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D.2. Metals Chronic Concentration-Response Gallery

The Metals Chronic Concentration-Response Gallery is a gallery of plots and source data describing the responses of aquatic organisms to chronic exposures to metals. The metals covered include arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium and zinc. Unlike the original test endpoints which were based on statistical hypothesis testing, these concentration-response relationships may be used to provide evidence that the concentrations at the impaired site are great enough to have caused the observed impairment. These data are particularly valuable because they include longer term exposures, multiple life stages and sublethal as well as lethal effects. Results are presented as fitted functions, concentrations resulting in prescribed proportions affected (EC5, EC10, EC20 and EC50) and confidence intervals may be found in the Model Parameters and Benchmarks worksheets.

Fig M2-1. Examples of modeled and interpolated plots from the Metals Chronic Exposure-Reponse Gallery

Where did the data come from?

The chronic concentration-response data used for these plots were extracted from toxicity test results originally published between 1968 and 1996. The tests selected were judged to be suitable for deriving national ambient water quality criteria by the database developers, David Hansen and Glenn Thursby of the U.S. EPA National Health and Environmental Effects Research Laboratory in Narragansett, RI. The version of the data base used here was quality assured, edited, and published in U.S. EPA (2005). The Citations section of this gallery lists that report, the methods paper (Kerr and Meador, 1996), and the primary publications contributing the data.

How were plots generated?

Plots were successfully modeled for 38 of the 120 datasets using the method described by Kerr and Meador (1996, example above left). For these plots, confidence intervals were calculated for both the exposure concentration (red dashed lines) and the proportion responding (blue dashed lines). Some papers reported only mean responses without standard deviations or results for replicates. For these sets, surrogate standard deviations were derived based on the expected variance for that type of response (see U.S. EPA 2005). Linear interpolation was also used to estimate the EC X benchmark values for those datasets exhibiting both a concentration-response relationship and sufficient data points (example above right). See U.S. EPA (2005) for more detail on the methods.

Download and browse the gallery

To download the gallery and supporting information:

1. Save Metal Chronic Concentration Response Gallery - V1 (1.7MB, .zip) to your computer.
2. Unzip the file by right clicking on the folder and selecting "extract all" to invoke the extraction wizard.

To browse the gallery and supporting information:

1. Open the file titled "Start Here - Chronic Metals Concentration Response Gallery V1.xls"
2. Enable macros and open as "read only" (if you wish to modify this file, open as read only, make your changes, then save it under a different name).
3. Review the background information before selecting the plots and source data of interest using the Browse the Chronic Metals Gallery worksheet.