Lead-based paint from deteriorating buildings still poses a hazard to wildlife on Midway Atoll, despite extensive environmental remediation efforts undertaken as part of the conversion of the site from a military base to a national wildlife refuge. A new study by researchers at the University of California, Santa Cruz, shows that Laysan albatross chicks in nests near the buildings are suffering lead poisoning as a direct result of eating paint chips from the soil in and around their nests.
Previous reports had documented lead poisoning in albatross chicks nesting near buildings on Midway, but the exact source of the lead remained unclear. The UCSC researchers used lead isotope ratios as a tracer to identify the source of the lead in the blood of affected chicks.
"We were able to pinpoint the cause of the lead poisoning. The chicks are eating paint chips directly--it's not from contaminated soil--and knowing that can help guide remediation efforts," said Myra Finkelstein, a graduate student in environmental toxicology and ocean sciences at UCSC.
Finkelstein conducted the study with Donald Smith, professor of environmental toxicology, and Roberto Gwiazda, a research toxicologist. Their findings will appear in the August issue of Environmental Science & Technology and have already been published on the journal's web site.
The lead levels in some albatross chicks on Midway are so high that the toxic metal damages their peripheral nervous systems, leading to a symptom known as "droopwing"--the chicks are unable to hold their wings tucked up against their bodies, and their wings often drag on the ground. It is a classic symptom of lead poisoning, comparable to the "wrist drop" symptom in humans, said Smith.
"If you found this level of lead in a child, the child would be hospitalized immediately," he said.
But Smith noted that the levels of lead in paint samples from Midway are not unusual considering the age of the buildings. "The situation is similar to many neighborhoods with older homes painted with lead-based paint," he said. "What's needed is better lead-hazard control, including building maintenance and clean-up of the site."
Lead-poisoned chicks are common around the buildings on the island, Finkelstein said. Many chicks with lead poisoning don't have droopwing, but likely suffer from other forms of toxicity that lower their chances of survival, she said. Chicks with droopwing may survive as long as their parents are feeding them, but once they reach the fledgling stage and their parents abandon them, they are doomed to starvation because they can't fly. Other affected chicks may die sooner from complications of lead poisoning, Finkelstein said.
Midway hosts the largest known breeding population of Laysan albatross, accounting for about 65 percent of the total global population. The most recent census, in 2001, counted 287,000 breeding pairs. Many other species of seabirds also nest on the atoll's tiny islands. The albatross nest on the ground and have no fear of humans, so their nests are found not only in open fields but also scattered among the buildings and beside roads and walkways.
"It's an amazing thing to see. The birds are everywhere," Finkelstein said.
Finkelstein looked at albatross chicks from two sites, one near buildings and another in an open field with no known source of lead contamination. She collected blood samples from the chicks and soil and paint chips from each chick's nest. All the samples were analyzed for lead levels and isotopic composition using a highly sensitive mass spectrometer.
There are four naturally occurring isotopes of lead, and their ratios may vary depending on the source of the lead sample. Different layers of paint on the buildings at Midway had different isotope signatures, and the blood samples and soil samples also varied widely in their isotope compositions. To identify the source of exposure, the researchers had to use a "case study" approach, looking at each chick individually and the samples taken from its nest. They found a strong correlation between the isotope signatures in a chick's blood and the signatures in paint chips from its nest. There was no correlation with isotope signatures from soil samples.
Lee Ann Woodward, a U.S. Fish and Wildlife Service contamination specialist for the Pacific Region, said it's not hard to understand how the chicks are ingesting paint chips.
"I call it the bored chick syndrome," she said. "They're sitting on the nest for six months and they constantly groom the nest and the area around it."
The Fish and Wildlife Service is taking steps to deal with the problem, Woodward said. Although the number of chicks affected by lead poisoning is small compared to other causes of mortality and is not a threat to the overall population, the agency takes the issue very seriously, she said.
"This study has been very helpful to us in pointing out the need to do something," Woodward said. "We have gotten funding this year to go out and determine how extensive the problem is and what it would take to deal with it. Because it's such a remote site and any equipment has to be sent out on barges, we really need to have a good idea ahead of time what the scope of the operation will have to be."
Smith said the situation on Midway underscores the potential for environmental and public health hazards on decommissioned military bases, many of which serve as wildlife refuges. Lead-based paint is just one of many potential hazards at these sites, he said.
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