Cindy - posted on 02/21/2012 ( 1 mom has responded )
The Telegraph - Roger Highfield, Science Editor - 03 Dec 2007
A chemical pollutant that is commonly found in water supplies could harm nursing babies, even lead to mental impairment in extreme cases.
Perchlorate-an industrial pollutant linked to thyroid ailments-has been found in US drinking water and a survey is currently under way to find out its extent and impact in the UK.
Now it has been discovered that it becomes actively concentrated in breast milk, according to a team at the Albert Einstein College of Medicine, New York, and the Johns Hopkins School of Medicine, Baltimore.
Because it can interfere with the thyroid gland of the unborn child, which secretes hormones that control a vast range of processes in the body, perchlorate contamination of drinking water may pose a greater health risk than previously realised, according to the study today in the Proceedings of the National Academy of Sciences.
Perchlorate is known to interfere with the ability of the thyroid, mammary glands and certain other tissues to absorb iodide from the bloodstream. "Our study suggests that high levels of perchlorate may pose a particular risk to infants," says Prof Nancy Carrasco, senior author of the study.
"Nursing mothers exposed to high levels of perchlorate in drinking water may not only provide less iodide to their babies, but their milk may actually pass on perchlorate, which could further deprive the infants' thyroid glands of iodide.
The thyroid requires iodide to synthesise the hormones T3 and T4 that are essential for normal development of the central nervous system.
Babies who don't make enough of these thyroid hormones may become mentally impaired."
Iodide is relatively scarce in the diet, and tissues that need to accumulate it-the breast and thyroid in particular-are equipped with a cell-surface protein called NIS (sodium/iodide symporter) that actively pulls iodide from the bloodstream and into the cells.
In the current study, Dr. Carrasco and her colleagues injected female rats with perchlorate and then extracted the animals' breast milk and tested it on cells that make NIS. The milk inhibited iodide transport in the cells, indicating that perchlorate had become concentrated in the milk. Thus cells that should be taking up iodide were taking up perchlorate instead.
"We found that the same protein-NIS-that actively recruits iodide into cells does the same thing for perchlorate," says Prof Carrasco. "In fact, NIS has a higher affinity for perchlorate than it does for iodide, which certainly heightens the risk posed by this contaminant."
Whereas several studies found no linkage between perchlorate exposure and thyroid function, recent work suggests that long-term exposure, even at lower doses, correlates with decreased manufacture of the hormone T3, as would be expected to occur based on the new work. The team warns that the perchlorate can be actively concentrated in breast milk. "This effect would have potentially serious consequences for the child's mental and physical development."
Perchlorate has been detected in drinking water in a number of countries including USA and Japan. But UK levels are not well understood and the UK National Centre for Environmental Toxicology, run by the WRc Group, has recently been awarded a contract with the Drinking Water Inspectorate /Department for Environment, Food and Rural Affairs, Defra, to survey its impact.
"Perchlorate has been detected in many drinking water sources in the USA. It has been shown to inhibit thyroid function, but the toxicological significance of the levels found in US drinking water is not clear at present and no guideline values have been set by the World Health Organization or a standard by the US Environmental Protection Agency," said Dr Paul Rumsby, Principal Toxicologist, National Centre for Environmental Toxicology.
"Perchlorate can occur naturally and in some industrial processes but the main source is thought to be from the disposal of rocket fuel. It seems unlikely that there will be significant contamination of UK drinking water, but there has been no systematic monitoring to date. In September 2007, WRc started a research project funded byDefra through the Drinking Water Inspectorate to assess the risk to English and Welsh drinking water sources based on usage and environmental behaviour. Some targeted monitoring of raw and treated drinking water will then be conducted to determine the levels of perchlorate. This monitoring is scheduled to finish in February 2009."
Perchlorate in raw and drinking water sources in England and Wales
Volume 25, Issue 4, pages 456–465 - December 2011
A well-known use of perchlorate is as a rocket fuel propellant; however, more widespread uses include in munitions and fireworks, and it also occurs naturally. Perchlorate suppresses the thyroid, which can lead to a variety of adverse effects. It is a widespread contaminant in the United States, but limited occurrence data in the United Kingdom exist, and even less for drinking water. Monitoring of 20 raw and treated drinking water sites in England and Wales, covering four seasonal periods, showed that perchlorate is a low-level background contaminant of raw and treated drinking water. Low concentrations (treated drinking water: