Species at Risk (SPEAR) index indicates effects of insecticides on stream invertebrate communities in soy production regions of the Argentine Pampas.

We investigated relationships among insecticides and aquatic invertebrate communities in 22 streams of two soy production regions of the Argentine Pampas over three growing seasons. Chlorpyrifos, endosulfan, cypermethrin, and lambda-cyhalothrin were the insecticides most frequently detected in stream sediments. The Species at Risk (SPEAR) pesticide bioassessment index (SPEARpesticides) was adapted and applied to evaluate relationships between sediment insecticide toxic units (TUs) and invertebrate communities associated with both benthic habitats and emergent vegetation habitats. SPEARpesticides was the only response metric that was significantly correlated with total insecticide TU values for all three averaged data sets, consistently showing a trend of decreasing values with increasing TU values (r2=0.35 to 0.42, p-value=0.001 to 0.03). Although pyrethroids were the insecticides that contributed the highest TU values, toxicity calculated based on all insecticides was better at predicting changes in invertebrate communities than toxicity of pyrethroids alone. Crustaceans, particularly the amphipod Hyalella spp., which are relatively sensitive to pesticides, played a large role in the performance of SPEARpesticides, and the relative abundance of all crustaceans also showed a significant decreasing trend with increasing insecticide TUs for two of three data sets (r2=0.30 to 0.57, p-value=0.003 to 0.04) examined. For all data sets, total insecticide TU was the most important variable in explaining variance in the SPEARpesticides index. The present study was the first application of the SPEAR index in South America, and the first one to use it to evaluate effects of pesticides on invertebrate communities associated with aquatic vegetation. Although the SPEAR index was developed in Europe, it performed well in the Argentine Pampas with only minor modifications, and would likely improve in performance as more data are obtained on traits of South American taxa, such as pesticide sensitivity and generation time.

Pyrethroid insecticides in urban salmon streams of the Pacific Northwest.

Urban streams of the Pacific Northwest provide spawning and rearing habitat for a variety of salmon species, and food availability for developing salmon could be adversely affected by pesticide residues in these waterbodies. Sediments from Oregon and Washington streams were sampled to determine if current-use pyrethroid insecticides from residential neighborhoods were reaching aquatic habitats, and if they were at concentrations acutely toxic to sensitive invertebrates. Approximately one-third of the 35 sediment samples contained measurable pyrethroids. Bifenthrin was the pyrethroid of greatest concern with regards to aquatic life toxicity, consistent with prior studies elsewhere. Toxicity to Hyalella azteca and/or Chironomus dilutus was found in two sediment samples at standard testing temperature (23 °C), and in one additional sample at a more environmentally realistic temperature (13 °C). Given the temperature dependency of pyrethroid toxicity, low temperatures typical of northwest streams can increase the potential for toxicity above that indicated by standard testing protocols.

Residential runoff as a source of pyrethroid pesticides to urban creeks.

Pyrethroid pesticides occur in urban creek sediments at concentrations acutely toxic to sensitive aquatic life. To better understand the source of these residues, runoff from residential neighborhoods around Sacramento, California was monitored over the course of a year. Pyrethroids were present in every sample. Bifenthrin, found at up to 73 ng/L in the water and 1211 ng/g on suspended sediment, was the pyrethroid of greatest toxicological concern, with cypermethrin and cyfluthrin of secondary concern. The bifenthrin could have originated either from use by consumers or professional pest controllers, though the seasonal pattern of discharge from the drain was more consistent with professional use as the dominant source. Stormwater runoff was more important than dry season irrigation runoff in transporting pyrethroids to urban creeks. A single intense storm was capable of discharging as much bifenthrin to an urban creek in 3h as that discharged over 6 months of irrigation runoff.

Trophic transfer of polychlorinated biphenyls in great blue heron (Ardea herodias) at Crab Orchard National Wildlife Refuge, Illinois, United States.

