Sulfonylurea backgrounder.pdf

Backgrounder on Sulfonyl Urea Herbicides
Written by Mark Flogel
September 3rd, 1998
Vermont Public Interest Research Group64 Main StreetMontpelier, VT 05602(802) 223-5221 Sulfonyl Urea Herbicides
Sulfonyl ureas (SUs) are a growing class of herbicides, first created in the mid-1970s and onthe market since 1982. Produced by a several manufacturers, SUs are touted as "safe"herbicides, because they are said by their manufacturers to be less likely to cause immediateharm to humans and animals than the chemicals they replace. Sulfonyl urea herbicides areextraordinarily potent, requiring application doses one hundred times smaller than theherbicides they were intended to replace.
The first SU— chlorosulfuron— was formulated by DuPont chemist George Levitt in June1975. Levitt intended the chemical as an insecticide, for killing spider mites. In the course oftesting, it was discovered chlorosulfuron has a devastating effect on plants. Altering thedevelopmental plan for the chemical, DuPont patented it as an herbicide in 1978 and promotedit to wheat farmers as "Glean" in 1982. In its commercial incarnation, chlorosulfuron has beenrefined to kill the broadleaf weeds in wheatfields, but leave the wheat itself unaffected. Since theintroduction of Glean, DuPont has introduced other, specifically targeted SU pesticides forcorn, barley, soybeans and rice1.
Rather than killing plants with chemical burn, as did early herbicides, sulfonyl urea herbicidesblock synthesis of essential branched chain amino acids (leucine, isoleucine and valine) byinhibiting the enzyme acetolactate synthase (ALS). For this reason, these chemicals aresometimes referred to as SU/ALS herbicides or merely ALS herbicides. Because the ALSenzyme does not exist in animals, makers of SU herbicides claim their products are safe forhumans and animals2.
Medical Effects of Sulfonyl Urea Herbicides
The same sulfonyl urea compounds used as herbicides are configured as pharmaceuticals andprescribed for humans precisely because they do effect our bodies. A class of SUs (carbutamide,chloropropamide, glibenclamide, glipentide, glipizide and tolbutamide) are prescribed forpeople suffering from non-insulin dependent diabetes mellitus (NIDDM)3. The pancreas of apatient suffering from NIDDM produces insulin, but not enough to meet the body's needs.
Sulfonyl urea drugs stimulate the pancreas to produce more insulin and assist insulin ingetting sugar into the body's cells and out of the bloodstream4.
Doctors are advised not to prescribe SU pharmaceuticals for pregnant women or nursingmothers (SUs can be passed to the infant through breast milk). Unwanted effects common topatients on SU drugs include convulsions, fainting, unconsciousness, hypoglycemia (low bloodsugar), blurred vision, cold sweats, difficulty concentrating, nausea, nervousness, nightmares,slurred speech, tiredness, weakness and unusual weight gain. Less common effects includechest pains, chills, coughing up blood, dark, fluid-filled skin blisters, sweating, sensitivity tosunlight, shortness of breath and unusual bleeding or bruising5.
Backgrounder on Sulfonyl Urea Herbicides Hazards of Sulfonyl Urea Use
Although all pesticides are poisonous, sulfonyl urea herbicides are 100 times more toxic thanherbicides used prior to 1982. This is appealing in that farmers can use a smaller volume ofherbicides to treat their crops, which is cheaper for the farmer and is claimed by chemicalmakers to cause less incidental damage to the local environment. It was hoped that SUs couldreplace such common herbicides as atrazine, which have contaminated groundwater in manyareas where it has been used6.
The use of such potent chemicals also carry some obvious drawbacks. When any pesticide isapplied from an airplane or helicopter, there is always some drift of the chemical away from thetarget crop into other areas. The National Research Council estimates that as much as 60percent of a given chemical may drift off-target7. Residues of drifting pesticides have beenfound as far as a mile away from target fields8. While this problem is serious enough withconventional pesticides, drifting SUs are strong enough to wipe out a neighboring farmer'sentire crop.
