Jerry Diamond

Making ecosystem reality checks the status quo

Holistic approaches to assessing stressors and managing aquatic ecosystems should be the rule; instead, they are the exception. Disjointed, overlapping, and competing environmental regulatory actions—all with the noble mission of protecting and restoring the environment—can no longer be justified. For at least 60 years, environmental regulatory programs in the United States, Europe, and other developed countries have relied heavily on various forms of assessing chemical risk to manage and protect ecosystems. Water quality, primarily focused on chemical regulation, emerged from the need to control water pollution problems caused by poor or nonexistent wastewater treatment. The result has been largely a singlechemical approach to environmental management and regulatory programs. To protect aquatic life uses for example, many countries developed water quality criteria for selected priority compounds. Legally enforcing these criteria (such as the Clean Water Act in the U.S.) has undoubtedly reduced chemical pollution, and many aquatic systems have benefited. Abundant information demonstrates, however, that singlechemical standards are just one approach to assess, manage, and regulate aquatic systems. For example, toxicity testing (e.g., the U.S. Environmental Protection Agency’s [U.S. EPA] whole effluent toxicity program [WET]) has been used successfully to help assess effects of chemical interactions and the effects of unknown chemicals that may be present. Such testing, however, addresses only direct toxicity effects. Many aquatic systems are impaired by non-chemical stressors, including invasive species, habitat degradation from agriculture and urbanization, and flowmodifications or are influenced by complex interactions among chemicals and other stressors (e.g., nutrients) that are not addressed using either a singlechemical approach or mixture toxicity testing.

Toxicity models of pulsed copper exposure to Pimephales promelas and Daphnia magna

Semiempirical models are useful for interpreting the response of aquatic organisms to toxicants as a function of exposure concentration and duration. Most applications predict cumulative mortality at the end of the test for constant exposure concentrations. Summary measures, such as the median lethal concentration, are then estimated as a function of concentration. Real-world exposures are not constant. Effects may depend on pulse timing, and cumulative analysis based only on integrated exposure concentration is not sufficient to interpret results. We undertook a series of pulsed-exposure experiments using standard toxicological protocols and interpreted the results (mortality, biomass, and reproduction) using a dynamic generalization of a Mancini/Breck--type model that includes two compartments, one for internal concentration as a function of exposure and one for site-of-action concentration or accumulated damage as a function of the internal dose. At exposure concentrations near the effects level, the model explained approximately 50% of the variability in the observed time history of survival, 43% of the change in biomass, and 83% of the variability in net reproduction. Unexplained variability may result from differences in organism susceptibility, amplified by the effects of small sample sizes in standard tests. The results suggest that response is sensitive to prior conditions and that constant-exposure experiments can underestimate the risk from intermittent exposures to the same concentration. For pulsed exposures, neither the average nor the maximum concentration alone is an adequate index of risk, which depends on both the magnitude, duration, and timing of exposure pulses. Better understanding about the impacts of pulsed exposures will require use of experimental protocols with significantly greater numbers of replicates.

Test of significant toxicity: A statistical application for assessing whether an effluent or site water is truly toxic

The U.S. Environmental Protection Agency (U.S. EPA) and state agencies implement the Clean Water Act, in part, by evaluating the toxicity of effluent and surface water samples. A common goal for both regulatory authorities and permittees is confidence in an individual test result (e.g., no-observed-effect concentration [NOEC], pass/fail, 25% effective concentration [EC25]), which is used to make regulatory decisions, such as reasonable potential determinations, permit compliance, and watershed assessments. This paper discusses an additional statistical approach (test of significant toxicity [TST]), based on bioequivalence hypothesis testing, or, more appropriately, test of noninferiority, which examines whether there is a nontoxic effect at a single concentration of concern compared with a control. Unlike the traditional hypothesis testing approach in whole effluent toxicity (WET) testing, TST is designed to incorporate explicitly both α and β error rates at levels of toxicity that are unacceptable and acceptable, given routine laboratory test performance for a given test method. Regulatory management decisions are used to identify unacceptable toxicity levels for acute and chronic tests, and the null hypothesis is constructed such that test power is associated with the ability to declare correctly a truly nontoxic sample as acceptable. This approach provides a positive incentive to generate high-quality WET data to make informed decisions regarding regulatory decisions. This paper illustrates how α and β error rates were established for specific test method designs and tests the TST approach using both simulation analyses and actual WET data. In general, those WET test endpoints having higher routine (e.g., 50th percentile) within-test control variation, on average, have higher method-specific α values (type I error rate), to maintain a desired type II error rate. This paper delineates the technical underpinnings of this approach and demonstrates the benefits to both regulatory authorities and permitted entities.

