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PubMed1990

Effects of burnrate, wood species, altitude, and stove type on woodstove emissions.

During the winter of 1986-87, the U.S. Environmental Protection Agency (EPA) conducted an emission measurement program in Boise, ID, as part of the Integrated Air Cancer Project (IACP). This program was designed to identify the potential mutagenic impact of residential wood burning on ambient and indoor air. One facet of this field sampling effort involved obtaining emission samples from chimneys serving wood burning appliances in Boise. As a companion to the field source sampling, a parallel project was undertaken in an instrumented woodstove test laboratory to quantify woodstove emissions during operations typical of Boise usage. Two woodstoves were operated in a test laboratory over a range of burnrates, burning either eastern oak or white pine from the Boise, ID, area. A conventional stove, manufactured in the Boise area, was tested at altitudes of 90 and 825 m. A catalytic stove was tested only at the high altitude facility. All emission tests were started with kindling a fire in a cold stove using black and white newsprint. Emissions were collected using the wood stove dilution sampling system (WSDSS) for a continuous period of about 8 hours, encompassing start-up and several wood additions. The results showed wide variability probably due primarily to the difficulty in duplicating conditions during start-up. Total WSDSS emissions showed the expected inverse correlations with burnrate for the conventional stove and nearly flat for the catalytic stove. While there appeared to be little or no correlation of total WSDSS emissions with altitude, the sum of the 16 polynuclear aromatic hydrocarbons (PAHs) quantified showed an inverse correlation with altitude: higher PAH emissions at the lower altitude.

Air Pollutants↗
PubMed2006

Fundamentals of successful monitoring, reporting, and verification under a cap-and-trade program.

The U.S. Environmental Protection Agency (EPA) developed and implemented the Acid Rain Program (ARP), and NO(x) Budget Trading Programs (NBTP) using several fundamental monitoring, reporting, and verification (MRV) elements: (1) compliance assurance through incentives and automatic penalties; (2) strong quality assurance (QA); (3) collaborative approach with a petition process; (4) standardized electronic reporting; (5) compliance flexibility for low-emitting sources; (6) complete emissions data record required; (7) centralized administration; (8) level playing field; (9) publicly available data; (10) performance-based approach; and (11) reducing conflicts of interest. Each of these elements is discussed in the context of the authors' experience under two U.S. cap-and-trade programs and their potential application to other cap- and-trade programs. The U.S. Office of Management and Budget found that the Acid Rain Program has accounted for the largest quantified human health benefits of any federal regulatory program implemented in the last 10 yr, with annual benefits exceeding costs by > 40 to 1. The authors believe that the elements described in this paper greatly contributed to this success. EPA has used the ARP fundamental elements as a model for other cap-and-trade programs, including the NBTP, which went into effect in 2003, and the recently published Clean Air Interstate Rule and Clean Air Mercury Rule. The authors believe that using these fundamental elements to develop and implement the MRV portion of their cap-and-trade programs has resulted in public confidence in the programs, highly accurate and complete emissions data, and a high compliance rate (> 99% overall).

Acid Rain↗
PubMed1991

Fumigants and related chemicals in foods: review of residue findings, contamination sources, and analytical methods.

Public concern over chemical residues in foods increased in the United States during the early 1980s. Potentially hazardous levels of ethylene dibromide (EDB), a relatively non-volatile fumigant, were detected in several finished grain-based products by governmental food-monitoring laboratories. As a result, the U.S. Environmental Protection Agency banned the use of EDB as a fumigant in 1983. Commercial fumigators then began using more of the highly volatile chemicals such as methyl bromide and phosphine. These chemicals are less likely to leave residues on stored crops than the previously used fumigants such as EDB, chloroform, and carbon tetrachloride. However, trace residues of many pest-control fumigants and related industrial chemicals are currently found in assorted foods. This contamination may come from the original fumigation of stored crops, or from the industrial chemicals occurring in the environment and in food processing chains. No potential health problem is indicated at this time. Yet scientists continue to uncover the sources of this chemical contamination, and to develop better methods to monitor foods for it. They also seek better ways to protect foodstuffs from pests prior to human consumption.

Ethylene Dibromide↗
PubMed1988

Performance assessment of radioactive waste repositories.

