Are you confused about the mercury-in-fish advisories? You are not alone. The mercury issue is complex, and unfortunately, answers are not black or white.

Our mothers tell us that fish is brain food. Health professionals encourage us to increase fish consumption because it is good for the heart. Scientists tell us that fish oils (omega-3 fatty acids) are essential for brain development and have great benefits in later years for a healthy heart and a long life.

Then we hear alarming news that mercury in tuna and other fish is dangerous, and that fish consumption should be limited. Consumers need good information to put this issue into perspective and to make informed diet choices.

Mercury is undoubtedly toxic at high levels, but its effects at the low levels that occur in open-ocean fish are uncertain and continue to be studied. We should be reminded that as with many substances, including salt, water and aspirin, the "dose makes the poison." There is substantial evidence that the same is true of mercury in fish.

Are the health advisories about mercury in fish for everyone? No, in fact the joint Environmental Protection Agency and Food and Drug Administration mercury-in-fish advisory is specific for pregnant women, those who may become pregnant and young children.

The general consumer is not part of this high-risk group and should continue to enjoy the health benefits of eating fresh Hawai'i tuna and other open-ocean fish. In fact, there are no mercury-in-fish advisories for the general population.

The danger of misinterpreting the mercury-in-fish advisory is that consumers may be unnecessarily scared into giving up eating fish altogether, depriving themselves of the known health benefits of eating fish to avoid the uncertain risk posed by trace amounts of mercury in fish. Pregnant women might give up eating fish altogether and deprive their babies of the healthy fish oils needed for brain development.

Is the concern about mercury in fish new, and is the risk increasing? No. The modern health concerns about mercury in fish date back to the tragic cases of mercury poisoning involving uncontrolled industrial pollution, highly contaminated fish and a population of heavy fish eaters in Minamata and Niigata, Japan, in the late 1950s and 1960s.

These accidental poisoning events alerted the world to the need to control pollution, not only to protect the environment but to protect ourselves. Mercury in these contaminated fish reached extremely high levels, up to 41 parts per million. The FDA defect action limit is 1 ppm. These are the only two mercury poisoning events associated with the consumption of fish, but these were not open- ocean fish like tuna.

What about mercury levels in Hawai'i fish? Mercury is found in trace amounts in Hawai'i's fish, with most testing well below 1 ppm. The newly released FDA mercury data on 13 bigeye tuna indicate an average of 0.64 ppm. However it is uncertain where these fish came from and what size fish were represented in the sample.

Is the mercury in Hawai'i tuna from pollution or natural sources? The naturally low trace amounts of mercury found in open-ocean fish — such as bigeye tuna in the middle of the Pacific Ocean, far from continental sources of industrial pollution — is more likely to represent natural environmental background levels.

Studies done on Hawai'i's yellowfin tuna found no change in the low levels of mercury in the 27 years between 1971 (0.22 ppm) and 1998 (0.21 ppm). During the same period, global atmospheric mercury emissions increased by up to 26 percent, leading scientists to conclude that the mercury in tuna is from natural sources and not manmade mercury pollution.

Are Hawai'i consumers at great risk? The recently released survey results of hair mercury levels in American consumers conducted by the Environmental Quality Institute and the University of North Carolina-Asheville included Hawai'i consumers with higher levels of mercury. Hair mercury levels provide an indication of mercury exposure over time, and most of the mercury comes from eating fish.

The EPA recommends that mercury exposure, as measured by hair mercury, be limited to less than 1 ppm. This guidance is conservative, precautionary and contains a wide safety margin.

In a study of heavy fish eaters in the Seychelles Islands in the Indian Ocean, researchers evaluated whether mercury from fish in the mothers' diet during pregnancy affected child development. These women had an average hair mercury level of 6.9 ppm and ranged up to 27 ppm. No adverse health effects were found in their children tested up to the age of 9.

The Seychelles study demonstrates that dietary mercury exposure from fish at 700 percent and even 2,700 percent above the EPA safety limit was still safe.

The current mercury-in-fish advisory is based on a safe daily intake (reference dose) designed to protect babies. The safe daily intake is based on the finding of subtle differences in testing scores in children born to mothers in the Faroe Islands (Danish territory in the North Atlantic), with a 1,000 percent safety factor built in.

However, the mothers in this study got most of their mercury from eating pilot whale meat and not from fish. We do not eat pilot whale or other marine mammals in Hawai'i, so what can be said about the safety of eating ocean fish like tuna?