William H. van der Schalie

Improved cell sensitivity and longevity in a rapid impedance-based toxicity sensor.

A number of toxicity sensors for testing field water using a range of eukaryotic cell types have been proposed, but it has been difficult to identify sensors with both appropriate sensitivity to toxicants and the potential for long‐term viability. Assessment of bovine pulmonary artery endothelial cell (BPAEC) monolayer electrical impedance with electric cell‐substrate impedance sensing (ECIS) showed promise in a previous systematic evaluation of toxicity sensor technologies. The goal of the study reported here was to improve toxicant responsiveness and field portability of this cell‐based toxicity sensor. A variety of human cells, non‐human mammalian cells, and non‐mammalian vertebrate cells were screened for sensitivity to 12 waterborne industrial chemicals. The results of this assessment show that bovine lung microvessel endothelial cell (BLMVEC) monolayers and iguana heart (IgH‐2) cell monolayers could detect nine out of the 12 waterborne industrial chemicals, an improvement over the seven chemicals previously detected using BPAEC monolayers. Both the BLMVEC and IgH‐2 cell monolayers were tested for their ability for long‐term survival on the ECIS test chips in a laboratory environment. Both cell lines were able to maintain high impedance readings on the ECIS electrodes for 37 days, a key trait in developing a field‐portable toxicity sensor for water. Cell line optimization has greatly contributed to the on‐going development of a field‐portable cell‐based biosensor that detects with sensitivity a wide range of waterborne toxicants. Published in 2009 by John Wiley & Sons, Ltd.

Long-term storage and impedance-based water toxicity testing capabilities of fluidic biochips seeded with RTgill-W1 cells

Rainbow trout gill epithelial cells (RTgill-W1) are used in a cell-based biosensor that can respond within one hour to toxic chemicals that have the potential to contaminate drinking water supplies. RTgill-W1 cells seeded on enclosed fluidic biochips and monitored using electric cell-substrate impedance sensing (ECIS) technology responded to 18 out of the 18 toxic chemicals tested within one hour of exposure. Nine of these chemical responses were within established concentration ranges specified by the U.S. Army for comparison of toxicity sensors for field application. The RTgill-W1 cells remain viable on the biochips at ambient carbon dioxide levels at 6°C for 78weeks without media changes. RTgill-W1 biochips stored in this manner were challenged with 9.4μM sodium pentachlorophenate (PCP), a benchmark toxicant, and impedance responses were significant (p<0.001) for all storage times tested. This poikilothermic cell line has toxicant sensitivity comparable to a mammalian cell line (bovine lung microvessel endothelial cells (BLMVECs)) that was tested on fluidic biochips with the same chemicals. In order to remain viable, the BLMVEC biochips required media replenishments 3 times per week while being maintained at 37°C. The ability of RTgill-W1 biochips to maintain monolayer integrity without media replenishments for 78weeks, combined with their chemical sensitivity and rapid response time, make them excellent candidates for use in low cost, maintenance-free field-portable biosensors.

Ecological risk assessment: A scientific perspective

Abstract Ecological risk assessment is becoming an increasingly important tool for ranking, assessing, reducing, and managing environmental risks. To pro- vide Agency-wide guidance in this area in the U.S., EPAs Risk Assessment Forum has begun a multi-year guidelines development program. The first step in this program was the publication of the report “Framework for Ecological Risk Assessment” which describes the principles, concepts, terminology, and structure of ecological risk assessments.

Rapid responses of a melanophore cell line to chemical contaminants in water.

We have evaluated a Xenopus cell line as a potential sensor for detecting toxins in water. X. laevis melanophores responded rapidly by dispersing melanosomes following exposure to six (ammonia, arsenic, copper, mercury, pentachlorophenol and phenol) of 12 tested chemicals in the desired sensitivity range. For two additional chemicals (nicotine and paraquat) the melanophore response improved upon the response capabilities of several available toxicity sensors. These results suggest that a melanophore‐based sensor could be useful for the rapid assessment of chemical toxicity in drinking water. Published 2009 by John Wiley and Sons, Ltd.

Hormesis and ecological risk assessment: Fact or fantasy?

