Arsenic in Seafood May Pose Health Risk

Arsenic is a known poison that is carefully monitored, but regulations might not be as strict as they should be, suggests new research.

A small and preliminary study found that certain forms of arsenic, which appear in seafood and are thought to be harmless, might actually be toxic.

Even more troubling, the researchers found that, while arsenic mostly passes right through some people, the substance seems to linger inside others for an extended period.

"Individuals vary enormously in the way they handle it," said Kevin Francesconi, an analytical chemist at the University of Graz in Austria.

"That, of course, is a concern for people wanting to set standards. You generally want to accommodate at-risk populations, but that might be difficult to do."

Arsenic is an odorless, tasteless element that occurs naturally in rocks, soil, air, plants and animals. Arsenic is also used in wood preservatives, fertilizers, and other industrial and agricultural applications, though most of the arsenic we consume is not pollution-related.

It's a complicated chemical. Arsenic comes in at least 50 forms, which can be grouped into two main categories: Inorganic forms that appear in water and rice, and organic ones that show up in seafood.

Long-term exposure to inorganic arsenic has been linked to cardiovascular disease and to cancers of the skin, bladder and other organs.

As a result, the Environmental Protection Agency and other organizations around the world have set strict limits for safe levels of it in drinking water.

Organic forms, on the other hand, have long been considered harmless, and levels in seafood are not currently regulated in most places. Francesconi and colleagues have been interested in finding out what actually happens to these organic arsenic compounds inside our bodies.

For the current study, the researchers created a pure form of organic arsenic that they fed as a liquid to six volunteers. The researchers had originally wanted to test 50 people, but medical ethics concerns limited the size of the study.

Over the next four days, testing of urine and blood showed that four of the six participants excreted into their urine at least 85 percent and as much as 95 percent of the arsenic they ingested, with most of it coming out in the first day. Of the remaining two volunteers, one excreted just 15 percent, and the other eliminated less than 4 percent of the arsenic she had swallowed.

Where in their bodies the missing arsenic ended up remains a mystery. So, too, does an explanation for the wide range of differences. Genetics, liver enzymes and bacteria in the gut could all play a role.

"It is quite worrying that if you eat arsenic in that form that it doesn't come out in the urine, because that opens up the possibility that we actually are accumulating it," said Jorg Feldman, an environmental and analytical chemist at the University of Aberdeen in Scotland. "When arsenic compounds accumulate in the body, that is not good news."

Results also showed that, over the course of digestion, the synthetic organic arsenic broke down into potentially toxic forms. This finding raises new concerns about levels of organic arsenic in seafood, which the European Food Safety Authority is already considering regulating.

Still, scientists have yet to establish that these breakdown products pose a health risk to humans or that naturally occurring organic forms of arsenic break down in the same way.

"We all enjoy Japanese sushi, Chinese soups or mussels that contain huge amounts of arsenic in these forms," Feldman said. "We should look at the metabolism a bit closer. This is one step towards unraveling the mystery of these things."

For now, there is no need to eliminate an occasional sushi habit, Francesconi said, at least not yet.

"I don't think this should panic anybody," he said. "But people should be aware that it's there and that we need to know more."