Assessment of ecological risk associated with lead shot at trap, skeet & sporting clay ranges.

Abstract

This paper summarizes information related to assessing ecological effects of lead and lead shot pellets from shooting practice ranges in Massachusetts. The facilities in question include trap, skeet and sporting clays facilities, where shotgun shells with lead pellet loads are used, herein referred to as shotgun practice ranges (SPRs). Wildlife exposures, assessment, and management approaches that have been applied at lead shot sites throughout the country are summarized. It is intended that this document will be a useful reference for policy makers when decisions are made on whether and how ecological impacts from SPRs should be addressed. Risks associated with residual lead shot in hunting areas are not specifically addressed, although information contained in this document could be useful in assessing any area where lead shot is used. The implications of applying the Massachusetts Contingency Plan (MCP) risk assessment guidance at lead shot sites are discussed. As of 2009, the MassDEP does not have a formal position on how SPRs should be handled under the MCP. The purpose of this discussion is to provide information that could be useful in management/policy decisions related to the level of regulation that may be warranted at SPRs that use lead shot. Specific risk management strategies and approaches are beyond the scope of this paper. Lead shot is used at practice ranges for shooting trap, skeet and sporting clays. The spent shot becomes dispersed in the environment at or near SPRs. Spent lead shot at these facilities can be found either intact or as weathered particles or ionized salts. Lead contamination associated with lead shot is normally limited to the soil or sediment surface in the immediate vicinity of deposition. In depositional environments, such as many ponds or wetlands, lead shot may become buried by sediments over several years making it less available, and therefore less of a risk, to wildlife. Rainfall increases the likelihood that lead will be mobilized in the environment, either through dissolution or erosion. The exposure pathway of greatest ecological concern at SPRs is ingestion of lead shot pellets from surface soil or sediment by birds and wildlife. This pathway is particularly hazardous to birds that ingest lead shot for grit as an aid in digestion. Incidental (accidental) ingestion of shot pellets by birds and wildlife preying on invertebrates and plants in soil or sediment where lead shot is dispersed may also pose a considerable risk of harm. Acute effects of environmental lead have been documented at a number of sites. Most of these cases have been attributed to ingestion of spent lead shot by birds. Toxic effects of lead shot vary depending on shot size, the species consuming the lead, diet, and a variety of other variables. Previous studies have shown that ingesting as little as one lead shot pellet can be fatal to a bird. A number of SPRs throughout the country have been cleaned up under federal jurisdiction. Lead shot ingestion probability models for birds and small mammals have been incorporated into a number of these risk assessments, and in several cases lead shot cleanup goals have been set in terms of shot pellet density (shot pellets/ft2). The clean up goals based on lead shot density vary according to site conditions, but generally fall in the range of 3-13 shot pellets/ft2. Concentrations of lead shot above this range have been thought to pose an ecological risk in those cases.