Maryland farmers will be asked this year to reduce their use of a popular but toxic weed killer that is showing up in drinking water and the Chesapeake Bay, state agriculture officials say.
The Maryland Department of Agriculture, which regulates farm chemicals, is preparing voluntary guidelines for farmers on how they can cut back application of the herbicide atrazine.
The guidelines are being drafted with the help of Ciba-Geigy Corp., the chemical's leading producer. The firm has proposed nationwide restrictions on atrazine and educational programs such as the one planned in Maryland to try to reduce contamination.
But one environmental group questions whether voluntary restrictions will work. Terry Shistar, who heads the National Coalition Against Misuse of Pesticides, says atrazine is still contaminating lakes and streams in Kansas, her home state, even though farmers there have cut their use of the chemical.
Maryland agriculture officials say they are not taking stronger action now because they have no evidence of unsafe levels of atrazine in anyone's drinking water here.
Atrazine is the second most widely used herbicide in Maryland, after metalachlor. Nearly 1.2 million pounds of atrazine were applied statewide in 1988, mainly on corn fields on the Eastern Shore and in Central Maryland.
Buck Morris, a farmer near Centreville who grows corn, soybeans and wheat on 2,600 acres, said that farmers already take precautions to prevent contaminating their wells and to limit runoff of soil and fertilizers from their fields.
Farmers could get by using less atrazine without seriously hurting their crop yields, he said, but tighter restrictions were not needed until there is proof a problem exists.
"We can't cut it out completely," he said. "In corn, that's one of your main herbicides."
The federal Environmental Protection Agency classifies atrazine as a possible human carcinogen, based on animal studies. Scientists say it is also moderately toxic to fish and other aquatic life.
The chemical persists for up to two months in water and up to six months in soil, and has been repeatedly detected over the past 15 years in the bay, its tributaries, in ground water and in Baltimore's drinking water reservoirs.
Concentrations near the EPA's safe drinking water limit of 3 micrograms per liter have been measured at Baltimore's water treatment plants. Higher levels have been measured in several state rivers and in rain running off farm fields.
Atrazine has also been detected in surface and ground water on farmland throughout the United States, especially in the Midwest. EPA officials say they may conduct a special review of the herbicide, which could lead to tighter regulation or even a ban.
The EPA just last week approved new label restrictions proposed by Ciba Geigy.
Farmers will have to reduce the amount they apply on corn and other crops by up to 50 percent, and they will be barred from spraying the chemical within 66 feet of streams and rivers, and within 200 feet of reservoirs and lakes.
It will no longer be allowed for controlling weeds along highways and rail lines.
These label restrictions do not take effect until 1993, and farmers may follow old labels until they use up existing chemical stocks in two or three years.
So state officials say they are trying to get farmers to take precautions voluntarily now and possibly to go beyond the federal restrictions.
Atrazine guidelines, based on evaluation of each farmer's fields, will be tested this spring and summer in Carroll and Queen Anne's counties, state officials say.
Based on response in those two counties, a statewide program will be developed by this fall.