From the viewpoint of protecting the natural environment, aquatic ecotoxicological assessment of new pesticides and many existing ones has increasingly become more important. To assess the impact of pesticides on aquatic organisms, international authorities (utilizing OECD and USEPA testing guidelines) require completion of many acute and chronic ecotoxicological studies. Among such studies is testing to measure the potential for bioconcentration. In addition, the authorities in these agencies insist that physico-chemical properties and environmental fate be determined for each registered pesticide. The rationale for such testing is based on the concept that, even if used in conformance with good agricultural practices, pesticides may enter surface waters by several routes such as spray drift, surface runoff, and field drainage, and they may be partitioned to bottom sediments (Katagi 2006). The endpoints of such ecotoxicological testing include mortality and effects on hatching, development, and reproduction. Such endpoints are usually expressed as median-lethal or median-effect concentrations (LC50 and EC50) and no-observed-effect-concentrations (NOEC); such values can be compared with predicted environmental concentrations in exposure media for purposes of risk assessment (Miyamoto et al. 2008). Because aquatic organisms interact with each other in the food web, knowledge of their tendency to bioconcentrate residues in water and from dietary exposure is important when evaluating real environmental pesticide effects. In general, bioconcentration is the most popular term for describing the process by which pesticides enter organisms directly from water through the gills or through epithelial tissues. In contrast, bioaccumulation includes the effect of dietary uptake through food consumption or intake of bottom sediments (Miyamoto et al. 1990). When the levels of a pesticide, accumulated by organisms, are concentrated through two or more trophic levels in a food web, the process is referred to as biomagnification (Connell 1988).

Bioconcentration, bioaccumulation, and metabolism of pesticides in aquatic organisms.

DISCLAIMER The use of company or product name(s) is for identification only and does not imply endorsement by the Agency for Toxic Substances and Disease Registry. This edition supersedes any previously released draft or final profile. Toxicological profiles are revised and republished as necessary. For information regarding the update status of previously released profiles, contact ATSDR at: Toxicological Profiles are a unique compilation of toxicological information on a given hazardous substance. Each profile reflects a comprehensive and extensive evaluation, summary, and interpretation of available toxicologic and epidemiologic information on a substance. Health care providers treating patients potentially exposed to hazardous substances will find the following information helpful for fast answers to often-asked questions. Chapter 1: Public Health Statement: The Public Health Statement can be a useful tool for educating patients about possible exposure to a hazardous substance. It explains a substance's relevant toxicologic properties in a nontechnical, question-and-answer format, and it includes a review of the general health effects observed following exposure. Chapter 3: Health Effects: Specific health effects of a given hazardous compound are reported by type of health effect (death, systemic, immunologic, reproductive), by route of exposure, and by length of exposure (acute, intermediate, and chronic). In addition, both human and animal studies are reported in this section. NOTE: Not all health effects reported in this section are necessarily observed in the clinical setting. Please refer to the Public Health Statement to identify general health effects observed following exposure. The following additional material can be ordered through the ATSDR Information Center: Case Studies in Environmental Medicine: Taking an Exposure History—The importance of taking an exposure history and how to conduct one are described, and an example of a thorough exposure history is provided. Other case studies of interest include Reproductive and Developmental viii HEXACHLOROCYCLOHEXANE Hazards; Skin Lesions and Environmental Exposures; Cholinesterase-Inhibiting Pesticide Toxicity; and numerous chemical-specific case studies. Managing Hazardous Materials Incidents is a three-volume set of recommendations for on-scene (prehospital) and hospital medical management of patients exposed during a hazardous materials incident. Volumes I and II are planning guides to assist first responders and hospital emergency department personnel in planning for incidents that involve hazardous materials. Volume III— Medical Management Guidelines for Acute Chemical Exposures—is a guide for health care professionals treating patients exposed to hazardous materials. Fact Sheets (ToxFAQs) provide answers to frequently asked questions about toxic substances. The National Center for Environmental Health (NCEH) focuses …

