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K Ashley

Publications and source records attributed to K Ashley.

16 recordsLinked to original sources
PubMed2001

Field screening test methods: performance criteria and performance characteristics.

Field-portable test methods may be quantitative, semi-quantitative, or qualitative and screening methods are often used in the field to determine if the concentration of a toxic substance exceeds regulatory or recommended standards or action levels. For on-site analysis, accurate quantitative tests for field measurements may not be available, depending on the analyte(s) or specific field situation. Thus, in lieu of more definitive test methods, screening tests which are based on qualitative or semi-quantitative methods are often used for making immediate decisions in the field, e.g. for compliance or risk assessment. Also, quantitative methods may be used for screening purposes in many instances. To ensure the quality of these screening tests and the decisions that are made based upon their results, screening methods need to be evaluated with sufficient data and should meet basic performance criteria prior to their being employed for decision-making purposes. Although quantitative, semi-quantitative and qualitative methods demonstrate different characteristics, it is desired that the performance criteria for all three method categories be consistent. If there is consistency, then one can have a sound basis for selecting the most appropriate test(s) for a given application. In order to unify the performance criteria for the different types of methods, a performance function is used to characterise both qualitative and semi-quantitative methods; in turn, this performance function is related to that for quantitative methods. False negative rates, false positive rates, sensitivity and specificity are key characteristics of screening methods that can be determined from the pertinent performance curves. The performance characteristics of each method are related to the uncertainty region that is associated with each method and the applicable uncertainty regions can be gleaned from the performance curves. Also, various options for using multiple test results to improve decisions based on test results are provided.

Environmental Monitoring↗
PubMed2001

Ultrasonic extraction and field-portable anodic stripping voltammetric measurement of lead in dust wipe samples.

Dust wipe samples were subjected to ultrasonic extraction (UE) in diluted nitric acid, and then analyzed for lead content using field-portable anodic stripping voltammetry (ASV). Recoveries of lead were determined from wipe materials which were spiked with certified reference materials (CRMs) containing known quantities of lead. Four different wipe materials and four different CRMs were tested, with and without filtration of aliquots of sample extract through 0.45 microm hydrophilic polytetrafluoroethylene filters. The CRMs consisted of paint, soil, particulate, and dust matrices. Wipe materials were chosen from those which have been found to meet the performance aspects of an ASTM standard specification. UE/ASV experiments were carried out in accordance with newly published ASTM procedures for on-site extraction and electroanalysis. Recoveries were found to vary for different wipe materials and CRMs. For several CRMs, quantitative (80--120%) recoveries for UE/ASV were observed for one wipe material whether filtration was used or not, while other wipe materials required filtration for quantitative recovery. In the case of one wipe material which contained detergents, quantitative recoveries could not be achieved whether filtration was used or not. The total analysis time for a sample set of 6--12 samples was 60--90 min, including extraction time and sample manipulation. The results of this work have provided information on the choice of wipe materials that can be used for quantitative lead measurements by UE/ASV in materials that are representative of sources of lead in surface dust.

Dust↗
PubMed2001

Evaluation of a portable blood lead analyzer with occupationally exposed populations.

BACKGROUND: This project evaluated a portable electroanalytical instrument that is used to rapidly analyze blood lead levels in individuals, using a fresh whole blood sample (venous). METHODS: Samples were obtained from 208 lead-exposed employees who donated two 2 ml venous blood samples into "lead-free" evacuated tubes. One blood sample was analyzed onsite using the portable field instrument while the second sample was analyzed using graphite furnace atomic absorption spectrometry (GFAAS). RESULTS: According to GFAAS results, employee venous blood lead levels ranged from 1 microg/dl to 42 microg/dl. The mean difference between the results from the field instrument and GFAAS was less than 1 microg/dl. Analysis indicates that the results from the field instrument yielded a slight positive bias overall (P value = 0.0213), with less bias for blood lead levels above 10 microg/dl (P value = 0.0738). CONCLUSIONS: Within the blood range evaluated (1-42 microg/dl), the instrument performed adequately according to Clinical Laboratory Improvements Amendments (CLIA) proficiency requirements. The ability of the instrument to perform rapid analysis makes it potentially valuable to occupational health professionals for medical monitoring or on-site investigations.

