ESTCP CU-0222: Validation of a Rapid and Low Cost Method for Prediction of the Oral Bioavailability of Lead from Small Arms Range Soils
Numerous small arms ranges are contaminated with lead from bullets. Models of risk assessment in these soils require a relative bioavailability term. The default value of 60 percent can be replaced with a more meaningful site-specific value by using an in vivo swine-feeding study. Although the swine model has been used to successfully adjust the default bioavailability at some Superfund sites, the uniqueness of small arms ranges, in terms of their small size, potential number, and main pollutant being lead, make it feasible to use an alternative and more cost-effective estimate of potential toxicity. The in vitro surrogate of mammalian digestion is intended to provide a rapid, cost-effective and robust alternative to the in vivo swine model for use at small arms ranges.
The relative bioavailability of lead in small arms range soils will be compared using both the in vivo and in vitro models. Soil samples from eight small arms ranges will be collected, dried and sieved to a particle size of less than 250 micrometers. For the in vivo model, weanling pigs will be orally dosed over a 15-day period and blood lead measurement will be used to assess absorption from the gastrointestinal tract. Absorption will be normalized to a lead acetate treatment group, giving the in vivo relative bioavailability. For the in vitro method, lead will be extracted in a simulated gastric solution with a pH of 1.5 at 37 degrees Celsius for 60 minutes, filtered, and analyzed for lead. This extractable lead will be normalized to the total lead in the sample, giving the in vitro relative bioavailability. A correlation coefficient of 0.8 or greater will be considered good evidence that the methods agree and that this technology can be applied to small arms range sites.
The use of a low-cost, rapid, in vitro test for lead in small arms range soils will enable site-specific bioavailability testing at these sites. Since the number of small arms ranges is thought to be in the hundreds, significant decrements in risk assessment costs would accrue by using the in vitro method over the in vivo swine model or the default assumptions. Furthermore, the in vitro test can be carried out at Army laboratories. (Anticipated Project Completion - 2005)
For more information, contact:
Dr. Desmond Bannon
U.S. Army Center for Health Promotion and Preventive Medicine
Health Effects Research Program
5158 Blackhawk Road
Aberdeen Proving Ground, MD 21010-5403