Model studies for the release of metals from embedded rifle bullet fragments during simulated meat storage and food ingestion

Abstract

Based on environmental as well as food safety concerns, lead is more and more substituted for “lead-free” rifle bullets for hunting. There is some concern if fragments of such lead-free bullets might release metals to the meat environment as well as in gastric or duodenal juice. In an attempt to provide a first estimate of exposure assessment of consumers, we analysed (1) the composition of eight commercially available lead-free bullets (0.308-in. calibre) for seven metals; (2) the release of metal when bullets were kept for 7 days in meat juice (0–2 °C), to simulate meat-embedded bullet fragments; and (3) the amount of metal released when bullets were subjected to a combined artificial gastric and duodenal digestion, to simulate accidental ingestion of meat containing bullet fragments. Regarding the composition of bullets, three main groups could be identified: copper (i.e. ≥98 % Cu), with or without galvanic coating; copper alloys containing >5 % Zn; and jacketed bullets (plated steel) with tin core. In six of the eight bullet types, Pb was <0.02 % of bullet mass. Release of Cu and Zn into meat juice did not exceed 0.0025 and 0.0015 % of the bullet mass, respectively. During simulated digestion, bullets released ≤0.01 % Cu and ≤0.0025 % Zn. From these data, a “worst-case” was calculated to amount to an additional quantity of 2.03 mg Fe, 1.18 mg Cu and 0.39 mg Zn (originating from 10 g embedded bullet material) per meat portion, which still would not exceed the recommended daily intake values. Aluminium tips of bullets released a max. of 0.61 mg Al per 10 g bullet material, which would not exceed limits, but here, the high average alimentary Al uptake should be considered. In contrast, release of nickel from coatings and of lead from alloys may be of concern. Although experiments were conducted in simulated environments, results indicate that Al, Ni and Pb contents in rifle bullets should be kept as low as possible.