EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

for this project.

As recommended in the Guidelines for the Evaluation and Control ofLead-Based Paint Hazards in Housing; U.S. Department of Housing and Urban Development: Washington, DC, 1995; Appendix 13.1: Wipe Samplingfor Settled Lead- Contaminated Dust, field spike wipe samples for lead analysis were prepared by the laboratory. The spike samples were sent to the sampling contractor and randomly inserted into the sample group for each building, for each day of sampling. In total, fourteen spike samples were sent indistinguishably to the laboratory with the actual wipe samples collected for lead analysis. These spike samples were labeled as ceiling wipe samples on the chain of custody in order to easily identify the sample results in the database.

Field spike samples were collected for lead analysis in order to assess if the laboratory digestion procedure used for the wipe material was capable of achieving recovery within the QC limits of 80 to 120 %. A summary of the results for the spiked samples and the calculated percent recovery is provided in Table 4-3. The results of the spike samples indicate that the laboratory was able to achieve the recovery required for the analysis of lead wipe samples within the QC limits with the exception of sample numbers 2 and 3 which were barely outside the QC limits at 79% and 78%, respectively.

Field blanks were collected for microvacuum, wipe and air samples to determine if the sample media could become contaminated during the sampling event. For air and microvacuum methods, these samples were collected by opening a separate air sampling cassette during the sample collection activities to expose it to the air and then closing the cassette. Wipe field blanks are collected by removing the wipe fi-om its container or package, shaking the wipe open and re­ folding it as would be done during the actual sampling procedure and placing the wipe back into the sample container. The field blanks are then labeled, packaged and shipped with the actual field samples for analysis. Results of these samples indicate that there was no contamination above the reporting limit or health-based benchmarks that would affect the results or quality of the data.

Lot blanks were collected for microvacuum, wipe and air samples to determine if the media used to collect the samples were contaminated. The lot blanks are then labeled, packaged and shipped with the actual field samples for analysis. Results of these samples indicate that there was no contamination above the reporting limit or health-based benchmarks that would affect the results or quality of the data.

WORLD TRADE CENTER BACKGROUND STUDY 14

NYC-WTC_000145889