In this study, polychlorinated biphenyl (PCB) concentrations were measured in great blue heron (GBHE) (Ardea herodias) chicks and eggs at Crab Orchard National Wildlife Refuge (CONWR) in southern Illinois. In addition, biomagnification factors (BMFs) from gizzard shad (Dorosoma cepedianum) and their effects on reproductive effort were examined. Total PCBs (SigmaPCBs) in chicks and shad were greater at the east end of Crab Orchard Lake (i.e., near the site of contamination) than the west end, but chick concentrations (4.1 to 10.1 mg/kg lipid weight) were lower than those typically associated with adverse effects. Chick BMFs based on shad from diet samples were greater than those based on shad collected from the lake. Furthermore, the two shad sources had dissimilar dioxin-like congener patterns and SigmaPCBs, suggesting that there was variation in PCB load and composition and that the more contaminated shad were a small proportion of the actual heron chick diet. The number of eggs laid per nest was similar between colonies, suggesting no observable population level effects. Further study may be necessary to evaluate long-term effects on GBHEs at CONWR.

Partitioning and photodegradation of ciprofloxacin in aqueous systems in the presence of organic matter.

Ciprofloxacin is an extensively used antibiotic that has been reported to occur in surface water. Previous studies have indicated that ciprofloxacin photodegrades and sorbs to particulate organic material within aquatic systems. The first objective of the current study was to evaluate the influence of organic material on photodegradation rates of ciprofloxacin. Using a bench top experimental design, ciprofloxacin was added to experimental chambers that contained only water or water and fine particulate organic matter (FPOM) followed by exposure to ultraviolet light. Sorption to FPOM was rapid, reducing the amount of ciprofloxacin that was available for photodegradation. Thus, the presence of FPOM initially decreased the ciprofloxacin concentration in the aqueous compartment. However by the end of the 16 h test, 42% of the ciprofloxacin was recovered from the test system with FPOM present, while only 2% of the ciprofloxacin was recovered in systems that did not contain FPOM. The second objective of this study was to compare the sorption coefficients for ciprofloxacin between two types of organic material: FPOM, classified as amphipod processed leaves, and coarse particulate organic matter (CPOM), represented by intact leaf disks. Sorption to FPOM (log Kd of 4.54+/-0.09 l kg(-1)) was 1.6 orders of magnitude greater than sorption to CPOM (log Kd of 2.92+/-0.10 l kg(-1)) potentially resulting in differential toxicity among similar organisms that occupy these different niches and leading to different estimates of environmental fate and effects.

Impact of atrazine on chlorpyrifos toxicity in four aquatic vertebrates.

Atrazine has been shown previously to potentiate chlorpyrifos toxicity in selected invertebrates. This study examined interactions of atrazine and chlorpyrifos in four aquatic vertebrates. Organisms were exposed to binary mixtures of atrazine and chlorpyrifos during toxicity bioassays. Inhibition of cholinesterase (ChE) enzyme activity and chlorpyrifos uptake kinetics were also examined with and without atrazine exposure. Atrazine alone did not affect organisms at concentrations up to 5000 microg/L; however, the presence of atrazine at 1000 microg/L did result in a significant increase in the acute toxicity of chlorpyrifos in Xenopus laevis. Mixed results were encountered with Pimephales promelas; some bioassays showed greater than additive toxicity, while others showed an additive response. No effect of atrazine on chlorpyrifos toxicity was observed for Lepomis macrochirus and Rana clamitans. Atrazine did not affect ChE activity or chlorpyrifos uptake rates, indicating that these toxicodynamic and toxicokinetic parameters may not be related to the mechanism of atrazine potentiation of chlorpyrifos toxicity. Based on the results of this study, it does not appear that a mixture toxicity of atrazine and chlorpyrifos at environmentally relevant concentrations presents a risk to the vertebrate organisms examined in this study.

Effects of triazine herbicides on organophosphate insecticide toxicity in Hyalella azteca.