Toxicological profile for alpha-, beta-, gamma, and delta-hexachlorocyclohexane

The effects of the antiepileptic drug carbamazepine (CBZ) were studied in three freshwater invertebrate species representing different taxonomic groups, life histories, and habitats in aquatic ecosystems. The oligochaete Lumbriculus variegatus was exposed by way of CBZ-spiked sediments at nominal concentrations between 0.625 and 10 mg/kg dry weight (dw) for 28 days. At the end of the test, reproduction and biomass were monitored as end points. The nonbiting midge Chironomus riparius was exposed to CBZ in a series of tests at nominal CBZ concentrations in sediment ranging from 0.16 to 100 mg/kg dw at 20°C and 23°C. Emergence and gender ratio were monitored at the end of the test. The freshwater snail Potamopyrgus antipodarum as the third test species was used in a chronic reproduction test for 28 days at aqueous CBZ concentrations from 0.4 to 250 mg/L. Whereas for the oligochaete and the snail no effects were observed, C. riparius exhibited a significant and concentration-dependent decrease of emergence in all test series. No observed effect concentrations and 10% effect concentrations were in the range of 33 to 140 and 70 to 210 μg/kg dw, respectively, based on measured CBZ concentrations in sediments. These low values indicate that CBZ may pose a potential threat for the survival of C. riparius and probably also for other aquatic insect populations in the field.

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Effects of Pharmaceuticals on Aquatic Invertebrates. Part I. The Antiepileptic Drug Carbamazepine

There is an ongoing debate regarding whether nonextractable (bound) pesticide residues in soils are occluded or may remain bioavailable in the long term in the environment. This study investigated the release of 14C-labeled residues, which were previously nonextractable after exhaustive extraction with organic solvents in soils, and their uptake by earthworms (Aporrectodea longa). After a 100-day incubation of soils treated with 14C-labeled atrazine, isoproturon, and dicamba and exhaustive Soxhlet extractions with methanol and dichloromethane, nonextracted 14C-labeled residues remaining in the soils were 18, 70, and 67%, respectively. Adding clean soil in the ratio of 7:1 increased the volumes of these extracted soils. After earthworms had lived in these previously extracted soils for 28 days, 0.02-0.2% of previously bound 14C activity was absorbed into the earthworm tissue. Uptake by earthworms was found to be 2-10 times higher in soils containing freshly introduced 14C-labeled pesticides as compared to soils containing nonextractable 14C-labeled residues. The differential bioavailability observed between freshly introduced 14C-labeled pesticides and those previously nonextractable may be related to the ease of transfer of the 14C activity into the solution phase. By the end of the 28-day incubation period, 3, 23, and 24% of previously nonextractable 14C-labeled isoproturon, dicamba, and atrazine residues, respectively, were extracted by solvents or mineralized to 14CO2. The amounts of 14C activity released were not significantly different in the presence or in the absence of earthworms in soils containing previously nonextractable residues. However, the formation of bound residues was 2, 2, and 4 times lower for freshly introduced 14C-labeled isoproturon, dicamba, and atrazine, respectively, suggesting that the presence of earthworms retarded bound residue formation.

Bioavailability of nonextractable (bound) pesticide residues to earthworms.

Fluoxetine, a selective serotonin reuptake inhibitor antidepressant and high-prescription-volume drug, is excreted unchanged or as a glucuronide from the human organism. Little is known about its fate in sewage treatment plants. Effects of fluoxetine on life-cycle parameters of the midge Chironomus riparius, especially development (mean emergence time), emergence, sex ratio, and fecundity, were assessed, as well as effects on reproduction of the oligochaete Lumbriculus variegatus and of the freshwater mudsnail Potamopyrgus antipodarum. Due to the moderate lipophilic properties of the compound with a log POW of 4.05, C. riparius and L. variegatus were exposed to fluoxetine via spiked artificial sediment at a nominal concentration range between 0.15 and 5.86 mg/kg (dry weight). Additionally, a test was performed exposing P. antipodarum via water in a nominal concentration range between 0.64 and 400 μg/L. As endpoints, emergence rate and timing, sex ratio, clutch numbers and clutch size of the midges, the number of worms in the oligochaete test, as well as the number of embryos in the snail test were monitored. For C. riparius, no clear substance-related effects were observed; for L. variegatus, the results indicated a slight increase in reproduction, which was statistically significant at nominal fluoxetine concentrations of 0.94 and 2.34 mg/kg. In P. antipodarum, the antidepressant reduced reproduction significantly. No observed effect concentration (NOEC) and 10% effect concentration (EC10) were determined to be 0.47 and 0.81 μg/L, respectively, based on measured fluoxetine concentrations in water. These low values indicate that P. antipodarum and possibly other aquatic mollusks are sensitive to fluoxetine and that the drug might pose a risk to gastropod populations in the field.

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G. Studinger

Papers

Bioaccumulation of lindane and hexachlorobenzene by tubificid sludgeworms (Oligochaeta) under standardised laboratory conditions