Combined effects of humic acids and salinity on solid-phase microextraction of DDT and chlorpyrifos, an estimator of their bioavailability

The unbound portion of dissolved hydrophobic environmental contaminants generally is presumed to be the most bioavailable to aquatic organisms. The effects of differing concentrations of Aldrich humic acid (HA) and salinity on the freely dissolved fraction of chlorpyrifos (CPF) and 4,4'-dichlorodiphenyltrichloroethane (DDT) in water were assessed through their relative uptake by solid-phase microextraction (SPME). This extraction method has been recently suggested as a valuable biomimetic tool. Increasing salinity (0-20 parts per thousand [parts per thousand]) alone had no effect on the uptake of DDT by the SPME fiber, but generally enhanced the SPME uptake of the more water soluble CPE Solid-phase microextraction uptake of DDT was decreased at an HA concentration of 10 mg/L, but 100 mg/L was required to decrease CPF uptake. Binding of CPF and DDT by HA was greatly reduced by the presence of salt at 5 to 20 parts per thousand. The extent of the HA and salinity effects appeared to be pesticide-dependent. These factors may ultimately impact the contaminant's environmental fate, transport, and bioavailability, for example, in estuarine situations.     

Bioaccumulation of atrazine and chlorpyrifos to Lumbriculus variegatus from lake sediments

The bioaccumulation of the pesticides chlorpyrifos and atrazine to the benthic oligochaeta Lumbriculus variegatus from four diverse artificially contaminated lake sediments (OC 0.13–21.5%) was studied in the laboratory. The steady state of bioaccumulation was not reached within 10 d. Chlorpyrifos showed stronger bioaccumulation than the less lipophilic atrazine, the biota-sediment accumulation factors (BSAFs) being 6.2–99 for the former and 1.9–5.3 for the latter. While bioaccumulation factors (BAFs) dropped with increasing organic content of the sediments, the high level and considerable range of the obtained BSAFs indicate other sediment qualities, such as the age and characteristics of the organic material, having a strong effect on the bioavailability of these compounds. The slow and incomplete desorption of chlorpyrifos from the most inorganic sediment indicates also that this compound may be strongly bound to some type of inorganic material. Any specific influential sediment fraction or characteristic could not be identified.     

Bioaccumulation of TNT and DDT in Sheepshead Minnows, Cyprinodon variegatus L., Following Feeding of Contaminated Invertebrates

The aim of this study was to determine the potential for dietary uptake by trophic transfer using the explosive 2,4,6-trinitrotoluene (TNT) and the substantially more hydrophobic dichlorodiphenyltrichloroethane (DDT) utilizing the amphipods Leptocheirus plumulosus as prey and the fish Cyprinodon variegatus as predator. Bioaccumulation did not change significantly over time for TNT but apparent steady-state was not reached for DDT at exposure termination after 7 days of dietary exposure. The bioaccumulation factor was 0.09 mg/mg for TNT and 0.34 mg/mg for DDT, confirming the low potential of TNT to bioaccumulate in fish.     

Effect of humic acids on toxicity of DDT and chlorpyrifos to freshwater and estuarine invertebrates

The effects of dissolved humic acids (HAs) on the acute toxicities of the organophosphate pesticide chlorpyrifos and the organochlorine pesticide 4,4'-dichlorodiphenyltrichloroethane (DDT) were assessed by using freshwater crustaceans (Ceriodaphnia dubia) and saltwater crustaceans (Americamysis bahia). The effects of filtered Aldrich HAs (10-100 mg/L) on organism mortality were determined. Humic acids had no effect on mortality of A. bahia for either pesticide at a salinity of 20 parts per thousand, but greatly reduced the mortality of C. dubia for both pesticides in freshwater (0 parts per thousand). In the latter case, the effect was proportional to the HA concentration. The difference in toxicity mitigation as a function of salinity is believed to be due to conformational changes in the HA molecules, which impact pesticide-HA binding, rather than to organismal effects.     