The current plans for permanent disposal of radioactive waste call for its emplacement in deep underground repositories mined from geologically stable rock formations. The U.S. Nuclear Regulatory Commission and U.S. Environmental Protection Agency have established regulations setting repository performance standards for periods of up to 10,000 years after disposal. Compliance with these regulations will be based on a performance assessment that includes (i) identification and evaluation of the likelihood of all significant processes and events that could affect a repository, (ii) examination of the effects of these processes and events on the performance of a repository, and (iii) estimation of the releases of radionuclides, including the associated uncertainties, caused by these processes and events. These estimates are incorporated into a probability distribution function showing the likelihood of exceeding radionuclide release limits specified by regulations.

Evaluation Studies as Topic↗
PubMedDate not supplied

A comparison of methods for determining lead content in drinking water: a portable anodic stripping voltammetry instrument method versus the standard EPA 239.2 method.

Lead levels in drinking water were measured by the standard U.S. Environmental Protection Agency (EPA)-approved atomic absorption spectroscopy-graphite furnace Method 239.2 and compared with determinations made with a newly available portable anodic stripping voltammetry (PASV) instrument. A standard curve was prepared at 2, 5, 10, 15, 20, 25, and 30 microg/L of lead. PASV instrument readings were lower than standard EPA method values, with a mean difference and standard error (SE) of the mean between the two of 1.538+/-0.588 microg/L (n = 7, p = 0.040, significant at the 95% confidence interval [CI]). First-flush drinking water samples collected from 144 water fountains/coolers were preserved with nitric acid. Total lead content was tested twice for 29 EPA method samples and 54 PASV instrument samples to determine the variation within each method; results were not significant at the 95% CI. Total lead content was determined for 144 samples by both methods. PASV instrument readings were lower than standard EPA method values (mean difference and SE of the mean 0.630+/-0.206 microg/L; n = 144, p = 0.0027, significant at the 95% CI). Mean and standard deviation of the 144 samples for the EPA method and the PASV instrument were 6.5+/-11.8 microg/L and 5.9+/-11.6 microg/L, respectively. Means were below the action level for lead of 15 ppb (microg/L), but some values were above the action level (18 [13%] using the EPA method; 20 [14%] using the PASV instrument). Retesting by EPA method showed two false positive PASV values. Results indicate that in some field situations the PASV instrument may prove useful due to its relatively low price, small size, ease of use, and quick readings.

Electrochemistry↗
PubMed2001

Drinking water standards for radionuclides: the dilemma and a possible resolution.

The U.S. Environmental Protection Agency (EPA) is undertaking a revision of existing standards for radionuclides in drinking water. The Safe Drinking Water Act specifies that any revision "shall maintain or provide for greater protection of the health of persons." This provision appears to require that existing standards (maximum contaminant levels, MCLs) cannot be relaxed. Such a requirement presents a dilemma for two reasons. First, EPA has shown that the MCL for radium was not cost-effective. Second, MCLs for beta/gamma-emitting radionuclides incorporate outdated approaches to estimating dose from ingestion of radionuclides and, thus, appear to violate provisions of the Safe Drinking Water Act concerning the use of sound science in setting standards. We suggest that this dilemma can be resolved based on an argument that the standard for protection of public health mandated by the Safe Drinking Water Act is one of applying best-available technology for removal of contaminants from drinking water at a reasonable cost, not one of meeting previously established MCLs.

Humans↗
PubMed2000

Exposure to air pollution is associated with lung hyperinflation in healthy children and adolescents in Southwest Mexico City: a pilot study.

Air pollution produces adverse health effects. The consequences of lifelong daily exposures to atmospheric pollutants upon the respiratory apparatus of healthy children are of considerable clinical importance. We investigated the association between exposure to a highly polluted urban environment with a complex mixture of air pollutants-ozone and particulate matter the predominant ones-and chest x-ray abnormalities in 59 healthy Mexican children who are lifelong residents of Southwest Metropolitan Mexico City (SWMMC), with a negative history of tobacco exposure and respiratory illnesses. Their clinical results and x-ray findings were compared to those of 19 Mexican control children, residents of a low-pollution area, with a similar negative history of tobacco exposure and respiratory illnesses. Ozone concentrations in SWMMC exceeded the U.S. Environmental Protection Agency (U.S. EPA) National Ambient Air Quality Standard (NAAQS) for O(3): 0.08 ppm as 1-h maximal concentration, not to be exceeded more than 4 times a year, on 71% of days in 1986 and 95% in 1997, with values as high as 0.48 ppm. Ozone maximal peaks are usually recorded between 2 and 5 pm coinciding with children's outdoor physical activities. Children in the control group reported no upper or lower respiratory symptomatology. Every SWMMC child complained of upper and/or lower respiratory symptoms, including epistaxis, nasal dryness and crusting, cough, shortness of breath, and chest discomfort. Children aged 7-13 yr had the most symptomatology, while 5- to 6-year olds and adolescents with the lowest number of statistically significant outdoor exposure hours had less respiratory symptoms. Bilateral symmetric mild lung hyperinflation was significantly associated with exposure to the SWMMC atmosphere (p = .0004). Chronic and sustained inhalation of a complex mixture of air pollutants, including ozone and particulate matter (PM), is associated with lung hyperinflation, suggestive of small airway disease, in a population of clinically healthy children and adolescents. Small airways are a target of air pollutants in SWMMC children, with ozone and PM being most likely responsible, based on experimental animal, controlled-chamber, and epidemiological data available. Our main concern is the potential likelihood for the development of chronic lung disease in this highly exposed population.