The frequent use of pesticides in agricultural and commercial settings has led some researchers to devote their attention to studying the effects of mixtures of these compounds as they co-occur in the environment. Recent studies have demonstrated the potentiating effects of triazine herbicides, such as atrazine and its analogs, to the toxicity of a variety of organophosphate (OP) insecticides. One such OP insecticide, chlorpyrifos, has been the topic of much concern because of its prevalence in the environment. This study focused on examining the effects of 10 select triazine herbicides at concentrations of 1 mumole/L (approximately 200 mug/L) to chlorpyrifos with Hyalella azteca. The compounds selected include atrazine, three of its degradation products, and six other herbicide active ingredients. Toxicity tests were performed using a two-way analysis of variance matrix design with effect levels determined by way of probit analysis. Atrazine was found to have the greatest acutely lethal effect to H. azteca, followed by its closest degradation product, deethylatrazine. Two of the six atrazine analogs, simazine and cyanazine, also showed significant effects to the insecticide's toxicity. Synergistic ratios (SRs) were calculated to compare the effect magnitudes for each of the herbicides. The highest ratio obtained was with atrazine (SR = 1.42). A majority of the past studies involving mixtures of triazines and OPs have examined the potentiation effects of active-use triazine herbicides on Chironomus species. However, compared with the acute effects previously obtained for Chironomus species, H. azteca show a higher tolerance to the presence of the triazine herbicides, even at levels often considered as being at the high end of environmentally relevant concentrations. When coupled with past studies from our laboratory, this research helps to provide a better understanding of the toxic effects of herbicide-insecticide interactions.

Comparative toxicokinetics of explosive compounds in sheepshead minnows.

Juvenile sheepshead minnows Cyprinodon variegatus were exposed to the explosive compounds 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and to the TNT transformation products 2-aminodinitrotoluene (2-ADNT) and 2,4-diaminonitrotoluene (2,4-DANT) in five separate water-only experiments. A one-compartment model was used to characterize uptake (k(u)) and elimination (k(e)) rate constants and to estimate bioconcentration factors (BCFs). The compounds investigated in this study are weakly hydrophobic. Kinetically derived BCFs (9.6, 13.1, 0.5, 1.7, and 0.5 ml g(-1) for TNT, 2-ADNT, 2,4-DANT, RDX, and HMX, respectively) confirmed the expected low bioaccumulative potential of those compounds and the positive relationship between log BCF and log K(ow) (1.6, 2.0, 0.8, 0.9, and 0.2 for TNT, 2-ADNT, 2,4-DANT, RDX, and HMX, respectively). The uptake clearance (k(u)) was relatively slow for all compounds (7.3, 12.6, 1.3, 0.15, and 0.06 ml g(-1)h(-1) for TNT, 2-ADNT, 2,4-DANT, RDX, and HMX, respectively), and overall, it decreased with decreasing compound hydrophobicity. Elimination was extremely fast for the nitroaromatic compounds (0.77, 0.96, and 2.74 h(-1) for TNT, 2-ADNT, and 2,4-DANT, respectively), thus resulting in very short biological half-lives (<1 hour), but it was much slower for the cyclonitramines (0.09 h(-1) for RDX and 0.12 h(-1) for HMX). Although ADNTs were present in fish exposed to TNT, the parent compound was the dominant compound in tissues during the uptake and elimination exposures. The rates of metabolite formation (0.06 h(-1)) and elimination (0.16 h(-1)) were much slower than the rate of elimination of the parent compound (0.80 h(-1)). Because of the fast elimination rate of TNT and its transformation products and the exceedingly low bioaccumulative potential of RDX and HMX, exposure conditions likely associated with the presence of explosives in aquatic systems are unlikely to pose unacceptable risks to fish.

Joint toxicity of triazine herbicides and organophosphate insecticides to the midge Chironomus tentans.

