Table 1. Source: Missouri Department of Health and Senior Services, 2017.

Eating fish is thought to have healthful benefits, including cognitive benefits for the young and a reduction in the risk of cardiovascular disease in adults. However, environmental toxins limit the amount of fish you should eat. The principle of bioaccumulation, which explains why, was reviewed in the previous post.

Whether fish are safe to eat depends on the water where they were caught. The Missouri Department of Health and Senior Services publishes a report identifying lakes, rivers, and streams where environmental contamination requires a fish advisory. This post looks at the report for 2017.

Table 1 lists the bodies of water for which fish advisories have been issued, the species of fish affected, the sizes of fish affected, the contaminants, and the limit that should be observed (serving advice).

Looking at the table, the toxins include chlordane, lead, mercury, and PCBs. In some cases the fish are safe to eat once weekly, in other cases only once monthly, and in some cases they should not be eaten at all. Several species from rivers near Missouri’s old lead belt tend not to be safe at all. I’ve posted on the Big River previously (here).

The advisories are separated into those that apply to all consumers, and those that apply to “sensitive populations.” Please look at who is included under “sensitive populations”: children younger than 13 and women who are either pregnant, nursing, or of childbearing age. Wow, that is a huge portion of the population! For them, there is no fish caught in any body of water in the United States that is safe to consume more than once weekly. And for them, several important species of game fish caught in Missouri waters should only be consumed once monthly.

Figure 1. Source: Missouri Department of Health and Senior Services.

Figure 1 shows a map of the affected bodies of water. Looking at the bodies of water affected, you can see that they cover a lot of territory: the entire lengths of the Mississippi and Missouri Rivers in the state, the major portion of the Big River, the Blue River, Clearwater Lake (ironic, no?), and Montrose Lake.

The contaminants of concern listed by the Missouri report include chlordane, PCBs (polychlorinated biphenyls), lead, and methylmercury. Chlordane was an insecticide. It was widely used as a termite control in residences, and it was used widely on crops. Starting in 1988, sales of chlordane were banned in the United States. However, chlordane persists in the environment. It adheres to soil particles in the ground and very slowly dissolves into groundwater, where it migrates to rivers and lakes. Once in the water of rivers and lakes, it bioaccumulates. That is why, even though banned in 1988, it is still a contaminant of concern in Missouri fish. Elevated levels of chlordane in the blood are associated with an increased risk of cognitive decline, prostate cancer, type-2 diabetes, and obesity. According to the Missouri report, levels of chlordane are gradually decreasing, but remain a concern in some bodies of water.

PCBs are a family of chemicals that were once widely used as insulating and cooling liquids in electrical mechanisms. PCBs were banned in the United States in 1979, however they are extremely long-lived compounds, and it is estimated that 40% of all PCB ever manufactured remain in use. Toxicity varies among specific chemicals in the family. Exposure to PCBs is capable of causing a variety of health effects, including rashes, reduced immune function, poor cognitive development in children, liver damage, and increased risk of cancer. PCBs in the environment generally enter bodies of water, where they enter the bodies of aquatic species and bioaccumulate up the food chain. According to the Missouri report, levels of PCB are gradually decreasing, but remain a concern in some bodies of water.

Lead is a heavy metal that was once heavily mined in Missouri. Lead mining continues, and as recently as 2014, more lead was released into the environment in Missouri than any other toxic chemical. (See here.) Lead used to be released into the environment through the inclusion of tetraethyl lead in gasoline, and through lead paint. Both of those uses have been banned in the United States. Today, lead enters the environment through mine tailings. Thus, it is of greatest concern in locations that either have or had significant lead mining activities (portions of Southeastern Missouri, for instance). Tailings containing lead were (are) dumped on the ground. From the tailings lead washes into nearby bodies of water, where it is ingested by aquatic species and then bioaccumulates. Lead is readily absorbed by living tissue. It affects almost every organ and system in the body. At high levels it can be immediately dangerous to life and health. At lower levels, symptoms include abdominal pain, weakness in fingers, wrists, and ankles, blood pressure increases, miscarriage, delayed puberty, and cognitive impairment.

Mercury enters the environment from many sources. One important source is coal. When coal is burned, it is emitted up the flue. Though the amount in any lump of coal is tiny, so much coal is burned to produce energy that tons and tons are emitted every year. The mercury falls out of the atmosphere, where it gets washed into bodies of water. There, it is converted by microbes into methylmercury, which is then ingested into aquatic species, and it bioaccumulates. In children a high level of methylmercury has been associated with language and memory deficits, reduced IQ, and learning disabilities. In adults, it has been associated with an increased risk of cardiovascular disease and autoimmune conditions.

It seems to me that for all of these contaminants, the situation may be slowly improving, though it is still problematic. The persistence of these contaminants in the environment, in many cases decades after their manufacture was banned, demonstrates an important environmental principle: the environmental problems you create may not go away quickly. They are likely to remain with you for a long, long time.

