Abstract
Considering the negative effect of lead (Pb) on children's neurodevelopment, Pb exposure should be minimized to the extent possible. House dust is one of the major routes of Pb exposure for Japanese children. To identify the contamination source of Pb in house dust, vacuum dust (particle size: >250 μm) samples taken from 10 homes in Japan in 2006–2007 were analyzed for lead by micro X-ray fluorescence spectroscopy (XRF) with the purpose of searching for and characterizing lead-containing materials. The 10 homes were selected from our vacuum dust collections because they were found to contain lead at high levels (126–1400 mg kg-1) in <250 μm fraction (designated as "house dust" in this study). Pb Lα mapping and XRF spectra of various fragments in the >250 μm vacuum dust were taken by a scanning XRF microscope. Seven fragments containing lead at elevated levels (estimated concentration: several % to several tens %) were found. Morphological observation, XRF spectrum and X-ray diffraction pattern of the fragment indicated that 6 of the 7 fragments were paint-chip-like materials of various colors. Paint containing lead at this elevated level was not produced and used in Japan, thus indicating that the paint had been produced in other countries where regulation of lead in paint was not present. A sheet-like fragment containing lead and chlorine at elevated level was indicated to be a chip of polyvinyl chloride (PVC) sheet, some of which are known to contain lead as a stabilizer. The present analysis suggested that paint and PVC used for some products are broken or peeled off, and are subsequently reduced to finer particles to contaminate house dust. Removal of these products from home environment will be an effective measure to reduce lead exposure levels of residents.
