Water-sediment controversy in setting environmental standards for selenium.

A substantial amount of laboratory and field research on selenium effects to biota has been accomplished since the national water quality criterion was published for selenium in 1987. Many articles have documented adverse effects on biota at concentrations below the current chronic criterion of 5 microg/L. This commentary will present information to support a national water quality criterion for selenium of 2 microg/L, based on a wide array of support from federal, state, university, and international sources. Recently, two articles have argued for a sediment-based criterion and presented a model for deriving site-specific criteria. In one example, they calculate a criterion of 31 microg/L for a stream with a low sediment selenium toxicity threshold and low site-specific sediment total organic carbon content, which is substantially higher than the national criterion of 5 microg/L. Their basic premise for proposing a sediment-based method has been critically reviewed and problems in their approach are discussed.

Selenium transport and bioaccumulation in aquatic ecosystems: a proposal for water quality criteria based on hydrological units.

Local water quality criteria for selenium should be based on an assessment of the degree of toxicological hazard to fish and wildlife, which is influenced by the spatial and temporal variation of the selenium cycle at the site under consideration. The physical area from which measurements are taken to evaluate selenium residues and biological effects, i.e., the database for setting site-specific criteria, must encompass more than an isolated segment of river, a tributary stream, etc. Because of hydrological connections between the various aquatic habitats that may be present in a watershed basin-wetlands, rivers, streams, and impoundments-the toxic threat from selenium contamination is also connected. For example, a criterion that is appropriate for a stream or river where low bioaccumulation occurs may result in seemingly harmless concentrations of selenium becoming a problem in downstream impoundments or in off-channel bays and wetlands where bioaccumulation is greater. The hydrologically connected parts of a basin downstream of a selenium discharge (natural or synthetic selenium source), extending to the point at which new sources of low-selenium water dominate the hydrology (e.g., confluence with larger tributary or river, spring or groundwater inflow), should be the area evaluated and given a specific criterion, not isolated components. Thus, a hydrological unit should be identified and used as the "site" for the purpose of setting criteria. Importantly, criteria derived in such a fashion will reflect the transport and bioaccumulation of selenium within the entire hydrological unit rather than simply focusing on a small, artificially designated segment of the system. Failure to use a hydrological unit approach can set the stage for significant biological and legal problems.

A position paper on selenium in ecotoxicology: a procedure for deriving site-specific water quality criteria.

This paper describes a method for deriving site-specific water quality criteria for selenium using a two-step process: (1) gather information on selenium residues and biological effects at the site and in down-gradient systems and (2) examine criteria based on the degree of bioaccumulation, the relationship between measured residues and threshold concentrations for reproductive effects in fish and wildlife, and any observed reproductive impacts. Several outcomes are possible--criteria can be left unmodified, adjusted upward by a fixed amount (50%), or adjusted downward by one of three amounts (25, 50, or 75%). A criterion (existing or proposed) is lowered or raised by an amount that is proportional to the magnitude of bioaccumulation and toxic effects present--i.e., the degree of biological hazard. Criteria can be modified under two circumstances: (1) diagnostic residues and toxic effects must be coupled (present) in order to lower a criterion or (2) diagnostic residues and toxic effects must be coupled (absent) in order to raise a criterion. Coupling residues and effects makes the procedure sensitive to the natural inter- and intraspecific variation in bioaccumulation and toxic responses exhibited by fish and wildlife in aquatic ecosystems. The goal is to establish criteria that keep food-chain bioaccumulation below levels that result in toxicity to fish and wildlife. Precautions are given for those attempting to apply the generic EPA model for implementing national water quality criteria to a site-specific selenium criterion.

A teratogenic deformity index for evaluating impacts of selenium on fish populations.

This paper describes a method for using teratogenic deformities in fish as the basis for evaluating impacts of selenium contamination. Teratogenic deformities are reliable bioindicators of selenium toxicosis in fish. They are produced in response to dietary exposure of parent fish and subsequent deposition of selenium in eggs. There is a close parallel between selenium concentrations in eggs, incidence of teratogenic deformities in larvae, and magnitude of reproductive failure. Using these relationships, an index was developed for teratogenic-based assessment of impacts to fish populations. The index is composed of three ratings that signify increasing levels of terata-induced population mortality: 1, negligible impact (< 5% population mortality); 2, slight to moderate impact (5-20% population mortality); 3, major impact (> 20% population mortality). Each rating is based on the anticipated population-level impact of the corresponding degree of mortality. Teratogenic-based impact assessment provides a conclusive cause-effect linkage between the contaminant and the fish. It is particularly useful for verifying selenium-induced impacts on reproductive success because poor reproduction can be caused by many things-i.e., fluctuating water levels, nest predation, food shortages, poor recruitment, etc. The index given here should be a useful tool for evaluating the effect of selenium on fish populations. Moreover, application of this technique may save considerable time and money by identifying the most efficient use of manpower and funds early in the assessment process.

