Environmental Protection Agency Limits Research Articles

Influence of Sungun copper mine on groundwater quality, NW Iran

Sungun mine is the largest open-cast copper mine in northwest of Iran and is in the primary stages of extraction. The influence of mining activity on the quality of regional groundwater has been taken in to consideration in this study. Accordingly, sampling was done from 22 springs in the study area. The concentrations of major anions and cations as well as Al, Cu, Cd, Cr, Fe, Mn, and Zn were determined for all 22 spring samples in mid-August 2005. The results showed that the concentrations of most of these elements were below the USA Environmental Protection Agency (EPA) limits; however, Al and Fe concentrations are considered to be more than limits in a couple of samples. Despite the fact that geological formations are highly weathered and fractured, the dissolution of minerals within the study area is low. This may be justified by the relatively high alkalinity of local underground water which keeps metals in solid phase and does not let them enter dissolved phase. Additionally, this may be attributed to the high velocity of groundwater flows, which do not give enough time for minerals to dissolve. Correlation coefficients among water chemistry components were determined and the weighted-pair group method was chosen for cluster analysis. Accordingly, high correlation among Al, Fe and Cr, Cd ,and Cu, sodium absorption ratio (SAR) and Na as well as total hardness (TH), Ca, and Mg were observed. The chemical characteristics of water compositions on the basis of major ion concentrations were evaluated on a Schoeller and Piper diagram. Accordingly, the dominant type of water in the region is considered to be Ca-HCO3 (calcium-bicarbonate type). However, this type of water is also rich in Na, K, and especially Mg. Regarding Schoeller diagram, the current status of local underground water is good for drinking purposes. By commencing mining excavation with designed capacity in near future, the minerals will come into contact with air and water resulting in dissolution, especially in ponds, which, in turn, will increase the concentration of toxic metals in groundwater. Considering future uses of this water including for drinking, irrigation, industrial purposes, etc., precautions must be taken in to consideration.

Heavy metal mobility in runoff water and absorption by eggplant fruits from sludge treated soil

Sewage sludge addition to agricultural lands requires judicious management to avoid environmental risks arising from heavy metal and nitrate contamination of surface water and accumulation in edible plants. A field study was conducted on a silty-loam soil of 10% slope at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge and yard waste compost mix (SS-YW) at 15 t acre−1, six plots were mixed with sewage sludge (SS) at 15 t acre−1, and six unamended plots that never received sludge were used for comparison purposes. Plots were planted with eggplant, Solanum melongena L. as the test plant. The objectives of this investigation were to: 1) assess the effect of soil amendments on the transport of NO3, NH4, and heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) into surface water; 2) investigate the effect of soil amendments on heavy metal bioavailability in eggplant fruits at harvest; and 3) assess chemical and physical properties of soil following addition of soil amendments and their impact on the yield and quality of eggplant fruit. SS-YW treatments reduced runoff water by 63% while plots incorporated with sewage sludge alone reduced runoff water by 37% compared to control treatment. The SS-YW treatments transported more mineral nitrogen (NO3-N and NH4-N) in runoff water than SS treatments. Total marketable yield (lbs acre−1) and number of eggplant fruits were greatest in SS-YW treatments. This response may be due to improved soil porosity, water, and nutrient retention of the soil amended with SS-YW mixture. Concentrations of heavy metals in soil amended with sludge were below the U.S. Environmental Protection Agency (USEPA) limits. Chromium, Ni, Zn, and Cu were taken up by eggplant fruits but their concentrations were below the Codex Commission allowable levels.

Chip-Based Scanometric Detection of Mercuric Ion Using DNA-Functionalized Gold Nanoparticles

We have developed a chip-based scanometric method for the detection of mercuric ion (Hg (2+)). This method takes advantage of the cooperative binding and catalytic properties of DNA-functionalized gold nanoparticles and the selective binding of a thymine-thymine mismatch for Hg (2+). The limit of detection of this assay in buffer and environmentally relevant samples (lake water) is 10 nM (2 ppb) Hg (2+), which is the U.S. Environmental Protection Agency (EPA) limit of [Hg (2+)] for drinkable water and 1 order of magnitude lower than previous colorimetric assays. This assay is capable of discriminating Hg (2+) from 15 other environmentally relevant metal ions. The method is attractive for potential point-of-use applications due to its high throughput, convenient readout, and portability.

