News last week about mercury levels in certain fish and their effect on mercury levels in humans raised lots of questions from readers, as well as comments from folks with special interests in the field.

The source of the most recent story was a study that compared mercury in human hair samples with the self-described frequency of fish consumption. Researchers found that people who say they eat more fish tend to have more mercury in their systems.

But as everyone hastened to add, that's only normally a health issue for the very young. The U.S. Food and Drug Administration and the state Department of Health have issued cautions for women of childbearing age, women who are breast-feeding and young children, since elevated levels of mercury can affect the development of the nervous system.

The FDA's level for concern about mercury in women and children is 1 part per million. But David Martosko, director of research for the Center for Consumer Freedom, wrote to say that this standard needlessly steers women away from a healthy diet of fish. He said 80 percent of people in Japan have mercury levels greater than the FDA standards and yet do not show widespread health issues. Martosko said international agencies use levels in the neighborhood of 5 parts per million, which is still half the amount at which experts believe health effects may begin to occur.

The Hawai'i Department of Health, as the local agency that enacts FDA guidelines, says it actively promotes fish in the diet but urges women to eat ones low in mercury.

Vegan nutritionist Hesh Goldstein of Honolulu argues there are lots of reasons besides mercury not to eat fish, and he provides a vegetarian's alternative. "Everyone extols the virtues of 'fish oil.' What they are actually talking about are the essential omega-3 fatty acids, which can be had, with better quality, from flax seed oil," Goldstein said.

Other correspondents urged Hawai'i residents to research the mercury they can take up from flu vaccines that contain mercury compounds as preservatives, and from the mercury in amalgam dental fillings.

The U.S. Centers for Disease Control says there is no convincing evidence of harm from the shots, but has reduced levels for shots given to children. The FDA continues to review the dental amalgam issue but at this time says "no valid scientific evidence has shown that amalgams cause harm to patients with dental restorations, except in the rare case of allergy."

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766 or jant@honoluluadvertiser.com. Or call him at (808) 245-3074.