Environmental hazard of selenium in the Animals La Plata water development project.

A hazard assessment of selenium was conducted for the Animas La Plata Project, a multiple-use water development proposed for Colorado and New Mexico by the United States Bureau of Reclamation. A published protocol for aquatic hazard assessment of selenium was applied to environmental monitoring data to assess current threats to biota in the water supply rivers (Animas, La Plata, and Mancos Rivers). Hazard evaluation were also made for two proposed reservoirs (Ridges Basin and Southern Ute Reservoirs) based on estimated concentrations of selenium. The assessment protocol indicated moderate hazard in the Animas and La Plata Rivers, and high hazard in the Mancos River and both of the proposed reservoirs. These ratings indicate that the risk of selenium poisoning in fish and aquatic birds is substantial. Moreover, the geology and climate of this site make it prone to irrigation-induced selenium contamination of water and biota. The water supplies already contain dangerously high concentrations of selenium that may increase further due to agricultural irrigation drainage. The stage is set for significant environmental problems unless a development scenario can be devised that will effectively reduce ecological risks.

Ecosystem recovery following selenium contamination in a freshwater reservoir.

Belews Lake, North Carolina, was contaminated by selenium in wastewater released from a coal-fired electric generating facility during 1974-1985. Selenium bioaccumulated in aquatic food chains and caused severe reproductive failure and teratogenic deformities in fish. Beginning in 1986, the electric utility company changed its ash disposal practices and selenium-laden wastewater no longer entered the lake. A survey of selenium present in the water, sediments, benthic invertebrates, fish, and aquatic birds was conducted in 1996. Concentrations were compared to pre-1986 levels to determine how much change occurred during the decade since selenium inputs stopped. The data were also examined using a hazard assessment protocol to determine if ecosystem-level hazards to fish and aquatic birds had changed as well. Results reveal that waterborne selenium fell from a peak of 20 micrograms/liter before 1986, to < 1 microgram/liter in 1996; concentrations in biota were 85-95% lower in 1996. Hazard ratings indicate that high hazard existed prior to 1986 and that moderate hazard is still present, primarily due to selenium in the sediment-detrital food pathway. Concentrations of selenium in sediments have fallen by about 65-75%, but remain sufficiently elevated (1-4 micrograms/g) to contaminate benthic food organisms of fish and aquatic birds. Field evidence confirmed the validity of the hazard ratings. Developmental abnormalities in young fish indicate that selenium-induced teratogenesis and reproductive impairment are occurring. Moreover, the concentrations of selenium in benthic food organisms are sufficient to cause mortality in young bluegill and other centrarchids because of Winter Stress Syndrome. At the ecosystem level, recovery has been slow. Toxic effects are still evident 10 years after selenium inputs were stopped. The sediment-associated selenium will likely continue to be a significant hazard to fish and aquatic birds for years.

Environmental implications of excessive selenium: a review.

Selenium is a naturally occurring trace element that is nutritionally required in small amounts but it can become toxic at concentrations only twice those required. The narrow margin between beneficial and harmful levels has important implications for human activities that increase the amount of selenium in the environment. Two of these activities, disposal of fossil fuel wastes and agricultural irrigation of arid, seleniferous soils, have poisoned fish and wildlife, and threatened public health at several locations in the United States. Research studies of these episodes have generated a data base that clearly illustrates the environmental hazard of excessive selenium. It is strongly bioaccumulated by aquatic organisms and even slight increases in waterborne concentrations can quickly result in toxic effects such as deformed embryos and reproductive failure in wildlife. The selenium data base has been very beneficial in developing hazard assessment procedures and establishing environmentally sound water quality criteria. The two faces of selenium, required nutrient and potent toxin, make it a particularly important trace element in the health of both animals and man. Because of this paradox, environmental selenium in relation to agriculture, fisheries, and wildlife will continue to raise important land and water management issues for decades to come. If these issues are dealt with using prudence and the available environmental selenium data base, adverse impacts to natural resources and public health can be avoided.

Evaluation of the hazard quotient method for risk assessment of selenium.