A series of recent studies demonstrated that the triazine herbicide atrazine, although not itself acutely toxic, potentiated the toxicity of certain organophosphate insecticides (OPs) to the midge Chironomus tentans. In the current study, a series of triazine herbicides and triazine herbicide degradation products were tested to determine if other triazines potentiate OP toxicity to midges. Chlorpyrifos and diazinon were the OPs tested. Toxicity tests were conducted using a factorial design and analysis of variance to statistically determine if each triazine had an effect on expected toxicity. Log-probit procedures were also used to evaluate the magnitude of change in median effective concentration (EC50) values during coexposure with each triazine. All of the triazine herbicides tested (atrazine, simazine, cyanazine, and hexazinone) were capable of potentiating the toxicity of the OPs, whereas the degradation products (s-triazine, deethylatrazine, and deisopropylatrazine) had less effect. In most cases, a triazine concentration of 100 microg/L was necessary to significantly increase OP toxicity, and higher concentrations of triazine caused a greater degree of potentiation. Changes in EC50 values ranged from no change to a 2.5-fold increase in toxicity. Generally, EC50 values changed by less than a factor of 2, indicating that the effect may be of limited concern in regard to future risk assessments of OPs.

Toxicity assessment of pesticide mixtures typical of the Sacramento-San Joaquin Delta using Chironomus tentans.

This study examined the effects of nine commonly detected pesticides in the Sacramento-San Joaquin Delta on the aquatic midge Chironomus tentans. Pesticides were chosen from a variety of chemical classes including organophosphate (OP) insecticides as well as triazine, triazinone, and substituted urea herbicides. Both single toxicant and binary mixture bioassays were performed. In addition, midges were pre-exposed to DDE at environmentally relevant concentrations and then challenged by exposing them to chlorpyrifos or diazinon in single-toxicant acute bioassays. Results indicate that most of the binary mixtures elicited additive responses in C. tentans, whereas OP insecticides in combination with various herbicides caused greater-than-additive responses. Pre-exposures with DDE did not have a significant impact on subsequent OP challenges at DDE concentrations of 0.2, 2, and 20 microg/kg. This study represents an important first step in understanding the interactions among various pesticides commonly detected throughout the Delta.

Aquatic toxicity due to residential use of pyrethroid insecticides.

Pyrethroids are the active ingredients in most insecticides available to consumers for residential use in the United States. Yet despite their dominance in the marketplace, there has been no attempt to analyze for most of these compounds in watercourses draining residential areas. Roseville, California was selected as a typical suburban development, and several creeks that drain subdivisions of single-family homes were examined. Nearly all creek sediments collected caused toxicity in laboratory exposures to an aquatic species, the amphipod Hyalella azteca, and about half the samples caused nearly complete mortality. This same species was also found as a resident in the system, but its presence was limited to areas where residential influence was least. The pyrethroid bifenthrin is implicated as the primary cause of the toxicity, with additional contributions to toxicity from the pyrethroids cyfluthrin and cypermethrin. The dominant sources of these pyrethroids are structural pest control by professional applicators and/ or homeowner use of insecticides, particularly lawn care products. The suburbs of Roseville are unlikely to be unique, and similar sediment quality degradation is likely in other suburban areas, particularly in dry regions where landscape irrigation can dominate seasonal flow in some water bodies.

A sonication extraction method for the analysis of pyrethroid, organophosphate, and organochlorine pesticides from sediment by gas chromatography with electron-capture detection.

A method was developed for the simultaneous determination of 5 pyrethroid, 1 organophosphate, and 20 organochlorine pesticides in sediment. Pesticide residues were extracted using sonication with acetone-methylene chloride (1:1 vol/vol) and the extracts were subsequently cleaned with deactivated Florisil (magnesium silicate; U.S. Silica, Berkeley Springs, West Virginia). Gas chromatography with an electroncapture detector was used for analyte determination, and two columns were used for confirmation of the analytes. Four control sediments from different sources were spiked with a pesticide mix and analyzed for method validation. The method detection limits ranged from 0.22 to 0.85 microg/kg dry sediment. Recoveries for spiked samples at four concentrations (1, 5, 20, and 400 microg/kg dry sediment) were 71.9% to 129.8% with relative standard deviations (RSDs) < 11%. Taking the matrix effect into account, 1 microg/kg was chosen for the threshold of detection, but 0.5 microg/kg of spiked control sediment still provided good recoveries and RSDs. This method was validated using field-collected sediment taken from agricultural areas of Fresno County, California.

