INDUSTRIAL HYGIENE INDUSTRIAL HYGIENE

QUALITY CONTROL FOR QUALITY CONTROL FOR SAMPLING AND LAB SAMPLING AND LAB

ANALYSISANALYSIS

UNIVERSITY OF HOUSTON - CLEAR LAKEUNIVERSITY OF HOUSTON - CLEAR LAKE

QUALITYQUALITY

Quality product (or service) as one that is Quality product (or service) as one that is free of defects and performs those free of defects and performs those functions for which it was designed and functions for which it was designed and constructed and produces Client constructed and produces Client satisfaction. (Juran) satisfaction. (Juran)

Quality Control: System of activities whose Quality Control: System of activities whose purpose is to control the quality of a purpose is to control the quality of a product or service so that it meets the product or service so that it meets the needs of users (Taylor). needs of users (Taylor).

QUALITY ASSURANCE (QA)QUALITY ASSURANCE (QA)

An additional QC system implemented to An additional QC system implemented to assess the efficacy of the QC system assess the efficacy of the QC system monitoring the product. This additional monitoring the product. This additional control system used to monitor the QC control system used to monitor the QC system is referred to as a QA program. system is referred to as a QA program.

Thus, quality assurance could be defined as Thus, quality assurance could be defined as quality control on quality control. quality control on quality control.

MANAGEMENT SYSTEMMANAGEMENT SYSTEM

Defines mission, goals, and values of the Defines mission, goals, and values of the organization. Also provides financial organization. Also provides financial systems, human resources, and systems, human resources, and administrative functions. The quality administrative functions. The quality management system provides policies, management system provides policies, procedures, and organization that defines procedures, and organization that defines the quality assurance programs and how the quality assurance programs and how they interact with and are supported by the they interact with and are supported by the overall management system. overall management system.

FIELD AND LABORATORY FIELD AND LABORATORY QUALITY MANAGEMENT PLANQUALITY MANAGEMENT PLANElements: Elements:

-- Organization Organization

-- Management System Management System

-- Document Control Document Control

-- Review of Requests/Tenders/ContractsReview of Requests/Tenders/Contracts

-- SubcontractingSubcontracting

-- Service to Customer Service to Customer

-- Purchasing Purchasing

FIELD AND LABORATORY FIELD AND LABORATORY QUALITY MANAGEMENT PLANQUALITY MANAGEMENT PLANElements: Elements: -- Control of Nonconformance Control of Nonconformance -- ComplaintsComplaints-- Improvement Improvement -- Corrective ActionCorrective Action-- Preventive ActionPreventive Action-- Control of RecordsControl of Records-- Internal AuditsInternal Audits-- Management Reviews and Reports Management Reviews and Reports

TECHNICAL QUALITY TECHNICAL QUALITY REQUIREMENTSREQUIREMENTS

Topics: Topics:

-- Selection and Training of Personnel Selection and Training of Personnel

-- Selection of MethodsSelection of Methods

-- Estimation of UncertaintyEstimation of Uncertainty

-- Control of DataControl of Data

-- Equipment and InstrumentationEquipment and Instrumentation

-- TraceabilityTraceability

TECHNICAL QUALITY TECHNICAL QUALITY REQUIREMENTS REQUIREMENTS

Topics: Topics:

-- Sampling Sampling

-- Handling of Test ItemsHandling of Test Items

-- Quality Assurance of ResultsQuality Assurance of Results

-- Reporting of Results Reporting of Results

These issues can be scaled and adjusted to These issues can be scaled and adjusted to the size of the organization and the scope of the size of the organization and the scope of the processes involved. the processes involved.

QUALITY CONTROL (QC)QUALITY CONTROL (QC)

Purpose of quality is to provide a level of Purpose of quality is to provide a level of assurance that the result of a process will assurance that the result of a process will meet specifications. meet specifications.

The terms: accuracy, bias, and precision The terms: accuracy, bias, and precision are terms often used to describe how close are terms often used to describe how close a result is to the true or expected value. a result is to the true or expected value.

ACCURACYACCURACY

““accuracy is qualitative term referring to accuracy is qualitative term referring to whether there is agreement between a whether there is agreement between a measurement made on an object and its measurement made on an object and its true (target or reference) value”. [NIST]true (target or reference) value”. [NIST]

BIASBIAS

““quantitative term describing the difference quantitative term describing the difference between the average of measurements between the average of measurements made on the same object and its true value.made on the same object and its true value.

Bias is the difference between the average Bias is the difference between the average of observed results and the true value, and of observed results and the true value, and is determined over a period of time. is determined over a period of time.

