Lead Exposure of Obligate Avian Scavengers in Eastern North America

Lead Exposure of Obligate Avian Scavengers in Eastern North America Shannon Behmke Lead is a toxic element within the body of living o rganisms. Lead poisoning cases still occur in both humans and wildlife on a regular basi s in the United States. Although the harmful effects of lead within the body are well known, suc h as decreased IQ in children, increased renal dysfunction, hypertension, anemia, and other morbid and mortal consequences in humans and wildlife, lead continues to be used in anthropogeni c activities today. Through the use of lead in ammunition and fishing sinkers, and its presence in coal-fired power plant and other industrial emissions, lead is dispersed throughout modern huma n and natural systems. Due to the persistence of anthropogenic lead-use, it is necess ary to understand the pervasiveness of this toxin in both modern ecosystems and throughout the body of individuals. To understand the degree to which wildlife populati ons are chronically exposed, we quantified lead levels within American black vultur es (Coragyps atratus) and turkey vultures (Cathartes aura); two species that are useful as environmental sen tinels in eastern North America. Individuals of both vulture species are kn ow to be more resistant to the effects of lead toxicity than are many other animals. This resistan ce allows vultures to accumulate and harbor lead for a longer period of time than more sensitiv e species, thus providing us with a lifetime lead exposure history. In our study, chronic lead e xposure was quantified from femur lead concentrations of 98 black vultures and 10 turkey v ultures and compared to lead concentrations of liver tissues sampled from the same individuals. We found that the extent to which vultures are exposed suggests that anthropogenic lead permea t s eastern North American ecosystems to a previously unrecognized degree. Discovery of an epi dem c of chronic lead exposure in such widespread and common species and the failure of so ft-ti sue sampling to diagnose this pattern has dramatic implications for understanding modern wildlife and human health concerns. Bone sampling, however, is difficult to replicate in living individuals. Although bone provides information regarding the depth and breadt h of lead exposure, blood is most commonly sampled in live individuals. This is because phlebo tomy is one of the most minimally invasive sampling techniques currently available, which make s it attractive despite the fact that blood and other soft tissues (liver, kidney) are indicative o f only recent exposure to lead. However, if an individual’s blood (collected by phlebotomy) or mus cle (collected by biopsy) lead levels could be statistically linked to the amount of lead found within its bone, it would permit use of less invasive sampling techniques to reveal total body l ead burden. Therefore, to determine if soft tissue lead concentrations have a quantifiable rela tionship with femur lead concentrations, we collected and analyzed multiple tissues (femur, liv er, kidney, breast muscle, and thigh muscle) from the 108 black and turkey vultures mentioned ab ove. We found that although all soft tissues were poor predictors of bone lead levels, kidney le ad concentrations best predicted femur lead concentrations. These poor relationships, however, between soft tissues and bone suggest that the sampling of tissues other than bone is unlikely to provide substantial insight into the long-term lead burden that birds face.