Distribution of some Heavy Metals in Leachates from a Municipal Waste Dumpsite

The distribution of heavy metals in leachates from a waste dumpsite was investigated. Soil samples were taken from a major dumpsite in Edo State located at Oluku near the National Institute for Oil Palm Research (NIFOR) and analyzed. The heavy metals considered were Iron, Lead, Zinc, Mercury, Chromium, Cadmium, Arsenic, Nickel, and Copper. The concentrations, in mg/l, of these heavy metals in the leachates from the soil samples over a distance of 80 meters were determined using the Atomic Absorption Spectrophotometer (AAS). The following results were obtained, the concentration of Iron ranged between 1.25-1.85 mg/l, Chromium: 0.01-0.07 mg/l, Zinc: 0.45-3.45 mg/l, Copper: 0.01-0.03 mg/l, Lead, Mercury, Cadmium, Arsenic, and Nickel had negligible values, i.e. less than 0.01 mg/l. From the results the concentrations of iron and zinc fell within Federal Environmental Protection Agency (FEPA) limits.

Assessment of Human Health Risks of Consumption of Cadmium Contaminated Cultured Oysters

ABSTRACT With farmed British Columbia (BC) oysters containing higher cadmium concentrations than wild oysters, long-term exposure to cadmium through consumption of oysters has the potential to cause health risks. This study reports on a risk assessment for cadmium intake resulting from the consumption of BC-cultured oyster. The study concludes that Health Canada's current recommended BC-cultured oyster consumption rate for Canadians of 12 oysters per month exceeds the Agency for Toxic Substances and Disease Registry chronic oral minimal risk levels (MRL) of 0.2 μ g·kg− 1·day− 1 by approximately 4-to 5-fold and reaches the Food and Agriculture Organization/World Health Organization (FAP/WHO) reference dose of 1 μg·kg−1·day−1 for cadmium consumption for Canadians. This suggests that although the current recommended maximum oyster consumption rates is consistent with the FAO/WHO and U.S. Environmental Protection Agency limits for acceptable risk, it leaves little or no room for error or uncertainty. This is noteworthy as recent studies demonstrate toxicological effects at cadmium intakes of 0.43 to 0.71 μ gCd·kg−1·day−1. This study indicates that a lower maximum BC-cultured oyster rate should be considered, particularly for high risk groups, including women with low iron stores, people with renal impairment, smokers, children, and indigenous people who consume organ meats of games and wildlife other than shellfish.

Effect of Types of Biosolids and Cattle Manure on Desert Grass Growth

We compared the effect of applying anaerobically produced biosolids, lime-stabilized biosolids, and cattle manure on the production of blue grama (Bouteloua gracilis [HBK] Lag. ex Steud.) and black grama (B. eriopoda [Torr.] Torr.) grown in pots with moderate soil water content. We also compared the physicochemical and bacteriological composition of these 3 amendments. All amendments produced similar increases in plant growth, despite their differences in plant nutrient concentrations, as a result of limitations in soil water. Heavy metal levels in biosolids were within the US Environmental Protection agency limits for Class A and Class B biosolids, but were higher than in manure. In contrast, pathogen levels were lower in biosolids than in manure. Application of biosolids and cattle manure increased the production of both grasses and may have equivalent effects under typical climatic and soil conditions of semiarid rangelands.

Optimum Dose Of Lime And Fly Ash For Treatment Of Hexavalent Chromium–Contaminated Soil

The presence of hexavalent chromium, Cr(VI), in soil is an environmental concern due to its effect on human health. The concern arises from the leaching and the seepage of Cr(VI) from soil to groundwater. In this paper, a stabilization technology to prevent this problem was simulated on an artificial soil contaminated with hexavalent chromium. The process is a physico-chemical treatment in which the toxic pollutant is physically entrapped within a solid matrix formed by the pozzolanic reactions of lime and fly ash to reduce its leachability and, therefore, its toxicity. This paper presents the optimum ratio of fly ash and lime in order to stabilize artificial soils contaminated with 0.4 wt.% of Cr (VI) in a brief term process. The degree of chromium released from the soil was evaluated using a modified Toxicity Characteristic Leaching Procedure (TCLP) by US Environmental Protection Agency (EPA). Overall, experimental results showed reduced leachability of total and hexavalent chromium from soils treated with both fly ash and quicklime, and that leachability reduction was more effective with increasing amount of fly ash and quicklime. Stabilization percentages between 97.3% and 99.7% of the initial chromium content were achieved, with Cr(VI) concentration in the TCLP leachates below the US EPA limit for chromium of 5 mg/l. Adequate treatment was obtained after 1 day of curing with just 25% fly ash and 10% quicklime.