Shortly after the introduction of DuPont's Glean (chlorosulfuron) for wheat, farmers raisingfruit and flowers in the canyons of south-central Washington State suffered crop failures. Theysuspected the cause to be SUs drifting down from the wheat fields in nearby Horse HeavenHills. A team of three scientists from the U.S. Environmental Protection Agency (EPA)conducted an experiment in which cherry trees were treated with a dose of Glean 1/500th aslarge as was applied to wheat crops. While there was no visible damage to the leaves of theexposed branch, it failed to bear any fruit. Also, it was impossible to detect any residual tracesof the herbicide.9 The scientists concluded, ". drifting sulfonyl ureas may severely reduce bothcrop yields and fruit development on native plants, an important component of the habitat andfoodweb for wildlife.10" The scientists expressed concern that if the problems in WashingtonState were the results of the first use of sulfonyl urea herbicides, then nationwide use on avariety of crops might have devastating effects on ecosystems.
The scientists' concerns were echoed by EPA bureaucrats. In the spring of 1989, Gary O'Neal,the Air and Toxics Division director for the Pacific Northwest wrote to his superiors inWashington, DC, "The growers who claim crop damage due to the use of sulfonyl ureas areparticularly upset because they cannot establish by chemical analysis that the damage was dueto herbicide drift. This issue will likely become more of a problem as sulfonyl ureas are morewidely used. Also, even more potent herbicides may be developed in the future11." In fact, EPA employees were raising concerns about the difficulty of detecting SUs even beforethe herbicides were approved for use. In 1981, as chlorosulfuron (Glean) was being evaluatedfor approval by the EPA, the Environmental Effects Division recommended that "SUs not beregistered" because they "are excessively persistent in the environment and they cannot bedetected at low levels12." The regulator's object of frustration is the corporate lawyer's cause for glee. If sulfonyl ureaherbicides can wipe out a crop without leaving any detectable residue, it is more difficult forvictims of drift, seeking compensation, to prove liability in court.
Backgrounder on Sulfonyl Urea Herbicides Sulfonyl Ureas Resistant Weeds Now Widespread
As with other herbicides, a few years after sulfonyl ureas were introduced, new strains ofweeds, which resist the effects of SUs, started appearing. Because of their immunity to SUs andthe lack of competition from other plants, the new strains of weeds starting spreadingrapidly— like weeds.
By 1992— ten years after it was first introduced— DuPont ceased selling Glean in seven GreatPlains states and now requires that Glean be mixed with other herbicides to ensure that evenresistant weeds are killed13. Instead of replacing expensive, poisonous herbicides, DuPont nowrequires that both the old and new types of weed killers be applied to together. In such cases,chemicals often work synergistically; toxic, carcinogenic and teratogenic effects created by themixture may be significantly greater than exhibited any of the individual chemicals.
Under this regime, the farmer is burdened with increased costs, while the environment and thepeople in it are subjected to an uncontrolled experiment in toxic chemistry. The only clearbenefit in all this accrues to the makers of herbicides, whose sales have increased once again.
Sulfonyl Urea Herbicides Damage Crops
Although sulfonyl urea herbicides have been on the market less than 20 years, the litigiouslandscape is already littered with numerous lawsuits.
These lawsuits are founded on incidents of crop damage. Often the victim— a small farmerwhose livelihood and personal fortune is now hanging in the balance— turns to DuPont,seeking an explanation and compensation. As a quick review of the cases below shows, DuPontconsistently supplies misleading and false information when confronted with damage caused byone of their products. Sulfonyl urea pesticides were the culprit in DuPont's most embarrassing moment. In 1991,over 2,000 growers in 40 states reported crop damage after using DuPont's Benlate fungicide.