Adult↗
PubMed2000

Comparison of three sampling and analytical methods for the determination of airborne hexavalent chromium.

A field study was conducted with the goal of comparing the performance of three recently developed or modified sampling and analytical methods for the determination of airborne hexavalent chromium (Cr(VI)). The study was carried out in a hard chrome electroplating facility and in a jet engine manufacturing facility where airborne Cr(VI) was expected to be present. The analytical methods evaluated included two laboratory-based procedures (OSHA Method ID-215 and NIOSH Method 7605) and a field-portable method (NIOSH Method 7703). These three methods employ an identical sampling methodology: collection of Cr(VI)-containing aerosol on a polyvinyl chloride (PVC) filter housed in a sampling cassette, which is connected to a personal sampling pump calibrated at an appropriate flow rate. The basis of the analytical methods for all three methods involves extraction of the PVC filter in alkaline buffer solution, chemical isolation of the Cr(VI) ion, complexation of the Cr(VI) ion with 1,5-diphenylcarbazide, and spectrometric measurement of the violet chromium diphenylcarbazone complex at 540 nm. However, there are notable specific differences within the sample preparation procedures used in three methods. To assess the comparability of the three measurement protocols, a total of 20 side-by-side air samples were collected, equally divided between a chromic acid electroplating operation and a spray paint operation where water soluble forms of Cr(VI) were used. A range of Cr(VI) concentrations from 0.6 to 960 microg m(-3), with Cr(VI) mass loadings ranging from 0.4 to 32 microg, was measured at the two operations. The equivalence of the means of the log-transformed Cr(VI) concentrations obtained from the different analytical methods was compared. Based on analysis of variance (ANOVA) results, no statistically significant differences were observed between mean values measured using each of the three methods. Small but statistically significant differences were observed between results obtained from performance evaluation samples for the NIOSH field method and the OSHA laboratory method.

Air Pollutants↗
PubMed1999

Field method for the determination of hexavalent chromium by ultrasonication and strong anion-exchange solid-phase extraction.

A simple, fast, sensitive, and economical field method was developed and evaluated for the determination of hexavalent chromium (CrVI) in environmental and workplace air samples. By means of ultrasonic extraction in combination with a strong anion-exchange solid-phase extraction (SAE-SPE) technique, the filtration, isolation, and determination of CrVI in the presence of trivalent chromium (CrIII) and potential interferents was achieved. The method entails (1) ultrasonication in basic ammonium buffer solution to extract CrVI from environmental matrixes; (2) SAE-SPE to separate CrVI from CrIII and interferences; (3) elution/acidification of the eluate; (4) complexation of chromium with 1,5-diphenylcarbazide; and (5) spectrophotometric determination of the colored chromium-diphenylcarbazone complex. Several critical parameters were optimized in order to effect the extraction of both soluble (K2CrO4) and insoluble (PbCrO4) forms of CrVI without inducing CrIII oxidation or CrVI reduction. The method allowed for the dissolution and purification of CrVI from environmental and workplace air sample matrixes for up to 24 samples simultaneously in less than 90 min (including ultrasonication). The results demonstrated that the method was simple, fast, quantitative, and sufficiently sensitive for the determination of occupational exposures of CrVI. The method is applicable for on-site monitoring of CrVI in environmental and industrial hygiene samples.

Air Pollutants, Occupational↗
PubMed1999

Ultrasonic extraction and portable anodic stripping voltammetric measurement of lead in paint, dust wipes, soil, and air: an interlaboratory evaluation.

