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Efficiency of final cleaning for lead-based paint abatement in indoor environments.

The effectiveness of procedures used for the final indoor cleaning after active lead-based paint abatement were evaluated in a 830 ft3 test chamber. Dry and wet scraping and dry machine sanding were applied to wooden doors obtained from lead-hazard control sites. The airborne particle concentration and size distribution were monitored using a real-time particle size spectrometer. Particulates were also collected on filters and analyzed for total dust and lead. The resulting airborne lead mass was determined for each cleaning procedure, and the potential floor lead loading resulting from the dust settling was calculated. Wipe samples were collected to measure the actual floor lead loading. The effectiveness of final cleaning was evaluated first for dry abatement methods. Various cleaning work practices were tested by applying wet and dry debris sweeping as well as no sweeping in combinations with wet and dry removal of plastic sheeting. Considerable resuspension of leaded particles was detected during dry sweeping: the airborne lead mass increase ranged between 65 and 220 percent. However, this increase did not exceed 22 percent when wet sweeping was applied. Minimal or no resuspension was found when the plastic was folded with leaded debris inside (no sweeping was performed prior to the sheeting removal). During folding activity, the "clean" (uncovered) floor surface may be significantly contaminated with leaded dust from workers' shoes and cleaning tools. The first HEPA vacuuming resulted in a 15- to 20-fold decrease of the airborne lead mass; however, it was not sufficient to reduce the floor lead loading to the U.S. Department of Housing and Urban Development (HUD) clearance level of 40 microg/ft2, as determined by wipe sampling. Wet mopping following the first HEPA vacuuming was proven to be effective to reduce the lead loading significantly below 40 microg/ft2. The second HEPA vacuuming resulted in further reduction of the airborne lead mass concentration. The floor lead loading remained much lower than 40 microg/ft2. These results were confirmed in the tests when using wet scraping. Overall, the HUD-recommended cleaning protocol was found to be sufficient in reducing the floor lead loading below 40 microg/ft2. At the same time, several modifications are proposed in this study to further improve the cleaning effectiveness.