ISSN:0730-7268    

DOI:10.1002/etc.5620080501

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractIt has been almost 25 years since the classic studies first described the pyrethroid mode of action on voltage—dependent sodium channels. In the interval that followed, this electrophysiological approach has been enlarged upon using a variety of preparations with essentially the same result. Thus, there is little disagreement that pyrethroids have an action at or near the sodium channel in the nerve. Recently, a number of additional mechanisms have been suggested, including the perturbation of the voltage—dependent calcium channels. Using a functional bioassay that consists of a calcium—dependent, potassium—stimulated pulsed release of norepinephrine from rat brain synaptosomes, Type II pyrethroids caused a substantial enhancement of norepinephrine release that was not apparent when Type I pyrethroids were used. The ED50 dose of deltamethrin that resulted in half—maximal enhanced norepinephrine release (i.e., 2.9 × 10−9M) correlated well with the ED50 dose of deltamethrin that resulted in half—maximal enhanced45Ca uptake (i.e., 2.4 × 10−9M). Norepinephrine release was only partially blocked by tetrodotoxin and a calcium channel antagonist, D595. Deltamethrin enhanced norepinephrine release in the presence of tetrodotoxin but was unable to enhance release in the presence of D595. These results are supportive of a highly sensitive action of Type II pyrethroids at presynaptic nerve terminals in the central nervous system and of the involvement of voltage—depende

ISSN:0730-7268    

DOI:10.1002/etc.5620080502

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe pyrethroid insecticides are extremely toxic to fish, with 96—h LC50 values generally below 10 μg/L and i.p. and i.v. LD50 values below 20 mg/kg. Corresponding LD50 values in mammals and birds are in the range of several hundred to several thousand milligrams per kilogram. This review examines pyrethroid toxicokinetics and toxicodynamics in fish as critical factors associated with species selectivity. Studies with permethrin, cypermethrin and fenvalerate have established that rates of metabolism and elimination in rainbow trout are significantly lower than those reported for birds and mammals. Comparatively low lethal brain pyrethroid concentrations and nonneural aspects of pyrethroid intoxication in fish suggest that variations in toxicodynamics are also crucial in evaluating pyrethroid selectivi

ISSN:0730-7268    

DOI:10.1002/etc.5620080503

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA selected review of the biological, chemical and environmental factors that affect the acute and chronic, lethal and sublethal toxicity of pyrethroid insecticides to fish is presented. Pyrethroid insecticides are extremely toxic to fish; for example, 96—h LC50 values are in the nmol/L range. The symptoms associated with acute lethality suggest that effects on the nervous system, respiratory surfaces and renal ion regulation are associated with the mechanism of lethal action in fish.Qualitative structure—activity relationships indicate that the structural features required for good insecticidal activity and for lethality to fish are the same. Lethality also varies with biological (species, size) and environmental (temperature, sediment) factors. Some of these effects may be related to bioavailability and rates of pyrethroid biotransformation.Chronic exposure studies indicate that newly hatched larvae or early juveniles are the life stages most sensitive to pyrethroids. Exposures of fish to sublethal concentrations of pyrethroids have resulted in decreased growth and impaired swimming performance. The effects on bioenergetics and energy metabolism are varia

ISSN:0730-7268    

DOI:10.1002/etc.5620080504

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractData on the acute and chronic toxicities of permethrin, fenvalerate, cypermethrin and flucythrinate to marine invertebrates and fish are reviewed. Generally, crustaceans are more sensitive than fish; oysters are comparatively insensitive. The mysidMysidopsis bahiaconsistently is among the most sensitive crustaceans tested, with 96—h LC50s of less than 0.02 μg/L for permethrin and of less than 0.01 μg/L for fenvalerate, cypermethrin and flucythrinate. The potential for chronic toxicity to fish is minimal for permethrin, moderate for fenvalerate and relatively great for flucythrinate.Laboratory toxicity tests were conducted with sediment—source fenvalerate and cypermethrin under static and flow—through conditions to determine the degree of contamination necessary to achieve acute lethal effects on mysids, grass shrimp (Palaemonetes pugio) and pink shrimp (Penaeus duorarum). Mortality was observed in test animals only in systems where the concentrations of sediment—source pyrethroids were sufficient to establish lethal concentrations in the overlying water through sediment/water partitioning. For fenvalerate, lethal effects occurred at nominal sediment concentrations of 0.1 mg/kg (static and flow—through) for mysids and grass shrimp and at 10 mg/kg for pink shrimp. Nominal sediment concentrations of cypermethrin of 0.1 mg/kg (static) or 1.0 mg/kg (flow—through) resulted in mortality in mysids and grass shrimp, whereas 1.0 mg/kg was the only test concentration that caused mortality in pink shrimp in the static and flow—through test systems. The correspondence between aqueous concentrations and LC50s for test animals demonstrated the importance of quantitating the bioavailable portion of pyrethroids in field samples to characterize accurately the environmental risk associated with pyrethroid runoff after agricultur