Recent studies have demonstrated the utility of ultrasonic extraction (UE), followed by portable anodic stripping voltammetry (ASV), for the on-site determination of lead in environmental and industrial hygiene samples. The aim of this work was to conduct an interlaboratory evaluation of the UE-ASV procedure, with a goal of establishing estimates of method performance based on results from collaborative interlaboratory analysis. In this investigation, performance evaluation materials (PEMs) with characterized lead concentrations were used for interlaboratory testing of the UE-ASV procedure. The UE-ASV protocol examined has been promulgated in the form of two separate national voluntary consensus standards (one for UE and another for electroanalysis, which includes ASV). The PEMs consisted of characterized and homogenized paints, soils, and dusts (the last of which were spiked onto wipes meeting national voluntary consensus standard specifications), and air filter samples (mixed cellulose ester membrane) generated using characterized paints within an aerosol chamber. The lead concentrations within the PEMs were chosen so as to bracket pertinent action levels for lead in the various sample matrices. The interlaboratory evaluation was conducted so as to comply with an applicable national voluntary consensus standard that can be used to estimate the interlaboratory precision of a given analytical test method. Based on the analytical results reported by the participating laboratories, relative standard deviations (RSDs) for repeatability and reproducibility were computed for three different lead contents of the four PEMs. RSDs for repeatability were 0.019-0.100 for paints; 0.030-0.151 for soils; 0.085-0.134 for dust wipes; and 0.095-0.137 for air filters. RSDs for reproducibility were 0.127-0.213 for paints; 0.062-0.162 for soils; 0.085-0.134 for dust wipes; and 0.114-0.220 for air filters. With the exception of one of the air filter samples and one of the paint samples, the precision estimates were within the +/- 20% precision requirement specified in the US Environmental Protection Agency National Lead Laboratory Accreditation Program (NLLAP). The results of this investigation illustrate that the UE-ASV procedure is an effective method for the quantitative measurement of lead in the matrices evaluated in this study.

Air Pollution, Indoor↗
PubMed1999

Evaluation of a portable X-ray fluorescence instrument for the determination of lead in workplace air samples.

Occupational Safety and Health Administration (OSHA) regulations for worker exposure to lead specify worker protection levels based upon airborne concentrations of lead dust. The rapid, on-site determination of lead in air filter samples using a portable x-ray fluorescence (XRF) instrument with an attachment to hold the filter would expedite the exposure assessment process and facilitate compliance with the OSHA standards. A total of 65 lead in air filter samples were collected at bridge blasting lead-abatement projects using closed-faced, 37-mm cassettes with pre-loaded 0.8 micron pore size mixed cellulose ester membrane filters. The lead loading range of the data set was 0.1-1514.6 micrograms (micrograms) of lead/sample. Samples were initially analyzed with a field portable XRF (NITON 700) using an experimental non-destructive XRF method. Samples were subsequently analyzed using National Institute for Occupational Safety and Health (NIOSH) Method 7105 (Graphite Furnace AA) as a reference analytical method. The paired data were not normally distributed; therefore, the non-parametric Wilcoxon signed rank test was used for statistical analysis. There was no statistically significant difference between data from the field portable XRF method and the NIOSH method (p-value = 0.72). Linear regression of the data resulted in a slope of 0.959, a y-intercept of 5.20 micrograms, and an r2 of 0.985. The XRF limit of detection and limit of quantitation were determined to be 6.2 and 17 micrograms of lead/sample, respectively. The XRF method accuracy was +/- 16.4% (7.1%-27%, 90% confidence interval). The data presented in this study indicate that field-portable XRF can be used for the analysis of lead air filter samples over the range of 17 to 1500 micrograms of lead/sample. The practicing industrial hygienist can use field-portable XRF to produce a rapid, on-site determination of lead exposure that can immediately be communicated to workers and help identify appropriate levels of personal protection. As the method is non-destructive, samples can subsequently be sent to a laboratory for confirmation. Confirmation would be recommended when greater than 16.4 percent accuracy from an analytical method is required. This study provided data of suitable quality for the development of NIOSH Method 7702, "Lead by Field Portable XRF."

Air Pollutants, Occupational↗
PubMed1999

An evaluation of worker lead exposures and cleaning effectiveness during removal of deteriorated lead-based paint.