Environmental contamination with selenium from industrial and agricultural sources has poisoned fish and wildlife at several locations in the United States. Monitoring and risk assessment activities are currently being conducted by many state and Federal agencies. The U.S. Environmental Protection Agency (EPA) recommends a hazard quotient (HQ) method (waterborne concentration divided by the national water quality criterion) to assess the toxic threat of individual waterborne elements, including selenium. An evaluation of the EPA HQ method was conducted by comparing it to a recently published protocol (Protocol) for selenium assessment. Hazard estimates obtained using HQ were found to be invalid because the EPA water quality criterion is outdated, and the procedure uses mean rather than maximum waterborne concentrations. The HQ method seriously underestimates hazard and could lead to risk management decisions that would not protect fish and wildlife from selenium toxicity. The Protocol method provides an accurate assessment because it evaluates hazard by examining multiple exposure pathways on a site-specific basis. Until a revised (lowered) national water quality criterion is available, the EPA HQ method should not be used for selenium. Even then, with the availability of the Protocol, HQ analysis should be restricted to data sets where water is the primary or sole source of information on environmental concentrations of selenium.

Risk assessment in the regulatory process for wetlands.

This paper presents an ecosystem-based approach to risk assessment in freshwater wetlands. The key concept in this approach is that the primary biotic and abiotic components that determine the structural and functional characteristics of wetlands are inseparable. Each component should be identified and its contribution to ecosystem functions or human values determined when deciding whether a stressor poses an unreasonable risk to the sustainability of a particular wetland. Understanding the major external and internal factors that regulate the operational conditions of wetlands is critical to risk characterization. Determining the linkages between these factors, and how they influence the way stressors affect wetlands, is the basis for an ecosystem approach. Adequate consideration of wetland ecology, hydrology, geomorphology, and soils can greatly reduce the level of uncertainty associated with risk assessment and lead to more effective risk management. In order to formulate effective solutions, wetland problems must be considered at watershed, landscape, and ecosystem scales.

Winter stress syndrome: an important consideration for hazard assessment of aquatic pollutants.

Winter Stress Syndrome (WSS) is a condition of severe lipid depletion in fish brought on by external stressors in combination with normal reductions in feeding and activity during cold weather. Fish can develop this syndrome in response to chemical stressors, such as water pollutants, or biological stressors such as parasites. Substantial mortality can result, potentially changing year-class strength and population structure of the affected species and altering community-level ecological interactions. Aquatic contaminants should be evaluated in the context of seasonal metabolic changes that normally occur in test organisms. WSS could be an important, but as yet unquantified, cause of mortality in many circumstances. Wastewater discharges may pose a greater toxic threat to fish during winter than at other times of the year. A comprehensive protocol for aquatic hazard assessment should include testing for WSS.

Wastewater discharges may be most hazardous to fish during winter.

Winter Stress Syndrome (WSS) is a condition of severe lipid depletion in fish brought on by external stressors in combination with normal reductions in feeding and activity during cold weather. Fish can develop this syndrome in response to chemical stressors such as water pollutants, or biological stressors such as parasites. Substantial mortality can result, potentially changing year-class strength and population structure of the affected species, and altering community-level ecological interactions. Aquatic contaminants should be evaluated in the context of seasonal metabolic changes that normally occur in test organisms. WSS could be an important, but as yet unquantified, cause of mortality in many circumstances. Wastewater discharges may pose a greater toxic threat to fish during winter than at other times of the year. A comprehensive protocol for aquatic hazard assessment should include testing for WSS.

Assessing the toxic threat of selenium to fish and aquatic birds.

A procedure is given for evaluating the toxic threat of selenium to fish and wildlife. Toxic threat is expressed as hazard, and is based on the potential for food-chain bioaccumulation and reproductive impairment in fish and aquatic birds, which are the most sensitive biological responses for estimating ecosystem-level impacts of selenium contamination. Five degrees of hazard are possible depending on the expected environmental concentrations of selenium, exposure of fish and aquatic birds to toxic concentrations, and resultant potential for reproductive impairment. The degree of hazard is given a numerical score: 5 = high hazard, 4 = moderate hazard, 3 = low hazard, 2 = minimal hazard, and 1 = no identifiable hazard. A separate hazard score is given to each of five ecosystem components; water, sediments, benthic macroinvertebrates, fish eggs, and aquatic bird eggs. A final hazard characterization is determined by adding individual scores and comparing the total to the following evaluation criteria: 5 = no hazard, 6-8 = minimal hazard, 9-11 = low hazard, 12-15 = moderate hazard, 16-25 = high hazard. An example is given to illustrate how the procedure is applied to selenium data from a typical contaminant monitoring program.

