results suggest that both aqueous- and dietary-exposure pathways contribute significantly to chronic Pb exposure and toxic effects in aquatic biota.