Bioaccumulation and metabolism of phthalate esters by oysters,brown shrimp,and sheepshead minnows

The bioaccumulation and metabolic fate of three phthalate esters, dimethylphthalate (DMP), dibutylphthalate (DBP) and di(2-ethylhexyl)phthalate (DEHP), were studied in three species. The species used, the oyster Crassostrea virginica, the brown shrimp Penaeus aztecus, and the sheepshead minnow Cyprinodon variegatus, were chosen for this study as previous studies indicated that these organisms possessed different capacities for detoxifying xenobiotics. The effects of concentration as well as ester chain length and species were studied. Bioaccumulation did not vary significantly among the three species, possibly due to high levels of individual variation. A trend to higher accumulation in oysters was noted. Bioaccumulation was significantly affected by chain length, with DBP accumulating to a greater extent than DMP or DEHP, and by the concentration of phthalate. Biodegradative indices, on the other hand, were not significantly affected by the ester used or by concentration, but did vary significantly with species. Oysters were less efficient in the biodegradation of the esters than fish or shrimp. The major metabolites found were the monoesters, phthalic acid, and a group of unidentified polar metabolites, probably conjugates. These latter metabolites did not appear in oysters, but were present in significant amounts in fish and shrimp.     

The bioconcentration and metabolism of chlorpyrifos by the eastern oyster,Crassostrea virginica

Eastern oysters (Crassostrea virginica) were exposed to [14C]chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridyl] phosphorothioate) at an average measured seawater concentration of 0.6 microg/L under flow-through conditions for 28 d. The compound O,O-diethyl-O-(3,5-dichloro-6-methylthio-2-pyridyl)phosphorothioate (DMP) was extracted and identified as the single metabolite observed, and this metabolite constituted the majority of the total [14C] activity in the oyster at all sampling times. Once oysters were exposed to clean water, both chlorpyrifos and DMP residues cleared rapidly from whole oysters, with elimination half-lives of <3 d. A simple two-compartment uptake/elimination model was adequate to describe total [14C] activity in whole oysters, edible tissue, and oyster liquor. The average bioconcentration factors (BCFs) for total [14C] activity in whole oysters, edible tissue, and oyster liquor were 565, 1,400, and 35 ml/g, respectively. The parent [14C]chlorpyrifos accumulated to a peak residue concentration of 135 microg/kg in whole oyster tissue, representing an empirical [14C]chlorpyrifos BCF value in the oyster of approximately 225 ml/ g; the BCF value for [14C]chlorpyrifos was lower than the BCF for total [14C] activity in whole oysters and edible tissue because of extensive metabolism to DMP and oyster elimination processes.     

DDT uptake and metabolism by a marine diatom

Conclusion Cylindrotheca closterium, Reimann and Lewin, was capable of absorbing and concentrating DDT above the level in seawater. DDT was metabolized by this organism only to DDE.     

Levels of fenitrothion in Oryzias eggs and the effects on hatchability

Levels of MEP in Oryzias eggs and the effects of MEP on hatchability were investigated. When Oryzias eggs were exposed to MEP-containing water, the eggs contained more MEP the higher the MEP concentration of the water, the more advanced the stage of development, and the longer the exposure. The MEP contents accumulated in the eggs were reduced to 2-19% after they were transferred to dechlorinated tap water for 96 h. There was a significant correlation between the MEP concentration in the water and the MEP content in the eggs. When Oryzias eggs in an early stage of development were exposed to 4 ppm MEP for 96 h or 64 ppm MEP for 6 h and were then placed in dechlorinated tap water until hatching, their hatching rates became significantly lower than those of the control, and abnormal fry occurred frequently. This experiment clarified that increases of MEP in Oryzias eggs were greatly affected by the MEP concentration in the water, and that the hatching rate was reduced and abnormal fry increased, even though the eggs contained the MEP only temporarily.     

Biological effects of fenitrothion in the diet of brook trout

Conclusions The possibility that aquatic and terrestrial insects, killed by operational spray doses of fenitrothion, may cause lethal or sublethal effects directly in salmonids, has been shown by these experiments to be unlikely. The highest level found in poisoned insects by Penney (personal communication) is 3,000 times less than the level at which behavioural effects were noted in Experiment 2. It remains possible that reductions in insect biomass, following spraying, may be of sufficient magnitude and persistence to significantly reduce ration and hence reduce salmonid production. This possibility can only be assessed by direct field observations.     

