The question of just how safe it is to eat Minnesota fish has even entered politics. In a television campaign ad promoting the Clean Water, Land, and Legacy Amendment, the voiceover paints a grim picture.
"Even I can't always tell by looking at them, but today 40 percent of the lakes and rivers tested in Minnesota are polluted. That means fish you can't eat and lakes kids can't swim in. Even our drinking water supply is at risk..."
The Health Department's newest fish consumption guidelines say it's safe to eat more fish than previously recommended. The guidelines are tailored to specific tested bodies of water, based on how contaminated they are.
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"Basically, I tried to see what the worst case scenario was within that population of fish," said Pat McCann, the research scientist who coordinates the fish consumption advisory program.
McCann said the advisory's old table structure didn't work well with new chemicals now found in Minnesota waters. So, revising the format gave her an opportunity to evaluate the entire guide.
McCann considered fish species with the highest concentration of contaminants from those you can eat on a monthly basis only, like walleye, and those you can eat on a weekly basis, like pan fish. She then added all those categories together to see if people would still fall within the safe range.
"And, it turned out that it was still below the safe dose, so we felt good about giving information that the public could eat more fish," McCann said.
McCann said research on the benefits of eating fish keeps accumulating. Fish is a lean source of protein with cardiovascular and nuerodevelopmental benefits.
The department finally feels comfortable adjusting the guidelines to consider the benefits, since fish consumption advisories only take into account the risks.
This recommendation made Ken Bradley scratch his head.
"Because you're encouraging the public to eat more fish, it gives the assumption that our waters may be cleaned up."
"I think people have always known that fish has health benefits," Bradley said. "I don't think that's disagreed."
Bradley is the Minnesota state director for Clean Water Action. He said it's natural for people to see a direct connection between contamination levels in the water and how much fish is safe to eat.
"Our issue with it is that because you're encouraging the public to eat more fish, it gives the assumption that our waters may be cleaned up and they are healthy now, and there are no more concerns to have, and that fish are fine," said Bradley.
One of the primary concerns is mercury, which can damage the nervous system and cause other health problems. According to the Minnesota Pollution Control Agency, the primary route of mercury exposure for most Minnesotans is through fish.
Air pollution is the major source of mercury contamination, which then falls on rivers and lakes. Fish absorb mercury, convert it into a more toxic form, and keep it in their tissue.
In order for Minnesotans to be able to eat certain kinds of fish more often than the Health Department recommends, MPCA scientists have calculated that the state has to reduce manmade mercury pollution falling on Minnesota rivers and lakes by about 93 percent from 1990 levels.
About 90 percent of that mercury pollution comes from outside of Minnesota. So, contamination in the water is the reason fish consumption guidelines exist, to help people pick what fish are safe to eat and how often.
Hillary Carpenter is a toxicologist with the health risk assessment unit at the Health Department. Carpenter said the fish advice is always conservative, and they make adjustments as they learn more about chemicals.
"When you think about a number that's been there for a while and say that's a safe level, that doesn't mean that there isn't another safe level," Carpenter said. "But we would have kept that same level if there hadn't been benefits, and that's what the real issue here is -- that the risk of eating fish is a range."
Carpenter said this year's data analysis shows it's safe to move further away from the range they've traditionally used because of the benefits from eating more fish.
"We can't tell you how much is going to benefit you, but we know from the information that's available that it will have a benefit that will override that potentially increased level of risk," Carpenter said.
To Betsy Wattenberg, a toxicologist and professor at the University of Minnesota, regularly re-evaluating those guidelines is a good public health practice.
"In this case, the benefits of eating fish are very direct because of their nutritional benefit," Wattenberg said. "So I think it was a good idea for them to go back, do the reassessment, realize that people could benefit very directly from eating more fish without increasing their risk of toxicity from exposure to the chemicals that are present in the fish."
Fish advisors at the department say the biggest challenge in communicating this advice is reaching certain populations that rely heavily on fish as a cheap food source. The department has plans in place to specifically target the Southeast Asian population on fish consumption.
Next year's advisory update is likely to come out in May, around the walleye opener. Details on the fish consumption advisory are on the Health Department's Web site.