New Government Fish Tests Raise Mercury Concerns

New Government Fish Tests Raise Mercury Concerns

Friday, September 28, 2007

New Food and Drug Administration (FDA) data show mercury contamination of fish is more serious than federal scientists previously assumed. Tests on mercury in fish found that four species — canned albacore tuna, grouper, sea bass and bluefish — have higher average mercury levels than historic data used by the FDA in developing its mercury health advisory, according to an analysis by the Environmental Working Group. EWG obtained the data through the Freedom of Information Act.

The EWG review shows that mercury levels in popular canned albacore tuna are of particular concern, challenging FDA's stance that fetuses face no risk if their mothers consume it. Canned albacore, known as white tuna, had mercury levels twice as high as past FDA estimates for canned tuna, and three times the levels in light tuna (see Figure 1).

Figure 1. New data show more mercury contamination in Canned Albacore Tuna

Figure 1

Source: Environmental Working Group analysis of Food and Drug Administration testing data.

These findings confirm the results of recent independent tests of canned albacore tuna showing that a small but significant percentage (2 to 5 percent) of albacore tuna tested exceeds the FDA action level for mercury of 1 part per million. Previous FDA studies have found albacore tuna with mercury levels over 1 part per million. Fish with mercury levels above 1 part per million have traditionally been included on the FDA "do not eat" list for pregnant women. In the data release by FDA to EWG, maximum mercury levels in canned albacore tuna were just shy of the 1 part per million limit.

Mercury is toxic to the developing brain and nervous system. Elevated exposures during fetal development can have long lasting adverse effects on intelligence, speech, and motor development. According to the Centers for Disease Control and Prevention, 8 percent of U.S. women of childbearing age have levels of mercury in their blood that present developmental risks for their babies. EWG has advocated that the FDA give strong, clear advice to pregnant women on fish consumption, and that the federal government cut mercury pollution from coal-burning power plants and other sources to eventually make tuna "baby safe."

Other fish were even more contaminated, but like canned albacore, they were not added to the FDA's new proposed list of fish that pregnant women should avoid. Grouper, in particular, had extremely high levels of mercury. Two out of 20 samples of grouper (10 percent) exceeded the FDA action level for mercury of 1 part per million. Average grouper levels were 30 percent higher than previous FDA data indicated.

Figure 2. Mercury levels higher in some important fish

Figure 2

Source: Environmental Working Group analysis of Food and Drug Administration testing data.

News of these high mercury levels in popular fish species comes in the midst of two important government public health developments. Just a week ago, the Bush Administration proposed a major rollback of the mercury pollution reduction goals adopted by the Clinton EPA, which will result in much higher levels of mercury pollution over a more prolonged period, increasing the risk of fish contamination. This week, the FDA's independent Food Advisory Committee will review an agency draft warning telling consumers how to protect themselves from mercury in seafood. The proposed warning does not encourage pregnant women to limit or avoid consumption of canned albacore.

The new fish test data were generated by FDA as part of a revision of the agency's mercury in seafood advisory - revisions that were requested by the Food Advisory Committee in the summer of 2002, following EWG reports that the agency had downplayed the risk of mercury in canned tuna. The Committee's request for revisions to FDA's advice reflects increasing concern among scientists about high levels of mercury in the blood of American women, and their conclusion that the FDA's current advice does not provide adequate protection to the American public from the health hazards of mercury.

FDA's current mercury advisory recommends that pregnant women and women of childbearing age not eat any swordfish, shark, king mackerel, or tilefish. The proposed revisions to the advisory do not add any fish to the "do not eat" list, but in developing its proposed revisions, FDA did test tilefish for mercury, a species added to the advisory in 2001.

In spite of its status as one of just four fish that FDA recommends women of childbearing age completely avoid, tilefish was not the most contaminated fish in this latest round of mercury testing.

FDA's new test results show that five fish--canned albacore tuna, grouper, sea trout, orange roughy and bluefish--have higher levels of mercury than tilefish (see Figure 3). Yet in spite of the elevated levels of mercury in canned albacore tuna and these other fish, the FDA's new health advisory provides no advice to women that they limit consumption of these heavily contaminated fish.

Figure 3. New FDA data show that five fish, including Canned Albacore Tuna, have higher levels of mercury than tilefish, a fish on the FDA "do not eat" list for pregnant women

Figure 3

Source: Environmental Working Group. Compiled from FDA 2003 mercury testing data.

In July 2002, the Food Advisory Committee asked the FDA to significantly increase testing of fish so that the agency could more confidently advise women of childbearing age on the fish they should avoid, the fish they should eat in moderation, and the fish they should eat freely.

The FDA devoted most of its resources to testing canned tuna, the one species for which the agency already had data sufficient to support warning pregnant women to significantly reduce consumption.

For nine of the top ten most commonly eaten seafood products, the FDA conducted no new tests for mercury at all. As a result, the agency has as many samples of canned tuna as it does for all other seafood in the top ten combined. The FDA reports mercury test results for just 6 clams and 8 samples of tilapia, the 8th and 9th most popular types of seafood in the US.


FDA 2001 - FDA Office of Seafood, "Mercury Levels in Seafood Species," May 2001. Available online at

FDA 1993 - Canned albacore tuna data: Yess, NJ. 1993. US Food and Drug Administration survey of methyl mercury in canned tuna. J. AOAC Int. 76(1): 36-38.

FDA 2003 - Canned albacore and light tuna data: FDA. 2003. Mercury levels in various fish. Available online at dockets/ac/03/briefing/4010b1-11-fish-data-revised.pdf (Accessed from