QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES USED DURING THE INDOOR AIR QUALITY MONITORING PROGRAMME IN WESTON VILLAGE, RUNCORN

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1 QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES USED DURING THE INDOOR AIR QUALITY MONITORING PROGRAMME IN WESTON VILLAGE, RUNCORN G Wilkinson 1, R Moss, D Crump 2, V Brown 2, J Rowley 2, T Hafkenscheid 3, R Kearn 4, A Carp 4, J Kristensson 5, P de Haven 6, P Dollar 6, T McAlary 6 1 ICI Regional and Industrial Businesses, Runcorn, Cheshire, UK, WA7 49F 2 BRE, Watford, Hertfordshire UK, WD25 9XX 3 NMi van Swinden Laboratory, Delft, The Netherlands 4 QinetiQ, Bridgwater, Somerset, UK, TA7 8AD 5 Chemik Labs AB, Norrtalje, Sweden 6 GeoSyntec Consultants, Inc., Guelph Ontario, Canada ABSTRACT As part of an assessment of the legacy of more than 160 years of industrial activity around the former ICI Runcorn site, an indoor air quality survey of 145 properties in Weston village, Runcorn in Northwest England was performed. Two redundant quarries near the village had been used for the historical disposal of chemical waste from about 1930 until the 1970 s. A borehole investigation showed concentrations of hexachlorobutadiene (HCBD) in the subsurface that had the potential to impact air quality in neighbouring properties. The Building Research Establishment (BRE) and QinetiQ developed an analytical method (Crump et. al., 2002), with a linear working range of parts-per-billion by volume (ppbv) to 10 ppbv, and the development work has been peer reviewed. This paper describes the importance of detailed quality control (QC), quality assurance (QA) and peer review procedures to ensure that air quality monitoring data meets data quality objectives and the expectations of all stake holders. INDEX TERMS Air monitoring, quality control, quality assurance, accreditation, hexachlorobutadiene INTRODUCTION In 1993 ICI initiated a voluntary assessment of the legacy of more than 160 years of industrial activity on and around its sites in Runcorn in Northwest England in order to establish whether there was any risk to people or the environment from historical contamination. Initial work involved a historical review of the site and this was followed by an initial set of 28 boreholes around the edge of quarries in Weston village formerly used as a disposal site. The two quarries (North and South) were first used for disposal in the 1920s and 1930s taking mainly limed waste and boiler ash from the ICI plant. The boreholes indicated the presence of some volatile organic compounds and one of the compounds, hexachlorobutadiene (HCBD) was found to be at levels that gave cause for some concern in respect of air quality in neighbouring properties. A range of property types constructed between 1650 and the 1980s are within 100 metres (m) of the filled quarries and some of those closest are constructed on rubble produced by the quarrying operations that had been piled up against the edge of the quarry wall. Contact author george_wilkinson@ici.com 950

2 A highly sensitive method of sampling and analysis of air was developed that could quantify levels of HCBD, pentachlorobutadiene (PCBD), tetrachlorobutadiene (TCBD) and hexachloroethane (HCE). This involved a collaborative programme of work involving the Building Research Establishment (BRE), QinetiQ Bridgwater (Somerset, UK), the Netherlands Measurement Institute (NMi; Delft, The Netherlands), GeoSyntec Consultants, Inc. (Guelph, Canada) and ICI (the work group ) (Crump et. al., 2002.) The method was designed to give a quantifiable range of parts-per-billion by volume (ppbv) to 10 ppbv with pumped Tenax TA sorbent tubes and a 24-hour sampling period (+/- 2 hours). Analysis was by Thermal Desorption Gas Chromatography with Mass Spectrometric detection using full scan mode for compound identification and selected ion monitoring for quantification. Subsequently, in June 2000 the UK Department of Health Committee on Toxicity (COT) advised that continuous exposure to a concentration of HCBD in air of less than 0.6 ppbv can be regarded as being without appreciable adverse health effects. This paper describes the quality control (QC), quality assurance (QA) and peer review procedures that were implemented as part of a detailed monitoring programme, of 145 properties by BRE on behalf of ICI, to evaluate the potential long term exposure of residents to HCBD. The approach followed had to ensure that the data generated (>33,000 data points) were suitable for assessment of subsurface vapour transport through Triassic sandstone and quarry fill into indoor air [McAlary et. al., 2002] and met the expectations of all stakeholders. METHODS Indoor air monitoring in residential properties in the immediate vicinity of contaminated land sites raises a number of serious issues that have the potential to impact on the scientific integrity of the work and shake the confidence of stakeholders in the process being undertaken. For example once permission for sampling has been given by the owner of the property, all efforts should be taken to ensure that sampling and analysis are performed to the highest quality avoiding the need for unnecessary repeat sampling. Quality control The quality control procedures implemented for this study are detailed below. They were designed to ensure that sampling and analysis errors were minimised in order to avoid the need for unnecessary repeat sampling: All of the indoor and outdoor air samples were collected in duplicate to minimise the need to re-enter a property in the event of a pumping irregularity or analytical problem invalidated the first sample. As this would lead to increased concern by residents this was unacceptable. Additionally, the duplicates provided a large data set to identify systematic errors in either sampling or analytical variability within a given laboratory (i.e., intraoperator variability). The flow rate of the sample pumps was recorded at the start and finish of the sampling. If the flow rate varied by > +/- 10% this was logged on the chain of custody form and recorded against the analysis results. If the flow rate difference exceeded +/-20% the sample was rejected. The flow rate had to be between 15 millilitres (ml) and 25ml per minute. Duplicate samples were analysed by BRE on different days (i.e., using different instrument runs on different calibrations with QC and QA standards) to isolate and identify any spurious results that may be caused by poor performance (i.e., machine failure) 951

