Last Updated: 2002-11-04 12:37:26 -0400 (Reuters Health)

By Dana Frisch

NEW YORK (Reuters Health) - A new study found minute quantities of mercury and lead in the breast milk of Austrian women, at concentrations far below levels at which they might damage an infant's nervous system or kidneys.

Mercury and lead can be toxic even at low levels. The authors, from the University of Vienna, write that infants are "especially susceptible" to these metals because their systems are too immature to filter them effectively. The study appears in the November issue of the journal Pediatrics.

There is little information on the mercury or lead content of Austrian women's breast milk, and no research has been done on whether lifestyle factors might influence levels of these metals. To investigate, Dr. Claudia Gundacker and colleagues studied the breast milk of 150 women from three different areas, an urban center (Vienna), an industrial center containing a metal processing plant (Linz) and a small rural town (Tulln).

The researchers also collected data on other factors that might have affected mercury and lead levels, including diet, weight and whether the infant was premature.

Women who ate wheat, took vitamin supplements and gave birth prematurely had slightly higher than average levels of mercury in their breast milk. Women who smoked and ate fish also had marginally high breast milk lead levels. But levels of both metals among all breast milk samples were far below critical levels capable of harming an infant, the authors note.

Geographic location also affected breast milk's metal content. Women from Linz had more lead in their milk, likely a consequence of the metal processing plant in the area, while researchers detected more mercury in the breast milk of women from Vienna. The findings confirm earlier research that showed that the milk of mothers living in urban areas had a higher metal content, the authors note.

The study also showed breast milk and cow's milk had higher mercury levels than formula, whereas the formula had more lead because it was made with tap water containing small amounts of the metal.

Dr. Richard Yang, a senior medical officer in the organic analytic toxicology branch of the National Center for Environmental Health at the US Centers for Disease Control and Prevention, noted that that methylmercury, a form of mercury, and lead are recognized as damaging to the nervous system, and are among the better studied chemicals.

Metals enter the body primarily through diet, accidental poisonings or from metals in the air that might settle upon food sources, as was the case with leaded fuels. Yang told Reuters Health that breast milk is a good way of assessing not only the infant's exposure, but also the exposure of the population as a whole.

Yang said he was not aware of any regulatory standards for levels of metals in breast milk, adding that permissible levels of a chemical are usually based on lifelong estimates.

"It is unclear right now what environmental metals in breast milk are significant and whether they have any significant implications to the baby's health," said Yang. The exception, he noted, is for acute poisonings.

"The monitoring of human breast milk, is in my mind, an important thing," said Yang.

SOURCE: Pediatrics 2002;110:873-878.

Copyright © 2001 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.