As of June 2013, the Department of Health and Human Services (NDHHS), in cooperation with the Department of Environmental Quality (NDEQ), the Game and Parks Commission, and the Department of Agriculture, has issued fish consumption advisories for 24 waterbodies (stream segments and lakes). Combined with the previous year's assessments, 94 waterbodies now are under fish consumption advisories. States across the nation participate in this national sampling program, and the overall contaminant trends found in Nebraska are similar to those in other states.
These advisories do not ban the consumption of fish from a particular waterbody but are designed to inform the public of how to safely prepare and eat what they catch, and provide suggested guidelines for limiting consumption. As a food source fish are a high quality protein, low in saturated fat, and high in omega-3 fatty acids, so anglers should not be discouraged from consuming fish in moderation.
The 2013 advisories are based on samples taken through 2011. Fish tissue samples are collected by the NDEQ, analyzed by the U.S. Environmental Protection Agency (U.S. EPA) and advisories are issued by the NDHHS. Fish tissue samples are analyzed for a variety of chemicals including: heavy metals, pesticides and other organic compounds.
Note: Samples collected in 2012 are still being analyzed by the U.S. EPA.
Chemicals of primary concern in Nebraska and most other Midwest states include:
- Methylmercury (organic mercury) which occurs naturally and is released into the environment from mining operations, fossil fuel combustion, trash incineration, and industrial waste discharges.
- Polychlorinated biphenyl compounds (PCBs) prior to 1971 were used in heat transfer fluids, hydraulic fluids, lubricants, and wax extenders, and later in electrical transformers and capacitors.
- Dieldrin is a breakdown product of the insecticide aldrin, which was generally used on corn prior to 1974.
- Selenium is a naturally occurring mineral that is also an essential nutrient but it can be a problem if present at high levels. Selenium is present in air, soil, water and food.
Fish tissue is collected and analyzed to assess human health risks associated with consumption using a risk-based assessment procedure. For non-cancer (noncarcinogenic) effects, such as those associated with exposure to mercury, the assessment procedure determines a Hazard Quotient for each contaminant. In addition to the concentration of a chemical contaminant found in fish tissue, this quotient is determined by taking into account an average body weight and ingestion rate for a consumer, and looks at how frequently (exposure frequency) and often (exposure duration), someone might eat fish from a particular waterbody.
If more than one contaminant is present in the fish tissue then the Hazard Quotients are summed to derive a Hazard Index. If the Hazard Index is less than 1.0, then adverse noncarcinogenic effects are not anticipated. If the Hazard Index equals or exceeds 1.0 then an advisory is issued.
For a contaminant that may also be associated with a potential cancer risk, the risk-based assessment procedure determines an estimated Cancer Risk. This estimate represents the probability of an individual developing cancer during their lifetime as a result of exposure to the potential carcinogen. If more than one potential carcinogen is present in fish tissue then the risk estimates are summed. Advisories are issued if the estimated Cancer Risk equals or exceeds 0.0001 (1 in 10,000).
Methylmercury is assessed using the Hazard Index approach, but Nebraska also limits the level of mercury in fish tissue to 0.215 milligrams (mg) methylmercury per kilogram (kg) of fish tissue. Therefore, for methylmercury, advisories are issued if the concentration in fish tissue equals or exceeds 0.215 mg/kg or if the Hazard Index exceeds 1.0. Exposure to high levels of mercury have been shown to adversely affect the developing nervous system, so women of child-bearing age, pregnant women, and children less than 15 years of age are the most sensitive to the effects of mercury.
Advisories remain in effect for a waterbody until it is re-sampled following a 6-year rotating basin monitoring approach. Re-sampled sites will be removed from the advisory list if fish tissue samples indicate contaminant levels below health risk criteria. Under a revised agreement with the U.S. EPA, the NDEQ in recent years has significantly increased the number of locations that are sampled. Most of Nebraska's advisories are based on high levels of mercury. About 20 percent of the sites have advisories for contaminants other than or in addition to mercury, including PCBs, Dieldrin, and Selenium. More information about these contaminants is listed below.
NDEQ’s 2013 Regional Ambient Fish Tissue Report provides more detail on the sampling and analysis of fish tissue in Nebraska. Samples collected in 2012 are still being analyzed by the U.S. EPA. A list of all waterbodies with advisories can be found at the List of Advisories along with a map showing their locations.
Information on U.S. EPA Fish Advisories
Chemical Contaminants Found in Nebraska Fish Tissue
The State monitors waterbodies for a variety of pesticides, metals, PCBs and other contaminants however it is chemicals such as banded pesticides, PCBs and methylmercury that are the most prevalent and persistent in the environment. Newer regulations, chemical formulations, use restrictions, and other changes, have markedly improved the quality of surface water in Nebraska and throughout the nation.
Mercury is a naturally occurring metal that exists in several forms. The most common of which is methylmercury. Methylmercury can be found in water and soil, fish and shellfish. Methylmercury accumulates in fish tissue, primarily in older and larger predacious fish such as walleye, northern pike, and largemouth bass.
Exposure to high levels of methylmercury may adversely affect the developing nervous system. So young children and pregnant or nursing mothers are the populations most at risk. Advisories are issued to protect these very sensitive consumers.
U.S. Food and Drug Administration - What You Need to Know About Mercury in Fish and Shellfish
Agency for Toxic Substances and Disease Registry’s ToxFAQs for Mercury
Polychlorinated Biphenyls (PCBs)
PCBs are man-made chemicals that have been widely used in electrical equipment as coolants and lubricants (manufacturing stopped in 1977). Their presence in the environment is primarily due to improper disposal, leaks from electrical transformers, and incineration. They do not break down easily, so they persist in the environment for a very long time. PCBs can be found in water and soil, fish, meat and dairy products.
PCBs are stored in the fatty tissue and organs of fish. Therefore consumers can reduce their PCB intake by trimming all visible fat from the fish fillet and then grilling, broiling or baking the fillets in a way that allows remaining fat to drip or drain away.
Below is a link to another resource that provides information about exposure to PCBs.
Agency for Toxic Substances and Disease Registry’s ToxFAQs for PCBs
Dieldrin is an insecticide that does not occur naturally in the environment. Dieldrin and aldrin, a similar insecticide, were used widely in Nebraska on corn crops. Aldrin breaks down to dieldrin in the body and in the environment. Dieldrin can be found in air, water, soil, fish or shellfish, root crops, meat and dairy products. Use of aldrin and dieldrin were banned in 1987.
Dieldrin is considered to be a probable human carcinogen. Animal studies have demonstrated that exposure to high levels of dieldrin may be associated with the development of liver cancer.
Below is a link to another resource that provides information about exposure to dieldrin.
Agency for Toxic Substances and Disease Registry’s ToxFAQs for Dieldrin
Selenium is a naturally occurring mineral that is also an essential nutrient. Selenium is present in air, soil, water, and food. The majority of a person’s daily intake comes from foods such as fish, meat, whole grains and vegetables.
Low doses of selenium are necessary to maintain good health. Selenium is an antioxidant, protecting the body from free-radical formation. It also helps to regulate thyroid hormones. Very high doses however, may be associated with a disease called selenosis. Selenosis may cause vomiting, diarrhea, nail brittleness, hair loss, and numbness/tingling in the extremities.
Below is a link to another resource that provides information about exposure to selenium.
Agency for Toxic Substances and Disease Registry’s ToxFAQs for Selenium