Sources:

Missouri Department of Health and Senior Services. 2017. 2017 Missouri Fish Advisory: A Guide to Eating Missouri Fish. Downloaded 3/9/17 from http://www.health.mo.gov/fishadvisory.

Wikipedia. Chlordane. Viewed online 3/15/2017 at https://en.wikipedia.org/wiki/Chlordane.

Wikipedia. Lead. Viewed online 3/15/2017 at https://en.wikipedia.org/wiki/Lead.

Wikipedia. Methylmercury. Viewed online 3/15/2017 at https://en.wikipedia.org/wiki/Methylmercury.

Wikipedia. Polychlorinated biphenyl. Viewed online 3/15/2017 at https://en.wikipedia.org/wiki/Polychlorinated_biphenyl.

Eating fish may be good for you, or it may poison you. (Pick one)

In the 1970s, researchers reported that native people living in Greenland (Inuits) had very low rates of heart disease compared with counterparts living in Denmark. Scientists attributed these health benefits to the consumption of fish and sea mammals containing high levels of long-chain polyunsaturated fatty acids. Recently, however, research has questioned the accuracy of these early studies, as more recent research shows that the rate of heart disease and heart attack among the Inuit are similar to those in non-Inuit populations. Thus, there has been some question regarding how strong the association is between reduced risk of cardiovascular disease and fish consumption. The situation reminds me of one of my favorite sayings: It ain’t what we don’t know that’s gonna hurt us, it’s what we do know that just ain’t so.

Over the years, thousands of research studies have been conducted, with the result that the consumption of fish is included in most dietary guidelines. The benefits are primarily considered to be the previously mentioned reduction in the risk of coronary heart disease in adults, but also an improvement in cognitive development in infants and young children.

The current dietary guidelines in the USA have moved away from the concept of the minimum daily requirement. Instead they describe recommended patterns of healthy eating. The recommendation for seafood has not changed, however: 8 oz. of seafood per week. (Dietary Guidelines, p. 18)

It is generally recognized, however, that some fish species contain significant levels of contaminants. These contaminants include a number of really nasty poisons, including chlordane, polychlorinated biphenyls (PCBs), lead, and methylmercury. These compounds can be toxic even in very small amounts, and they are bioaccumlative.

Bioaccumulation is an important concept in understanding environmental toxins. The basic idea is that even tiny amounts of toxin can build up in the body. Here’s how: at any given feeding, a toxin may be eaten in such tiny amounts that there is no immediate effect on the animal that consumes it. However, it is absorbed by the body, and it is not readily eliminated by natural processes. Thus, over time, the amount in the body builds up each time the animal eats a little more.

Imagine a lake. Mercury emitted by coal-burning power plants falls into the lake, where microbes convert it to methylmercury. Algae living in the lake take in some of that methylmercury. Along comes a tiny fish fry, and it eats some of that algae. Now with each mouthful of algae, the fish fry ingests a dose of methylmercury. And it starts to build up. How many mouthfuls of algae does a fish fry eat? I don’t know, but it is quite a lot. Now, along comes a medium-sized fish, and it eats the fish fry. With one bite, it has ingested not just a tiny amount of methylmercury, but all the methylmercury that built up in the body of the fish fry during its lifetime. How many fish fry does a medium-sized fish eat? I don’t know, but it is quite a few, and the medium-sized fish ingests all of the methylmercury built up in the bodies of each fish it eats. Now, along comes a large fish, and it eats the medium-sized fish. With one bite, it has ingested not just a tiny amount of mercury, but all the methylmercury built up in the body of the medium-sized fish. How many medium-sized fish does a large fish eat? I don’t know, but it is quite a few, and the large fish ingests all of the methylmercury built up in the bodies of each fish it eats.

Now, let’s imagine that our fish are living in a Missouri lake. Along comes a fisherman, and he catches one fish per week and eats it. That will be 52 fish per year. Now, I don’t know what the actual numbers are, but let us assume that a fish fry eats 1,000 individual alga, while a medium-sized fish eats 100 fry, and a large fish eats 100 medium-sized fish. These estimates may be wildly wrong, but the point is to illustrate the principle of bioaccumulation, and they will allow us to do so.

Using the estimates above, each fish fry will ingest the methlymercury contained in 1,000 algae; each medium-sized fish will ingest the amount contained in 100,000 algae; each large fish will ingest the amount contained in 10 million algae, and in a year, our fisherman will ingest the amount contained in 520 million algae. If he continues for 10 years, he will consume the amount contained in 5.2 billion algae.

Over time, the amount of methylmercury in our fisherman’s body will build up, perhaps eventually reaching the point where it starts to poison him.

Now, my presentation is over-simplified; in real life bioaccumulation is much more complex. Further, the numbers I chose for my progression were totally arbitrary. Nonetheless, they illustrate the basic idea of bioaccumulation. And the principle applies not only to methylmercury, but also to lead, PCBs, and dioxins.

The result is that, however good for you eating fish may be in theory, there are limits due to environmental contaminants. The next post will look at what those limits are in Missouri.