Microbial Communities and Fecal Indicator Bacteria Associated with Cladophora Mats on Beach Sites along Lake Michigan Shores

A high biomasses of Cladophora, a filamentous green alga, is found mainly during the summer along the shores of Lake Michigan. In this study, the abundance and persistence of the fecal indicator bacterium Escherichia coli and sulfate-reducing bacteria (SRB) on Cladophora mats collected at Lake Michigan beaches were evaluated using both culture-based and molecular analyses. Additionally, 16S rRNA gene cloning and sequencing were used to examine the bacterial community composition. Overall, E. coli was detected in all 63 samples obtained from 11 sites, and the average levels at most beaches ranged from 2,700 CFU/100 g (wet weight) of Cladophora to 7,500 CFU/100 g of Cladophora. However, three beaches were found to have site average E. coli densities of 12,800, 21,130, and 27,950 CFU/100 g of Cladophora. The E. coli levels in the lake water collected at the same time from these three sites were less than the recommended U.S. Environmental Protection Agency limit, 235 CFU/100 ml. E. coli also persisted on Cladophora mats in microcosms at room temperature for more than 7 days, and in some experiments it persisted for as long as 28 days. The SRB densities on Cladophora mats were relatively high, ranging from 4.4x10(6) cells/g (6.64 log CFU/g) to 5.73x10(6) cells/g (6.76 log CFU/g) and accounting for between 20% and 27% of the total bacterial counts. Partial sequences of the 16S rRNA gene clones revealed a phylogenetically diverse community, in which the Cytophaga-Flavobacterium-Bacteroides cluster and the low-G+C-content gram-positive bacteria were the dominant organisms, accounting for 40% and 12.8%, respectively, of the total clone library. These results further reveal the potential public health and ecological significance of Cladophora mats that are commonly found along the shoreline of Lake Michigan, especially with regard to the potential to harbor microorganisms associated with fecal pollution and odor-causing bacteria.

Effect of Types of Biosolids and Cattle Manure on Desert Grass Growth

We compared the effect of applying anaerobically produced biosolids, lime-stabilized biosolids, and cattle manure on the production of blue grama (Bouteloua gracilis [HBK] Lag. ex Steud.) and black grama (B. eriopoda [Torr.] Torr.) grown in pots with moderate soil water content. We also compared the physicochemical and bacteriological composition of these 3 amendments. All amendments produced similar increases in plant growth, despite their differences in plant nutrient concentrations, as a result of limitations in soil water. Heavy metal levels in biosolids were within the US Environmental Protection agency limits for Class A and Class B biosolids, but were higher than in manure. In contrast, pathogen levels were lower in biosolids than in manure. Application of biosolids and cattle manure increased the production of both grasses and may have equivalent effects under typical climatic and soil conditions of semiarid rangelands.

