GOVERNMENT
Government steps up pressure on pesticides Recent joint action restricting use of 2,4,5-T herbicide portends changes in pesticide regulations and testing When Sen. Philip A. Hart (D.-Mich.) opened a Congressional inquiry into the hazards of 2,4,5-T earlier this month, he cautiously suggested that questions on the widely used herbicide's safety "might in the end appear to be much ado about very little indeed" or portend "the most horrible tragedy ever known to mankind." The hearings fell short of proving the latter. But they did provide new evidence that catalyzed government suspension and cancellation of consumer and food crop uses of 2,4,5-T and a halt to its use in Vietnam. What's more, pesticide producers and formulators were again put on notice that Congress intends to scrutinize other products and that pesticide regulations and testing will likely change. The multipronged action suspended use of liquid formulations containing 2,4,5-T around the home, near lakes and ponds, and on ditch banks and canceled use of nonliquid formulations around the home and on apples, blueberries, barley, corn, oats, rye, rice, and sugar cane. Not restricted are uses for weed and brush control on range, pasture, forest, rights-of-way, and nonagricultural land. But defoliation in Vietnam with a 2,4,5-T and 2,4-D mixture ("agent orange") will be suspended; use of a 2,4-D and picloram mixture ("agent white") will continue. Of the two steps against U.S. uses, suspension is the more drastic: It halts interstate sales immediately. Cancellation provides for a 30-day period for industry comment. Appeals are possible for both steps, and if a company appeals, only suspension prevents marketing during the appeal process. Dow Chemical, a major producer of the herbicide had not announced what action it would take, if any, at press time. Some 107c of total 2,4,5-T sales are affected by the orders, Dow estimates. Production of the herbicide in 1968, the latest year for which figures are available, was 17.5 million pounds. With the home gardening season now in full swing, 2,4,5-T formulations are already on retailers' shelves. Although these products may continue to be sold, one industry source suggests that state agencies may be under pressure not to buy and may ride out the year 60 C&EN APRIL 27, 1970
without new purchases for those uses still registered. New evidence. For some time 2,4,5-T has been under attack for its use in Vietnam defoliation and because of research findings by Bionetics Research Laboratories that it caused birth defects in laboratory animals. Dow, one of three current producers along with Monsanto and Hercules, had contested these findings, however. The company contended that the teratogenic (fetus deforming) effects were due to dioxin contaminants in a Diamond Alkali (now Diamond Shamrock) sample taken in 1965. (Diamond Shamrock no longer makes 2,4,5-T. Various estimates of that sample place one contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin, at from 16 to 27 p.p.m.) And Agriculture witnesses, testifying before the Hart Commerce Subcommittee, early this month judged the evidence insufficient to recommend any new restrictions (C&EN, April 13, page 2 1 ) . But further research by the National Institute of Environmental Health Sciences (NIEHS) overturned the Agriculture position. The data were analyzed April 11 and 12, presented to HEW, federal regulatory officials, and Cabinet members on April 13, and disclosed by Surgeon General Jesse Steinfeld on April 15 to the Hart subcommittee. The joint AgricultureInterior-HEW announcement for taking the action states that "2,4,5,-T, as well as its contaminant dioxines, may produce abnormal development in unborn animals. Nearly pure 2,4,5-T was reported to cause birth defects when injected at high doses into . . . pregnant mice, but not in rats. No data on humans are available." A summary of NIEHS data indicates that the 2,4,5-T, comparable to that available commercially from Dow, Monsanto, and Hercules, was administered subcutaneously in dimethyl sulfoxide solution to three strains of mice—random bred Charles River, C57B1/6, and DBA/2. Charles River rats received an orally administered sucrose suspension of 2,4,5-T. Dioxin was also administered to both mice and rats. Under questioning by the subcommittee, Dr. Steinfeld professed his "surprise" at the research results and
said that HEW judged that an "imminent hazard" existed and that the suspension action was taken to protect women of child-bearing age. But lie stressed that HEW was "not aware of any reliable evidence that 2,4,5-T : indeed any of the pesticidal chemicals, has resulted in human birth abnormalities." Further scientific evidence against 2,4,5-T was presented by Dr. M. Jacqueline Verrett of the Food and Drug Administration. She testified that
V.