A protocol for aquatic hazard assessment of selenium.

A procedure is described for conducting an aquatic hazard assessment of selenium. Hazard is characterized in terms of the potential for food-chain bioaccumulation and reproductive impairment in fish and aquatic birds, which are the most sensitive biological responses for estimating ecosystem-level impacts of selenium contamination. Five degrees of hazard are possible depending on the expected environmental concentrations of selenium, exposure of fish and aquatic birds to toxic concentrations, and resultant potential for reproductive impairment. The degree of hazard is given a numerical score: 5, high hazard; 4, moderate hazard; 3, low hazard; 2, minimal hazard; and 1, no identifiable hazard. A separate hazard score is given to each of five ecosystem components: water, sediments, benthic macroinvertebrates, fish eggs, and aquatic bird eggs. A final hazard characterization is determined by adding individual scores and comparing the total to the following evaluation criteria: 5, no hazard; 6-8, minimal hazard; 9-11, low hazard; 12-15, moderate hazard; 16-25, high hazard. An example is given to illustrate how the protocol is applied to selenium data from a typical contaminant monitoring program.

Mining in northern Canada: expanding the industry while protecting Arctic fishes--a review.

Northern Canada has a long tradition of mining activity with a poor record of environmental protection. Pollution is acknowledged as the biggest issue currently facing the mining industry. The arctic and subarctic fishes of this region are very sensitive to heavy metals, trace elements, and other contaminants in mine wastes. High sensitivity, combined with an inherently low capacity for recovery, make this aquatic resource particularly vulnerable to impacts. At least 22 fish species with major commercial, recreational, or subsistence value may be affected as the mining industry expands. The number of mines in northern Canada is steadily increasing and a metals-mining boom is expected to take place during the next decade. Prudent planning based on comprehensive mine-site evaluation, biological risk assessment, and research is essential to reduce the threat of environmental damage. There are several progressive mining techniques that can help make mining compatible with sensitive northern fisheries while also maintaining the profitability and growth of the mining industry. Thus far, this technology has been used very little in northern Canada.

Teratogenic effects of selenium in natural populations of freshwater fish.

The prevalence of abnormalities and associated tissue selenium residues were assessed for the fish population of Belews Lake, North Carolina, and two reference lakes in 1975, 1978, 1982, and 1992. Teratogenic defects identified included lordosis, kyphosis, scoliosis, and head, mouth, and fin deformities. Many fish exhibited multiple malformations and some were grossly deformed and distorted in appearance. Other abnormalities observed were edema, exophthalmus, and cataracts. Whole-body tissue residues of selenium in the fishes of Belews Lake were up to 130 times those in the reference lakes and the incidence of abnormalities was some 7 to 70 times greater. Teratogenic defects increased as selenium levels rose between 1975 and 1982 and fell with declining selenium levels between 1982 and 1992 as selenium inputs into Belews Lake were curtailed. The relationship between selenium residues and prevalence of malformations approximated an exponential function (R2 = 0.881, P < 0.01; cubic model) for centrarchids over the range of 1-80 micrograms/g dry wt selenium and 0-70% deformities. This relationship could be useful in evaluating the role of teratogenic effects in warm-water fish populations suspected of having selenium-related reproductive failure. Unique conditions may have existed in Belews Lake which led to the high frequency and persistence of deformities in juvenile and adult fish. In other, less-contaminated locations competition and predation may eliminate malformed individuals in all but the larval life stage. Teratogenesis could be an important, but easily overlooked phenomenon contributing to fishery reproductive failure in selenium-contaminated aquatic habitats.

Subsurface agricultural irrigation drainage: the need for regulation.

Subsurface drainage resulting from irrigated agriculture is a toxic threat to fish and wildlife resources throughout the western United States. Studies by the U.S. Department of the Interior show that migratory waterfowl have been poisoned by drainwater contaminants on at least six national wildlife refuges. Allowing this poisoning to continue is a violation of the Migratory Bird Treaty Act under U.S. Federal law. Critical wetlands and waterfowl populations are threatened in both the Pacific and Central flyways. The public is also at risk and health warnings have been issued in some locations. Subsurface irrigation drainage is a complex effluent containing toxic concentrations of trace elements, salts, and nitrogenous compounds. Some of the contaminants are classified by the U.S. Environmental Protection Agency (EPA) as priority pollutants and they can be present in concentrations that exceed EPA's criteria for toxic waste. The on-farm drainage systems used to collect and transport this wastewater provide point-source identification as well as a mechanism for toxics control through the National Pollutant Discharge Elimination System (NPDES) permit process. A four-step approach is presented for dealing with irrigation drainage in an environmentally sound manner. This regulatory strategy is very similar to those commonly used for industrial discharges and includes site evaluation, contaminant reduction through NPDES, and compliance monitoring. The EPA must recognize subsurface irrigation drainage as a specific class of pollution subject to regulation under the NPDES process. Active involvement by EPA is necessary to ensure that adequate controls on this wastewater are implemented.