3 Additional samples were taken in 10 % of all properties and sent for analysis at a second (quality control) laboratory (QinetiQ, Bridgwater). This was to identify any betweenlaboratory variability whilst maintaining the check on intraoperator variability. Both BRE and QinetiQ used independently prepared HCBD standards for their own instruments. Additionally, the laboratories exchanged calibration solutions to check the ability of each laboratory to produce accurate calibration solutions. These were analysed each day prior to any samples. If the analysis results for these solutions deviated by +/- 25% then the calibrations were repeated prior to the analysis of samples NMi provided quality control standards of known concentration (nominally 10 nanograms (ng) and 300ng) loaded onto Tenax TA thermal desorption tubes using first principles (i.e., preparing known standard atmospheres of HCBD based on fundamental physical laws and exposing the tubes to these atmospheres). If the analysis results for these tubes exceeded the reference values by more than 25% the calibrations were repeated prior to running further samples. Travel blanks were included with each day s shipment. These unexposed tubes were sent in the same packaging as the exposed tubes to identify any contamination from packaging or HCBD transfer between sample tubes. Quality Assurance A two-tier quality assurance programme was adopted. This involved: The development of a quality assurance scheme managed by NMi as an independent laboratory, involving the supply of blind (undisclosed concentration) samples to BRE and QinetiQ for analysis, the results of which were evaluated against the reference values a detailed programme of auditing (one audit per sampling round) to assess all elements of the sampling and analysis protocols and procedures. Independent accreditation of the sampling and analysis programmes at BRE and QinetiQ by the United Kingdom Accreditation Service (UKAS). Peer Review Chemik Lab AB. (Dr J Kristensson) undertook a third party peer review of the sampling procedures, analytical method development and resulting procedures. The objectives of the review were to assess whether: The sampling procedures and protocols being employed by the investigation were suitable for the purpose of assessing the nature, extent and variability of any potential indoor air quality issues The analytical method being used for the determination of the levels of HCBD was sufficiently sensitive and free from interference to allow quantification. The quality assurance and quality control protocols in place were sufficient to ensure that the data were reliable RESULTS AND DISCUSSION Figure 1 shows the HCBD analysis results for duplicate samples taken in the same property and analysed by BRE. 952

4 Second sample Indoor air data Points First sample Indoor air guideline value Figure 1 Scatter plot of the indoor air duplicate samples The results show good agreement between the duplicate analyses carried out on different days under different calibration conditions. This provided confidence in the precision of the method across all 4 sample rounds and show that the method is reliable in the region of interest (0.6 ppbv). As one would expect the agreement between duplicates starts to diverge as the concentration falls and approaches the limit of detection of the method. Figure 2 shows the analysis results for the calibration solutions that were exchanged between the two analytical laboratories. During the definition of the data quality objectives, prior to the method development, the work group agreed that an error of +/- 25% at a concentration of ppbv would be acceptable. % Deviation from 100% recovery QC Run number BRE analysis of QinetiQ solution QinetiQ analysis of BRE solution 25% Action limit Figure 2 Analysis results for QC solutions Both laboratories prepared their own calibration solutions and aliquots were exchanged between laboratories. This was performed to assess the ability of each laboratory to prepare accurate calibration solutions. In those instances where the action limit (±25%) was exceeded fresh calibration runs were performed before further field samples were analysed. Throughout the 15-month programme there were only three occasions when repeat calibrations were required prior to the analysis of the field samples

