In October, Governor Jerry Brown signed AB 711 making it illegal to use lead ammunition for hunting, a ban that will be phased in from 2015 to 2019. For UC Santa Cruz environmental toxicologists Donald Smith and Myra Finkelstein, the bill represents the translation of years of scientific research into a new policy to protect people and wildlife from lead poisoning.
"This is a landmark policy bill that will have direct impacts on improving environmental and human health in California," said Smith, professor of microbiology and environmental toxicology at UCSC.
Over the past decade, research in Smith's lab has repeatedly confirmed that lead-based ammunition is the main source of lead poisoning in California condors. Condors are scavengers and ingest bullet fragments when they feed on felled game or "gut piles" left behind by hunters. Finkelstein, adjunct professor of microbiology and environmental toxicology, led a study published in the Proceedings of the National Academy of Sciences in 2012 showing that the condor population can never recover as long as lead poisonings from ammunition continue.
Since 1982, when only 22 condors remained in the wild, intensive human intervention has brought the total population (captive and free-flying) up to more than 400 birds. But lead poisoning is an ongoing problem that continues to kill condors despite regular monitoring and clinical treatment of poisoned birds.
Smith's lab has been studying the sources of lead in the environment for nearly 20 years. Using a "fingerprinting" technique based on the isotope ratios found in different sources of lead, researchers are able to compare the lead in a blood sample to a source in the environment. Smith's lab has used this technique to find the sources of lead poisoning in both humans and wildlife. In condors, the evidence clearly shows that free-flying condors are chronically lead poisoned, and the lead in their blood matches the lead used in ammunition.
Although wildlife biologists had long suspected that bullet fragments were the cause of lead poisoning in condors, the first solid scientific evidence to support this was presented in a paper Smith's group published in 2006 in Environmental Science & Technology. That paper helped support the passage in 2007 of the first bill to limit the use of lead ammunition in California, establishing partial restrictions on its use in areas of condor habitat. But that law proved to be ineffective, Smith said.
"Our 2012 paper in PNAS showed that there was no reduction in lead poisoning in condors after that law went into effect," he said.
After publication of the second paper, Smith and Finkelstein decided that it would helpful to publish a consensus statement on the scientific evidence from scientists with expertise in the area of lead and environmental health. "Health Risks from Lead-Based Ammunition in the Environment - A Consensus Statement of Scientists," signed by 30 experts in the field, was published in March 2013. The group also published an editorial on the subject in Environmental Health Perspectives, the leading environmental health journal in the United States.
Smith and Finkelstein have both testified at hearings in Sacramento before State Senate and Assembly committees considering the bills to ban lead ammunition. According to Smith, solid scientific evidence was essential to counteract the opposition to such bills from hunter-advocacy groups.
"We know from talking to legislators that if the scientific evidence did not exist, the bill would not have passed. But the evidence to support it was overwhelming," he said.
The new statewide ban on lead ammunition will benefit other scavengers in addition to condors, including eagles, ravens, and turkey vultures. In passing the bill, lawmakers also cited human health concerns. Because lead bullets often fragment on impact, particles of lead can remain in the meat people consume from deer and other game.
The new bill makes California the first state to ban lead-based ammunition. Other states have enacted partial bans on lead ammunition, and the U.S. Fish and Wildlife Service banned lead shot for hunting waterfowl nationwide in 1991. Smith said he hopes California's action on this issue will prompt other states to consider similar legislation.
"To those of us who study lead contamination in the environment, it's always been a contradiction that we as a society are so concerned about lead in commercial products like window blinds, while there has been comparatively little concern about the substantial amount of lead in ammunition that is being knowingly discharged into the environment," he said.