PRECISIONPRECISIONQuantitative measurement of the normal Quantitative measurement of the normal distribution of results due to the random error in distribution of results due to the random error in the system. The term “standard error” is used to the system. The term “standard error” is used to describe precision measurements. The smaller describe precision measurements. The smaller the standard error, the more precise are the the standard error, the more precise are the measurements. measurements. Precision is a measurement of the variability or Precision is a measurement of the variability or standard error observed between the average standard error observed between the average value and the individual readings.value and the individual readings.Measures of variability include statistics like the Measures of variability include statistics like the range, variance, standard deviation, coefficient of range, variance, standard deviation, coefficient of variation, and the standard error.variation, and the standard error.

PRECISIONPRECISION

Measures of variability that are often used to Measures of variability that are often used to evaluate precision are: evaluate precision are:

-- range – maximum minus minimum;range – maximum minus minimum;-- sample variance – differences sample variance – differences

between the average of a series of measurement between the average of a series of measurement and the individual measurements;and the individual measurements;

-- sample standard deviation – square sample standard deviation – square root of variance;root of variance;

-- coefficient of variation – standard coefficient of variation – standard deviation divided by the mean; and, deviation divided by the mean; and,

-- standard error – estimate of expected standard error – estimate of expected error in the sample estimate of a population mean error in the sample estimate of a population mean or the sample SD divided by the sq root of size.or the sample SD divided by the sq root of size.

QA FOR SAMPLING QA FOR SAMPLING In order to draw conclusions about airborne In order to draw conclusions about airborne contaminant concentration, the extent of contaminant concentration, the extent of current or future worker exposure, efficacy current or future worker exposure, efficacy of control measures, samples must be of control measures, samples must be properly collected and analyzed. properly collected and analyzed.

Sample collection and analysis are inter-Sample collection and analysis are inter-related, and both are critical components of related, and both are critical components of accurate data production. There must be accurate data production. There must be goals and objectives for each operation.goals and objectives for each operation.

SAMPLING VARIABILITYSAMPLING VARIABILITY

Caused by several factors: Caused by several factors: -- Training, attitude, and attention of Training, attitude, and attention of samplersampler-- Representativeness of samplesRepresentativeness of samples-- Environmental factors – T/%RH/BP; Environmental factors – T/%RH/BP;

sampling handling and transport; sampling handling and transport; contaminant contaminant concentration during concentration during samplingsampling-- Sample collection factors – flow rate, Sample collection factors – flow rate,

time, and time, and collection efficiency collection efficiency

VARIABILITY VARIABILITY

Rigid adherence to written sampling Rigid adherence to written sampling methods can reduce inherent variability. methods can reduce inherent variability. Materials must be consistent in quality and Materials must be consistent in quality and use. Equipment and instruments used must use. Equipment and instruments used must be appropriate for the procedures employed. be appropriate for the procedures employed.

Metrics for monitoring the sampling plan is Metrics for monitoring the sampling plan is through the use of samples that produce through the use of samples that produce results that provide comparisons: results that provide comparisons: duplicate, duplicate, split, spiked, and blank samples.split, spiked, and blank samples.

EVALUATION OF SAMPLING EVALUATION OF SAMPLING PERFORMANCEPERFORMANCE

Control samples: Control samples:

-- Duplicate samples – evaluate methodDuplicate samples – evaluate method

-- Split samples – e.g. bulk samples to labsSplit samples – e.g. bulk samples to labs

-- Spiked samples – most common; apply Spiked samples – most common; apply known mass of contaminant on mediaknown mass of contaminant on media

-- Blank samples – field blanks; transport Blank samples – field blanks; transport blanks; and, media blanks. blanks; and, media blanks.

WRITTEN SAMPLING METHODWRITTEN SAMPLING METHOD

Use of reference method – NIOSH/OSHA Use of reference method – NIOSH/OSHA Documentation of modifications, etc.Documentation of modifications, etc.Validated methods.Validated methods.Identify variables that cannot be controlled.Identify variables that cannot be controlled.Written sampling method/protocol – Written sampling method/protocol – equipment; sampling intervals; equipment; sampling intervals; personal/area; handling and transport; personal/area; handling and transport; “blanks”; data recordkeeping; “blanks”; data recordkeeping; decontamination process; data check decontamination process; data check sequences; and personnel training.sequences; and personnel training.