DuPont recalled the Benlate and paid out $510 million in damage claims, $400 million of whichwent to growers in Florida, a state particularly hard-hit. Although the blight was obviouslytied to the use of Benlate, victims could not— and DuPont would not— explain what had gonewrong.
In 1993, researchers from the Florida Department of Agriculture initiated a secret project toisolate the components of the tainted Benlate. The project was conducted secretly because theresearchers feared attorneys for DuPont would attempt to gain a court order to stop their workif word leaked out. In April 1994, Florida Agricultural Commissioner Bob Crawfordannounced the team had found eight batches of Benlate contaminated by the DuPont sulfonylurea Londax. Although DuPont denied the allegation, a few days later the company agreed topay another $214 million to 220 farmers in compensation for damage caused by the taintedBenlate. In all these settlements, DuPont has accepted no liability14.
Backgrounder on Sulfonyl Urea Herbicides DuPont's troubles in Florida are hardly exceptional. Consider: • Ruling in a case involving contaminated Benlate in the state of Georgia, U.S. District Judge J. Robert Elliott fined DuPont $115 million and said, "This court found DuPont's conductto be the most serious abuse in its years on the bench and the most serious abuse reflectedin legal precedents. DuPont consciously and deliberately withheld data. and elicited falsetestimony. DuPont's conduct. was willful, deliberate, conscious, purposeful, deceitful andin bad faith. Put in layperson's terms, DuPont cheated15." • In a Hawaiian Benlate case, a jury awarded growers $23.9 million and the judge added an additional fine of $1.5 million, citing a pattern of abuse and withholding of evidence onDuPont's part16.
• In a Florida Benlate case, Judge Amy Steele Donner wrote, "DuPont and its lawyers have participated and continue to participate in utter disregard for orders or the court, and forthe rules of evidence and ethics. This is a pattern, it is willful, it is deliberate and it isintended to thwart the orders of this court.17" • In 1989, four Colorado farmers won a $7.4 million lawsuit against DuPont after a jury agreed that a DuPont insecticide, Asana, had been contaminated with SUs18.
Sulfonyl Urea Pesticides in Vermont
According to information obtained from the Vermont Department of Agriculture, an average ofslightly more than 198 pounds of sulfonyl urea herbicides were used by registered commercialapplicators in Vermont each year from 1994 through 1996. During this period, the greatestquantity of SUs were used on railroad rights of way, followed by agricultural usage on corn(although corn became the top usage category in 1996 with 108.27 pounds compared with93.39 pounds on railroads). Other uses of SUs reported in Vermont in Vermont include agrowing quantity on electrical utility rights of way, field and forage, highways, and a categoryknown as “Grass, Turf, Poison Ivy, Weeds.” SUs came to the attention of Vermonters througha widely reported incident at a Shoreham organic farm in July 1997.
In the summer of 1997, Will and Judy Stevens of Shoreham operated the thriving 12-acreorganic Golden Russett Farm; their produce appeared in restaurants and a food co-operative,more was sold through a retail farm stand and subscriptions.
As June ripened into July, tragedy struck the farm. All the Stevens's crops, some days awayfrom harvest, died in the fields— onions rotted in the ground, broccoli twisted and yellowed,beans died on the vine19.
Although organic farmers battle a host of bugs and blights every year, this was eerily different.
Every variety of crop was blighted, the only exception being a row of squash which wascovered by a plant cloth.
Backgrounder on Sulfonyl Urea Herbicides Upon investigation, it was discovered that a few days earlier the Stevens's neighbor had hiredan aerial spraying company to treat a field of cow corn with sulfonyl urea herbicides. Thechemicals— one hundred times as potent as conventional pesticides— drifted off the neighbor'sfield and attacked crops at Golden Russett Farm.
"It wasn't a classic case of drift," Will Stevens said recently. "It was more of an inversion. Itwas dead calm the morning he sprayed, but then it warmed up and I guess everything justlifted and spread out20." Experts from the state Department of Agriculture were called and tests were conducted.