An approach for determining bioassessment performance and comparability.

Many organizations in the USA collect aquatic bioassessment data using different sampling and analysis methods, most of which have unknown performance in terms of data quality produced. Thus, the comparability of bioassessments produced by different organizations is often unknown, ultimately affecting our ability to make comprehensive assessments on large spatial scales. We evaluated a pilot approach for determining bioassessment performance using macroinvertebrate data obtained from several states in the Southeastern USA. Performance measures evaluated included precision, sensitivity, and responsiveness to a human disturbance gradient, defined in terms of a land disturbance index value for each site, combined with a value for specific conductance, and instream habitat quality. A key finding of this study is the need to harmonize ecoregional reference conditions among states so as to yield more comparable and consistent bioassessment results. Our approach was also capable of identifying potential areas for refinement such as reevaluation of less precise, sensitive, or responsive metrics that may result in suboptimal index performance. Higher performing bioassessments can yield information beyond “impaired” versus “unimpaired” condition. Acknowledging the limitations of this pilot study, we would recommend that performance evaluations use at least 50 sites, 10 of which are ecoregional reference sites. Efforts should be made to obtain data from the entire human disturbance gradient in an ecoregion to improve statistical confidence in performance measures. Having too few sites will result in an under-representation of certain parts of the disturbance gradient (e.g., too few poor quality sites), which may bias sensitivity and responsiveness estimates.

Effects of pulsed copper exposures on early life-stage Pimephales promelas.

Effects of pulsed copper exposures were investigated using Pimephales promelas aged less than 24 h in short-term chronic testing (7 or 14 d) with moderately hard synthetic water. Concentrations tested were between the species mean chronic value (22 microg/L at a hardness of 100 mg/L as CaCO3) and the 7-d continuous exposure EC50 for survival (40 microg/L) to examine exposures that were not acutely toxic and representative of actual wastewater discharge permit exceedences. Factors tested included pulse duration, recovery time between pulses, and pulse frequency. Survival was the main endpoint affected in all treatments (analysis of variance, p < 0.05). Effects on fish biomass, independent of survival effects, were observed in only 2 of 86 treatments examined. Fish survival was negatively affected at average copper concentrations between 7 and 50% of the 7-d continuous exposure EC50. Exposures having a 48- to 96-h recovery time between pulses had less effect on fish survival than did treatments with shorter (12-24 h) or longer (>120 h) recovery times. Results suggest that the criteria averaging periods used in the United States, and the averaging periods typically used in wastewater discharge permit limits for copper, may not protect against effects of certain pulsed exposures.

Evaluation of whole effluent toxicity data characteristics and use of Welch's T‐test in the test of significant toxicity analysis