Food Safety: A Tea-Time Mystery

When a 52-year-old Missouri woman approached physicians in 1998 complaining of stiffness and pain in her spine, the symptoms were at first attributed to “disc disease.” But a series of laboratory tests showed that the woman had abnormally thick, dense bones and strikingly high levels of fluoride in her urine—hallmarks of skeletal fluorosis, a disease that has been diagnosed only a handful of times in the United States. The only way to develop skeletal fluorosis is to ingest or inhale too much fluoride. The woman’s drinking water had only about 2.8 parts per million (ppm) fluoride, well below the Environmental Protection Agency (EPA) limit of 4.0 ppm. Other sources of fluoride were also eliminated: She didn’t swallow her toothpaste, she didn’t work with pesticides, and she didn’t live near a mine. So where was she getting all the fluoride? Then the woman revealed she had drunk up to two gallons of extra-strength instant tea every day of her adult life. Physician Michael Whyte of Washington University School of Medicine and his colleagues decided to measure the fluoride levels in her tea preparation. They found that, counting the fluoride in her water, the woman was ingesting 37–74 milligrams of fluoride per day. EPA studies suggest that severe skeletal fluorosis could occur over the course of 20 years from a continuous exposure of 20 milligrams of fluoride per day. Whyte and colleagues then tested 10 instant teas available in grocery stores. They found average fluoride concentrations of 1.0–6.5 ppm in regular-strength tea made with fluoride-free water, with several brands exceeding the Food and Drug Administration limit of 1.4–2.4 ppm for bottled beverages. Their study appears in the January 2005 issue of The American Journal of Medicine. Whyte believes that individuals who drink large volumes of instant tea for a prolonged period may be putting themselves at risk for skeletal fluorosis. But Joe Simrany, president of The Tea Association of the USA, believes that the Missouri incident was highly unusual. “It had less to do with tea than it had to do with excessive behavior,” he says. So should the average tea drinker be concerned? “It may be that certain brands ought to cut down the amount of fluoride in their tea or add a warning label to their product,” says Michael Kleerekoper, director of research for bone and mineral metabolism at Wayne State University, “but it would be a real mistake to throw out the baby with the bathwater.” He adds, “I drink tea—it’s wonderful on a hot summer’s afternoon.” Whyte, who also hasn’t stopped drinking tea, says, “Our research is a call for better understanding of fluoride levels in various teas.” He is now investigating the fluoride levels of bottled tea preparations. Meanwhile, the woman in Missouri has stopped drinking tea, and her pains have abated. She has since switched to lemonade.

Chromate ion adsorption by agricultural by-products modified with dimethyloldihydroxyethylene urea and choline chloride

The use of cellulose-containing agricultural by-products modified with the cross-linking reagent dimethyloldihydroxyethylene urea (DMDHEU) and the quaternary amine, choline chloride, as anion exchange resins, has not been reported. The objective of the present study was to convert the readily available by-products, soybean hulls, sugarcane bagasse and corn stover to functional anion exchange resins using DMDHEU and choline chloride. Optimization of the modification method was achieved using soybean hulls as a substrate. The optimized method was additionally used to modify sugarcane bagasse and corn stover. Adsorption efficiency results with chromate ion showed that modification with both DMDHEU and choline chloride was required for the highest efficiencies. Adsorption capacities of the modified by-products were determined using chromate ion and found to be 1.97, 1.61 and 1.12 mmol/g for sugarcane bagasse, corn stover and soybean hulls, respectively. Competitive adsorption studies were conducted at 10 and 50 times US Environmental Protection Agency (US EPA) limits for arsenic, chromium and selenium in a simulated wastewater at pH 7. The results showed preferential adsorption of chromate ion over arsenate or selenate ion. Estimated product costs for the three resins ranged from $0.88/kg to $0.99/kg, which was considerably lower than the market costs for the two commercial anion exchange resins QA-52 and IRA-400 also used in this study. DMDHEU/choline chloride modification of the three by-products produced an anion exchange resin with a high capacity to adsorb chromate ion singly or competitively in the presence of other anions from aqueous solutions.

Evaluation of electrokinetic removal of heavy metals from sewage sludge

The presence of heavy metals is one of the main obstacles for agricultural use of million tonnes of dewatered sewage sludge produced in wastewater treatment plants. Electrokinetic (EK) treatment can be applied to remove heavy metals from sludge. The aim of this study was to increase the efficiency of electrokinetic removal of heavy metals from dewatered sewage sludge. EK experiments were carried out with and without pH adjustment in cathode chamber of acidified sewage sludge. The selective sequential extraction (SSE) was used to determine the fractionation of heavy metals in sewage sludge. The mobility of heavy metals in sludge significantly increased after its acidification at pH 2.7 and followed the order: Ni, Zn, Cu, As, Cr, Pb. Removal efficiencies of heavy metals in the experiment with acidified sewage sludge and pH adjustment at cathode chamber at 2.0 were: 95% for Zn, 96% for Cu, 90% for Ni, 68% for Cr, 31% for As and 19% for Pb. The concentrations of Zn, Cu, Ni, Cr and Pb after EK treatment were below the United States Environmental Protection Agency limits for biosolids applied to agricultural land, forest, public contact sites or reclamation sites.

