Response characteristics of an aquatic biomonitor used for rapid toxicity detection.

The response characteristics of an aquatic biomonitor that detects toxicity by monitoring changes in bluegill (Lepomis macrochirus Rafinesque) ventilatory and movement patterns were evaluated in single chemical laboratory studies at concentrations near the 96-h LC(50) concentration and at the EILATox-Oregon Workshop in sequential tests of multiple unknown samples. Baseline data collected prior to exposure allows each fish to serve as its own control. When at least 70% of exposed fish exhibit ventilatory or movement parameters significantly different from baseline observations, a group alarm is declared. In the laboratory studies, the aquatic biomonitor responded to the majority of chemicals at the 96-h lc(50) within an hour or less, although substantially higher response times were found for malathion and pentachlorophenol. Workshop tests of single chemical concentrations presented as blind samples were consistent with the laboratory test results. There were no alarms under control conditions in any test. Although data are limited, the aquatic biomonitor appears to respond more rapidly to chemicals causing membrane irritation, narcosis or polar narcosis than to acetylcholinesterase inhibitors or oxidative phosphorylation uncouplers. All four monitored parameters (ventilatory rate, cough rate, ventilatory depth and movement) contributed to identification of first alarms at acutely toxic levels. Understanding these response patterns can be useful in data interpretation for biomonitor applications such as surface water monitoring for watershed protection, wastewater treatment plant effluent monitoring or source water monitoring for drinking water protection.

Using higher organisms in biological early warning systems for real-time toxicity detection.

Many biological early warning systems (BEWS) have been developed in recent years that evaluate the physiological and behavioral responses of whole organisms to water quality. Using a fish ventilatory monitoring system developed at the US Army Centre for Environmental Health Research as an example, we illustrate the operation of a BEWS at a groundwater treatment facility. During a recent 12-month period, the fish ventilatory system was operational for 99% of the time that the treatment facility was on-line. Effluent-exposed fish responded as a group about 2.8% of the time. While some events were due to equipment problems or non-toxic water quality variations, the fish system did indicate effluent anomalies that were subsequently identified and corrected. The fish monitoring BEWS increased treatment facility engineers' awareness of effluent quality and provided an extra measure of assurance to regulators and the public. Many operational and practical considerations for whole organism BEWS are similar to those for cell- or tissue-based biosensors. An effective biomonitoring system may need to integrate the responses of several biological and chemical sensors to achieve desired operational goals. Future development of an 'electronic canary', analogous to the original canary in the coal mine, could draw upon advances in signal processing and communication to establish a network of sensors in a watershed and to provide useful real-time information on water quality.

Histopathology of Japanese medaka (Oryzias latipes) chronically exposed to a complex environmental mixture.

Japanese medaka (Oryzias latipes) were used to evaluate the carcinogenicity of a complex groundwater that contained 5 U.S. Environmental Protection Agency priority pollutant heavy metals and 13 chlorinated aliphatic hydrocarbons. A test protocol that used 10 mg/L diethylnitrosamine (DEN) prior to groundwater exposure was designed to assess both initiation and promotion. The fish were exposed continuously for 9 mo with 0, 1, 5, or 25% groundwater, by volume, with either West Branch of Canal Creek water (Aberdeen Proving Ground-Edgewood Area, Aberdeen Proving Ground, MD) or dechlorinated tap water as the diluent, while concurrent controls were run in the laboratory. Incidental findings included various neoplasms in the nares, ovary, skeletal muscle, skin, swim bladder, testis, thymus, and thyroid. Factors evaluated during statistical analyses of fish neoplasm prevalence included diluent type, groundwater percentage, fish gender, and DEN initiation. Liver neoplasm prevalence was higher in DEN-initiated fish and was frequently higher in males. Concentrations of up to 25% groundwater, by volume, showed no evidence of being a complete carcinogen and showed no consistent, conclusive evidence of being a promoter.

Amoscanate as a topically applied chemical for prophylaxis against Schistosoma mansoni infections in mice.

Amoscanate (0.1% w/v) in methanol solution applied to skin by tail immersion 1 day prior to cercarial exposure provided mice with better than 90% protection against mature Schistosoma mansoni infections. Cercariae penetrated and schistosomula migrated from treated skins as readily as in control skins. Lung incubation assays, however, indicated that day 7 lung worm burdens were only about half those of control values. By day 20, worm burdens were reduced further to approximately 15% of those for control mice. The delayed prophylactic activity was apparently not due to percutaneously absorbed compound. Wipe application of amoscanate to the skin was nearly as effective as immersion.