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Low levels of pollutant won’t harm

Environment: Study on early pregnant women shows small amounts of perchlorate has no thyroid effect

Posted: March 31, 2011 1:55 a.m.
Updated: March 31, 2011 1:55 a.m.
 

Pregnant women in the Santa Clarita Valley need not worry about extremely low levels of perchlorate adversely affecting them or their unborn children, a Boston study examining four world cities concludes.

Perchlorate, a toxic salt, has been known to disrupt the functioning of the thyroid gland.

Despite the recent study, local officials who have been grappling with the cleanup of the Whittaker-Bermite property at the center of the city for decades, were nonplussed. They will continue to remove the salt from the soil at the 996-acre site as well as from the groundwater it has seeped into.

Endocrinologist Elizabeth N. Pearce works at the Boston University School of Medicine, researching nutrition.

She and other researchers spent three years studying the effects of perchlorate on 134 pregnant women in Los Angeles and 107 in Cordoba, Argentina. The women were all in their first trimester.

This study confirms the results of a previous study involving larger groups of pregnant women in Wales and Italy. That study, released last year, also found no adverse effects from consuming low levels of perchlorate.

The follow-up study, The Effect of Environmental Perchlorate on Thyroid Function in Pregnant Women from Cordoba, Argentina, and Los Angeles, California, was published online last month.

“We did not see any effects on thyroid hormone production,” Pearce said Wednesday. “These results are very reassuring. If we found any adverse effects that would have been a concern, but we did not see that.”

In testing the urine of the women studied, Pearce and her team found levels of iodine and perchlorate, indicating that perchlorate does not affect the thyroid processing of iodine.

She concluded: “No effect of environmental perchlorate on thyroid function was observed in first trimester pregnant women residing in Cordoba, Argentina and Los Angeles, California.”

Thyroid hormone
Perchlorate stands in the way of the body’s natural ability to absorb and process small amounts of iodine, which the human body needs. But Pearce and her team wanted to find out if extremely low levels of perchlorate adversely affect fetal development.

The short answer is, “no.”

The U.S. Food and Nutrition Board and Institute of Medicine both recommend a daily allowance of iodine from 150 micrograms per day for adults, and 290 micrograms a day for lactating mothers.

Pearce also looked at the effect of tiny perchlorate amounts in breast-feeding infants, and found no harmful consequence.

Small amounts of iodine are essential in the normal brain development of a fetus in its first trimester. The thyroid, found in the neck, processes iodine and regulates metabolism.

Perchlorate is a naturally-occurring salt that, by its composition, contains four oxygen atoms.

High doses of perchlorate are harmful since they can adversely affect thyroid hormone production.

What level is safe?
The Environmental Protection Agency hasn’t yet set a national limit on perchlorate. A state department handling perchlorate cleanup sets a maximum limit for perchlorate in surface water of 6 parts per billion, according to one state official monitoring toxic substances.

According to the Pearce study, levels of perchlorate in urine measuring 7.8 micrograms per liter — a median calculation for the Los Angeles group — are safe for pregnant mothers and their unborn children.

One microgram is equal to 1 part per billion.

High levels of perchlorate — considered levels above 245 parts per billion — can temporarily effect the thyroid’s ability to absorb iodide from the bloodstream, according to the National Academy of Sciences.

Although no safety threshold has been established for a child’s exposure to perchlorate, the EPA adopted a limit of 24.5 ppb, a tenfold reduction of the 245 ppb limit allowed for adults.

The limit for contaminated soil to a depth of 10 feet is 500 ppb.

The health concerns of perchlorate has remained a priority for local civic leaders, given the Whittaker-Bermite property, which tested weapons, exploded dynamite and expended rocket fuel from before World War II until 1987.

Land cleanup
Munitions companies made munitions and exploded rocket fuel on the property.

In the 1980s, Whittaker-Bermite filed cleanup plans and in 1992, officials from the Department of Toxic Substances Control have monitored the Whittaker Corp.’s cleanup effort since the 1980s.
Whittaker has excavated one of the seven contaminated areas and is expected to start excavating five other areas this summer.

Jose Diaz, the department’s Senior Project Manager for the site, said perchlorate is one of the main reasons for the excavation.

“That’s why we’re cleaning it up,” he said. “The idea is to go after hot spots as much as we can.”

His department recently cleaned the first segment identified in the cleanup plan, known as Operable Unit 1, or OU-1.
“We hope to start excavating on areas OU-2 through OU-6 by the start of summer,” he said. Those operable units are of the surface area. The seventh unit is the soil underneath. It will be cleaned up later.

One of the “hot spots” uncovered by the department had soil containing 60,000 parts per billion.

“Our interpretation of perchlorate is the textbook definition,” he said. “I’m not a doctor. All I know is that perchlorate interferes with the ability of the thyroid gland to process iodine.”

Water cleanup
In the fall, Castaic Lake Water Agency officials began their own perchlorate treatment of groundwater at two wells.

Agency General Manager Dan Masnada said the “pump and treat” program will likely continue for a “number of decades before the contaminant plume is completely cleaned up.”

Continuous pumping and treatment of the contaminated water from the two wells — part of a $32 million cleanup project — serves two purposes, he explained.

For one, the pumping and treatment restores well capacity that was lost when four other wells were shut down in 1997, Masnada said.

Second, pumping slows the perchlorate plume from spreading out further, and contaminating other wells, he said.

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