Adolescent↗
PubMed2005

Workgroup report: workshop on source apportionment of particulate matter health effects--intercomparison of results and implications.

Although the association between exposure to ambient fine particulate matter with aerodynamic diameter < 2.5 microm (PM2.5) and human mortality is well established, the most responsible particle types/sources are not yet certain. In May 2003, the U.S. Environmental Protection Agency's Particulate Matter Centers Program sponsored the Workshop on the Source Apportionment of PM Health Effects. The goal was to evaluate the consistency of the various source apportionment methods in assessing source contributions to daily PM2.5 mass-mortality associations. Seven research institutions, using varying methods, participated in the estimation of source apportionments of PM2.5 mass samples collected in Washington, DC, and Phoenix, Arizona, USA. Apportionments were evaluated for their respective associations with mortality using Poisson regressions, allowing a comparative assessment of the extent to which variations in the apportionments contributed to variability in the source-specific mortality results. The various research groups generally identified the same major source types, each with similar elemental makeups. Intergroup correlation analyses indicated that soil-, sulfate-, residual oil-, and salt-associated mass were most unambiguously identified by various methods, whereas vegetative burning and traffic were less consistent. Aggregate source-specific mortality relative risk (RR) estimate confidence intervals overlapped each other, but the sulfate-related PM2.5 component was most consistently significant across analyses in these cities. Analyses indicated that source types were a significant predictor of RR, whereas apportionment group differences were not. Variations in the source apportionments added only some 15% to the mortality regression uncertainties. These results provide supportive evidence that existing PM2.5 source apportionment methods can be used to derive reliable insights into the source components that contribute to PM2.5 health effects.

Air Pollutants↗
PubMed1991

EPA use of in vivo germ cell mutagenicity data.

The Toxic Substances Control Act (TSCA) provides the U.S. Environmental Protection Agency, Office of Toxic Substances (EPA, OTS) with the authority to regulate chemical use by requiring testing and use restrictions as appropriate to protect human health. Regulation on the basis of heritable mutation induction is specifically mentioned in the Test Rule section of the law and has also been pursued for new chemical substances. A tiered scheme of mutagenicity testing has been employed and recently revised to assess mutagenicity hazard. In vivo assay systems play key roles at all three levels in the scheme, beginning with the first level of determining intrinsic mutagenicity hazard. Once intrinsic mutagenicity has been identified, the revised scheme requires an assay or assays to assess chemical interaction with gonadal DNA. Finally, the scheme contains tests that permit risk assessment for a chemical. The recently-revised Office of Pesticide Programs (OPP) mutagenicity testing requirements closely parallel those of OTS.

Animals↗
PubMed2004

Selecting appropriate animal models and experimental designs for endocrine disruptor research and testing studies.

Evidence that chemicals in the environment may cause developmental and reproductive abnormalities in fish and wildlife by disrupting normal endocrine functions has increased concern about potential adverse human health effects from such chemicals. US laws have now been enacted that require the US Environmental Protection Agency (EPA) to develop and validate a screening program to identify chemicals in food and water with potential endocrine-disrupting activity. EPA subsequently proposed an Endocrine Disruptor Screening Program that uses in vitro and in vivo test systems to identify chemicals that may adversely affect humans and ecologically important animal species. However, the endocrine system can be readily modulated by many experimental factors, including diet and the genetic background of the selected animal strain or stock. It is therefore desirable to minimize or avoid factors that cause or contribute to experimental variation in endocrine disruptor research and testing studies. Standard laboratory animal diets contain high and variable levels of phytoestrogens, which can modulate physiologic and behavioral responses similar to both endogenous estrogen as well as exogenous estrogenic chemicals. Other studies have determined that some commonly used outbred mice and rats are less responsive to estrogenic substances than certain inbred mouse and rat strains for various estrogen-sensitive endpoints. It is therefore critical to select appropriate biological models and diets for endocrine disruptor studies that provide optimal sensitivity and specificity to accomplish the research or testing objectives. An introduction is provided to 11 other papers in this issue that review these and other important laboratory animal experimental design considerations in greater detail, and that review laboratory animal and in vitro models currently being used or evaluated for endocrine disruptor research and testing. Selection of appropriate animal models and experimental design parameters for endocrine disruptor research and testing will minimize confounding experimental variables, increase the likelihood of replicable experimental results, and contribute to more reliable and relevant test systems.

