Discovering unrecognized lead-smelting sites by historical methods.

OBJECTIVES: Our objective was to enumerate unrecognized former lead smelters in the United States. METHODS: Defunct smelters were identified by historical research. The compiled list was compared with government registries of hazardous sites. Soil samples were taken from 10 sites. RESULTS: Approximately 430 sites were unknown to the federal authorities. Only 5 of 319 sites were known to authorities in the top 8 states. Nine of the 10 sites sampled exceeded residential standards for soil lead level. CONCLUSIONS: Approximately 430 former lead-smelting sites were unrecognized in the United States. Sampling results indicate that the sites may pose a threat to public health.