Are Mercury Warnings Bad for Public Health?

See this related seafood lobby fable:
Fable: People are eating less fish because of mercury warnings

Concern exists that public-health advisories about mercury in fish could have unintended, counterproductive effects. If people misunderstand the advisories, for example, and simply eat less fish, they could lose out on the health benefits of fish in the diet, and over the long term, public health might suffer.

This is a reasonable concern. The seafood lobby has not been shy about raising this issue, and has waged a campaign of fear around it, often asserting as a fact that Americans are eating less fish because they are frightened by mercury warnings. But is that true?

Fable: People are eating less fish because of mercury warnings.

Facts: Some individuals may have cut back their fish consumption because of concern about mercury, but there is very little evidence of a general trend in this direction. And, to the extent that a problem might exist, the solution is to improve the clarity and effectiveness of risk communication, not to abandon soundly-based advice about mercury hazards.

In 2001, when the FDA first issued a warning about mercury in fish, a study of a group of mothers-to-be in Boston showed that their reported fish consumption after the warning was issued was 17 percent less than before the advisory. However, the women did not reduce their intake of all types of fish equally; mostly, they cut back on eating canned tuna. Since canned tuna is by far the largest source of mercury in the US diet, the fish-consumption changes the women reported substantially reduced their babies’ mercury exposure and were almost certainly beneficial, not harmful.

There is very little solid research that shows any effects of current government advisories (e.g., the 2004 EPA/FDA advice) about mercury on Americans’ fish-eating behavior. Data on overall US fish consumption show a rising trend. Over the past 20 years, per capita consumption grew from around 15 to about 16.4 pounds per year, and the level has remained above 16 pounds per year for the last five years. Over the same interval, there has been a slight decrease in average blood mercury among women of childbearing age, tested by the Centers for Disease Control. This suggests that on the whole, women may be following the EPA/FDA advice and avoiding higher-mercury fish without decreasing their overall fish intake.

The kinds of seafood Americans are eating have also been changing. Over the past 20 years or so, consumption of shrimp and of fresh and frozen fish steaks and fillets have each risen steadily, to all-time high levels. Consumption of breaded fish products and canned fish, including tuna, has been declining gradually for 20 years. These changes undoubtedly reflect many factors, including price, availability and changing consumer preferences, that are unrelated to mercury warnings. The dramatic increases in consumption of fresh and frozen fish and shrimp may reflect Americans’ increasing awareness that eating fish is a healthful choice, as well as expanded offerings of fresh fish in supermarkets.

Several surveys have suggested that various mercury advisories have not effectively informed consumers. Most people are not aware of specific government advice on mercury; those who know that mercury is a concern generally cannot say which fish they should avoid to reduce mercury exposure, or which fish are low in mercury and should be chosen often.

Overall, while warnings about mercury definitely need to be carefully worded, to guide consumers to choose low-mercury fish rather than to avoid eating fish, there is very little evidence that current advisories have had negative public health impacts. Instead, an opportunity apparently exists to substantially reduce mercury exposure and encourage increased consumption of low-mercury fish, through more effective communication of the risks and benefits involved.

If all the interested parties—health researchers, government agencies, consumer groups and the seafood industry—would unite behind a single, simple message, “Eat more low-mercury fish,” public health could benefit enormously. The benefits of fish consumption could increase while mercury exposure decreased, and the industry could enjoy increased overall sales, although with some shifts in types of fish sold (e.g., less tuna, more salmon).