RE "FISHING for facts' (g, Dec. 14): Contrary to what you suggest, mercury in fish sold in the United States has not "been directly implicated in severe neurological problems." The entire medical literature doesn't contain a single documented such case.

The same is true for developing fetuses: There are no cases of fetal mercury toxicity on record in the United States.

In a report issued this month, the Centers for Disease Control and Prevention noted: "Finding a measurable amount of mercury in blood or urine does not mean that levels of mercury cause an adverse health effect."

The only cases of neurological problems ever linked to mercury in commercial fish were in Japan more than 40 years ago, in a case involving a massive industrial chemical spill. Today's Japanese eat more than eight times as much fish as Americans, and they suffer no ill effects. The well-documented health benefits of consuming fish far outweigh any hypothetical health risks. It's time that fish regained its old reputation as "brain food." David Martosko Director of research Center for Consumer Freedom Washington