Animals↗
PubMed2003

Effect of particles on the recovery of cryptosporidium oocysts from source water samples of various turbidities.

Cryptosporidium parvum can be found in both source and drinking water and has been reported to cause serious waterborne outbreaks which threaten public health safety. The U.S. Environmental Protection Agency has developed method 1622 for detection of Cryptosporidium oocysts present in water. Method 1622 involves four key processing steps: filtration, immunomagnetic separation (IMS), fluorescent-antibody (FA) staining, and microscopic evaluation. The individual performance of each of these four steps was evaluated in this study. We found that the levels of recovery of C. parvum oocysts at the IMS-FA and FA staining stages were high, averaging more than 95%. In contrast, the level of recovery declined significantly, to 14.4%, when the filtration step was incorporated with tap water as a spiking medium. This observation suggested that a significant fraction of C. parvum oocysts was lost during the filtration step. When C. parvum oocysts were spiked into reclaimed water, tap water, microfiltration filtrate, and reservoir water, the highest mean level of recovery of (85.0% +/- 5.2% [mean +/- standard deviation]) was obtained for the relatively turbid reservoir water. Further studies indicated that it was the suspended particles present in the reservoir water that contributed to the enhanced C. parvum oocyst recovery. The levels of C. parvum oocyst recovery from spiked reservoir water with different turbidities indicated that particle size and concentration could affect oocyst recovery. Similar observations were also made when silica particles of different sizes and masses were added to seeded tap water. The optimal particle size was determined to be in the range from 5 to 40 micro m, and the corresponding optimal concentration of suspended particles was 1.42 g for 10 liters of tap water.

Animals↗
PubMed1994

A commentary on the NRC report "Science and judgment in risk assessment".

This article provides a brief overview of the report "Science and Judgment in Risk Assessment," prepared by a Committee of the National Research Council/National Academy of Science in response to a U.S. Environmental Protection Agency request mandated by the Clean Air Act Amendments of 1990 (CAAA-1990). The report critiques EPA's current approaches for characterizing human cancer risks from exposure to chemicals and offers recommendations for the conduct of future cancer risk assessments, especially those required in implementing the CAAA-1990 provisions which are concerned with hazardous air pollutants. The report offers specific recommendations that address the role of default options, data needs, methods and models, uncertainty, variability, and the aggregation of data. A cross-cutting theme of the report is the use of an iterative approach in which screening assessments with limited data and, of necessity, default options used in the absence of specific scientific data may be performed initially followed by subsequent assessments, as needed, in which increasing amounts of data are developed and incorporated. In some instances, the specific data on a given chemical or pollutant source will replace conservative default options used in earlier assignments. The report includes two authored appendices that address issues related to the use of default options and their replacement by specific scientific information. One appendix by Finkel advocates a principle of "plausible conservatism" for choosing and altering default options and in making cancer risk estimates. A second appendix by McClellan and North advocates the full use of scientific information in the risk assessment process. This article gives major attention to the key aspects of the NRC/NAS report, especially those dealing with the use and replacement of default options. The default options and the extent to which the options are replaced with specific science have major impact on the final quantitation of cancer risk for exposure to chemicals.

Air Pollution↗
PubMed1996

Use of genetic toxicology data in U.S. EPA risk assessment: the mercury study report as an example.