ACCEPTABLE MATERIALS ACCEPTABLE MATERIALS Testing of supplies and materials – QA programsTesting of supplies and materials – QA programs

Statistical sampling protocolsStatistical sampling protocols

Labels – lot-specific certificates of analysisLabels – lot-specific certificates of analysis

Material QA/QC issues – sampling mediaMaterial QA/QC issues – sampling media

Lab/field blanksLab/field blanks

SAMPLER CALIBRATIONSAMPLER CALIBRATION Calibration – “set of operations used to determine Calibration – “set of operations used to determine

the accuracy of the reading of a test device to a the accuracy of the reading of a test device to a stated uncertainty” [AIHA]stated uncertainty” [AIHA]

Equipment calibration and recordkeeping Equipment calibration and recordkeeping Description of environmental conditions for Description of environmental conditions for

calibration performancecalibration performance Realistic pre- and post-calibration intervalsRealistic pre- and post-calibration intervals Written methodology for calibrationWritten methodology for calibration Mechanisms used for establishing traceability of Mechanisms used for establishing traceability of

calibration standards (i.e. NIST) or other calibration standards (i.e. NIST) or other recognized organizationsrecognized organizations

PORTABLE INSTRUMENTSPORTABLE INSTRUMENTS Portable instruments perform same function Portable instruments perform same function

as a laboratory. Purpose to provide a results as a laboratory. Purpose to provide a results that is used to made decisions. that is used to made decisions.

Subject to many of the same quality Subject to many of the same quality assurance principles as a lab. assurance principles as a lab.

Users should be trained on equipment. Users should be trained on equipment. Calibration before and after use; Calibration before and after use;

maintenance.maintenance. QC samples for accuracy and precision on a QC samples for accuracy and precision on a

regular basis with appropriate data analysis. regular basis with appropriate data analysis.

ACCREDITATIONACCREDITATIONFormal recognition by a national or Formal recognition by a national or international authority of a laboratory’s international authority of a laboratory’s capability to perform certain testing and capability to perform certain testing and measurements activities. Purpose is to measurements activities. Purpose is to provide information that will help in making provide information that will help in making informed decisions regarding laboratory informed decisions regarding laboratory selection. Demonstrates lab competence selection. Demonstrates lab competence and capabilities. (e.g. AIHA)and capabilities. (e.g. AIHA)AIHA – voluntary program; ISO/IEC AIHA – voluntary program; ISO/IEC Standard 17025; participate in inter-Standard 17025; participate in inter-laboratory proficiency programs, and meet laboratory proficiency programs, and meet other technical requirements.other technical requirements.

CONTROL CHARTCONTROL CHART

Normal distribution properties: Normal distribution properties:

Symmetrical distribution in which the mean, Symmetrical distribution in which the mean, median, and the mode all have the same median, and the mode all have the same value.value.

See: Figure 13.3See: Figure 13.3

+/- 1 SD = 68%+/- 1 SD = 68%

+/- 2 SD = 95%+/- 2 SD = 95%

+/- 3 SD = 99.7% +/- 3 SD = 99.7%

CENTRAL LIMIT THEOREMCENTRAL LIMIT THEOREM

For random samples of size n drawn from a For random samples of size n drawn from a population with mean and SD, as n population with mean and SD, as n increases: the mean of sampling increases: the mean of sampling distribution of means approaches the distribution of means approaches the population mean; the SD of the sampling population mean; the SD of the sampling distribution of means approaches the SE of distribution of means approaches the SE of the mean; and the shape of the distribution the mean; and the shape of the distribution of sampling means will approach the of sampling means will approach the normal.normal.

CONTROL CHARTCONTROL CHART

Extend lines that segment the distribution Extend lines that segment the distribution curves by standard deviation, then rotate by curves by standard deviation, then rotate by 90 degrees to form a control chart.90 degrees to form a control chart.

See: Figure 13.4See: Figure 13.4

mean +/- 3 sigma of average is UCL/LCLmean +/- 3 sigma of average is UCL/LCL

mean +/- 2 sigma of average is UWL/LWLmean +/- 2 sigma of average is UWL/LWL

VARIABILITYVARIABILITY

Two general types in data-producing Two general types in data-producing systems:systems:

-- assignable (or determinate) causes is assignable (or determinate) causes is systematic error (i.e. control chart data)systematic error (i.e. control chart data)

-- unassignable (indeterminate) causes is unassignable (indeterminate) causes is random errorrandom error

Need two types of control charts – one to Need two types of control charts – one to deal with bias and another for precision.deal with bias and another for precision.

CONTROL CHARTSCONTROL CHARTS

Since bias is related to central tendency, a Since bias is related to central tendency, a common type of control chart for bias plots common type of control chart for bias plots MEANS (xbar)MEANS (xbar)..

Precision is a measure of variability, and is Precision is a measure of variability, and is commonly monitored by the use of commonly monitored by the use of RANGESRANGES.. Combination of charts is referred to an Combination of charts is referred to an

xbarxbar and and r chartr chart. .

