Fish advisories should include multiple contaminants, study says

By MORGAN LINN

Capital News Service

Fishing advisories could be exposing people to unsafe levels of contaminants. Image: Pixabay

Fishing advisories could be exposing people to unsafe levels of contaminants. Image: Pixabay

LANSING — Great Lakes fish consumption advisories could be inadequate and exposing consumers to higher levels of toxic chemicals than anticipated.

A new study says that advisories don’t include what happens when more than one chemical is present in a fish. This means the advisories are “probably deficient in protecting the health of human consumers,” the study says.

In Canada, fish eaters who follow advisories could be exposed to four or more times the amount of contaminants than is considered safe, the study says.

Though the study was done in the Canadian waters of the Great Lakes, the findings could be highly applicable to Great Lakes states as well, Nilima Gandhi, co-author of the study and a researcher at the University of Toronto, said in an email.

In Michigan, a new set of conservative guidelines was developed in 2012 to keep fish consumers safe, said Michelle Bruneau, a health educator for the Michigan Department of Health and Human Services.

Prior to 2012 two types of advisories existed — a conservative one for pregnant women and children, and a less restrictive one for the general public, she said.

The new guidelines removed the general public advisories, and instead applied the more conservative advisories to everyone, Bruneau said. This made sure all people, especially those who might have chronic health issues, are protected from contaminants.

So Michigan’s advisories may not be impacted by the more restrictive multi-chem approach because they are already conservative.

The study advises that each advisory agency should decide if its advisories are conservative enough to protect against the additive effects of contaminants.

If they don’t cover the added health threat, agencies should change their advisories to include a multi-chem approach, the study says.

Trout have elevated levels of PCBs because they are fatty. Image: USFWS Midwest.

Trout have elevated levels of PCBs because they are fatty. Image: USFWS Midwest.

The major contaminants of concern are PCBs (polychlorinated biphenyls) and mercury. Both have serious health consequences when consumed in unsafe amounts.

“PCBs can affect our neurological, reproductive and immune systems, can have developmental effects and can also cause cancer,” Gandhi said. “Mercury can affect our neurological, immune and digestive systems.”

Most Great Lakes states’ fish advisories and advisories in Canada follow the “one-chem approach,” which is based only on the most harmful contaminant, she said.

In this approach, researchers calculate a safe number of meals per month for each contaminant present, then choose the smallest number of meals. This means advisories are based on a single contaminant – the most harmful one.

Advisories based on this approach don’t consider how chemicals interact with one another. When there is more than one contaminant present, their health effects can be additive. That means they are even more damaging when combined.

Walleye are top predators, meaning they have elevated levels of mercury. Image: Gavin Peterson on Wikipedia

Walleye are top predators, meaning they have elevated levels of mercury. Image: Gavin Peterson on Wikipedia

The study recommends that advisories instead be based on a “multi-chem” approach, which would take into account the additive effects. This approach could mean more restrictive advisories for some of the most popular fish, such as walleye, salmon, bass and trout, Gandhi said.
In Canada, that approach would require half of the advisories for the general population to be twice as restrictive, the study says. That means the recommended number of meals per month would be cut in half.

For around 10 percent of advisories, the meals per month would be even more strict – a quarter of what is currently recommended. The “do not eat” advice would also increase by 5 percent.

Some Great Lakes states’ advisories could be similarly impacted because they follow the same approach. But not all. Changing advisories should be done on a case by case basis, Gandhi said.

For example, New York advisories may not be impacted. They are based on a one-chem approach, but only when there is one major chemical of concern. But when many chemicals are present, the advisories include the additive effects, according to the New York State Department of Health.

Some advisories may have conservative measures built-in for extra protection and might not have to be changed, Gandhi said.

Fish consumers should also consider the benefits of eating fish in addition to the risk, Gandhi said. Overall the best method is to “account for risk and benefit at every step of the advisory calculation.”

Morgan Linn reports for Great Lakes Echo