Assessment of human health risks of environmental agents has often been limited to consideration of the potential for the agent to cause cancer or general systemic toxicity after long-term exposure. The U.S. Environmental Protection Agency (U.S. EPA) is increasingly moving toward the development of integrated assessments, which consider all potential health end points including developmental toxicity, neurotoxicity, immunotoxicity, reproductive effects, and germ cell mutagenicity. The U.S. EPA has a responsibility to assess risks to nonhuman species or ecosystems when appropriate data are available. An example of a recent integrated human health and ecological risk assessment can be found in the U.S. EPA Mercury Study Report to Congress. This report covers the following topics in separate volumes: an inventory of anthropogenic mercury emissions in the United States; an exposure assessment using measured and predicted values and including indirect dietary exposure; an evaluation of human health risks; an assessment of ecologic risk wherein water criteria are presented for several wildlife species; an overall integrated characterization of human and nonhuman risk; and a discussion of risk management considerations. In the evaluation of human health risk, genetic toxicology data were considered for three forms of mercury: elemental, inorganic (divalent), and methylmercury. These data were used in judgments of two types of potential health effects (carcinogenicity and germ cell mutagenicity). In assessment of potential carcinogenicity of inorganic and methylmercury, genetic toxicity data were key. Data for clastogenicity in the absence of mutagenicity supported the characterization of inorganic and methylmercury as materials that produce carcinogenic effects only at high, toxic doses. The evidence for clastogenicity, coupled with information on metabolism and distribution, resulted in a judgment of a moderate degree of concern (or weight of evidence) that inorganic mercury can act as a human germ cell mutagen. For methylmercury, the degree of concern for germ cell mutagenicity is high.

Animals↗
PubMed2000

Development of a single-meal fish consumption advisory for methyl mercury.

Methyl mercury (meHg) contamination of fish is the leading cause of fish consumption advisories in the United States. These advisories have focused upon repeated or chronic exposure, whereas risks during pregnancy may also exist from a single-meal exposure if the fish tissue concentration is high enough. In this study, acute exposure to meHg from a single fish meal was analyzed by using the one-compartment meHg biokinetic model to predict maternal hair concentrations. These concentrations were evaluated against the mercury hair concentration corresponding to the U.S. Environmental Protection Agency's reference dose (RfD), which is intended to protect against neurodevelopmental effects. The one-compartment model was validated against blood concentrations from three datasets in which human subjects ingested meHg in fish, either as a single meal or multiple meals. Model simulations of the single-meal scenario at different fish meHg concentrations found that concentrations of 2.0 ppm or higher can be associated with maternal hair concentrations elevated above the RfD level for days to weeks during gestation. A single-meal fish concentration cutoff of > or = 2.0 ppm is an important consideration, especially because this single high exposure event might be in addition to a baseline meHg body burden from other types of fish consumption. This type of single-meal advisory requires that fish sampling programs provide data for individual rather than composited fish, and take into account seasonal differences that may exist in fish concentrations.

Adult↗
PubMed1994

Evaluating health risks from occupational exposure to pesticides and the regulatory response.

In this study, we used measurements of occupational exposures to pesticides in agriculture to evaluate health risks and analyzed how the federal regulatory program is addressing these risks. Dose estimates developed by the State of California from measured occupational exposures to 41 pesticides were compared to standard indices of acute toxicity (LD50) and chronic effects (reference dose). Lifetime cancer risks were estimated using cancer potencies. Estimated absorbed daily doses for mixers, loaders, and applicators of pesticides ranged from less than 0.0001% to 48% of the estimated human LD50 values, and doses for 10 of 40 pesticides exceeded 1% of the estimated human LD50 values. Estimated lifetime absorbed daily doses ranged from 0.1% to 114,000% of the reference doses developed by the U.S. Environmental Protection Agency, and doses for 13 of 25 pesticides were above them. Lifetime cancer risks ranged from 1 per million to 1700 per million, and estimates for 12 of 13 pesticides were above 1 per million. Similar results were obtained for field workers and flaggers. For the pesticides examined, exposures pose greater risks of chronic effects than acute effects. Exposure reduction measures, including use of closed mixing systems and personal protective equipment, significantly reduced exposures. Proposed regulations rely primarily on requirements for personal protective equipment and use restrictions to protect workers. Chronic health risks are not considered in setting these requirements. Reviews of pesticides by the federal pesticide regulatory program have had little effect on occupational risks. Policy strategies that offer immediate protection for workers and that are not dependent on extensive review of individual pesticides should be pursued.

Adult↗
PubMed2000

Air toxics and health risks in California: the public health implications of outdoor concentrations.