Radon concentration in Jordanian drinking water and hot springs

The radon concentration in Jordanian drinking water and hot springs has beenmeasured using the electret-passive environmental radon monitoring method. Thisstudy maps out Jordanian water sources from the north to the south as wellas the area around the capital Amman and the Jordan valley. Samples from 30sources were collected and analysed during the period from November 2001 toJune 2002. We have found that 60% of the drinking water sources have radonconcentrations above the proposed US Environmental Protection Agency limit of11 Bq l−1; these are mostly situated in the northern region of the country. Fortunately,these sources supplied only a small number of people since they weremainly located in rural areas. Tap water in the capital Amman, whereapproximately 35% of the population live, has a very low radon concentration,3.9 Bq l−1. However, the isolated northern drinking water wells did show a radon level as high as117 Bq l−1. Hot springs in Jordan have a radon level ranging between 63 and81 Bq l−1, again mainly in the northern region. In general we conclude that Jordanian drinkingwater is safe as far as radon concentration is concerned with the exception of a few isolatedlocal drinking water wells.

A 17-Month Evaluation of a Chlorine Dioxide Water Treatment System to Control Legionella Species in a Hospital Water Supply

To assess the safety and efficacy of a chlorine dioxide water treatment system in controlling Legionella in a hospital water supply. For 17 months following installation of the system, we performed regular water cultures throughout the building, assessed chlorine dioxide and chlorite levels, and monitored metal corrosion. Sites that grew Legionella species decreased from 41% at baseline to 4% (P = .001). L. anisa was the only species recovered and it was found in samples of both hot and cold water. Levels of chlorine dioxide and chlorite were below Environmental Protection Agency (EPA) limits for these chemicals in potable water. Further, enhanced carbon filtration effectively removed the chemicals, even at chlorine dioxide levels of more than twice what was used to treat the water. After 9 months, corrosion of copper test strips exposed to the chlorine dioxide was not higher than that of control strips. During the evaluation period, there were no cases of nosocomial Legionella in the building with the system, whereas there was one case in another building. Our results indicate that operation of a chlorine dioxide system effectively removed Legionella species from a hospital water supply. Furthermore, we found that the system was safe, as levels of chlorine dioxide and chlorite were below EPA limits. The system did not appear to cause increased corrosion of copper pipes. Our results indicate that chlorine dioxide may hold promise as a solution to the problem of Legionella contamination of hospital water supplies.

Influence of gold mine on groundwater quality (Efemçukuru, Izmir, Turkey)

Currently, exploration of gold ores is under discussion in Turkey, without considering its adverse affect on the environment. Studying the adverse affect on environment is extremely important because significant civic activities are already taking place on the geological units that contain gold ore bodies in Turkey. Such an area is located at the southeast of Izmir City (Turkey), and approximately 2-km-long gold-bearing ore veins occur close to the Efemcukuru Village. The objective of this study was to describe the characteristics and seasonal variation of the groundwater chemistry and pollution of the aquifer in the ore deposit site, and to determine the impact of ore deposits on groundwater quality. The gold-bearing formation is highly weathered and fractured. The fractures in the geological units control the permeability and the depth of groundwater in the area. The concentrations of Al, Ag, Cu, Cd, Cr, Fe, Pb, Mn, Zn, Ni, and Sb were determined for four well samples and two stream waters for wet and dry seasons. The results showed that the concentrations of most of these elements were below the USA EPA (Environmental Protection Agency) limits; however, Pb and Cd concentrations are slightly above the limits. The results indicate that minerals in gold bodies do not dissolve although the weathering of formations is high. The low concentration of elements in groundwater and streams may be attributed to the high velocity of ground and surface water.

Evaluation of Contaminated Sediments by Toxicity Characteristic Leaching Procedure Extraction Techniques

The metals Cr, Cu, Hg, Pb, and Zn were measured by using the Total Characteristic Leaching Procedure (TCLP) extracts from sediment samples taken from Bayou d'Inde, southwestern Louisiana. Bayou d'Inde has been severely contaminated by numerous industrial and municipal outfalls along its length. Fishing advisories have been posted to prevent excessive consumption of fish caught within the bayou. Sediment samples were crushed and allowed to pass through a 20-mesh sieve (<0.85 mm), well below the maximum particle size of 9.5 mm mandated by the TCLP extraction procedure. Despite the small particle size used in this study and the extraction of heavy metals from contaminated sediments, none of the studied metals in the extracts exceeded the U.S. Environmental Protection Agency limits of 100 times the maximum contaminant levels given in the primary and secondary drinking water standards.

