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DDT's LEGACY Yellowstone fish reveal traces of banned pesticide 1950s spraying program shows lingering effects By MICHAEL MILSTEIN Gazette Wyoming Bureau Testing of fish in the Yellowstone River drainage has found traces of the long-banned pesticide DDT in cutthroat trout from the heart of Yellowstone National Park, offering lasting evidence of a widespread DDT spraying campaign undertaken by the National Park Service and U.S. Forest Service during the 1950s. The results emerged from a U.S. Geological Survey study of pesticides in the Yellowstone River system. While levels of DDT in the cutthroat collected from the Yellowstone River at the outlet of Yellowstone Lake last year fall far below those considered hazardous to wildlife or humans, levels in Yellowstone park fish have been higher. Following DDT spraying of 55,000 acres in Yellowstone and another 77,000 acres outside the park in 1955 to control the spruce budworm, biologists and fisherman noticed thousands of dead fish drifting in the Yellowstone River. Studies following the spraying of another 71,000 acres in 1957 found that many Yellowstone Park fish contained more DDT than is considered safe by today's standards. "The DDT contents of these fish indicate that an accumulation of DDT took place in the tissues as has been shown by numerous authorities reporting on warm-blooded vertebrates," says a paper that appeared in Transactions of the American Fisheries Society in 1961, but was not publicized at the time. "The rate of consumption of DDT by fish in the Yellowstone River is not known, but apparently there was considerable buildup of DDT." The United States banned DDT in 1972 after studies implicated it in environmental damage. DDT thinned eggshells, leading to the downfall of raptors - such as eagles and peregrine falcons. Both species have largely recovered since the pesticide was banned. DDT also causes cancer in laboratory animals and, when ingested in large amounts, can damage the liver and nervous system in humans. Environmental groups also fear that DDT and other pesticides are "endocrine disrupters" that disturb the bodily systems governing critical processes such as reproduction in wildlife and humans, a lasting concern because DDT is a stable chemical compound that lingers in the environment. Osprey and other park waterfowl suffered poor reproduction following DDT spraying in Yellowstone, said John Varley, director of the Yellowstone Center for Resources, the park's resource management arm. "It was about a dozen years after the last spraying that reproductive success started improving," he said, noting that other factors including the recovery of park cutthroat trout from overfishing may have also aided the resurgence of waterfowl. "It's remarkable how resilient this place is - that they were able to make a comeback," he said. Aerial spraying began in 1953, covering 2,000 acres in Yellowstone Park and resumed in 1955 and 1957 mainly on the park's northern range to control the spruce budworm, which was damaging trees in the park and surrounding national forests. In 1957, studies found that only about 18 percent of the DDT released by planes reached the ground immediately beneath them, suggesting that the other 82 percent drifted elsewhere. "It apparently could get caught up in the air currents and get spread over a wide area," said Roy Renkin, a Yellowstone biologist who has researched the spraying program. The 1961 paper that appeared in the fisheries journal reported that biologists at the time found DDT in Pelican Creek, a tributary of Yellowstone Lake that they had assumed would have had no exposure to the pesticide. Since Yellowstone Lake itself fell outside the DDT target area, the chemical's presence in fish from the outlet of Yellowstone Lake today reaffirms its tendency to travel long distances. Since DDT is still legally used in some parts of the world, it may continue to spread through the atmosphere. "The presence of DDT as a parent compound there since it was banned in 1972 (in the United States) is very interesting," said Dave Peterson, a biologist with the U.S. Geological Survey. "It tells us that these chemicals last for a long time out there." Peterson served as lead biologist for the Geological Survey's National Water Quality Assessment of the Yellowstone River, part of a national program to examine the quality of major watersheds. Last year, Geological Survey scientists tested fish for pesticides and other hazardous chemicals called PCBs throughout the Yellowstone River system, from Yellowstone Lake to Eastern Montana. More than half of the fish - trout, white sucker and carp, depending on the location - showed evidence of one or more pesticides, but at very low levels well within national standards. "The results were very positive compared to most of the rest of the country," Peterson said. "In a lot of places they're seeing PCBs at levels dangerous to wildlife. We have hardly any PCBs." Fish from Yellowstone Lake contained among the highest levels of DDT and sister compounds DDE and DDD - even more than fish from the Yellowstone River near Corwin Springs north of Yellowstone Park, suggesting the source of the chemicals was upstream, inside the park, Peterson said. The park fish contained .065 parts per million of DDT, DDE and DDD, well below the national limit of 1 part per million which if exceeded would be cause for concern. The studies reported in the 1961 paper found DDT levels as high as 14 parts per million in fish from Cache Creek in Yellowstone Park and 11 parts per million in fish from the park's Lamar River, far exceeding the threshold. The same studies found "drastic reductions" of insect populations of park streams following the spraying and found that aquatic plants had also absorbed DDT. "It is probable ... that the DDT contained in aquatic plants enters the bodies of fish, directly or indirectly, and that enough may be ingested to affect the welfare of the fish or be stored in their tissues," the 1961 article said. Last year's testing by the U.S. Geological Survey also found low levels of DDT, DDE and DDD in fish from the Shoshone River in Wyoming and the West Fork of Mill Creek near Pray, Mont. Once introduced into a watershed, DDT can dwell in sediments for many years and gradually accumulate in plants and the fatty tissues of fish and other wildlife. It is generally thought to accumulate in greater concentrations up the food chain - a bird, for instance, could accumulate DDT from the many fish it ate. "It degrades over time, but you can have it in small amounts forever," Varley said. "It doesn't just go away." It's unlikely that people eating contaminated fish would ingest such high amounts of DDT because the chemical builds up mainly in fatty tissues that are normally removed from fish when they are cleaned and prepared, officials said. The use of DDT in Yellowstone in the 1950s illustrates the contrast between national park management then, when park authorities carried out the "good neighbor" approach of controlling insect pests with DDT, and now, when park managers give natural processes free reign. The lingering presence of DDT "is just a classic case of continuing to pay and pay for the mistakes of the past," said Jon Catton of the Greater Yellowstone Coalition. "What a validation that is of the national parks to allows natural systems to function. If you have a hands-off approach, you don't have the hands-on mistakes that you see elsewhere."
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