医師の一分

アクセスカウンタ

zoom RSS 過塩素酸による母乳汚染

<<   作成日時 : 2007/12/10 21:26   >>

なるほど(納得、参考になった、ヘー) ブログ気持玉 1 / トラックバック 0 / コメント 0

画像 過塩素酸塩という化学物質が母乳に濃縮され、飲んだ乳児の認知・運動発達に障害をもたらすということがわかった。
 1940年代以降、爆発物やロケット燃料を製造するために使われ、飲食物が広範囲に汚染されている。
 乳児の甲状腺ホルモン産生能力に影響を及ぼすと推測されている。さらに、母親のヨードを乳児に渡す量を減少させている可能性もある。甲状腺ホルモンは中枢神経系、骨格筋、肺の発育と成熟にとって極めて重要で必須のものである。
 マウスの研究で、過塩素酸塩は乳腺に輸送されるヨウ化物の量を制限することがわかった。以前の研究で、母乳に蓄積されることがわかっていたが、アクティブに乳児に移行するとは思われていなかった。
--------------------------------------
Environmental Toxin Collects in Breast Milk
Perchlorate can then be passed on to nursing infants, rat study shows
By Carolyn Colwell, HealthDay Reporter
http://health.msn.com/nutrition/articlepage.aspx?cp-documentid=100183250
画像Perchlorate can then be passed on to nursing infants, rat study shows.

FRIDAY, Dec. 7 (HealthDay News) -- Scientists have discovered the mechanism by which a chemical known as perchlorate can collect in breast milk and cause cognitive and motor deficits in newborns.

Used since the 1940s to manufacture explosives and rocket fuel, the contaminant is still widely present in the water and food supply, experts say.

And high concentrations of perchlorate in breast milk can be passed to an infant and affect it's ability to manufacture essential thyroid hormone, the new study suggests. Perchlorate can also lessen the amount of iodide available to a mother to pass on to her infant, and a baby needs iodide to produce thyroid hormones.

"The deficit of thyroid hormone is particularly delicate if it's at the beginning of life because the central nervous system has not completely matured," said study author Dr. Nancy Carrasco, a professor of molecular pharmacology at Albert Einstein College of Medicine, in New York City.

Thyroid hormones are "absolutely critical" for the development and maturation of the central nervous system, skeletal muscles and lungs, she explained.

In laboratory and rat research, Carrasco's team found that perchlorate limited the amount of iodide transported to a mother's mammary glands. The only source of iodide a baby typically has is mother's milk, she explained.

Her team discovered that perchlorate accumulates in mother's milk, but before this study, "we didn't know it would be passed on as actively to the baby," she said.

Carrasco and her colleagues at Einstein and at Johns Hopkins University reached this conclusion after experimental studies on how sodium iodide carries perchlorate to, and concentrates it in, mammary glands.

The next steps in this research will include animal studies looking at the effects of perchlorate exposure during pregnancy, she said.

The debate continues on how much perchlorate is a high and harmful concentration, Carrasco said. But scientists have long known that iodide deficiency contributes to lowered IQ.

The new finding is relevant to the Environmental Protection Agency's standards for acceptable perchlorate levels, added R. Thomas Zoeller, a professor of biology at the University of Massachusetts-Amherst who has served on the EPA's peer review panels for the assessment of perchlorate.

At the time the current safety standards were established, the EPA was not thinking about how perchlorate is concentrated in breast milk, he said.

Zoeller said the study's discovery of how perchlorate is transported to breast milk is important to setting safety standards because perchlorate has a half-life of about eight hours and doesn't accumulate in the body. But because of the new findings, "we no longer have to debate whether perchlorate is being concentrated in milk," he added. "We have enough data to know that this is a very dangerous thing."

Large studies need to be done to confirm the findings, Zoeller added.

It's now "enormously important to find out if perchlorate in [breast] milk is affecting thyroid hormones in infants," he said. Such a study would be difficult to conduct because it would involve drawing blood from 1- and 2-week old infants, Zoeller said.

Tyrone Hayes, a professor of integrative biology at the University of California at Berkeley, said the discovery of a mechanism by which perchlorate can be transmitted to nursing infants is important.

"I think probably the most obvious significance is that we have a very common contaminant in the environment that has a profound negative impact, and that the most profound impact is on humans that don't have a choice at a critical development stage that can impact the rest of their lives," he said.

More information

The Environmental Protection Agency has more on perchlorate.

テーマ

関連テーマ 一覧


月別リンク

ブログ気持玉

クリックして気持ちを伝えよう!
ログインしてクリックすれば、自分のブログへのリンクが付きます。
→ログインへ
気持玉数 : 1
なるほど(納得、参考になった、ヘー)

トラックバック(0件)

タイトル (本文) ブログ名/日時

トラックバック用URL help


自分のブログにトラックバック記事作成(会員用) help

タイトル
本 文

コメント(0件)

内 容 ニックネーム/日時

コメントする help

ニックネーム
本 文
過塩素酸による母乳汚染 医師の一分/BIGLOBEウェブリブログ
文字サイズ:       閉じる