Metal Madness: Lead Doesn't Just Poison Birds, It Scrambles Everything They Need to Survive
Thursday, 09 October 2014 00:00 By
Lindsey Konkel,
Environmental Health News
Source:
http://www.truth-out.org/news/item/26724-metal-madness-lead-doesn-t-just-poison-birds-it-scrambles-everything-they-need-to-survive
NOTE: this is not the full article.
North Grafton, Massachusetts - By the time the veterinarian saw the Canada goose, it was starving. Lumpy bulges ran the length of its neck, from its white chinstrap to its shrunken breast. It was too weak to squabble – so sluggish, in fact, that the veterinarian could scoop up the goose and move it to the stainless steel table without throwing a blanket over it.
A team of four rushed in to treat the goose, flushing a bucketful of sand from its esophagus. But X-rays of its digestive tract bore out another problem – tiny flecks in the sand. A blood test confirmed the veterinarian's suspicions: lead poisoning. The goose had eaten sand laced with lead at a pond near Boston.
It's well-known that high levels of lead kill birds. But now it's becoming clear that amounts commonly encountered by waterfowl and raptors can mess up their digestion, brains, hearts, vision and other body processes critical for their
survival in the wild.
Fledglings exposed to low levels may wander from nests and stumble around, while their parents may be unable to maneuver around power lines or swerve out of oncoming traffic.
No one knows how many birds die of lead poisoning and how many more are contaminated with lower doses. But some studies of scavengers such as condors and eagles have suggested that more than 90 percent have detectable lead in their blood.
Despite the emergency treatment at the Tufts clinic, the goose had to be euthanized because the damage to its digestive tract was too severe. Lead scrambles the muscle contractions that move food through the esophagus into organs that can absorb nutrients. "The bird was literally starving to death on a full stomach," Pokras said.
Lead Still Ubiquitous
It's not clear where the lead that poisoned the goose might have come from. Scrapings of old house paint, fragments of lead shot or shavings of scrap metal were a few of Pokras' guesses. Urban soils and waterways across the country are littered with lead, deposited there by centuries of human activity, that pose a health risk to people as well.
While lead has been removed from gasoline and most paints, today's sources include hunting ammunition, fishing tackle, abandoned smelters, old bridge paints and car batteries.
"It surprises some people, because we think we've solved the lead problem, but it remains a serious problem in the environment," said Joanna Burger, a biologist at Rutgers University in New Jersey.
Lead is one of the most-studied environmental toxicants. In ancient Rome, people were poisoned by lead pots used to store wine. But it wasn't until centuries later that people started to link the symptoms to the source. In the 1700s, an English physician showed that severe abdominal cramps commonly experienced by cider drinkers were caused by lead leaching from the presses used to crush the apples.
Half of all condor deaths in Arizona are attributed to lead poisoning.
Scientists working on Midway Island in the 1980s described a "droop wing" in albatross that had eaten paint chips near an abandoned building. Their wings hung flaccidly by their sides. For centuries, physicians had observed a similar problem with wrist nerves in lead-poisoned people.
Researchers began to realize that many of the health problems caused by lead in the environment were not specific to humans. The gastrointestinal symptoms found in England's early cider drinkers, for instance, are similar to the signs found in birds.
Everything Disrupted
"Lead literally impacts every system of the body," he said.
Its chemical structure is very similar to calcium, so the body confuses the neurotoxic metal for the vital nutrient. Humans, birds and just about every other living thing on the planet need calcium to send brain signals from cell to cell. Important connections are lost when lead disrupts those pathways.
Herring gull chicks exposed to lead were slower to recognize siblings and parents. In the late 1980s, Burger was studying herring gulls on Long Island when she
noticed their chicks acting weirdly. Some would wander from the nest into neighboring gull territories, where they were killed. "It was happening at some nests and not others. I was seeing these behavioral abnormalities that I just couldn't account for," she said.
Burger collected feathers and found that some had elevated lead levels. She had a hunch that the young birds, like children, suffered from neurological problems when exposed to lead. Over the next two decades, Burger and her husband Dr. Michael Gochfeld, a human physician and lead expert at the University of Medicine and Dentistry of New Jersey, performed a series of
experiments to test that hypothesis.