5 Figure 3 shows the BRE analysis results of 10ng QC standards prepared by NMi. A concentration of 10ng is equivalent to 0.030ppbv under the conditions used for sampling Observed concentration (ng) QC Run number BRE results 25% Action limit Aveage NMi concentration 9.95ng Figure 3 BRE analysis results of the 10ng QC standards supplied by NMi The results show that - with the exception of one determination - all of the analysis results for the QC standards were within the 25% action limit. The average concentration of the BRE determinations over the 15-month sampling period was 9.72ng, with a coefficient of variation (CV) of 11.3% and a 95 % confidence interval (CI) of 9.72nng +/- 0.36ng. This agrees well with loaded concentration (9.95ng) demonstrating that the calibration process was in control. Figure 4 shows the BRE analysis results of 300ng QC standards prepared by NMi. A concentration of 300ng is equivalent to 1ppbv under the conditions used for sampling. Observed concentration (ng) QC Run number BRE results 25% Action limit Average NMi concentration 297.4ng Figure 4 BRE analysis results for the 300ng QC standards supplied by NMi The BRE results show that a number of the early determinations were outside the Action limit of 25%. These results related to the first round of monitoring and were the result of using a 1 microlitre (µl) injection volume for the preparation of the BRE calibration standards. In subsequent rounds a less concentrated calibration solution was prepared and a 5µl injection volume was used in order to reduce the error due to injection. The average value of the BRE determinations over the 15 month sampling period was 284.6ng with a CV of 10.5% and a 95% CI of 284.6ng +/- 0.3ng. This agreed well with the NMi average loaded concentration (297.4ng) a difference of -4%, demonstrating that the calibration process was in control. Figure 5 shows the results for the quality assurance standards analysed by BRE in the form of average z-scores for each sampling round calculated by comparison with NMi reference values. Although the QC results (figures 2-4 inclusive) showed that the calibration process was within acceptable limits, the results for analysis of the QA standards (figure 5) show that there BRE s (z < -3) performance could be improved. 954

6 Average z-score (4 samples) QA number z-scores Figure 5 BRE z-scores for NMi QA standards As a result of corrective actions implemented following quality assurance, continuous improvement in the z-scores was achieved from rounds 1 to 4 (over 15 months). Both the overall and the actual QA performance of QinetiQ (10% QC laboratory) were satisfactory. CONCLUSION AND IMPLICATIONS The quality control programmes was an extremely important tool and provided evidence that the analysis process was under control. The comprehensive quality assurance programmes used in this study appropriate protocols and procedures were in place and that the process was under control. It enabled performance to be monitored and corrective actions to be taken when required. It did not provide evidence of the accuracy of the analytical results. This information was provided by analysis of quality control standards of known concentration. The results demonstrate the need to ensure a clearly define the data quality objectives before undertaking a monitoring programme and to ensure that appropriate quality control / quality assurance schemes are in place. The results from all elements of the quality control programme were used to assess the overall uncertainty of the analytical method, from sampling through analysis, using the principles of ISO Guide to the Expression of Uncertainty in Measurement. This work is reported as a separate paper to be presented at Indoor air 2002 (Hafkenscheid et. al., 2002.) Independent third party review found the methods and protocols adopted by this monitoring programme appropriate for the determination of HCBD at concentrations of 0.6 ppbv in indoor air. REFERENCES Crump D, Brown V, Rowley J, Llewellyn J, Wilkinson G, Moss R. Sampling of hexachlorobutadiene in the air of homes at a site contaminated by chlorinated industrial waste in England, Proceedings of the 9 th International conference on Indoor Air Quality and Climate Indoor air McAlary T, Dollar P, de Haven P, Wilkinson G, Moss R, Llewellyn J, Crump D, Lawrence A, Cheney C. Assessment of subsurface vapour transport through Triassic Sandstone and quarry fill into indoor air in Weston village, Runcorn, UK. Proceedings of the 9 th International conference on Indoor Air Quality and Climate Indoor air 2002 Hafkenscheid T, Wilkinson G,. Assessment of the uncertainty of measurement results of chlorinated butadienes in indoor air. Proceedings of the 9 th International conference on Indoor Air Quality and Climate Indoor air