This is in contrast to the soil samples, in which the lead concentration always exceed the arsenic concentration. In some of the air particulate samples, arsenic constituted 27 percent of the total particulate mass. The reason for the arsenic enrichment of suspended air particulates is not known. Therefore, arsenic was detected in ambient air particulate samples from the site at concentrations that may pose a health hazard. Therefore, under some circumstances, zinc would actually provide a protective effect from lead toxicity.
Soil constitutes a significant fraction of house dust.
Therefore, the same action level could apply to both media. An action level of 20 ppm arsenic in soil would be protective of public health for ingestion of soil. Some residents of the area raise horses and other domestic animals. Therefore, soil action levels to protect animals may have to be even lower than what is needed to protect human health. The EPA is proposing to use HEPA vacuum cleaners to remediate interior contamination when dust levels of lead and arsenic equal or exceed outdoor soil levels.