“It’s the gape,” says Prof. Todd O’Hara. “The size of the mouth will dictate the trophic level in a lot of fish.” O’Hara says long-lived predators like lingcod are likely to have higher concentrations of mercury. But so far, Alaskan seafood remains far below levels considered dangerous by the World Health Organization. (Flickr photo/Allie Caulfield)

It’s an unpleasant fact for everyone who eats fish in Alaska: Mercury is in the food chain, and it’s particularly prevalent in seafood.

And while the amount of mercury found in Alaskan seafood remains far below dangerous levels, a pair of researchers want to keep an eye on it long-term. The best way to do this, they’ve found, is not by testing fish coming over the docks, but by testing human hair. They’re in Sitka to report the findings of a pilot study begun five years ago.

Note: Todd O’Hara and Maggie Castellini will report to the public on their mercury study 6 p.m. Wednesday, April 12, in Harrigan Centennial Hall. 

Todd O’Hara is a veterinarian, but don’t bring him your cat to be spayed.

“I’m a veterinarian who has a PhD in toxicology,” he said. “I’ve never had any desire to be a clinical veterinarian. I’ve applied my veterinary degree to wildlife and fish research in toxicology and environmental agents of disease. So that’s how I got into this business.”

O’Hara is a researcher with Texas A&M and the University of Alaska Fairbanks. A lot of pathologists who study human disease are veterinarians, which is not surprising when you consider how closely humans and animals are linked on this planet.

Maggie Castellini, however, is not a veterinarian.

“Maggie is a marine mammal physiologist, by the way,” said O’Hara, “she’s actually trained in marine mammal physiology.”

“That’s correct,” said Castellini. 

“Which greatly applies to what we do,” said O’Hara.

We’ll come back in a moment to why a marine mammal physiologist is important  for research about mercury in seafood. Castellini – until last summer – was with the UAF College of Natural Sciences and Mathematics, and working in the vet department. In 2018, she and O’Hara won funding from the National Institute of Health to study the accumulation of mercury in the marine food web.

The pair had often been to Sitka for the annual symposium on humpback whales – called WhaleFest – and the community, they realized, provided a diverse pool of people who live closely with the marine environment. They launched a pilot study, hosted by the Sitka Tribe of Alaska, and began to collect samples – not of the sea creatures consumed by Sitkans, but of human hair, which can reveal a lot about the head it’s growing out of.

“And hair is just a really easy tissue to be able to work with,” said Castellini. “it’s a very good indicator of mercury in the rest of the body. It’s obviously very easy to sample: You don’t have to stick a needle in somebody or anything like that. And we would just take a very small – maybe about the width of a pencil – from the very back of a person’s scalp, and just cut it right close to the scalp. And that’s all you need to do. It doesn’t hurt and you can’t even tell that the hair has been cut away. So it’s really nice to be able to do effective monitoring with such an easy collection and sample, and also something that’s pretty easy to analyze as well after the fact.”

The pilot study tested mercury levels in the hair of 70 subjects, both in Sitka and in another, smaller community in Southeast Alaska. The objective was to be as broad-based as possible, rather than focus on any specific ethnic group or demographic. Really broad-based.

“And one of the things we like is when vegans and vegetarians participate in the study,” said O’Hara, “because that shows us sort of a control, a non meat consuming person.” 

The upshot of the study is that the tested population showed mercury levels far below the cutoff for the World Health Organization. O’Hara says most people came in at around one part per million of mercury, a couple of people were at five parts per million. The WHO cutoff is ten parts per million.

This is good news for Alaskans who live by – and from – the sea. But it’s not the full story. Mercury accumulates in different species at different rates. O’Hara and Castellini want to expand mercury monitoring, to better specify any risk.

“For a long time, the types of advisories that would be sent out – and there still are in some parts of the country – that basically treat all fishes equally, ‘Don’t eat more than this many meals of fish a week if you’re a woman who’s of childbearing age.’ But that’s not at all true with mercury. Some species of fish have vanishingly small amounts of mercury because of their lifestyle, whereas others can have – especially the bigger ones – can have fairly high levels.”

“The gape, the size of the mouth,” said O’Hara, “will dictate trophic level in a lot of fish. So the bigger the fish, the larger fish they can consume. And those tend to be at a higher position in the food web.”

And higher still are marine mammals. Alaska, the pair agree, has a pretty good advisory system for fish – but not for the animals that eat those fish, and then are consumed by people, primarily Alaska Natives.

“So we would like to include marine mammals, in our study,” said O’Hara, “to give people here in Southeast Alaska, better representation of their diet.”

Note: O’Hara is scheduled to present to the Sealaska Heritage Institute on mercury pathways in marine mammals. View a link to a YouTube video of the presentation.

Some places are famously contaminated with mercury: San Francisco Bay, with Gold Rush-era mining residue. Minamata Bay in Japan, with industrial mercury at such high concentrations that the resulting neurological damage is called Minamata Disease. Alaska’s mercury is less likely to be caused by human activity: There’s naturally-occuring cinnabar, for example, and volcanoes.

O’Hara and Castellini hope that their pilot study with the National Institute of Health will take off into more permanent monitoring of mercury in coastal Alaska. They see monitoring as an incentive to a healthy diet, rather than a deterrent. 

“If that’s all people hear about, then they start to be afraid to eat good, healthy foods,” said Castellini. “And so it’s really nice to be able to get a broad study where we can look at communities and say actually ‘You might eat a lot of fish, but your mercury concentrations in general are still not that high.’ And it’s a good reassurance.”