Mercury (Hg) and lead (Pb) in interior and exterior New Orleans house paint films

Abstract

Pre-1992, latex paint was formulated with mercury (Hg) as phenylmercuric acetate (PMA). Hg vaporizes reducing its content, and lead (Pb) is stable and remains unchanged. The objective of this study is to describe the content of Hg and Pb in existing paint coatings. Forty paint chip samples were collected from both interior and exterior surfaces of homes in metropolitan New Orleans and analyzed for Hg and Pb. The median Hg in exterior paints is 26.9 mg kg −1 (0.8–214.0) compared with 7.1 mg kg −1 (0.03–39.2) for interior paints. The median Pb content is 76 603 mg kg −1 (464–317 151) and 416 mg kg −1 (24–63 313) respectively, for exterior and interior paints. The Spearman correlation coefficients for Hg and Pb are −0.312 ( P = 0.13) and −0.471 ( P = 0.07) respectively, in exterior and interior samples. Hg and Pb vary independently with each other in paint films. Median Hg in exterior paints is four times larger than for interior paints. Median Pb in exterior paints is 184 times larger than interior paints. The Pb and Hg content in exterior and interior paint chips are significantly different (Mann–Whitney Rank Sum Test, P ⩽ 0.001 and P = 0.006, respectively). Only 1 of the 25 exterior paints contained less than the current 5000 mg kg −1 US standard for Pb, the criteria for exemption from the power-sanding restrictions of the New Orleans Lead Ordinance. Prior to banning PMA in paint, Hg poisonings presented as acrodynia were reported for children living in homes freshly painted with latex paint. Because of the affinity of Hg and Pb for sulfur-containing amino acid proteins, their presence in paint coatings poses an increased hazard when released as dust.