The U.S. Environmental Protection Agency (U.S. EPA) and state agencies evaluate the toxicity of effluent and surface water samples based on statistical endpoints derived from multiconcentration tests (e.g., no observed effect concentration, EC25). The test of significant toxicity (TST) analysis is a two-sample comparison test that uses Welchs t test to compare organism responses in a sample (effluent or surface water) with responses in a control or site sample. In general, any form of t test (Welchs t included) is appropriate only if the data meet assumptions of normality and homogeneous variances. Otherwise, nonparametric tests are recommended. TST was designed to use Welchs t as the statistical test for all whole effluent toxicity (WET) test data. The authors evaluated the suitability of using Welchs t test for analyzing two-sample toxicity (WET) data, and within the TST approach, by examining the distribution and variances of data from over 2,000 WET tests and by conducting multiple simulations of WET test data. Simulated data were generated having variances and nonnormal distributions similar to observed WET test data for control and the effluent treatment groups. The authors demonstrate that (1) moderately unequal variances (similar to WET data) have little effect on coverage of the t test or Welch t test (for normally distributed data), and (2) for nonnormally distributed data (similar in distribution to WET data) TST, using Welchs t test, has close to nominal coverage on the basis of simulations with up to a ninefold difference in variance between the effluent and control groups (∼95th percentile based on observed WET test data).

Evaluation of effluent toxicity as an indicator of aquatic life condition in effluent-dominated streams: A pilot study

ABSTRACT The types and quality of data needed to determine relationships between chronic whole effluent toxicity (WET) test results and in-stream biological condition were evaluated using information collected over a 1.5-y period from 6 different sites across the United States. A data-quality-objectives approach was used that included several proposed measurement quality objectives (MQOs) that specified desired precision, bias, and sensitivity of methods used. The 6 facilities used in this study (4 eastern and 2 western United States) all had design effluent concentrations >60% of the stream flow. In addition to at least quarterly chronic Ceriodaphnia dubia, Pimephales promelas (fathead minnow), and Selenastrum capricornutum (green algae) WET tests, other tests were conducted to address MQOs, including splits, duplicates, and blind positive and negative controls. Macroinvertebrate, fish, and periphyton bioassessments were conducted at multiple locations upstream and downstream of each facility. The test acceptance criteria of the US Environmental Protection Agency (USEPA) were met for most WET tests; however, this study demonstrated the need to incorporate other MQOs (minimum and maximum percent significant difference and performance on blind samples) to ensure accurate interpretation of effluent toxicity. More false positives, higher toxicity, and more “failed” (noncompliant) tests were observed using no-observed-effect concentration (NOEC) as compared to the IC25 endpoint (concentration causing ≥25% decrease in organism response compared to controls). Algae tests often indicated the most effluent toxicity in this study; however, this test was most susceptible to false positives and high interlaboratory variability. Overall, WET test results exhibited few relationships with bioassessment results even when accounting for actual effluent dilution. In general, neither frequency of WET noncompliance nor magnitude of toxicity in tests were significantly related to differences in biological condition upstream and downstream of a discharge. Periphyton assessments were most able to discriminate small changes downstream of the effluent, followed by macroinvertebrates and fish. Although sampling methods were robust, more replicate samples collected upstream and downstream of each facility were needed to increase detection power. In general, macroinvertebrate and periphyton assessments together appeared to be sufficient to address project objectives.

It is time for changes in the analysis of whole effluent toxicity data.

The whole effluent toxicity (WET) program in the United States, Canada, and other countries typically requires multi concentration testing of effluents. While multiconcentration testing of chemicals is desirable for regulatory and scientific reasons, we believe this requirement is not as efficient for evaluating effluent compliance in a WET program. The key regulatory question of concern is whether an effluent is toxic or not, which is best answered statistically using a hypothesis approach, not a point estimate approach. However, the traditional hypothesis approach currently recommended does not reward high within-test precision. This report describes the need for 3 specific changes in the analysis of WET compliance data that we believe would yield a more robust WET regulatory program: (1) restate the null hypothesis so that test power is associated with demonstrating that the effluent is not toxic, (2) use USEPAs Test of Significant Toxicity (based on the noninferiority approach) to identify unacceptable toxicity as well as acceptable effects with a high probability, and (3) evaluate only the test control and the critical concentration of concern (e.g., instream waste concentration). We demonstrate that instituting these 3 changes would provide: Positive incentives for permittees to produce high-quality WET data, a transparent analysis approach in which the permittee could have greater control over regulatory decisions based on test results, and potentially a less expensive testing program because fewer effluent concentrations need to be examined within a test. As a result, WET test frequency could be increased for the same cost as current testing programs while providing greater representativeness of effluent quality.

