Trace of Aldicarb May Alter Body Immunity, Study Says
Ingestion of even small amounts of the widely used pesticide aldicarb may alter the human immune system, according to a study by the U.S. Centers for Disease Control.
The study, conducted in Wisconsin, revealed a “strong association” between aldicarb and changes in the immune systems of 23 women who had been drinking water contaminated by the pesticide, said Dr. Michael Fiore, a CDC researcher.
Fiore reported that the 23 women showed an increased level of T-8 lymphocyte cells in their blood and lymph systems that was 28% higher than in a comparable group of women who drank aldicarb-free water. This is “the first suggestion of T-cell changes in humans resulting from chronic exposure to an environmental contaminant,” Fiore said.
No clinical signs of adverse health effects were reported. But results of the Fiore study “raise important questions,” said Dr. James Stratton, head of the California Department of Health Services’ pesticide hazard evaluation unit. If more research proves these findings are valid, scientists must determine what impact this is having on the body’s ability to respond to disease.
Delicate Balance
That ability to fight off disease depends upon a delicate balance between a variety of lymphocytes, including T-8 cells that mediate and control the immune system responses, said Dr. Susan Plaeger-Marshall, a UCLA research immunologist.
“The numbers (reported in Fiore’s study) are pretty impressive,” said Plaeger-Marshall, explaining that an increase in T-8 cells might unbalance the immune system’s ability to respond, thereby increasing the potential susceptibility to cancers and infections.
The women had unknowingly been exposed to levels of the pesticide--from 1 to 100 parts per billion--for several years because wells in farming areas had been contaminated by aldicarb. State health officials asked for the Centers for Disease Control study after University of Wisconsin researchers reported aldicarb radically suppressed the immune-system functions in laboratory mice.
Warning Issued
Wisconsin health officials also warned people last year not to drink tap water if testing in their area showed aldicarb contamination of more than 1 part per billion, a more stringent standard than the 10-ppb limit set by the U.S. Environmental Protection Agency.
Known by the trade name Temik, aldicarb in granular form is plowed into the soil and taken in by plants systemically. California farmers buy 300,000 pounds of the insecticide annually for use in cotton, fruit and vegetable crops. Until recent years Temik’s only known drawback has been its acute toxicity for humans exposed to it.
In 1985, aldicarb was blamed for poisoning 1,000 people in the West who became ill after eating aldicarb-contaminated watermelons. The pesticide is not authorized for watermelon crops and had been used illegally by three Kern County farmers.
‘Acutely Toxic’
At that time, Dr. Kenneth W. Kizer, state health director, called aldicarb “the most acutely toxic pesticide registered in the U.S.”
Traces of aldicarb--a highly soluble chemical--have been found in the underground aquifers in 50 counties in 15 states, including Del Norte County, California.
Results of the Fiore study, which are being disputed by Union Carbide, manufacturer of aldicarb, were reported to a scientific conference in St. Paul, Minn., this week and will be published in the December issue of Environmental Research.
“What concerns us is that we saw changes after short-term exposure. . . . We believe any environmental agent that modulates the immune system should be avoided,” Fiore said.
Because his study raises questions without providing any answers, Fiore has recommended that larger studies be conducted.
Opposite Results
Union Carbide ordered its own tests after results of the University of Wisconsin research were reported. Company spokesman Harvey Cobert said its study of laboratory mice showed that aldicarb caused “no alterations in the immune system.”
As for Fiore’s tests, Cobert said: “Our studies in mice do not find any alterations, so we disagree with his findings.”
The EPA is questioning the validity of the Wisconsin mice study because “the Union Carbide findings don’t confirm the (Wisconsin) findings,” said EPA toxicology branch chief Ted Farber. The Fiore study “is still being reviewed,” he added.