Of the 188 hazardous air pollutants (HAPs) listed in the Clean Air Act, only a handful have information on human health effects, derived primarily from animal and occupational studies. Lack of consistent monitoring data on ambient air toxics makes it difficult to assess the extent of low-level, chronic, ambient exposures to HAPs that could affect human health, and limits attempts to prioritize and evaluate policy initiatives for emissions reduction. Modeled outdoor HAP concentration estimates from the U.S. Environmental Protection Agency's Cumulative Exposure Project were used to characterize the extent of the air toxics problem in California for the base year of 1990. These air toxics concentration estimates were used with chronic toxicity data to estimate cancer and noncancer hazards for individual HAPs and the risks posed by multiple pollutants. Although hazardous air pollutants are ubiquitous in the environment, potential cancer and noncancer health hazards posed by ambient exposures are geographically concentrated in three urbanized areas and in a few rural counties. This analysis estimated a median excess individual cancer risk of 2.7E-4 for all air toxics concentrations and 8600 excess lifetime cancer cases, 70% of which were attributable to four pollutants: polycyclic organic matter, 1,3 butadiene, formaldehyde, and benzene. For noncancer effects, the analysis estimated a total hazard index representing the combined effect of all HAPs considered. Each pollutant contributes to the index a ratio of estimated concentration to reference concentration. The median value of the index across census tracts was 17, due primarily to acrolein and chromium concentration estimates. On average, HAP concentrations and cancer and noncancer health risks originate mostly from area and mobile source emissions, although there are several locations in the state where point sources account for a large portion of estimated concentrations and health risks. Risk estimates from this study can provide guidance for prioritizing research, monitoring, and regulatory intervention activities to reduce potential hazards to the general population. Improved ambient monitoring efforts can help clarify uncertainties inherent in this analysis.

Acrolein↗
PubMed2000

Improving cancer dose-response characterization by using physiologically based pharmacokinetic modeling: an analysis of pooled data for acrylonitrile-induced brain tumors to assess cancer potency in the rat.

Historically, U.S. regulators have derived cancer slope factors by using applied dose and tumor response data from a single key bioassay or by averaging the cancer slope factors of several key bioassays. Recent changes in U.S. Environmental Protection Agency (EPA) guidelines for cancer risk assessment have acknowledged the value of better use of mechanistic data and better dose-response characterization. However, agency guidelines may benefit from additional considerations presented in this paper. An exploratory study was conducted by using rat brain tumor data for acrylonitrile (AN) to investigate the use of physiologically based pharmacokinetic (PBPK) modeling along with pooling of dose-response data across routes of exposure as a means for improving carcinogen risk assessment methods. In this study, two contrasting assessments were conducted for AN-induced brain tumors in the rat on the basis of (1) the EPA's approach, the dose-response relationship was characterized by using administered dose/concentration for each of the key studies assessed individually; and (2) an analysis of the pooled data, the dose-response relationship was characterized by using PBPK-derived internal dose measures for a combined database of ten bioassays. The cancer potencies predicted for AN by the contrasting assessments are remarkably different (i.e., risk-specific doses differ by as much as two to four orders of magnitude), with the pooled data assessments yielding lower values. This result suggests that current carcinogen risk assessment practices overestimate AN cancer potency. This methodology should be equally applicable to other data-rich chemicals in identifying (1) a useful dose measure, (2) an appropriate dose-response model, (3) an acceptable point of departure, and (4) an appropriate method of extrapolation from the range of observation to the range of prediction when a chemical's mode of action remains uncertain.

Acrylonitrile↗
PubMed2006

Statistical procedures for determination and verification of minimum reporting levels for drinking water methods.

The United States Environmental Protection Agency's Office of Ground Water and Drinking Water has developed a single-laboratory quantitation procedure: the lowest concentration minimum reporting level (LCMRL). The LCMRL is the lowest true concentration for which future recovery is predicted to fall, with high confidence (99%), between 50% and 150%. The procedure takes into account precision and accuracy. Multiple concentration replicates are processed through the entire analytical method and the data are plotted as measured sample concentration (y-axis) versus true concentration (x-axis). If the data support an assumption of constant variance over the concentration range, an ordinary least-squares regression line is drawn; otherwise, a variance-weighted least-squares regression is used. Prediction interval lines of 99% confidence are drawn about the regression. At the points where the prediction interval lines intersect with data quality objective lines of 50% and 150% recovery, lines are dropped to the x-axis. The higher of the two values is the LCMRL. The LCMRL procedure is flexible because the data quality objectives (50-150%) and the prediction interval confidence (99%) can be varied to suit program needs. The LCMRL determination is performed during method development only. A simpler procedure for verification of data quality objectives at a given minimum reporting level (MRL) is also presented. The verification procedure requires a single set of seven samples taken through the entire method procedure. If the calculated prediction interval is contained within data quality recovery limits (50-150%), the laboratory performance at the MRL is verified.

Analysis of Variance↗