Biomedical subjects

A Dennis Lemly

Publications and source records attributed to A Dennis Lemly.

4 recordsLinked to original sources

PubMed2004

Aquatic selenium pollution is a global environmental safety issue.

Selenium pollution is a worldwide phenomenon and is associated with a broad spectrum of human activities, ranging from the most basic agricultural practices to the most high-tech industrial processes. Consequently, selenium contamination of aquatic habitats can take place in urban, suburban, and rural settings alike--from mountains to plains, from deserts to rainforests, and from the Arctic to the tropics. Human activities that increase waterborne concentrations of selenium are on the rise and the threat of widespread impacts to aquatic life is greater than ever before. Important sources of selenium contamination in aquatic habitats are often overlooked by environmental biologists and ecological risk assessors due to preoccupation with other, higher priority pollutants, yet selenium may pose the most serious long-term risk to aquatic habitats and fishery resources. Failure to include selenium in the list of constituents measured in contaminant screening/monitoring programs is a major mistake, both from the hazard assessment aspect and from the pollution control aspect. Once selenium contamination begins, a cascade of bioaccumulation events is set into motion which makes meaningful intervention nearly impossible. However, this cascade of events need not happen if adequate foresight and planning are exercised. Early evaluation and action are key. Prudent risk management based on environmentally sound hazard assessment and water quality goals can prevent biological impacts.

Agriculture↗

PubMed2002

Regulatory implications of using constructed wetlands to treat selenium-laden wastewater.

The practice of using constructed wetlands to treat selenium-laden wastewater is gaining popularity in the United States and elsewhere. However, proponents of treatment wetlands often overlook important ecological liabilities and regulatory implications when developing new methods and applications. Their research studies typically seek to answer a basic performance question--are treatment wetlands effective in improving water quality--rather than answering an implicit safety question-are they hazardous to wildlife. Nevertheless, wetland owners are responsible for both the operational performance of treatment wetlands and the health of animals that use them. This is true even if wetlands were not created with the intent of providing wildlife habitat; the owner is still legally responsible for toxic hazards. If poisoning of fish and wildlife occurs, the owner can be prosecuted under a variety of federal and state laws, for example, the Migratory Bird Treaty Act and the Endangered Species Act. In considering this type of treatment technology it is important to document the selenium content of the wastewater, understand how it cycles and accumulates in the environment, and evaluate the threat it may pose to fish and wildlife before deciding whether or not to proceed with construction. Many of the potential hazards may not be obvious to project planners, particularly if there is no expressed intention for the wetland to provide wildlife habitat. Ecological risk assessment provides an approach to characterizing proposed treatment wetlands with respect to wildlife use, selenium contamination, and possible biological impacts. Proper application of this approach can reveal potential problems and the associated liabilities, and form the basis for selection of an environmentally sound treatment option.

Animals↗

PubMed2002

A procedure for setting environmentally safe total maximum daily loads (TMDLs) for selenium.

This article presents a seven-step procedure for developing environmentally safe total maximum daily loads (TMDLs) for selenium. The need for this information stems from recent actions taken by the U.S. Environmental Protection Agency (EPA) that may require TMDLs for selenium and other contaminants that are impairing water bodies. However, there is no technical guidance from EPA or elsewhere that deals exclusively with selenium. This leaves biologists and environmental contaminant specialists without the tools needed to effectively address the TMDL issue for selenium. This article provides guidance by laying out an assessment method that links the basic components of EPA's TMDL process to the contaminant-specific information required for selenium. The underlying principle in this process is that selenium concentrations be kept below levels that threaten reproduction of fish and aquatic birds. The steps are: (1) Delineate and characterize the hydrological unit (HU, i.e., water body) of interest. (2) Determine selenium concentrations and assess biological hazard. (3) Determine sources, concentrations, and volumes of selenium discharges; calculate existing selenium load. (4) Estimate retention capacity of HU for selenium. (5) Calculate the total allowable selenium load and specify reductions needed to meet the target loading. (6) Allocate selenium load among discharge sources. (7) Monitor to determine effectiveness of selenium load reduction in meeting environmental quality goals. Proper application of this procedure will ensure compliance with EPA regulatory requirements and also protect fish and wildlife resources.

Animals↗

PubMed2002

Symptoms and implications of selenium toxicity in fish: the Belews Lake case example.

Belews Lake, North Carolina was contaminated by selenium in wastewater from a coal-fired power plant during the mid-1970s, and toxic impacts to the resident fish community (20 species) were studied for over two decades. Symptoms of chronic selenium poisoning in Belews Lake fish included, (1) telangiectasia (swelling) of gill lamellae; (2) elevated lymphocytes; (3) reduced hematocrit and hemoglobin (anemia); (4) corneal cataracts; (5) exopthalmus (popeye); (6) pathological alterations in liver, kidney, heart, and ovary (e.g. vacuolization of parenchymal hepatocytes, intracapillary proliferative glomerulonephritis, severe pericarditis and myocarditis, necrotic and ruptured mature egg follicles); (7) reproductive failure (reduced production of viable eggs due to ovarian pathology, and post-hatch mortality due to bioaccumulation of selenium in eggs); and (8) teratogenic deformities of the spine, head, mouth, and fins. Important principles of selenium cycling and toxicity were documented in the Belews Lake studies. Selenium poisoning in fish can be 'invisible', because, the primary point of impact is the egg, which receives selenium from the female's diet (whether consumed in organic or inorganic forms), and stores it until hatching, whereupon it is metabolized by the developing fish. If concentrations in eggs are great enough (about 10 microg/g or greater) biochemical functions may be disrupted, and teratogenic deformity and death may occur. Adult fish can survive and appear healthy despite the fact that extensive reproductive failure is occurring--19 of the 20 species in Belews Lake were eliminated as a result of this insidious mode of toxicity. Bioaccumulation in aquatic food chains causes otherwise harmless concentrations of selenium to reach toxic levels, and the selenium in contaminated sediments can be cycled into food chains for decades. The lessons learned from Belews Lake provide information useful for protecting aquatic ecosystems as new selenium issues emerge.

Abnormalities, Drug-Induced↗