Evaluation of desulfuration methods for pyrethroid, organophosphate, and organochlorine pesticides in sediment with high sulfur content.

This study investigated different cleanup procedures to eliminate sulfur interference from sediments from a reclaimed mining site in Sparta, Illinois. Sonication extraction with activated copper powder was the most effective method to eliminate elemental sulfur. Extracts were then cleaned with a Florisil column before pyrethroid, organophosphate, and organochlorine pesticides were determined using gas chromatography with electron-capture detection. The method detection limits ranged from 0.03 to 0.68 microg/kg dry sediment. Recoveries for spiked samples were from 82.2% to 132.7% with relative standard deviations < 15%. Fifty-four sediment samples collected from 15 lakes and 1 stream in the proposed Illinois National Guard Armory were analyzed using the desulfuration procedure. Of the 26 target pesticides analyzed in sediment, 20 were detected above the detection threshold of 1 microg/kg. DDT was detected most frequently (found at 50% of the sampling sites), whereas permethrin was found at the greatest concentration.

Distribution and toxicity of sediment-associated pesticides in agriculture-dominated water bodies of California's Central Valley.

The agricultural industry and urban pesticide users are increasingly relying upon pyrethroid insecticides and shifting to more potent members of the class, yet little information is available on residues of these substances in aquatic systems under conditions of actual use. Seventy sediment samples were collected over a 10-county area in the agriculture-dominated Central Valley of California, with most sites located in irrigation canals and small creeks dominated by agricultural effluent. The sediments were analyzed for 26 pesticides including five pyrethroids, 20 organochlorines, and one organophosphate. Ten-day sediment toxicity tests were conducted using the amphipod Hyalella azteca and, for some samples, the midge Chironomus tentans. Forty-two percent of the locations sampled caused significant mortality to one test species on at least one occasion. Fourteen percent of the sites (two creeks and four irrigation canals) showed extreme toxicity (>80% mortality) on at least one occasion. Pyrethroid pesticides were detected in 75% of the sediment samples, with permethrin detected most frequently, followed by esfenvalerate > bifenthrin > lambda-cyhalothrin. Based on a toxicity unit analysis, measured pyrethroid concentrations were sufficiently high to have contributed to the toxicity in 40% of samples toxic to C. tentans and nearly 70% of samples toxic to H. azteca. Organochlorine compounds (endrin, endosulfan) may have contributed to the toxicity at a few other sites. This study provides one of the first geographically broad assessments of pyrethroids in areas highly affected by agriculture, and it suggests there is a greater need to examine sediment-associated pesticide residues and their potential for uptake by and toxicity to benthic organisms.

Assessing the impact of triazine herbicides on organophosphate insecticide toxicity to the earthworm Eisenia fetida.

A standard Organization for Economic Cooperation and Development (OECD) filter paper test was used to assess the acute toxicity of chlorpyrifos, atrazine, cyanazine, and simazine to the earthworm Eisenia fetida. Acute toxicity of chlorpyrifos was also determined in combination with the three-triazine herbicides. Surprisingly, atrazine and cyanazine caused mortality at concentrations lower than chlorpyrifos. Atrazine and cyanazine also increased the toxicity of chlorpyrifos 7.9- and 2.2-fold, respectively. However, simazine caused no toxicity to the worms and did not affect chlorpyrifos toxicity in binary mixture experiments. Possible mechanisms for the greater-than-additive toxicity for the binary combinations of atrazine and cyanazine with chlorpyrifos were investigated, including changes in uptake and biotransformation rates of chlorpyrifos in the presence of atrazine. Uptake of chlorpyrifos into the worms decreased slightly when atrazine was present in the system, therefore eliminating increased uptake as a possible explanation for the increased toxicity. Body residue analysis of worms indicated increased metabolite formation, suggesting the greater-than-additive response may be due to increased biotransformation to more toxic oxon metabolites.

