During 2004 and 2005, the Massachusetts Department of Environmental Protection (MassDEP) conducted a large double-blind laboratory evaluation study, involving 19 commercial laboratories that provide the majority of analytical support services to parties assessing and cleaning up hazardous waste sites in Massachusetts. A "double-blind" study is one in which a laboratory is unaware that they have been sent samples that contain known concentrations of contaminants. The study was undertaken by MassDEP as part of a multi-year/multi-component data enhancement effort, in order to obtain a direct, real world sense of data quality and reliability in its waste site cleanup program.
MassDEP contracted with a well-known laboratory Proficiency Testing company to prepare test samples. To maintain the confidentiality of the study, the company set up mock consulting firms to send out samples and pay for analyses. Each laboratory was shipped a soil sample and groundwater sample spiked with measured concentrations of 5 common Volatile Organic Compounds (VOCs). This procedure was repeated on 3 different occasions -- in July, September, and November of 2004 -- at identical spiking concentrations.
In addition to these 19 commercial laboratories, double-blind samples were also delivered to the MassDEP state analytical laboratory (the Wall Experiment Station), by an agency employee, under the pretense of being samples from a confidential enforcement case.
MassDEP believes the results of this study are very encouraging. The vast majority of the laboratories evaluated were able to consistently quantify most analytes within 20% of the actual value. This excellent result is well within the most stringent acceptance criteria in use by the industry.
In a few cases, false positive or false negative results were reported, particularly with respect to vinyl chloride in water, which is known to be a problematic analyte. MassDEP is conducting further review of analytical data generated by the study to attempt to determine the reasons for these results.
Given these findings, MassDEP believes the public can have confidence in the integrity of the commercial laboratory community, and in the accuracy of the analytical data used to confirm cleanup of sites contaminated with Volatile Organic Compounds (VOCs), which are among the most pervasive and problematic pollutants at hazardous waste sites(.
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