Guidelines for evaluating selenium data from aquatic monitoring and assessment studies.

It is now possible to formulate diagnostic selenium concentrations in four distinct ecosystem-level components; water, food-chain, predatory fish (consuming fish or invertebrate prey), and aquatic birds. Waterborne selenium concentrations of 2 µg/l or greater (parts per billion; total recoverable basis in 0.45 µ filtered samples) should be considered hazardous to the health and long-term survival of fish and wildlife populations due to the high potential for food-chain bioaccumulation, dietary toxicity, and reproductive effects. In some cases, ultra-trace amounts of dissolved and particulate organic selenium may lead to bioaccumulation and toxicity even when total waterborne concentrations are less than 1 µg/l.Food-chain organisms such as zooplankton, benthic invertebrates, and certain forage fishes can accumulate up to 30 µg/g dry weight selenium (some taxa up to 370 µg/g) with no apparent effect on survival or reproduction. However, the dietary toxicity threshold for fish and wildlife is only 3 µg/g; these food organisms would supply a toxic dose of selenium while being unaffected themselves. Because of this, food-chain organisms containing 3 µg/g (parts per million) dry weight or more should be viewed as potentially lethal to fish and aquatic birds that consume them.Biological effects thresholds (dry weight) for the health and reproductive success of freshwater and anadromous fish are: whole body=4 µg/g; skeletal muscle=8 µg/g; liver=12 µg/g; ovaries and eggs=10 µg/g. Effects thresholds for aquatic birds are: liver=10 µg/g; eggs=3 µg/g. The most precise way to evaluate potential reproductive impacts to adult fish and aquatic bird populations is to measure selenium concentrations in gravid ovaries and eggs. This single measure integrates waterborne and dietary exposure, and allows an evaluation based on the most sensitive biological endpoint. Resource managers and aquatic biologists should obtain measurements of selenium concentrations present in water, food-chain organisms, and fish and wildlife tissues in order to formulate a comprehensive and conclusive assessment of the overall selenium status and health of aquatic ecosystems.

The growth, biomass, and fecundity of Bothriocephalus acheilognathi in a North Carolina cooling reservoir.

An investigation of differences in growth, maturation, biomass, and fecundity of Bothriocephalus acheilognathi in 3 host species was conducted on metapopulations from 3 distinct communities in Belews Lake, North Carolina. The results indicated that host-specific differences in growth and biomass were additive among metapopulations from different localities. However, species-specific differences in maturation and fecundity exhibited differential variation between the sites. These site X host interactions were related to host-specific differences in bioaccumulation of selenium at sites that were exposed to effluent from a coal-fired power plant. Significant (alpha = 0.001) statistical associations were observed between selenium concentration in tapeworm tissue and fecundity measures. The results of this study demonstrate that host suitability is determined by morphological, physiological, and behavioral differences in the host species which affect transmission dynamics and the quality and stability of the enteric environment.

A behavioral assay for assessing effects of pollutants on fish chemoreception.

Behavioral assays are sensitive to sublethal levels of pollution but they usually require highly trained personnel and long observation periods. We describe a system that combines the sensitivity of a behavioral assay with commercially available automated monitoring equipment. The observation system consists of a special aquarium coupled to a recirculating water system, and an Opto-Varimex-Aqua activity tracking meter (Columbus Instruments, Columbus, Ohio) interfaced to a microcomputer. The tracking meter forms an intersecting, planar grid of light beams which, when interrupted by fish movements, is translated into a digitized signal and fed to the computer. The assay is based on the response of fish to natural chemical stimuli such as food odors or pheromones. When these stimulus solutions are injected into the water circulation the response of the fish is monitored by the computer system, which is capable of discriminating and quantifying changes in eight parameters. Normal responses to stimuli are compared with the response of fish that have been exposed to pollutants. We have successfully used this technique to examine effects of reduced pH on the response of fathead minnows, Pimephales promelas, to chemical feeding stimuli. The system should be easily adapted to any laboratory concerned with testing for effects of toxic substances, and will identify effects of pollution that have thus far been difficult or impossible to assess.