We evaluated worker lead exposures and cleaning effectiveness during initial cleanup of 19th-century buildings with highly deteriorated lead-based paint. Eighteen rooms of similar size and condition in two university-owned buildings were selected for a pilot project to compare three methods for removing loose paint, paint chips, and dust. The methods used were: dry scraping followed by dry sweeping (no engineering or work practice controls); wet scraping and high-efficiency particulate air (HEPA) vacuuming; and the latter method with the addition of a portable HEPA-filtered exhaust fan in the room providing about 40 air changes per hour. The final step for all methods was wet-mopping once with tri-sodium phosphate solution. During a single day 18 rooms were cleaned; each of three two-person work crews cleaned six rooms, two with each method. Air and surface samples were collected before, during, and after cleaning. All of the methods were potentially hazardous to workers: 44 percent of the method-based exposures (range: 5.0-360 micrograms/m3) and one of five full-shift exposures exceeded the OSHA PEL (range 9.4-110 micrograms/m3). Lowest worker exposures were during the wet scraping and vacuuming method (mean: 24 micrograms/m3). Providing general ventilation in rooms did not reduce worker exposures and appeared to increase them (mean: 73 micrograms/m3). Overall, the mean floor surface lead levels were reduced 50 percent after cleaning (from 2,600 to 1,300 micrograms/ft2), but the effectiveness of the three methods in reducing floor lead levels did not differ significantly. Overall, the method, mean paint lead concentration, pre-cleaning surface lead concentration, and work crew were significantly associated with the mean worker exposures during cleaning (p = 0.023), but not with the post-cleaning surface lead concentrations (p = 0.13).

Air Pollutants↗
PubMed1998

Ultrasonic extraction and field-portable anodic stripping voltammetry for the determination of lead in workplace air samples.

An on-site, field-portable analytical method for the determination of lead in workplace air samples, based on the use of ultrasonic extraction and anodic stripping voltammetry (ASV), was evaluated. Workplace air samples were obtained using a standard method involving particulate collection onto mixed cellulose ester membrane filters. Samples were collected at work sites where airborne particulates were generated from the abrasive blasting of lead-containing paint on highway bridges. Ultrasonic extraction (UE) of air filter samples in diluted nitric acid, followed by portable ASV, was used for the determination of lead. Also, performance evaluation samples consisting of reference materials of known lead concentration were subjected to the UE-ASV procedure for lead determination. Confirmatory analyses of the air filters and performance evaluation samples subjected to the UE-ASV lead measurement method were conducted by hotplate digestion in concentrated nitric acid and 30% hydrogen peroxide, followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination of lead. Recoveries of lead from performance evaluation materials (when using the UE-ASV method) were found to be quantitative. The performance of the UE-ASV method for lead in air filters was found to be acceptable, as evaluated by comparison with results from hotplate strong acid digestion followed by ICP-AES analysis. Based on the results of this study, the ultrasonic extraction/portable ASV procedure demonstrates potential for the on-site determination of lead in personal breathing zone and area air samples.

Air Pollutants, Occupational↗
PubMed1997

Determination of hexavalent chromium in industrial hygiene samples using ultrasonic extraction and flow injection analysis.

A simple, fast, and sensitive method was developed for the determination of hexavalent chromium (CrVI) in workplace samples. Ultrasonic extraction in alkaline solutions with 0.05 M (NH4)2SO4-0.05 M NH3 provided good extraction efficiency of CrVI from the sample and allowed the retention of CrVI on an ion-exchange resin (95%). The CrVI in the sample solution was then separated as an anion from trivalent chromium [CrIII] and other cations by elution from the anion-exchange resin with 0.5 M (NH4)2SO4 in 0.1 M NH3 (pH 8) buffer solution. The eluate was then acidified with hydrochloric acid and complexed with 1,5-diphenylcarbazide reagent prior to flow injection analysis. By analyzing samples with and without oxidation of CrIII to CrVI using CeIV, the method can measure CrVI and total Cr. For optimizing the separation and determination procedure, preliminary trials conducted with two certified reference materials (CRMs 013-050 and NIST 1633a) and three spiked samples (ammonia buffer solution, cellulose ester filters and acid washed sand) indicated that the recovery of CrVI was quantitative (> 90%) with this method. The limit of detection for FIA-UV/VIS determination of the Cr-diphenylcarbazone complex was in the sub-nanogram range (0.11 ng). The technique was also applied successfully to a workplace coal fly ash sample that was collected from a power plant and paint chips that were collected from a heating gas pipe and a university building. The principal advantages of this method are its simplicity, sensitivity, speed and potential portability for field analysis.