Abstract Hormesis is a widespread phenomenon across occurring many taxa and chemicals, and, at the single species level, issues regarding the application of hormesis to human health and ecological risk assessment are similar. However, interpreting the significance of hormesis for even a single species in an ecological risk assessment can be complicated by competition with other species, predation effects, etc. In addition, ecological risk assessments may involve communities of hundreds or thousands of species as well as a range of ecological processes. Applying hormetic adjustments to threshold effect levels for chemicals derived from sensitivity distributions for a large number of species is impractical. For ecological risks, chemical stressors are frequently of lessor concern than physical stressors (e.g., habitat alteration) or biological stressors (e.g., introduced species), but the relevance of hormesis to non‐chemical stressors is unclear. Although ecological theories such as the intermediate disturbance hypothesis offer some intriguing similarities between chemical hormesis and hormetic‐like responses resulting from physical disturbances, mechanistic explanations are lacking. While further exploration of the relevance of hormesis to ecological risk assessment is desirable, it is unlikely that hormesis is a critical factor in most ecological risk assessments, given the magnitude of other uncertainties inherent in the process.

Evaluation and refinement of a field‐portable drinking water toxicity sensor utilizing electric cell–substrate impedance sensing and a fluidic biochip

The US Armys need for a reliable and field‐portable drinking water toxicity sensor was the catalyst for the development and evaluation of an electric cell–substrate impedance sensing (ECIS) device. Water testing technologies currently available to soldiers in the field are analyte‐specific and have limited capabilities to detect broad‐based water toxicity. The ECIS sensor described here uses rainbow trout gill epithelial cells seeded on fluidic biochips to measure changes in impedance for the detection of possible chemical contamination of drinking water supplies. Chemicals selected for testing were chosen as representatives of a broad spectrum of toxic industrial compounds. Results of a US Environmental Protection Agency (USEPA)‐sponsored evaluation of the field portable device were similar to previously published US Army testing results of a laboratory‐based version of the same technology. Twelve of the 18 chemicals tested following USEPA Technology Testing and Evaluation Program procedures were detected by the ECIS sensor within 1 h at USEPA‐derived human lethal concentrations. To simplify field‐testing methods further, elimination of a procedural step that acclimated cells to serum‐free media streamlined the test process with only a slight loss of chemical sensitivity. For field use, the ECIS sensor will be used in conjunction with an enzyme‐based sensor that is responsive to carbamate and organophosphorus pesticides. Copyright

Ecological risk assessment: implications of hormesis

Hormesis is a widespread phenomenon across many taxa and chemicals, and, at the single species level, issues regarding the application of hormesis to human health and ecological risk assessment are similar. For example, convincing the public of a ‘beneficial’ effect of environmental chemicals may be problematic, and the design and analysis of laboratory studies may require modifications to detect hormesis. However, interpreting the significance of hormesis for even a single species in an ecological risk assessment can be complicated by considerations of competition with other species, predation effects, etc. Ecological risk assessments involve more than a single species; they may involve communities of hundreds or thousands of species as well as a range of ecological processes. Applying hormetic adjustments to threshold effect levels for chemicals derived from sensitivity distributions for a large number of species is impractical. For ecological risks, chemical stressors are frequently of lessor concern than physical stressors such as habitat alteration or biological stressors such as introduced species, but the relevance of hormesis to non‐chemical stressors is unclear. Although ecological theories such as the intermediate disturbance hypothesis offer some intriguing similarities between chemical hormesis and hormetic‐like responses resulting from physical disturbances, mechanistic explanations are lacking. Further exploration of the relevance of hormesis to ecological risk assessment is desirable. Aspects deserving additional attention include developing a better understanding of the hormetic effects of chemical mixtures, the relevance of hormesis to physical and biological stressors and the development of criteria for determining when hormesis is likely to be relevant to ecological risk assessments.

Environmental sentinel biomonitors: integrated response systems for monitoring toxic chemicals

Operational environments for military forces are becoming potentially more dangerous due to the increased number, use, and misuse of toxic chemicals across the entire range of military missions. Defense personnel may be exposed to harmful chemicals as a result of industrial accidents or intentional or unintentional action of enemy, friendly forces, or indigenous populations. While there has been a significant military effort to enable forces to operate safely and survive and sustain operations in nuclear, biological, chemical warfare agent environments, until recently there has not been a concomitant effort associated with potential adverse health effects from exposures of deployed personnel to toxic industrial chemicals. To provide continuous real-time toxicity assessments across a broad spectrum of individual chemicals or chemical mixtures, an Environmental Sentinel Biomonitor (ESB) system concept is proposed. An ESB system will integrate data from one or more platforms of biologically-based systems and chemical detectors placed in the environment to sense developing toxic conditions and transmit time-relevant data for use in risk assessment, mitigation, and/or management. Issues, challenges, and next steps for the ESB system concept are described, based in part on discussions at a September 2001 workshop sponsored by the U.S. Army Center for Environmental Health Research.