Mercury Dangers For Unborn

(CBS)  Doctors and nutritionists have expressed concern about the potential hazards of mercury consumption contained in certain fish, specifically for pregnant women.

A new study, conducted in part by the Harvard School of Public Health, suggests that in addition to the hazards facing a pregnant mother, mercury consumption more seriously affects her unborn baby, and can cause irreversible brain damage in children as they age.

Jane Houlihan, a spokesperson for Environmental Working Group, has studied this subject for years. On The Early Show, she discussed the most recent findings.

She says, "This new study shows a baby's brain can be permanently damaged from the mercury pollution in the fish women eat during pregnancy. This is a big deal because one in six babies born in the U.S. is exposed to mercury at unsafe levels in the womb from a mother's consumption of canned tuna and other fish high in mercury."

Researchers say the data proves that the damage done to the brain of the fetus or child is irreversible, Houlihan says the way it may affect a toddler, for example, is delay in walking or talking and may have permanent deficits in IQ, attention, and memory. The other problem is that the damage caused is "irreversible and permanent. These children were age 14."

Mercury exposures among the children in the study were assessed through analyses of cord blood samples at birth and hair samples taken at ages 7 and 14. Some 1,022 mothers and their children from the Faroe Islands participated in the research. The mothers' hair mercury levels at childbirth in most cases exceeded 1 microgram per gram, the exposure limit recommended by the National Research Council and the U.S. Environmental Protection Agency (EPA). Follow-up testing of the children showed much lower exposure levels. At the most recent follow-up, more than 850 14 year-olds participated in the study.

She says, "Safe levels are set based on studies in human populations, large populations of 1,000 children and more."

The Faroe Islands are located in the North Atlantic Ocean between Norway and Iceland. The islands' economy is centered on the fishing industry and fish processing. The diet of the inhabitants includes high intake of seafood and whale meat.

To assess the impact of the exposure to mercury, brainstem auditory evoked potentials (BAEP) were recorded using surface electrodes placed on the skull. At two different sound frequencies, the researchers measured the transmission of electrical signals in the brain from the acoustic nerve, via the pons (connecting the medulla oblongata to the thalamus) to the midbrain. The latency of the electrical transmission from the acoustic nerve to the pons was significantly increased at higher intrauterine exposure to mercury. This observation was found to be true both at 7 years and at 14 years, suggesting that this effect is lasting.

Some Fish With High Levels of Mercury:

• Canned tuna (especially chunk white)
  
• Tuna steak
  
• Halibut

Some Better Choices (safer sources of omega-3 fatty acids):

• Wild salmon
  
• Shellfish
  
• Haddock
  
• Flounder

Houlihan points out, "63,000 babies born in the U.S. are overexposed to mercury. Rolling back pollution from coal fired plants. The administration is not giving women good advice right now about fish that are safe to eat and it's incumbent on a woman to educate herself and choose wisely."

The study appears in the February issue of The Journal of Pediatrics.