Although no traces of sulfonyl ureas were found in the soil at Golden Russett Farm, residuewas found on the plant cloth. That, taken in conjunction with the facts that a wide range ofplants were suddenly blighted and that only the covered crops were spared was enough tobring a settlement from the cropduster's insurance company.
This year, Golden Russett is once again a certified organic farm. Mr. Stevens said twoseparate laboratories tested his soil "down to 1.5 parts per billion" and found no trace ofchemicals. The farm was re-certified by Vermont Organic Farmers and crops planted on thefields blighted last year are healthy and thriving21. As a result of the Shoreham incident, the state suspended all aerial spraying of herbicides. JimLeland, Agricultural Chemical Program Supervisor for the state's Department of Agriculturesaid there have been no permit applications for any aerial herbicide spraying this year. "Allwe've had is Bacillus thuringiensis and fertilizers." (Bacillus thuringiensis, a bacteria, isconsidered a "biological insecticide.") Mr. Leland said the state will no longer allow aerialspraying of SUs. Any other herbicide "would have to be considered on its own merits," he said.
Sulfonyl urea herbicides continue to be used in Vermont. Mr. Leland said no towns or countiesuse them for clearing rights-of-way, but the state Agency of Transportation uses an SUherbicide along guardrails22.
Backgrounder on Sulfonyl Urea Herbicides REFERENCES
1 Carl Weiser, Sulfonylureas: Miracle Herbicide or Menace?, Sunday News Journal,Wilmington, DE, 26 December 1993, reprinted in Pesticides and You, Spring 1994, p. 19.
2 ChemicalWatch factsheet, Sulfonylureas, National Coalition Against the Misuse of Pesticides(NCAMP), 701 E St SE, Second Floor, Washington, DC 20003, March 1991.
4 Mediconsult homepage, http://Mediconsult.com.
6 John S. Fletcher, Thomas G. Pfleeger and Hilman C. Ratsch, Potential Environmental RisksAssociated with the New Sulfonylurea Herbicides, Environmental Science and Technology,vol. 27, no. 10, 1993, p. 2250.
7 Caroline Cox, Indiscriminately From the Skies, Journal of Pesticide Reform, Spring 1995,vol. No. 15, no. 1, p.2.
8 ChemicalWatch factsheet, Sulfonylureas, NCAMP, 701 E St SE, Second Floor, Washington,DC 20003, March 1991.
9 John S. Fletcher, Thomas G. Pfleeger and Hilman C. Ratsch, Potential Environmental RisksAssociated with the New Sulfonylurea Herbicides, Environmental Science and Technology,vol.
27, no. 10, 1993, p. 2250.
11 Gary O'Neal, director, Air and Toxics Division, Region 10, Environmental ProtectionAgency, memorandum to Anne Lindsay, director, Registration Division, Office of PesticidePrograms, 28April 1989.
12 The EPA's herbicide history, Organic Gardening magazine, March 1997, p. 18 13 Carl Weiser, Sulfonylureas: Miracle Herbicide or Menace?, Sunday News Journal,Wilmington, DE, 26 December 1993, reprinted in Pesticides and You, Spring 1994, p. 19.
14 Mike McGrath, DuPont: A Threat To Plants And Now To Freedom, Organic Gardeningmagazine, November 1996, p. 5.
15DuPont Gets Fined Again, Organic Gardening magazine, December 1996, p. 16.
Backgrounder on Sulfonyl Urea Herbicides 18 Carl Weiser, Sulfonylureas: Miracle Herbicide or Menace?, Sunday News Journal,Wilmington, DE, 26 December 1993, reprinted in Pesticides and You, Spring 1994, p. 19.
19 John Dillon, Organic Farm is Withered in Shoreham, Rutland Herald, 18 July 1997, p. 1.
20 Personal communication with Will Stevens, 18 August 1998.
22 Personal communication with Jim Leland, 19 August 1998.
Backgrounder on Sulfonyl Urea Herbicides

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