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Study shows potential dangers of BPA

A chemical found in many common products, including plastic bottles and canned food linings, is linked in a new study to thyroid hormone changes in pregnant women and baby boys.

The findings raise concerns because thyroid hormones play a crucial role in growth and brain development in young children, health experts note.

The study by University of California Berkeley researchers is the first to analyze the effect of bisphenol A, or BPA, on thyroid hormone levels in pregnant women and newborns.

BPA has drawn increased scrutiny in recent years as the public has become aware of how easy it is to be exposed to the estrogen-like compound and how little is known about the health effects.

In July, the U.S. Food and Drug Administration prohibiting the chemical in baby bottles and cups. Many manufacturers had already begun phasing out BPA in such products.

The UC Berkeley researchers analyzed BPA levels in urine samples taken from 335 women.

Most of the women and their newborns had normal thyroid hormone levels.

But for each doubling of BPA levels in some women, researchers found a corresponding decrease in one type of thyroid hormone known as T4.

They then looked at thyroid hormone levels in newborns and found the exact opposite effect -- the higher the BPA level in the mother, the greater the signs of a more active thyroid in their baby boys.

The American Chemistry Council maintains that the weight of scientific evidence thus far is that BPA is safe. The organization also notes that BPA does not accumulate and is rapidly eliminated from the body.

If pregnant women are concerned, however, Kim Harley of UC Berkeley's Center for Environmental Research and Children's Health notes that there are ways to reduce exposure, including buying plastic bottles that are labeled BPA free, consuming less items that come in cans, and washing their hands before eating if they touch a receipt.



Notes and Vocabulary
lining n.
/ˈlaɪnɪŋ/
a substance or material that covers the inside of part of the body;
material that covers the inner surface of something  

thyroid n.甲狀腺的
/ˈθaɪˌroɪd/
an organ in your neck that produces substances that affect the way your body grows and the way you behave

hormone n.
a natural substance that is produced in the body and that influences the way the body grows or develops

bisphenol A
Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics and epoxy resins.

scrutiny n. to look at something closer
/ˈskru:təni/
the act of carefully examining something especially in a critical way : the act of scrutinizing something [noncount]

estrogen n. 雌(甾)激素
/ˈɛstrəʤən,/
a substance (called a hormone) that occurs naturally in women 

phase out [phrasal verb]
/ˈfeɪz/
phase (something) out or phase out (something) :
to stop using, making, or doing (something) gradually over a period of time

metabolism n.
/məˈtæbəˌlɪzəm/
the chemical processes by which food is changed into energy in your body:

Discussion Questions
- Are you concerned about BPA levels? Why or why not?

- What Is a Normal T4 Thyroid Level?
The thyroid is the gland in your body that regulates metabolism. It produces two hormones--T4 and T3. The normal reading for the Total T4 is considered to be between 4 and 11. However, the T4 level alone does not indicate whether you have a thyroid problem. The test must be combined with a test for TSH (thyroid stimulating hormone)

- What Is T4?
T4 is a thyroid hormone that has four iodine units. Iodine is used by the thyroid in production of thyroid hormone and is ingested through the foods we eat. There is more T4 in your body than T3, but it is T3 that is the active hormone.


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