Collateral Benefits and Hidden Hazards of Soil Arsenic during Abatement Assessment of Residential Lead Hazards

Abatement of soil-lead hazards through excavation or capping may reduce human exposure to other soil hazards such as soil arsenic, thereby achieving significant collateral benefits that today are not accounted for. This proposition was tested by analyzing 1,726 residential soil samples for lead and arsenic. Both constituents were present in most samples, but their concentrations were weakly correlated, presumably reflecting the differing sources of origin and corresponding different collection locations in residential yards. Of the total samples collected, 25% showed lead concentrations high enough to require abatement (> 400 mg/kg). Of these, 18% also showed elevated arsenic concentrations, indicating that there is indeed a significant collateral benefit of lead abatement in many residential soils. Of the 75% of the samples with lead concentrations below abatement thresholds, however, 27% had elevated arsenic levels (> 10 mg/kg) representing a hidden hazard from arsenic that is not adequately represented by standard lead hazard sample collection and analysis techniques. A total of 29% of the samples had soil arsenic concentrations above the common action threshold of 10 mg/kg. The results suggest that soil samples collected under HUD programs should be tested for arsenic as well as lead, and that soil abatement decisions consider soil-arsenic as well as soil-lead guidelines.