The young hospital worker immdiately recognized the woody, grayish-white plant Byan J. Huxtable brought into her office as the herb she used to make tea; at least, she said, it certainly looked like it.

For her sake, Huxtable hopes it wasn't. The plant he held in his hands had killed a boy.

The dried plant had been sold in a popcorn bag to the parents of a Phoenix infant by a registered pharmacist as gordolobo, an herb often used as a tea by Mexican-American families who believe it is a cough remedy. The infant, a 2-month-old boy, son died from a liver disease that Huxtable, an associate professor of pharmacology at the University of Arizona Health Services Center here, attributes to the folk medicine his parents had given him.

His death in March is the first in this country attributed to gordolobo tea but is undoubtedly only the "tip of the iceberg" of a much larger problem that many explain why Arizona's rate of cirrhosis of the liver is about 15 per cent higher than the national average, Huxtable says. Nor is the problem confined to Arizona, but probably can be found throughout the Southwest and in any other area with a large Mexican-American population, he believes.

The boy was poisoned because the tea he drank came from a toxic plant, Senecio longilbus, that closely resembles another species, Gnaphelium macounii, also sold under the herbal name gordolobo in Southwestern health food stores and pharmacies.

The toxic plant and its relatives long have been recognized as a major problem in underdeveloped countries such as Afghanistan, India, Jamaica and South Africa, Huxtable says.But little research has been done on how many victims it may have claimed in the United States, even though Huxtable believes the wrong herb has been sold for at least 50 years.

Unlike many other poisons, Senecio's effects aren't immediately visible and, once its effects do begin to appear, the cause can be attributed to many other things, he says.

In larger doses, the toxic plant causes irreversible liver cirrhosis, liver cancer or scarring of vessels that carry blood to the liver, Huxtable says. These signs would be more likely to appear in young children who receive much larger doses of the herbal tea in relationship to their body weight than do adults.

Huxtable also suspects that, in smaller doses, Senecio can cause lung and heart problems. It even may be responsible, he speculates, for a protein deficiency common in underdeveloped countries that causes and abnormally large abdomens and reddish skin color often shown in photographs depicting the plight of children in such countries.

Huxtable's research into the herbal tea began after he was introduced to Dr. Alfred E. Stillman, a Tucson physician whose own interest was aroused when he started treating a 6-month-old girl for cirrhosis of the liver.

Stillman, who had read about problems caused in Jamaica by toxic herbs, suspected that such an herb could be the cause of the girl's problems. She had many of the symptoms of such poisoning - vomitting, fluid buildup in the stomach, abdominal pains and an enlarged liver. A biopsy of her liver "looked just like the description of the biopsies I'd read about," Stillman says.

Her parents confirmed that they brewed a tea at home for the girl. Tests on samples of the herb they used proved it was the poisonous Senecio.

Because they were able to test the herb used for the children's tea and confirm that it was Senecio, Stillman and Huxtable are certain it was responsible for both the body's death in Phoenix and the Tucson girl's injuries. Huxtable says they since have learned of many other cases of death or irrevirtible injury they believe can be blamed on the folk medicine, but weren't able to run confirming tests on the herbs used by the victims.

"I've been rather horrified at the number of people, even upper-middle-class whites, who rely on these herbs," Huxtable says. "Apparently, herbal used is so widespread among Mexican-Americans that I'm sure that wherever there's a sezeable population, they're using them."

Most of the gordolobo sold in the Southwest is imported from Mexico, with Tucson a major distribution point for cities in Nevada, Oregon, Utah, California, New Mexico, Colorado and Texas, Huxtable says. Sales here of any plant labeled gordolobo have been stopped and distributors have called their wholesale customers and told them to destroy any stock they have.

Because the toxic herb is common as a wild plant throughout the Southwest, Huxtable has other fears. For one, some people may be picking their own tea, although only a botonist can tell the difference between the two species, he says.

For another, the toxic plant has been recognized as poisonous to cattle and other stock that graze on Southwestern range lands.

"One of the things that concerns me is the possibility of a low-level exposure (to the plant's toxin) to the whole population in milk, honey and meat," Huxtable says. "It's something that needs further study."

The popularity of "natural" remedies among many Americans of all ethnic backgrounds also may mean that the toxic herb's effects will be seen more frequently in the future, Huxtable says. The young medical technician who told him she used gordolobo tea, for example, was not Mexican-American.

"It could be a carry-over of this natural foods things," he says. "Now it's natural poisons."