Reducing Nitrogen Oxide Emissions by Staged Combustion of Low Calorific Value Gas derived from Agricultural Wastes

The design, construction and testing of a low nitrogen oxide (NOx), staged combustor to burn low calorific value gas derived from agricultural wastes is described in this paper. A cyclone combustor was used as the first stage combustor. Nitrogen oxide emissions during combustion of low calorific value gas derived from gasification of cotton gin trash were reduced from 1400 ng/J without staged combustion to less than 100 ng/J with staged combustion. An equivalence ratio in the first stage between 1·4 and 1·8 for the stoichiometric mass of air to actual mass of air, and a minimum delay time between stages of 0·2 s were found to be sufficient to achieve NOxemissions below the Environmental Protection Agency limit of 260 ng/J.

COMBINING PERIODIC AND CONTINUOUS SODIUM HYPOCHLORITE TREATMENT TO CONTROL BIOFILMS IN DENTAL UNIT WATER SYSTEMS

This study evaluated the efficacy of combined intermittent and continuous treatment with diluted sodium hypochlorite, or NaClO, to improve dental unit water quality in a clinical setting. In this prospective study, 10 dental units were fitted with separate water reservoir systems. Dental units were maintained with weekly rinses with 1:10 NaClO. Treatment water consisted of 750 milliliters of tap water and one drop of undiluted commercial bleach. Bacterial contamination in the effluent coolant water was assayed via microbiologic culture on a weekly basis. At the end of the study, scanning electron microscopy of the inner surfaces of the dental unit waterlines corroborated the results. All 10 dental units consistently delivered water with less than 10 colony-forming units per milliliter, or CFU/mL, with a mean bacterial contamination of less than 1 CFU/mL. Baseline scanning electron microscopy demonstrated biofilm formation. Scanning electron microscopy at the end of the study demonstrated the lack of features consistent with biofilm formation. Although tri-halomethanes were detected in output water, all samples were below Environmental Protection Agency limits for drinking water. Weekly treatment with 5.25 percent NaClO diluted 1:10, and concomitant use of chlorinated treatment water (3 parts per million chlorine) consistently attained the proposed American Dental Association goal of fewer than 200 CFU/mL in the unfiltered output. The effects of continuous treatment on dentin and enamel bond strength may require further evaluation. The success of this protocol suggests that optimal attainment of dental water quality goals may require a combination of approaches.

Stabilization/Solidification of Hazardous Wastes Using Fly Ash

A simple and inexpensive method of stabilization/solidification (S/S) of hazardous wastes using C-grade fly ash as the only binding agent is presented. The process involves mixing the waste and fly ash and compacting the mixture for less than 3 s at 1.4–6.9 MPa to form a monolith. Toxicity characteristic leaching procedure (TCLP) results for a simulated mixed waste showed that the chromium concentration in the leachate is well below current Environmental Protection Agency (EPA) limits. For this particular waste, TCLP results were not significantly affected by the ratio of waste:fly ash in the block due to the limited range of waste concentration that can be processed. Furthermore, it is shown that the optimum operating conditions are at a waste pH of 9.2 and an applied pressure of 4.65 MPa.

Risk, Uncertainty in Risk, and the EPA Release Limits for Radioactive Waste Disposal

A conceptual model for the organization and execution of a performance assessment of a radioactive waste disposal site, including uncertainty and sensitivity analysis, is described. This model is based on a formal definition of risk as a collection of ordered triples, where the first element in each triple is a set of similar occurrences, the second element is the probability or frequency of the first element, and the third element is a vector of consequences associated with the first element. This division of risk into its three constituent parts provides a useful model for the structure of a performance assessment for several reasons. First, it provides a clear distinction between the major parts of a performance assessment. Second, it provides a way to distinguish between different types of uncertainty, including completeness, aggregation, model selection, imprecisely known variables, and stochastic variation. Third, it leads naturally to the representation of stochastic variation with a complementary cumulative distribution function (CCDF) and the representation of state of knowledge uncertainty with a family or distribution of CCDFs. Fourth, it provides a context in which the U.S. Environmental Protection Agency limits for radioactive releases to the accessible environment can be represented and calculated. The preceding ideasmore » are illustrated with results obtained in a preliminary performance assessment for the Waste Isolation Pilot Plant in southeastern New Mexico.« less