The Inspector Who Sampled His Own Work
You are the field inspector on a large project. Because the project is behind schedule, your supervisor asks you to perform both the abatement work and the post-abatement clearance sampling on the same units to 'save a day.' You also learn that the laboratory you have been using is owned by the same company that employs the abatement crew, and that the lab's quality-control blanks have shown intermittent contamination with lead at low levels. The project manager says the blanks are 'just noise' and the results are 'probably fine.'
1. What quality-assurance and independence problems exist, and what should you do?
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Two distinct problems:
Independence: performing abatement and then clearing your own work is a conflict of interest that undermines the credibility of the clearance. Clearance should be performed by someone independent of the abatement crew.
Laboratory QA: a lab affiliated with the abatement contractor is not independent, and intermittent blank contamination indicates a possible source of false positives or unreliable low-level results. 'Probably fine' is not an acceptable QA position.
Actions: refuse to clear your own abatement work; raise the independence issue in writing; request the lab's QA data (blanks, duplicates, control samples) and consider a different accredited laboratory; do not rely on results whose QA is in question.
2. How do contaminated blanks affect interpretation of low-level dust results, and what should the report say?
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Blank contamination means the analytical system may be contributing lead, so low-level results cannot be attributed confidently to the surface sampled. If blanks are contaminated at levels near the reporting limit, results at or near that level are unreliable.
The report should:
- Disclose the QA problem.
- Qualify affected results.
- Recommend re-sampling with a laboratory whose blanks are acceptable, or re-analysis.
- Not present qualified results as definitive passes or failures without explanation.