The inhaled effects of fenitrothion powder on blood cholinesterase in rats

Effects of fenitrothion (Sumithion) powder on red cell acetylcholinesterase (AChE) and plasma cholinesterase (PChE) were studied in vitro and in vivo. Experiments in vitro revealed that fenitrothion has almost the same potency to inhibit AChE (in pre-washed red cell membrane) and PChE. Rats (Wistar, male) were exposed to fenitrothion powder for 4 hours using a new apparatus which can generate powder constantly over a long period. In this experiment, however, no apparent suppression of AChE was found while PChE was markedly inhibited. This inhibition persisted for 3 days after the exposure. This discrepancy was interpreted to be due to the inevitable procedure in preparing red cell specimens, i.e., washing of the red cells. After acute exposure in vivo, fenitrothion appears to be easily removed from the red cells by washing. Thus, PChE, rather than AChE, seems to be a good indicator of an acute exposure to fenitrothion powder in vivo.     

Toxic effects of chlorpyrifos on morphology and acetylcholinesterase activity in the earthworm,Eisenia foetida

The acute toxicity of chlorpyrifos (O, O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) was determined in the earthworm, Eisenia foetida. A 48-h contact test as described by the Organization for Economic Cooperation and Development (OECD) guideline 207 was carried out. The LC(50) of chlorpyrifos was 0.063 microg/cm(2). Inhibition of acetylcholinesterase (AChE: EC 3.1.1.7) activity indicated by in vitro neurotoxic potentiality revealed competitive inhibition and altered K(m) values widely in a dose-dependent manner. The K(i) value of chlorpyrifos was 4.20 x 10(-6)M. AChE activity of LC(50)-exposed worms was 62%, 79%, 85%, and 91% inhibited at 12, 24, 36, and 48h, respectively. Scanning electron microscopic studies revealed the morphological abnormalities in the worms. The present study demonstrates a dose- and time-dependent exposure of chlorpyrifos through skin results, morphological abnormalities, and inhibition of AChE in the earthworm, E. foetida.     

Bioaccumulation and bioamplification of mercury compounds in a second level consumer,Gambusia affinis-temperature effects

Conclusion These results underline the importance of setting up experimental models in ecotoxicology. The use of trophic chains, in conditions that are perfectly controlled and quantified, makes it possible to determine, from a fundamental and applied point of view, the mechanisms responsible for the contamination of natural systems. Nonetheless, such models should be progressively complexified in order to approach the conditions found in situ.We are pursuing our research at the moment on two higher trophic levels, represented by a second level carnivore Salmo gairdneri and a terrestrial mammal at the end of the chain, Rattus norvegicus. The ecotoxicological effects on the level trout are being investigated through research on the tissular distribution of the contaminant and modifications caused to the liver (optic and electronic microscopies, quantitative enzyme and protein analysis) and blood (circulating proteins and enzymes). Using the rat as terminal consumer enables us to simulate the trophic position of man and to measure precisely the degree of contamination in conditions close to those found in the natural environment.     

Comparative metabolism of fenitrothion in aquatic organisms. III. Metabolism in the crustaceans, Daphnia pulex and Palaemon paucidens

When the waterflea Daphnia pulex and the shrimp Palaemon paucidens were exposed to 1.0 ppb [14C]fenitrothion in a flowthrough system, the concentrations of fenitrothion and 14C in the body reached equilibrium, and the maximum bioaccumulation ratios of fenitrothion were 71 and 6 in the daphnia and shrimp, respectively. These crustaceans primarily metabolized the compound by oxidation of P = S to P = O, hydrolysis of P-O-aryl linkage, and demethylation. The liberated phenol was found to be conjugated with sulfate in the daphnia and with glucose in the shrimp. When the organisms were transferred to a freshwater stream, fenitrothion and its metabolites were rapidly excreted from their bodies, and the half-life of the parent compound was less than 0.2 day in both species.