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From Boyhood Curiosity to Scientific Discovery
Biologist Tyrone Hayes Links Pesticides to Amphibian Deformities

CARL T HALL / SF Chronicle 4nov02

Tyrone Hayes may not fit the stereotype of the big-time scientist. But he figures it doesn't hurt that he sometimes stands out in a crowd of his peers.

Tyrone Hayes

Tyrone Hayes

"I give a talk at a meeting, and everybody remembers the black guy in the braids," he said. "They may not remember what I said, but they tend to remember me."

Now, it's not his braids but his work that is starting to draw most of the attention.

Hayes, 35, an African American biology professor at UC Berkeley, has produced a series of high-profile studies challenging the ecological safety of atrazine, the most widely used pesticide in the United States.

His latest research suggests that the weed-killer may be short-circuiting the reproductive machinery of amphibians exposed to farm chemicals in spring runoff. A summary of the latest findings appears in the Oct. 31 issue of the journal Nature.

The mysterious ill health of amphibians native to North America is one of the more alarming environmental stories of recent years, and Hayes is the first to find a link to pesticides, both the laboratory and in field studies.

He and his colleagues have found large numbers of "feminized" male frogs in water containing traces of atrazine. The results are being challenged and have not been replicated, but Hayes is not one to back down easily.

"From our study, the only fair conclusion you can make is that if there are abnormalities, there's atrazine," he said. "We wanted to find out if atrazine has an effect or not. The answer is that it does."

'ONE OF THE LEADERS IN THIS FIELD'

Now, Hayes and a large coterie of students are busily working on at least seven related papers, including gene studies and more ambitious field investigations. He also has had to spend time rebutting charges from other scientists that his approach is all wrong and his data are riddled with major inconsistencies.

That's not to suggest Hayes lacks supporters defending his work.

"He's an outstanding scientist, one of the leaders in this field," said Andrew Blaustein, an ecologist and amphibian specialist at Oregon State University. "Everybody better start waking up. We have all these chemicals out there permeating the environment, and when anyone says something may be wrong, people start jumping on the person making the statement."

Last week's paper in Nature -- and a story about the controversy and research appearing a day later in the competing journal Science -- mark the high point in a remarkable scientific odyssey that began in the muck of the great Congaree Swamp in South Carolina.

Hayes grew up near Columbia, and one of his favorite boyhood pastimes was messing with the turtles, snakes, toads and many other slithery creatures native to the region.

He was not expected to become an eminent scientist. His father, Romeo Hayes, never graduated from high school, and he worked as a carpet installer. His mother, Susie, tended to the family at home.

Tyrone, the eldest son, landed a scholarship to attend Harvard University in 1985. His flight to Massachusetts as an incoming freshman was his first time on an airplane. When he graduated, he became the first in his family to earn a college degree. He earned his doctorate in animal endocrinology at Berkeley.

Colleagues and former students describe him as a careful, hardworking researcher and an impassioned teacher. His large laboratory is a magnet for a diverse group of students and researchers who approach their work as a calling.

"He gets very excited about the work that he's doing, and he's very charismatic, so he's able to project his interest and get other people interested," said Dan Buchholz, a former doctoral student in Hayes' lab now working at the National Institutes of Health.

TAKING ON AGRIBUSINESS GIANTS

In his zeal, however, Hayes can demand little short of total commitment from those around him.

"At one time he got everybody in the lab, even if they had other projects going on, to devote a couple of months to weighing tadpoles on one of his big projects, because there was a big wave of work that had to be done," Buchholz said.

That took a fair amount of mostly good-natured arm-twisting. Now, the challenges have escalated far beyond the lab, as Hayes takes on some of the biggest powers in agribusiness -- most notably atrazine's manufacturer, Syngenta, the agribusiness giant based in Switzerland that reported $6.3 billion in sales last year in 20 countries.

Scientists aligned with Syngenta argue that Hayes is the only one coming up with results casting aspersions on one of the world's most widely used weed- killers.

"Everybody took potshots at Tyrone, including me," said Richard Wenning, a senior manager at Environ, an Emeryville consulting firm that has had Syngenta as a client, work that included a critical evaluation of Hayes' frog research.

Hayes has reported laboratory work and field studies suggesting that even low-dose exposure to atrazine might pose a hazard to amphibians. He makes a case that atrazine functions as an "endocrine disrupter" in wild amphibians -- a chemical that plays havoc with their natural hormones.

The herbicide is said to promote activity of an enzyme called aromatase, which converts the male hormone testosterone into estradiol, a form of estrogen, the female hormone.

If that happens at the wrong time in a young frog's development, the result can be a high incidence of males with feminized gonads, as well as smaller- than-normal voice boxes, Hayes said. The effects do not appear to be limited to any particular species but are masked by the fact that affected frogs show no obvious, outward signs of defects.

Detailed gene studies are under way that might help explain the basic physiological processes at work when a frog is exposed to pesticides. Hayes said at least one more "major impact" paper is imminent, while other research is showing odd effects in amphibians exposed to cocktails of atrazine and other pollutants.

"We are now approaching everything I have been dreaming about since becoming a scientist," Hayes said. "We're trying to put it all together."

GETTING THE EPA'S ATTENTION

Hayes' first bombshell came in April with a paper in the Proceedings of the National Academy of Sciences, focusing on a species of African clawed frog widely used in laboratory studies of amphibians. The Environmental Protection Agency was nearing the critical stage of a years-long re-review of atrazine, part of a broader look the agency is taking at all pesticides.

"Here it was, the 11th hour of the EPA review, and then Tyrone comes out with this study, and says, 'Hey, this is a huge endocrine disrupter, and maybe that's why the amphibian populations are declining in the Midwestern United States.' Man, did that get their attention," Wenning said.

Interest has escalated with the latest high-profile studies. They showed essentially the same hermaphroditic effects in the common American leopard frog, Rana pipiens.

This time, however, Hayes sampled watersheds in the field, where he found the same mutations he had observed in his laboratory studies. The finding attracted a steady stream of reporters and camera crews to his fifth-floor offices and basement specimen housing on the Berkeley campus.

Hayes appeared to tolerate the media interest in good humor, inviting one reporter to sit in on some of his lectures. He also issued his own detailed rebuttal when asked what he thought of his critics' appraisal of his work.

His goals seem to be getting ever more ambitious the more controversy he generates. Now, he is laying plans to sample the vast Missouri River drainage from its relatively pristine source all the way down to its terminus on the Mississippi, to see how changing pesticide levels might affect amphibian health all the way down the river.

Hayes sees his work coming back around to his boyhood, an extension of his exploration of the swamps of South Carolina. Now it's just being done with greater sophistication. While others have found no evidence of damage from atrazine runoff, Hayes said that's because "nobody's really looked."

"Besides," he said, "you have to know what you're looking for."

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