Sources:

Committee on a Framework for Assessing the Health, Environmental, and Social Effects of the Food System; Food and Nutrition Board; Board on Agriculture and Natural Resources; Institute of Medicine; National Research Council; Nesheim MC, Oria M, Yih PT, editors. A Framework for Assessing Effects of the Food System. Washington (DC): National Academies Press (US); 2015 Jun 17. ANNEX 1, DIETARY RECOMMENDATIONS FOR FISH CONSUMPTION. Available from: https://www.ncbi.nlm.nih.gov/books/NBK305180.

Missouri Department of Health and Senior Services. 2017. 2017 Missouri Fish Advisory: A Guide to Eating Missouri Fish. Downloaded 3/9/17 from www.health.mo.gov/fishadvisory.

U.S. Department of Health and Human Services and U.S. Department of Agriculture.
2015–2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines.

An acquaintance who serves as a volunteer water quality monitor dropped by to regale me with stories of the many meetings and intense lobbying that occurred over the writing of the regulations that govern water quality monitoring in Missouri. These regulations determine what becomes a classified stream or lake (see the last 5 posts), and how they determine what beneficial uses each are used for. Classified streams and lakes come under water quality protections established by the federal government. Unclassified streams come under water quality protections established by the state, which may be significantly more lax.

According to my source, the Department of Conservation does most of the actual water quality monitoring, but it is the Department of Natural Resources that is responsible for preparing the biennial 503 report and submitting it to the EPA. The state was evidently under pressure from the EPA to tighten and improve what EPA regarded as inadequate water quality monitoring. In opposition were lobbying groups representing the farmers, utilities, and other interests.

I thought it might be useful to see whether Missouri was significantly out of step with the rest of the country in terms of the amount of its surface water that is assessed for quality, and in terms of the results of the assessments.

Figure 1. Data source: Environmental Protection Agency. Missouri Department of Natural Resources 2015.

Figure 1 shows two charts. The top chart shows the percentage of classified stream miles that were assessed for quality in Missouri and in the USA as a whole in 2014. The chart shows that nationally, 31% of classified streams were assessed, while in Missouri only 9% were. Missouri is badly lagging behind on that one. The bottom chart shows the percentage of assessed stream miles that were assessed as impaired vs. unimpaired. Missouri’s data may be less accurate because so few miles are assessed, but of those that are assessed, results roughly parallel national results. In both cases, somewhat more than half of assessed stream miles are impaired.

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Figure 2. Data Source: Environmental Protection Agency. Missouri Department of Natural Resources 2015.

Figure 2 shows similar data for lake acres. Here, Missouri assessed a significantly higher percentage: 85% of lake acres vs. 44% for the USA as a whole. And only 27% of Missouri’s lake acres were impaired, whereas nationally a whopping 70% of lake acres were.

I wouldn’t run too far with this data. There is a lot of controversy over what constitutes clean water. For instance, if at a cove on a lake, the water tests clean 50 weeks of the year, but contaminated 2 weeks of the year, is it clean or impaired? A lot of dollars are on the line, and truth always becomes hard to find in such situations.

At first glance, it is heartening that Missouri assesses such a large percentage of its lakes, but then again, Truman Reservoir, Missouri’s largest lake, has 0.2% of the surface area of Lake Superior. You wouldn’t expect Minnesota to be monitoring the water quality way out in the middle of Lake Superior as intensively as you might expect Missouri to be monitoring the quality of its smaller lakes. Even Kentucky Lake and Lake Mead are 3 times Truman Reservoir’s size.

It is rather disheartening that Missouri assesses such a small percentage of its stream miles when other states seem to be able to do much better.

[Addition 6/19/16: The same acquaintance suggests to me an alternative explanation for why Missouri has surveyed a relatively high percentage of lake acres: Missouri has relatively little lake acreage to survey. All our large lakes are man-made reservoirs, and it may require less effort to survey such a small acreage of lakes. To check this out, I did some quick research on the Internet. Indeed, Missouri is below average in the total number of lake acres, coming in 32nd out of 50 states. This is unusual for such a large state as Missouri, and indeed, only about 1.4% of Missouri’s total area is water. This puts us 40th out of 50 in the fraction of our state that is surface water. Minnesota touts itself as “the land of 10,000 lakes.” Well, that is certainly not us here in Missouri. Perhaps my acquaintance is on to something. Thanks for the suggestion.]

Sources:

Environmental Protection Agency. National Summary of State Information. Data retrieved 5/28/16 from https://ofmpub.epa.gov/waters10/attains_nation_cy.control#STREAM/CREEK/RIVER.

Missouri Department of Natural Resources. 2015. Missouri Integrated Water Quality Report and Section 303(d) List, 2014. Downloaded 4/20/2016 from http://dnr.mo.gov/env/wpp/waterquality/303d/303d.htm.

List of Largest Lakes of the United States by Area. Wikipedia. Viewed online 5/28/16 at https://en.wikipedia.org/wiki/List_of_largest_lakes_of_the_United_States_by_area.