Concentrations of Pb in human hair from the Salt Lake City region population had very high levels from 1916 to 1969 before the establishment of the EPA, with individual values ranging between 28 and 100 ppm (Table 1 and Fig. 1). In the decades of the 1970s through the 1990s, the average values declined from about 50 ppm in the 1970s to 10 ppm in the 1990s. The decline has continued to the present day with average values post-2020 of <1 ppm (Fig. 1 and Table 1). Therefore, the lead concentrations in hair have declined by about 2 orders of magnitude since the establishment of EPA and implementation of measures to reduce human exposure to Pb.
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This study shows that the urban population of Utah has seen a ca. 100-fold decline in average exposure to lead due to the combined effects of reducing above-ground emissions from local industrial activities and from the change nationally from leaded to unleaded gasoline that took place from the 1970s through the late 1980s and other measures to reduce Pb exposure. After the smelters closed and leaded gasoline was phased out, Pb concentrations in hair continued to decline for more than the next 30 y. This study demonstrates the effectiveness of environmental regulations controlling the emissions of pollutants which in this case is Pb.