OUTLIEROUTLIER

Defined as a data point that “appears to be Defined as a data point that “appears to be markedly different from other members of markedly different from other members of the sample in which it occurs”. Not the sample in which it occurs”. Not discarded or deleted, but indicated in set.discarded or deleted, but indicated in set.

Data could be an extreme value in the Data could be an extreme value in the distribution; results from some gross distribution; results from some gross deviation from analytical method or math deviation from analytical method or math error; so, investigate process and error; so, investigate process and calculations first. calculations first.

EVALUATE LAB METHODSEVALUATE LAB METHODS

Most methods used in industrial hygiene Most methods used in industrial hygiene address both sampling and lab analysis. address both sampling and lab analysis. Methods have been validated. Sampling Methods have been validated. Sampling part of methods is often accepted as part of methods is often accepted as published and then evaluated further based published and then evaluated further based on field studies and comparison with other on field studies and comparison with other methods. Lab portion of method should be methods. Lab portion of method should be validated for the analytes, instrumentation, validated for the analytes, instrumentation, and the procedures involved (i.e. spiked and the procedures involved (i.e. spiked samples). samples).

SPIKED SAMPLESSPIKED SAMPLES

Sample to which has been added a known Sample to which has been added a known amount of analyte. The analysis of spike amount of analyte. The analysis of spike samples can be used to determine the bias samples can be used to determine the bias and precision of a test method, the accuracy and precision of a test method, the accuracy of a lab measurement process, and/or to of a lab measurement process, and/or to detect changes in the analytical process. detect changes in the analytical process.

Need to know ranges of concentrations of Need to know ranges of concentrations of interest and the relationship between recovery interest and the relationship between recovery and concentration(s). and concentration(s).

REPORTING LIMITSREPORTING LIMITSAIHA definition: “the lowest concentration of AIHA definition: “the lowest concentration of an analyte in a sample that can be reported an analyte in a sample that can be reported with a defined, reproducible level of certainty”. with a defined, reproducible level of certainty”.

Environmental chemistry limits: Environmental chemistry limits:

-- Critical Limit – analyte detectionCritical Limit – analyte detection

-- Detection Limit – distinguish from zeroDetection Limit – distinguish from zero

-- Quantitation Limit – relatively close to the Quantitation Limit – relatively close to the true value.true value.

SIGNIFICANT FIGURESSIGNIFICANT FIGURESLabs report results to reflect the “true” value. Labs report results to reflect the “true” value. Number of significant figures implies the precision Number of significant figures implies the precision that can be attributed to the result. General rules that can be attributed to the result. General rules to apply: to apply: -- The least precise measurement determines The least precise measurement determines the number of significant figures.the number of significant figures.-- All digits are retained during the calculation All digits are retained during the calculation and the final result is rounded to significant digits.and the final result is rounded to significant digits.-- Other rules for significant figures on page Other rules for significant figures on page 324 of third edition.324 of third edition.

UNCERTAINTYUNCERTAINTYTwo types of error that contribute to uncertainty: Two types of error that contribute to uncertainty: random errors and biases. random errors and biases. -- Biases – contributors that can be corrected Biases – contributors that can be corrected or minimized (e.g. calibration of standards or or minimized (e.g. calibration of standards or references by labs, material prep, environ references by labs, material prep, environ conditions). Overall average deviation.conditions). Overall average deviation.-- Random errors – results of contributors that Random errors – results of contributors that cannot be corrected (e.g. instruments, inability to cannot be corrected (e.g. instruments, inability to repeat a process, variability, etc.). Predominant repeat a process, variability, etc.). Predominant contributor to the precision control chart. It can be contributor to the precision control chart. It can be measured but cannot be corrected.measured but cannot be corrected.

INTERLABORATORY TESTS INTERLABORATORY TESTS

Proficiency Testing Programs by: Proficiency Testing Programs by: American Industrial Hygiene American Industrial Hygiene

Association Association (AIHA)(AIHA)Proficiency Analytical Testing (PAT) – Proficiency Analytical Testing (PAT) – evaluate labs analyzing workplace samples evaluate labs analyzing workplace samples by use of reference samples (i.e. metals, by use of reference samples (i.e. metals, silica, organics, asbestos, lead, microbial). silica, organics, asbestos, lead, microbial). Statistical data analysis to assess Statistical data analysis to assess proficiency according to defined criteria. proficiency according to defined criteria. Round-robin approach.Round-robin approach.

CALCULATIONS/CALCULATIONS/PROBLEM EXAMPLESPROBLEM EXAMPLES

StatisticsStatistics

Normal distributionsNormal distributions

QA/QCQA/QC

Control chartsControl charts