EVALUATION OF THE TEST OF SIGNIFICANT TOXICITY FOR DETERMINING THE TOXICITY OF EFFLUENTS AND AMBIENT WATER SAMPLES

The test of significant toxicity (TST) is a hypothesis-testing approach based on bioequivalence developed by the U.S. Environmental Protection Agency (U.S. EPA) for analyzing whole-effluent toxicity (WET) and ambient toxicity data. The present study compares results of acute and chronic toxicity tests of effluent, storm-water, and ambient (i.e., receiving-water) samples using both the TST and the standard no-observed-effect concentration (NOEC) approach. Valid WET data were analyzed from 890 tests provided by more than 25 dischargers in California and Washington, USA, representing the majority of test methods used in the U.S. WET program. An additional 3,201 freshwater chronic toxicity tests, obtained from ambient monitoring programs in California, were also analyzed. The TST and NOEC approaches both declared a low number (<6.5%) of tests toxic if effects were below the unacceptable toxicity regulatory management decision (RMD) of 25% effect in chronic tests or 20% effect in acute tests. However, those test methods having generally lower within-test variability and greater test power (e.g., urchin fertilization test) had a much lower percentage of tests declared toxic than the NOEC approach when effects were below the unacceptable toxicity RMD. In addition, the TST showed fewer tests to be nontoxic than NOEC if the test exhibited effects greater than the toxicity RMD (0.1 and 9.6% for TST and NOEC, respectively, for effluents and 0 and 9.5%, respectively, for ambient samples). Our results demonstrate that the TST is more likely to identify a toxic sample when effects are fairly substantial (≥ 25% effect in chronic testing and ≥ 20% effect in acute tests) and less likely to identify a sample as toxic when effects are negligible (≤ 10% effect). Furthermore, these results demonstrate that appropriate WET data interpretation benefits from having well-designed test methods with sufficient power to identify significant toxicity or biologically insignificant effects when they occur.

Development of Diagnostic Tools for Trace Organic Compounds and Multiple Stressors

This WERF sponsored research presents a preliminary screening process and ecological diagnostic approaches that could be used to help prioritize and evaluate treated wastewater-influenced sites that may be most at risk from trace organic chemical (TOrC) exposure. This work builds on the TOrC prioritization research completed earlier in this research and demonstrates how current diagnostic approaches used in the U.S. (CADDIS) and Canada (Environmental Effects Monitoring) could be extended to evaluate potential risks due to TOrCs. The screening process uses indicators in four categories: (1) wastewater influent and population served, (2) wastewater treatment characteristics, (3) ecological characteristics of the site, and (4) exposure or effects information from the site if available. The indicators included in the screening process are hypotheses, to be tested further using case studies in this research, and should not be taken as validated measures to be used to infer TOrC issues at a site. The diagnostic approach described in this research could be applied prospectively (could ecological effects due to TOrCs occur at my site?) and retrospectively (I have observed ecological effects at my site; are TOrCs a contributing cause?). However, given our current lack of knowledge concerning modes of action for many TOrCs, as well as the factors that determine whether TOrC effects on individuals are translated to community-level ecological effects, the diagnostic approach in this research focuses on retrospective applications at this time. The screening process has been used with some modification for sites in the Ohio Erie Drift Plain ecoregion and some of these, as well as other sites, will be evaluated using diagnostic approaches in Task 3 (case studies) of this research. A web-based database application ( ) has been developed for this project to help end users eventually search and evaluate TOrC data collected by many organizations in the U.S. and to assist in screening and diagnosing risks due to TOrCs. Comments are welcome on the various search features and metadata available for TOrCs within the current database. This title belongs to WERF Research Report Series . ISBN: 9781843395348 (eBook)