Microscope, Vol 43:4 187-191
A chemical works located in a city in the southeastern United States formerly produced a lead-arsenic pesticide. A number of soil samples collected from the site and in surrounding yards had shown that arsenic and lead concentrations were elevated in the neighborhood around the plant. Samples of accumulated settled dust were collected from the attic space and/or living areas of 48 residences or, in a few cases, commercial buildings surrounding the site. The results of atomic absorption measurements for lead and arsenic were reported as both concentrations (amount of element to amount of dust) and loadings (amount of element per area sampled). In general, the highest levels of arsenic and lead were found in attics where dust had accumulated for some time. Dust arsenic loading values for 48 residences and other buildings ranged from below detection to 64,000 ug/ft2 and 5,000 ppm. For lead in the attics, the loadings were from below detection to 1,000,000 ug/ft2 and 18,000 ppm. Sills and door frames were higher in lead loading than floors. A few of the wet wipe samples for lead were above the HUD guidelines of 200 ug/ft2 for floors, 500 ug/ft2 for window sills and 800 ug/ft2 for window wells. A few microvacs and wet wipes from inside the living areas of the home showed arsenic concentrations above the 1.0 ug/kg (10 kg/child) action level. Based on its chemistry, the lead to arsenic ratio in lead arsenate is about 4:1. Near the former production site, the average relationship of lead to arsenic in the dust for several residences was about 4:1 but some homes had much higher lead values. Scanning electron microscopy was used to determine the form of the lead and arsenic in the residential dust particles. In one residence, particles of lead arsenate, leaded paint, and leaded automobile exhaust were found near each other.
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