Paint samples for Round 22 were prepared from paint chips collected from a variety of sites in North Carolina and Ohio, including a school, a hospital, and a warehouse. The chips were ground to a maximum particle size of 120 micrometers (microm). Soil samples came from driplines around North Carolina residences. Soil samples were dried and then sterilized by heating the soil to 325°F for a minimum of 2 hours, and finally sieved to a maximum particle size of 150 microm. Round 22 dust wipes were prepared from dust collected from households in North Carolina and Milwaukee, Wis. Following sterilization by gamma-irradiation, the household and post-abatement dust was sieved to 150 microm and then gravimetrically loaded on a premoistened PaceWipe(™), which has been shown to meet ASTM E 1792(1) specifications. The loaded wipes were stored under refrigeration until shipment, as an antimicrobial measure. Also, it was recommended that dust wipe samples be refrigerated until the laboratory analyses were performed, as an additional precaution to reduce/prevent the growth of mold. A total of 355 laboratories were enrolled for Round 22 of the ELPAT Program, with 330 laboratories (93%) submitting results. Table I lists summary statistics of reference laboratories for each matrix and sample number. Agreement among reference laboratories using a variety of sample preparation techniques and analytical methods is demonstrated by relative standard deviations (RSDs) ranging from 5.8 to 7.7% for paint chips, 6.0 to 10.7% for soils, and 6.7 to 9.0% for dust wipes. The RSDs are similar to the findings on previous ELPAT rounds. Table II shows the number of all participating laboratory analyses that were identified as outliers. The percentage of outliers for all analyses was less than 7.1% (5.0 to 7.1% for paint chips, 4.2 to 6.0% for soils, and 2.3 to 5.0% for dust wipes). This is similar to the frequency of outliers reported on the earlier rounds of ELPAT for each matrix. Table III shows a summary of acceptable results for the three lead matrices by sample preparation technique and instrumental method used by participating laboratories. Analytical methods that were not identified by laboratories were omitted from the table. Sample extraction techniques are grouped into hotplate, microwave, and "other" techniques reported by participants. Hotplate digestion categories are NIOSH 7082/7105 (a nitric acid/hydrogen peroxide digestion method modified from the NIOSH Manual of Analytical Methods, Method 7082);(2) EPA SW846-3050N3) (an EPA nitric acid/hydrogen peroxide method); American Society for Testing Materials (ASTM) hotplate methods;(4,S) and other hotplate techniques. Microwave digestion categories are EPA SW846-3051(6) (a nitric acid digestion method); ASTM microwave methods;(7,8) and other microwave techniques. The "other" category includes nonmicrowave and nonhotplate techniques, such as X-ray fluorescence sample preparation, leaching techniques, ultrasonic extraction, and Parr bomb. Instrumental methods are categorized into flame atomic absorption (FAA), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), graphite furnace atomic absorption (GFAA), laboratory X-ray fluorescence (LAB-XRF), anodic stripping voltammetry (ASV), and others, which includes inductively coupled plasma-mass spectroscopy (ICP-MS).
Curtis A. Esche, NIOSH, US Dept HHS, PHS, CDC, Robert A Taft Labs, 4676 Columbia Pkwy, MS-R8, Cincinnati, OH 45226