They found that lead-exposed chicks stumbled more when they walked, often missed the mark when pecking at their parents' bills for food and were slower to recognize their siblings, parents and nest site in the wild or their caretaker in captivity. All of these are important learning tasks for chicks that may be killed if they wander away from the nest and approach the wrong adult.
"Almost every test we did, lead impaired them," Burger said.
British researchers studying mute swans
found that those with moderately-elevated lead levels were more likely to suffer injuries from collisions with power lines than birds with very low lead levels or birds with very high levels. Birds with extremely high lead levels may be too weak to fly at all.
Poisoned Condors
For condors, the
survival of the species may
hinge on reducing lead exposures. In the 1980s, only 22 remained alive in the wild. Intensive conservation programs have brought the population up to around 400. In certain parts of the birds' range – in northern Arizona and Utah – scientists have struggled to reintroduce the condor. Lead poisoning is the major culprit.
"Lead is the number one problem. It accounts for about 50 percent of the deaths in our [condor] program. Without getting lead out of the environment, we have very little hope of recovering the species in all parts of its range," Parish said.
"Lead is a very, very severe poison. It's silly that in the 21st century we still allow this," said John Fitzpatrick, director of the Cornell Lab of Ornithology.
Roughly 98.5 percent of the eagles admitted to Minnesota's Raptor Center had measurable levels of lead in their blood. In Maine, about one-third of the eagles treated over the past decade at Avian Haven, a rehabilitation center, had blood lead levels above 10 micrograms per deciliter, according to executive director Diane Winn. Out of those 44 eagles, 28 died either from a lethal dose of lead or from an injury to which their lead exposures may well have contributed.
Lead hunting ammo left behind in gut piles poisons birds of prey. It's not clear what amount of lead is deadly to birds. Lethal exposures seem to vary a great deal between species, and even among individuals. Geese and ducks apparently tolerate higher levels of lead than eagles or condors. Effects may start to appear at lead levels between 20 and 60 micrograms per deciliter. With treatment, prognosis for survival is generally good below 100 micrograms, according to Dr. Pat Redig, a wildlife veterinarian at the University of Minnesota. Many rehabilitators begin treatments to remove the toxic metal from the blood around 20 micrograms.
In comparison, for lead-exposed children, the Centers for Disease Control and Prevention
recommends action for levels higher than five micrograms per deciliter, although it adds that
"no safe level has been identified."
Far less is known about the subtle effects of lead on the animal brain. A handful of studies have documented aggressive behaviors in dogs and cats as well as in rodents and songbirds.
"In humans we've observed that chronic low levels of lead exposure in early childhood may have a greater effect on cognition than higher levels of exposure, but we don't know whether that holds true for birds," said Dr. Bruce Lanphear, a professor at Simon Fraser University in British Columbia who specializes in children's health.
Permanently Impaired
Even with treatment, the road to recovery – and release – can be an uncertain one. Many birds treated at clinics and wildlife centers for lead poisoning are left with permanent brain damage.
Sometimes the birds "show signs of mental illness," Redig said. "A healthy eagle should hiss at you, open its wings or show some kind of fear response. Many times when you approach these birds, it's like nobody's home."
Other birds are permanently weakened because lead interferes with heart function. "We'll try to exercise a bird and discover it has no stamina," Redig said.
In severe cases of lead poisoning, lesions are found in parts of the brain that control the body's auto-pilot processes, such as heart rate and breathing. Deformities also are found in the ventricles that pump blood in the heart.
In less severe cases, the damage can be harder to spot, but the deficits are often lasting. One bald eagle was thin and dehydrated when it arrived at SOAR Raptor Rehab center in Dedham, Iowa in 2011.
A blood test showed lead levels exceeding 20 micrograms per deciliter. The eagle went through chelation therapy to clear the toxic metal from its blood. Over the next couple of weeks, she gained weight steadily, but she navigated clumsily about the flight pen.
"Her vision was permanently impaired. We couldn't release her," said Kay Neumann, executive director at SOAR.
Although the eagle survived, Neumann counts her as a "wild mortality." She will never return to the wilderness to hunt, nest or reproduce, and she won't pass her genes along to the next generation of Iowa's rebounding eagle population.
