The use of composite dust wipe samples as a means of assessing lead exposure

This study investigated two methods for analyzing composite dust wipes for lead. The term composite means two or more wipes collected from common comp onents in a dwelling that are combined in the field and analyzed as a singl e sample, Two methods-a modified Environmental Protection Agency (EPA) Meth od 3050A and a Wisconsin Occupational Health Laboratory (WOHL) method-were selected based on their anticipated ability to handle the added mass of mat erials and dust expected in a composite, The study used off-the-shelf wipes to prepare single-, two-, and four-wipe samples. Wipes were spiked with a standard reference material at either a low dust loading level or a high le vel, and three laboratories analyzed the samples using both methods and bot h flame atomic absorption spectrometry and inductively coupled plasma-atomi c emission spectrometry techniques (ICP). Good agreement with known spiked levels was possible using either method; the modified EPA 3050A showed part icular promise. When up to four wipes were combined, all three laboratories found that modified EPA Method 3050A resulted in recoveries between 89 and 101% of the known standard. Although it was possible to achieve good agree ment with spiked levels using the WOHL method, some difficulties were encou ntered, particularly when followed by ICP analysis and when using four wipe s, The increased time required to digest the multiwipe composites was not p roportional to the number of wipes in a composite: the two- and four-wipe c omposites did not take two to four times as long as a single-wipe sample. L aboratory analysis of a four-wipe sample cost an average of 65% less than a nalysis of four single-wipe samples for each method.