ISSN:0730-7268    

DOI:10.1002/etc.5620080505

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThis report reviews the laboratory toxicity data on freshwater target and nontarget invertebrates exposed to pyrethroids and evaluates the state of the data. Early in their development, pyrethroids were shown to be highly effective insecticides against mosquitoes, blackflies and chironomids. Acute LC50 values for these target animals were often less than 1 μg/L. Acute exposures of nontarget invertebrates showed that some species were as sensitive as the target insects. Longer exposures, up to 28 d, showed that lethal effect concentrations were lowered with increased exposure duration. Unfortunately, the long—exposure tests were limited to a few species and a few pyrethroids, so no general commentary on no effect concentrations is possible. Some species were affected at concentrations near the analytical detection limit for pyrethroids. The data reviewed show that temperature, life cycle stage and exposure duration will be critical factors in developing the no effect concentrations that are important in risk assessments for nontarget invertebrates exposed to these insecticid

ISSN:0730-7268    

DOI:10.1002/etc.5620080506

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA review of the acute, subacute and chronic effects of four synthetic pyrethroids —permethrin, cypermethrin, deltamethrin and fenvalerate —on freshwater zooplankton is presented. Acute toxicities in the laboratory were found to range from 0.12 to 5.0 μg/L for cladocerans and copepods. Lower concentrations of pyrethroids (≤0.01 μg/L) reduced reproduction and rates of filtration of food by daphnids. Similar results were observed in field experiments. Simulation of direct overspray of aquatic ecosystems resulted in subsurface concentrations of pyrethroids greater than the levels known to be toxic in the laboratory (>1 μg/L). At these concentrations, populations of cladocerans were reduced. At concentrations of 0.05 μg/L or greater, rates of filtration by cladocerans were depressed. Indirect effects on communities included increases in populations of rotifers and green algae (Chlorophyta). Higher levels of contamination (>10 μg/L) caused reductions in copepods, rotifers and ostracods. Levels of pyrethroids of 0.01 μg/L or less were found to have no detectable effects on zooplankton i

ISSN:0730-7268    

DOI:10.1002/etc.5620080507

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractField and laboratory toxicity tests were conducted on the grass shrimp,Palaemonetes pugio, to evaluate the usefulness of laboratory testing in estimating mortality from fenvalerate exposure associated with agricultural runoff. The study examined an integrated approach for assessing the impacts of fenvalerate on estuarine fauna, using 96—h static—renewal and 6—h pulsed—dose laboratory toxicity tests and in situ toxicity tests. The laboratory toxicity tests with fenvalerate gave 96—h LC50 values ranging from 0.007 to 0.071 μg/L and 6—h PDLC50 values ranging from 0.100 to 0.130 μg/L. Comparisons of the results of two field toxicity tests with laboratory—derived LC50 values showed good agreement between field and laboratory toxicity data. The variation between field and laboratory toxicity tests may have been due to the limitations of the water sampling regime used in characterizing the pesticide exposure during the field toxicity tests. These comparisons suggest that a combination of laboratory and field toxicity testing is required to estimate the actual field mortality from fenvalerate exposure associated with agricultural runoff. Future studies should include composite water sampling and more frequent discrete sampling methods to better characterize field e

ISSN:0730-7268    

DOI:10.1002/etc.5620080508

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe additivity model developed earlier for 65 substituted benzenes has been extended to 105 compounds for the fathead minnow system. Toxicity is predicted for 10 compounds not included in the original data set. Four new substituents have been evaluated and their toxicity contributions have been determined by regression analysis. For the whole data set, the following statistics were obtained for the 12—variable model:r=0.921,s=0.31,F=43. The order of toxicity contributions for all substituents now investigated is as follows: —NO2≈ —Cl>—Br>—CHO>—CH3≈ —F>—NH2≈ —CN>—OH ≈ —OCH3>—COCH3. Also identified in these analyses is the additional toxicity conferred by theortho—hydroxybenzaldehyde combination. Such a structural arrangement increases toxicity by 1.45 units over both themetaandparaarrangements. For the 11 substituents, relationships have been sought between the toxicity contribution and physicochemical parameters, including partition coefficient (π) and electronic parameters, but no significant relation has been found. Also evaluated were five additional substituents for which there are few data. Approximate toxicity contributions a

ISSN:0730-7268    

DOI:10.1002/etc.5620080509

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA comparative ecological and toxicological investigation was conducted on a secondary wastewater treatment plant point—source discharge and the receiving system, a fourth—order freshwater stream in the Kentucky River basin. Biological, chemical, hydrological and on—site toxicological studies were performed at 10 monitoring stations, including reference sites. The principal objectives were to assess downstream persistence of aquatic contaminants, to quantify their effects on structure and function of aquatic communities and to evaluate the 8—d fathead minnow embryo—larval test for measuring instream toxicity and estimating chronic effects on aquatic biota. The principal ecological endpoints included species richness, diversity (H'), density and dominance (D) of macroinvertebrates and diversity of fish species. Macroinvertebrates were further analyzed by trophic groups. Marked downstream gradients existed for effluent dilution, decreasing concentration of selected chemicals, improvement in ecological conditions and decreasing toxicity, as measured in on—site static—renewal tests. A good predictive correlation was found between embryo—larval survival and independent ecological parameters, especially species richness of macroinvertebrates. In addition, static—renewal and flow—through toxicity tests were performed with effluent dilutions to determine LC50 and toxicity threshold values (LC1), expressed as percent effluent by volume. The estimated toxicity thresholds correlated closely with the actual percent instream effluent dilution observed at the first downstream station at which no ecological imp

ISSN:0730-7268    

DOI:10.1002/etc.5620080510

出版商:Wiley Periodicals, Inc.    

年代:1989

数据来源: WILEY