Air Pollutants↗
PubMed1996

Evaluation of a chemical spot-test kit for the detection of airborne particulate lead in the workplace.

A commercial rhodizonate-based test kit was evaluated for its potential use in the detection of lead in airborne particulate samples at work sites. Over 350 air samples were collected at abrasive blasting lead paint abatement sites using cellulose ester membrane filters and personal sampling pumps. The filter samples were tested with the chemical spot test and then analyzed by graphite furnace atomic absorption spectrophotometry. No positive readings were recorded for lead masses below 1.3 micrograms Pb/filter, and no negative readings were observed for lead amounts above 8.1 micrograms Pb/filter. Experimental data were statistically molded in an effort to estimate the performance parameters of the spot test kit. The identification limit of the kit was found to be approximately 3.6 microgram/filter sample. For lead mass values above approximately 10 micrograms Pb/filter, 95% confidence of a positive reading was found, while 95% confidence of a negative reading was found for lead masses below approximately 0.6 micrograms Pb/filter. Based on the results of this study the rhodizonate-based test kit for lead demonstrates potential for use in field screening for lead in personal breathing zone and area air samples.

Air Pollution↗
PubMed1994

Evaluation of wipe sampling materials for lead in surface dust.

The suitability of several commercially available wipe sampling materials for the determination of lead in dust on solid surfaces was evaluated. Criteria for the selection of wipe materials appropriate for field use and subsequent laboratory analysis were identified. These included (a) uniform background lead levels in the materials (preferably < 5 micrograms); (b) ease of digestion in nitric acid/hydrogen peroxide or nitric acid/perchloric acid leachate; (c) > or = 80% recoveries of lead from standard reference material spikes; and (d) ease of use in the field. Other candidate wipe materials that were not examined in this study can be evaluated in a similar manner.

Adult↗
PubMed1990

A comparison of transcranial Doppler ultrasound (TCD) and radioactive microspheres in determining cerebral perfusion in normal and low flow states.

We have previously utilized the technique of transcranial Doppler (TCD) ultrasound to determine cerebral perfusion in patients undergoing cardiopulmonary resuscitation (CPR). In order to assess if TCD can reliably measure alterations in cerebral perfusion under conditions of normal and low cardiac outputs, we compared TCD measured blood flow velocities in the middle cerebral artery (MCA) of six piglets with radioactive microsphere determinations of total cerebral perfusion at baseline normal sinus rhythm (NSR), during CPR, and following return of spontaneous circulation (ROSC). Peak systolic and mean blood flow velocities were compared to the microsphere perfusion results on 15 different occasions; six during NSR, five during CPR, and four following ROSC. Although qualitative alterations in TCD measurements reflected changes in microsphere perfusion, we could not find a statistically significant correlation between either peak systolic or mean MCA blood flow velocities and microsphere perfusion measurements either overall or in any subgroup. The possible reasons which may explain the findings are discussed.

Animals↗
PubMed1988

A combinatorial method for grouping cases with multiple malformations.

A combinatorial method is described for grouping cases with multiple malformations for the purpose of identifying previously undescribed syndromes. This method includes ways of carrying out 'tight' or 'loose' grouping, of allowing for variability of reporting of physical features by different observers, and of minimising the number of 'spurious' groups. Evaluation using a test data set of known dysmorphic syndromes showed that the method provides a feasible and useful means of grouping undiagnosed cases.

Abnormalities, Multiple↗
PubMed1985

ITA, a portable program for the interactive analysis of data from tracer experiments.

ITA is a portable program for analysing data from tracer experiments, most of the mathematical and graphical work being carried out by subroutines from the NAG and DASL libraries. The program can be used in batch or interactive mode, commands being typed in an English-like language, in free format. Data can be entered from a terminal keyboard or read from a file, and can be validated by printing or plotting them. Erroneous values can be corrected by appropriate editing. Analysis can involve elementary statistics, multiple-isotope crossover corrections, convolution or deconvolution, polyexponential curve-fitting, spline interpolation and/or compartmental analysis. On those installations with the appropriate hardware, high-resolution graphs can be drawn.

Biometry↗