Got a reply from Swarovski today - here's the emailed explanation:
Swarovski is the world leader in the manufacture of crystal for industrial and consumer applications including figurines and jewelry. Our proprietary formulas and processes are based on years of experience, and the quality of our products is recognized throughout the world.
Recently, there has been an increased regulatory focus on potential human exposure to lead from various consumer products, including jewelry. In 2006, the California Attorney General settled a lawsuit brought in his state alleging exposure to lead from jewelry. The court approved settlement agreement as well as the later legislatively enacted Californian AB 1681 established limits for lead in metals and several other components, with stricter standards for jewelry intended for children 6 and younger. Significantly, in recognition of the limited risk of availability of lead from crystal, the settlement agreement standards as incorporated under California AB 1681 allows the continued use of crystal without limitation in jewelry not intended for children. For children 6 or younger, up to 1 gram of crystal may be used in such jewelry. Swarovski crystals also meet the ASTM F963-03 standard on lead availability for toys.
Crystal has unique properties. While made with lead, the crystal manufacturing process creates a matrix which greatly retards the mobility of lead. By contrast, lead in other materials such as unplated metal containing lead may be available for surface exposures. Swarovski believes that the use of their products poses no significant risk to human health.
Several states have passed or are proposing laws to ban materials containing lead in various consumer products including jewelry. Swarovski is working closely with industry trade groups, regulators, and legislators to develop enforceable standards with consistent lead limits and which take into account the low accessibility of lead from crystal.