The Art of Air Sampling
After the results are in, good reasons may exist to challenge MSHA’s sampling results. Consider a challenge when: (1) overexposures are out of line with previous surveys or side-by-side sampling, (2) a single overexposure is so high that only sampling or lab error can account for the error, (3) overexposures are low, bordering on the permissible exposure limits. Where previous surveys were in compliance and no changes in conditions occurred, perhaps MSHA is mistaken. A borderline overexposure may not stand if sampling errors, calibration, and/or lab errors exist.
MSHA dust sampling consists of a battery-operated air pump and a sampling head worn on the worker in the breathing zone. The sampling head contains a filter-cassette in which the respirable dust is collected. Prior to passing through the filter, the sampled air passes through a nylon cyclone, a size-selective device which removes the larger non-respirable particles. Cyclones used for dust or silica must maintain proper orientation during sampling. A cyclone that tips over may dump additional non-respirable material into the cassette.
With any sampling, determine if the monitoring equipment was properly positioned. Look for indications that the sampling cassette was grounded and pulled in contaminants from sources other than the air. A cassette placed outside of the breathing zone (an area within 12 inches of the nose and mouth) is not a representative sample.
Fairly large overexposures in line with historic sampling may not be worth fighting. However, uncovering small errors of a few percentage points may be enough to vacate a borderline overexposure. In a recent OSHA case, an administrative law judge dismissed several lead overexposure citations. The administrative law judge held that the calibration device used with the inspector’s pumps produced an additional 2 percent error that had not been properly calculated. Additionally, the results were called into question when OSHA’s laboratory deviated from its published procedure while preparing samples for analysis. In an MSHA case, a violation was vacated where the inspector’s pump stopped during sampling.
When challenging an agency’s sampling results, a Freedom of Information Act request is a good place to begin. Obtain the laboratory’s certifications, sampling protocols, and procedures. Acquiring the inspector’s file will provide information on pre- and post-calibration, field survey notes, photos, and any worksheets prepared by the inspector. The inspector’s notes from the inspection may document problems and challenges encountered. Compare the inspection procedures and sample processing to the agency’s published industrial hygiene and laboratory protocols. Errors may creep into sampling results anywhere along the process. The old adage “garbage in, garbage out” applies to the science of air sampling. The difference between being in compliance versus accepting substantial citations and penalties is knowing how and when to challenge inaccurate sampling results.
Daniel J. Pubal is an associate at Patton Boggs LLP’s Washington, D.C., office where he advises clients on environmental, health, and safety issues, as well as litigation and dispute resolution. Pubal may be reached via phone at 202-457-6165 or via e-mail at firstname.lastname@example.org.
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