Isotopic ratio analysis in residential lead-based paint and associated surficial dust

Objectives: This investigation assessed the contribution of lead in lead-ba sed paint (7 samples) to lead-laden dust (8 samples) in a single suburban v acant residence using isotopic ratio analysis, Methods: Interior/exterior l ead-based paint surface concentration was measured by X-ray fluorescence wh ile dust and scrapings were analyzed chemically for total lead content and by mass spectrometry for the associated isotopic ratios. Results: Four out of 5 comparisons of paint (7 samples) and dust (8 samples) for a given loca tion did not match isotopically, In the one location where the isotopic rat io of the paint and dust samples matched closely, some portions of the pain t were not intact. One explanation for the isotopic ratio match is that the dust sample may have actually been contaminated with paint flecks. This ex planation appears likely since the isotopic ratio for the lead in the dust and paint sample were not in the modern average range of US environmental l ead, strongly indicating a local point source of the lead in this dust samp le, namely the paint at this location. Lead dust samples whose isotopic rat io lies in the modern average range for US environmental lead cannot be cor related to the paint which is beneath them, since the isotopic ratio of lea d in the dust may actually be a composite of many sources of lead over time , as suggested by an isotopic ratio in the modern average range. Conclusion s: From the samples from this one house, the data dispute the contention th at intact lead-based paint chalks and creates lead-contaminated dust on its surface. While leaded household dust may contribute to children's lead exp osure, intact paint need not contribute to surficial lead-laden dust. Isoto pic ratio measurements can be useful for point-source determination by virt ue of sample match and by placement of the ratio on the spectrum of isotopi c ratio values for lead. Point-source assessment based on isotopic ratio wa s either strengthened or weakened by placement outside or within the averag e range for US environmental lead, respectively.