By Margaret Pizer
When Xiaoyu Xu asked people in Tidewater Virginia about their seafood consumption habits, she found a lot of confusion. Xu, who recently competed her Ph.D at Virginia Institute of Marine Science (VIMS) as a Virginia Sea Grant Graduate Research Fellow, says that on the one hand people hear a lot about the health benefits of fish—a source of protein that is low in saturated fat and high in omega-3 fatty acids. But they’re also hearing about mercury contamination in seafood and may be modifying their eating habits in response.
“I think people are always more serious about the risks compared to the benefits,” says Xu. In reality, how concerned consumers should be about mercury in seafood depends on how much and what kind of fish they are eating. So Xu tested mercury levels in Chesapeake Bay fish and compared fish consumption rates to mercury levels in hair samples from three communities in Tidewater Virginia.
Mercury in Virginia Seafood
Xu began her thesis research by getting a handle on how much mercury is in local fish. She tested mercury levels in ten lower Chesapeake Bay fish species commonly consumed by people (the fish sampled were Atlantic Croaker, American Eel, Blue Catfish, Channel Catfish, Spot, Striped Bass, Summer Flounder, Weakfish, White Catfish, and White Perch). She chose a range of fish with a variety of life cycles and roles in the food web and fish that live in different habitats. The fish samples came from VIMS’s Juvenile Fish Trawl Survey. All of the fish tested had mercury levels that were well below the EPA’s maximum advisable concentration to protect human health. However, Xu is careful to point out that the trawl survey mainly collects smaller Striped Bass, so the data for that species may not be complete.
The relatively low levels of mercury Xu found in Bay fishes is good news, but even low levels of mercury could still be an issue for people who consume a lot of fish. To learn more about people’s mercury exposure levels, Xu needed to talk to them about how much and what kind of fish they eat. She also compared seafood consumption and mercury exposure rates in different ethnic communities, expecting that different cultures eat different types and amounts of seafood.
She reached out to Chinese, Vietnamese, and non-immigrant communities in Hampton Roads churches. At first, finding people comfortable enough to reveal details of their daily habits and give her a hair sample for testing turned out to be quite a challenge.
With the support of her outreach mentor Erica Holloman, Xu learned a lot about how to make these connections and how to ask the right questions. Holloman studied fish consumption in African Americans living in Newport News when she was a VIMS student working with Newman. Her research suggested that mercury exposure from seafood may pose a health risk for some women in the Southeast community of Newport News. Holloman, who graduated in 2010, now works for the non-profit Greater Southeast Development Corporation in Newport News.
In Xu’s study, Vietnamese immigrants had the highest fish consumption of the groups she sampled and the highest mercury levels. Members of the Chinese church consumed less seafood than Vietnamese immigrants but more than non-immigrants, and they also had intermediate mercury levels. Chinese church members also consumed more non-local fish species such as salmon. Non-immigrant church-goers ate the least seafood and had the lowest mercury levels.
Mercury–It’s What’s For Dinner?
So should the tidewater Vietnamese church-goers be concerned about mercury exposure from fish? Not necessarily, says Xu. Hair samples tested were on average well below the level deemed harmful by the World Health Organization (WHO).
Some individuals did have relatively high mercury levels, but “it’s a judgment call whether they need to change their behavior or not,” says Xu. “If I were them I would like to reduce my level a bit—maybe shift to a fish that has low mercury concentrations.” But she points out that some of those individuals are subsistence fishers who eat what they catch and do not have a lot of control over what they pull in day to day. “It might be easy for me to say change species, but it might be really hard for them to do that.”
Xu suggests that people in the Chinese and non-immigrant churches may actually have reduced their fish consumption in reaction to information about mercury in fish. The low levels of mercury exposure in those populations suggest that this reaction is not warranted, and that people may be needlessly missing out on the health benefits of seafood.
“Several people reported that they quit eating fish because mercury is so dangerous,” says Xu. Substituting less healthy foods for fish carries its own risks, she points out. To help alleviate this confusion, Xu is working on brochures that will help people in the communities she worked with better understand their mercury exposure risk.
This is part one of a two part series on Xiaoyu Xu’s research on mercury in seafood. Stay tuned for part 2, which covers the global context for mercury pollution.