An assessment of water quality, physical habitat, and biological integrity of an urban stream in Wichita, Kansas, prior to restoration improvements (phase I).

Urban development alters the natural hydrological conditions of many streams and rivers often resulting in the degradation of water quality, physical habitat, and biotic integrity of lotic systems. Restoration projects attempt to improve and maintain the ecological integrity of urban streams; however, few projects have quantified improvements to stream ecology following implementation of restoration measures. This paper summarizes pre-restoration data collected as part of an urban stream restoration project on Gypsum Creek in Wichita, Kansas. Water quality monitoring revealed eutrophic conditions in the stream and the presence of pesticides. Channelization has led to changes in physical habitat including bank erosion, sedimentation, loss of substrate and channel diversity, elimination of in-stream aquatic habitat, removal of riparian vegetation, and decreased base flows. Benthic macroinvertebrate communities appear degraded with more than 90% of individuals collected described as tolerant to anthropogenic stressors. Fish communities were assessed with an Index of Biotic Integrity and were rated as poor to fair, with trophic structure dominated by generalists, no sensitive species present, and one-third of the species collected considered non-native. Overall, the data collected strongly suggest that site-specific restoration measures need to be implemented in order to improve and maintain the ecological condition of Gypsum Creek. Recommendations for improvements have been made to city managers, with implementation beginning in spring 2003 (dependent upon funding availability).

Remediation of heavy metal-contaminated soils using phosphorus: evaluation of bioavailability using an earthworm bioassay.

This study investigated the effectiveness of phosphorus (P) as an in situ remediation technique in site soils collected from the Tri-State mining area. The site soils were treated with two different types (KH(2)PO(4) and Super Triple Phosphate fertilizer) and levels (600 and 5,000 mg/kg) of phosphorus. A toxicokinetic approach was used to determine whether phosphorus amendments reduced heavy metal bioavailability to the earthworm Eisenia fetida. Bioaccumulation factors were used as a measure of bioavailability. Depuration patterns of lead, zinc, and cadmium also were studied after removing earthworms from contaminated soils and then placing them in noncontaminated artificial soil. Results showed that the high phosphorus treatments significantly reduced lead, zinc, and cadmium bioavailability to the earthworms, probably due to formation of metal-phosphate complexes in the soils. Results also indicated that other soil characteristics in addition to amended phosphorus have an affect on bioavailability. Depuration experiments showed a biphasic elimination pattern for each metal. The current results indicate that phosphorus soil amendments may reduce ecological risk to soil-inhabiting invertebrates exposed to heavy metal-contaminated soils.

Bioavailability of sediment-associated benzo(a)pyrene within single- versus multiple-species systems.

A series of experiments were conducted with benzo(a)pyrene (B(a)P) spiked sediments to determine if bioavailability of sediment-associated contaminants is affected by multiple species interactions. Three benthic invertebrates, Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus, were exposed to sediments spiked with radiolabeled B(a)P that was aged for 60 days. Organisms were introduced into the spiked sediments in single, binary, and ternary combinations. Changes in bioavailability were then determined for each species by estimating uptake clearance coefficients (ks) and bioaccumulation factors (BAFs) during 7-day exposures. In general, there was a trend toward lower ks values in binary and ternary exposures compared to the single-species systems. In contrast, BAF estimates were more variable with fewer significant differences noted among treatments. BAF estimates were highest for L. variegatus followed by C. tentans and H. azetca and appear to be dependent on specific feeding and habitat requirements as well as the relative biotransformation/elimination potential of each species. Overall, these results suggest that animal-animal interactions may be important to consider when estimating bioavailability of sediment-bound chemicals.