Columbia River Basin State of the River Report for Toxics - Status and Trends
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Mercury, DDT, PCBs, and PBDEs contaminate the Basin from a variety of sources and can potentially result in health concerns for wildlife or people. To know if current toxics reduction efforts under way in the Basin are working or if other activities could help, we need to know if contaminant levels are increasing or decreasing over time. Even though a lot of information has been collected over the past 20 years, we cannot tell if the contaminants are increasing or decreasing Basin-wide. This report highlights the toxics trend information that we have now.
Mercury
Mercury contaminates the Basin from industrial and energy-related activities within and outside of the Basin. Mercury is a special challenge because much of the Basin’s mercury pollution comes from sources outside of the Basin via atmospheric deposition. But at a watershed scale, local and regional sources are significant mercury contributors to the Basin. Fish consumption advisories for mercury continue to be issued in every state throughout the Basin.
High mercury levels lead to Basin-wide fish consumption advisories
Mercury can affect the nervous system and brain, and even low doses can impair physical and mental development in babies exposed via the mother’s diet. Fish consumption advisories in the Basin discourage the consumption of many fish species, particularly larger and predatory fish, since they often have higher mercury levels.
Several pathways introduce mercury into the Columbia River Basin
Mercury enters the Columbia River and its tributaries from atmospheric deposition, runoff, wastewater discharges, industrial discharges, and mines. Atmospheric deposition appears to be the major pathway for mercury loading to the Basin. Mercury air deposition includes industrial emissions in and near the Basin and mercury fallout transported from sources as far away as Asia and Europe. Mercury is also directly discharged to rivers and streams from wastewater treatment plants, industrial discharges, stormwater runoff from streets and other developed areas, and historic mercury and gold mining. These sources may be low in concentration, but high in volume. Although these sources contribute less mercury to the basin than the air deposition, they are significant locally because they discharge directly to the Basin’s rivers and streams.
Mercury trends in the Basin are difficult to evaluate
We have some mercury level information for resident fish species in the Basin, but there are few locations with consistent, comparable data from different time periods that can be used to evaluate changes in mercury concentrations over time. Two exceptions are mercury concentrations in northern pikeminnow from the Willamette River Basin and mercury concentrations in osprey eggs in the Lower Columbia River, both of which have been increasing in the last decade. The Columbia River sturgeon population living in the pool behind Bonneville Dam has much higher concentrations of mercury in their livers than sturgeon in the estuary or other Columbia River reservoir pools. Mercury concentrations vary across the basin, but only in some cases are the sources known, such as the historic gold mines in the Owyhee River basin.Top of page
DDT: Banned in 1972, This Pesticide Still Poses a Threat to the Environment
The pesticide DDT was banned in the 1970s and reduction efforts have lowered their levels in the Basin. Unfortunately, DDT persists in the environment and continues to pollute the Basin’s waterbodies from stormwater, agricultural runoff, and other sources. In many areas, DDT levels are still high enough to require fish consumption advisories throughout the Basin. The chemical structure of DDT is very stable in the environment, which is why DDT and its breakdown products DDE and DDD continue to be an environmental and human health threat.
Soil erosion from agricultural runoff is the main source of DDT
The primary source of DDT to the Columbia River Basin is the considerable acreage of agricultural soils in which DDT accumulated over three decades of intensive use into the 1970s. DDT pollutes rivers and streams when farm soils are eroded by wind and water. Other potential sources of DDT are areas where pesticides were handled or stored, such as barns or farm supply sheds, or areas where containers or unused pesticides were disposed. Disturbance of contaminated sediments within the Columbia River and its tributaries may also release DDT to the water column, which can directly or indirectly be taken up by fish.
DDT levels are declining with better soil conservation practices, but still at levels of concern
The ban on DDT combined with improved soil conservation by farmers has reduced DDT pollution to the Columbia River Basin. DDT levels in the Columbia River and wildlife in the Basin have decreased over the last 20 years. However, DDT is still found in the Basin’s fish, plants, and sediments, which shows that DDT continues to cycle through the food web. Fish consumption advisories continue to be issued for DDT in Lake Chelan. DDT is also a problem for fish-eating birds such as bald eagles and osprey.
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PCBs: Stable chemicals Continue to Persist in the Environment
The group of industrial chemicals known as PCBs were banned in the 1970s and reduction efforts have lowered their levels in the environment. Unfortunately, PCBs persist in the environment and continue to pollute the Basin’s waterbodies from various sources, such as stormwater and hazardous waste releases. PCBs tend to concentrate in fish and other animals and can be passed from mother to young. PCBs have been linked to liver damage, development and reproductive problems, and cancer. In many areas of the Basin, PCB levels are still high enough to require fish consumption advisories.
PCBs enter the Basin from many sources and pathways
PCBs in the Basin are associated with industrial locations, where spills or historic handling practices were more likely to occur. Known PCB disposal sites in the Lower Columbia River include Bradford Island at Bonneville Dam; Alcoa Smelter in Vancouver, Washington; and Portland Harbor on the Willamette.
PCBs in fish are declining but still above health concern levels in some areas
PCBs can hurt the ability of mink and otter to reproduce. Mink are especially sensitive to the toxic effects of PCBs. PCB levels in mink and otter have declined dramatically since the 1970s, but despite these declines mink remain scarce in the Lower Columbia. The otter population is relatively dense in the Lower Columbia River, but otters there have higher PCB concentrations than otters in other areas of Oregon and Washington.
Juvenile fall Chinook salmon in the Basin are also accumulating toxic contaminants, including PCBs, in their tissues. We do not have enough information to know if PCB levels are increasing or decreasing in the Columbia River. However, in salmon at some sites in the River, PCB levels are high enough to harm juvenile salmon.
PCBs bioaccumulate in bald eagles and osprey. Since the 1980s, when PCBs in eagle eggs from the Lower Columbia River were the highest recorded in the western U.S., PCB levels are decreasing in both of these top predators.
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PBDEs: Concern over Flame Retardants is Growing
PBDE flame retardants —and other emerging contaminants of concern such as pharmaceuticals and personal care products—are a growing concern because their levels are increasing in fish and wildlife throughout the Basin. PBDEs have been added to plastics and fabrics since the 1960s, to reduce the likelihood that these materials will catch fire or burn when exposed to flame or high heat. PBDEs are released slowly to the environment from manufacturing, use, and disposal of these products and remain in the environment for a long time.Many industries and states, including Washington, are phasing out products containing PBDEs, but their levels have increased rapidly in soil, air, wildlife, and human tissue and breast milk. The health effects of PBDEs have not been studied in people. Laboratory animal studies show neurological, behavioral, reproductive, and developmental effects and even cancer at very high doses.
Information on how PBDEs enter the environment is limited
We have limited understanding on how PBDEs enter the environment, but studies have shown that municipal wastewater could be a pathway. PBDEs in dust and air are a direct pathway of exposure to people, but the importance of air and atmospheric deposition of PBDEs as a source to the Columbia River Basin is unknown.
Levels of PBDEs in the Columbia River are increasing
PBDE concentrations in sucker, mountain whitefish, and rainbow trout are increasing in most reaches of the Spokane River. The most dramatic increases are found in mountain whitefish downstream from the Spokane metropolitan area. Although relatively little PBDE data have been collected in the Basin, studies show that PBDEs are increasing in the waters of the Columbia and several of its tributaries. PBDEs are accumulating in larger fish and are being taken up by juvenile salmon as well..
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