? Dow's Julius Johnson Not an imminent hazard
chick embryo studies and preliminary hamster data indicate that current production 2,4,5-T with 0.5 p.p.m. of the tetradioxin "is teratogenic and embryotoxic." Surgeon General Steinfeld, however, expressed concern over the tests' "degree of reliance" and said that "they do not clarify the uncertainties as to the significance for man." Climate of pressure. Confronted with the Government's ban, Dr. Julius E. Johnson, Dow vice president and director of research, told Sen. Hart that he could not agree with the decision "as far as [2,4,5-T] is an imminent hazard" but that he would have to agree "in the climate of pressure today." Dr. Johnson argued that: • Low mammalian toxicity of 2.4,-
5-T and absence of reports of increased incidence of birth defects in cattle or sheep grazing rangelands sprayed with 2,4,5-T make it "difficult to believe that any practical hazard existed" from registered uses. • Tests with Sprague-Dawley rats administered both regular productiongrade 2,4,5-T and 2,3,7,8-tetrachlorodibenzo-p-dioxin, at dosages bracketing those given in the Bionetics study, did not cause birth defects in the case of 2,4,5-T, but did indicate a high level of maternal and fetal toxicity from the dioxin. Dr. Ian Mitchell of the National Cancer Institute told Dow that the rat tests, according to Dr. Johnson, would be superior to tests with mice. • Production of 2,4,5-T under specifications requiring less than 1 p.p.m. of the tetradioxin "presents no practical hazard when used in accordance with good agricultural practices. • "If a 130-pound (60 kg.) person
Sen. Philip A. Hart Safe or unsafe?
eats 3.3 pounds (1.5 kg.) of food daily and all of this food contains 0.2 p.p.m. 2,4,5-T (a proposed negligible residue tolerance ), the total amount of 2,4,5-T ingested per day would be 300 micrograms. If the 2,4,5-T contained 1 p.p.m. of the tetradioxin, the food would contain 300 picograms. If a person ingested this amount of dioxin each day for 100 years, the total amount ingested would be only 11 micrograms . . . which represents a 6000-fold safety factor over the amount required to cause embryonic effects in rats. (By contrast, FDA monitored 5300 food samples for 2,4,5-T, found 25 samples with trace residues, and only two with 0.19 and 0.29 p.p.m. 2,4,5-T/')
Support for the NTEHS and FDA studies came from Dr. Samuel S. Epstein, cochairman of the teratogenicity panel of HEW's Commission on Pesticides. Dr. Epstein testified that these studies "clearly confirm" 2,4,5-T s teratogenicity. Although Dr. Epstein says that the teratogenic data on 2,4-D is "far less conclusive" than that for 2,4,5-T, he suggested, under questioning, that there is a "strong presumption" for suspending phenoxy herbicides "under any circumstances in the environment." He raises questions about restricting captan, carbaryl, organomercury compounds, and PCNB (pentachloronitrobenzene). And he concludes that there is an "urgent need" for restricting human exposure to dioxins—particularly in light of the lack of toxicology data—and that similar restrictions should extend to polychlorophenols, polychlorophenoliccontaining compounds, and their combustion products. Scientific challenge. What effect the 2,4,5-T hearings will have on other pesticides isn't immediately clear. But Dr. Steinfeld promises that HEW will, "in the very near future," set up a clearinghouse for information on all types of pesticides. On the related question of exchanging scientific information, Dovv's Johnson strongly urges that research results be subject to open discussion and scientific challenge. The Bionetics results were leaked to the press and to Capitol Hill, but chemical company officials as well as members of the Mrak Commission (Secretary's Commission on Pesticides and Their Relationship to Environmental Health) had difficulty in obtaining the results. Dr. Lee A. Dubridge, President Nixon's science adviser, in a statement submitted for the record, indicated that more federal funds might have to be spent on the "background research relating to health and other effects of environmental agents, including pesticides." He also pointed out that the Administration is considering a series of proposed amendments to federal laws regulating pesticides. One, not alluded to by Dr. DuBridge, would require Agriculture to inspect plants making pesticides. This is currently blocked, however, by the Bureau of the Budget. Another may involve what Dr. DuBridge called the lack of a mechanism for Government to "exercise prudent and unequivocally effective restraint temporarily on new, unexpected information and while awaiting more definitive results." Meanwhile, an industry spokesman tells C&EN, "Everyone is looking at their costs and companies are either cutting back or combining their research efforts."
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A P R I L 27, 1970 C & E N
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