Environmental contamination with heavy metals remains a critical health problem. In particular, lead and mercury are known to affect avian health. Predatory birds (e.g. bald eagles) become exposed to these metals through their diets. In the mid-Atlantic USA, some studies found a decreasing trend in lead contamination but no trend for mercury. Chesapeake Bay was found to have higher mercury contamination than Delaware and Barnegat Bays, but similar lead contamination. We evaluated the prevalence of lead and mercury in bald eagles across time (2004 -2013) and space (state county level) in 3 mid-Atlantic states (Delaware, New Jersey, Maryland). Blood samples from bald eagles presenting at the Tristate Bird Rescue and Research Inc., (TSBRR) in Delaware, were analyzed for blood lead levels (BLL) and blood mercury levels (BML) using atomic absorption spectrometry at PADLS Toxicology Laboratory of the University of Pennsylvania. Threshold detection limits for lead and mercury were reported as 0.05ppm, and 0.3ppm, respectively. We categorized BLL > 0.6ppm, and BML > 1ppm, as clinically significant. Wilcoxon score tests for censored data were used to detect trends in BLL and BML prevalence over time. State counties of origin for birds with clinically significant BLL and BML were identified.
There were no significant trends in lead and mercury prevalence over time. We found that bald eagles with clinically significant BLL originated from counties near Chesapeake and Delaware Bays, whereas most bald eagles with clinically significant BML originated from counties near Delaware, and Barnegat Bays. There was only one eagle that had both clinically significant BLL and BML, which originated from Charles County, Maryland. The study’s findings suggest that lead and mercury contamination in the environment continues to persist in the mid-Atlantic USA. By routinely monitoring bald eagles for these contaminants, we can ensure that they do not negatively impact their populations, while at the same time, gain knowledge of the degree and trend of heavy metal contamination in the environment. The latter is crucial for protecting the health of animals, humans and the environment.