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http://www.theglobeandmail.com/servlet/ArticleNews/TPStory/LAC/20051105/PLASTIC0\

5/TPScience/

 

 

Is plastic killing us? It's a chemical controversy

 

 

 

By ZOE CORMIER

 

Saturday, November 5, 2005 Page F6

 

 

Few chemicals on the planet enjoy more use than bisphenol A. We come

into contact with it every day in tin-can linings, CDs, electronics,

sports equipment, cars and baby bottles, just to name a few products.

More than six billion pounds of it are made each year.

 

However, tiny amounts of BPA can leach out and new research shows it

can get into us -- a study done this year for the U.S. Centers for

Disease Control found the chemical in 95 per cent of American urine

samples.

 

More than a hundred other studies suggest that BPA is linked to a

staggering number of health problems, including prostate and breast

cancer, obesity, attention deficit and hyperactivity disorder, brain

damage, immune suppression, lowered sperm counts and early puberty.

 

The plastics industry maintains that BPA is completely safe. But

academic and government researchers say the chemical needs to undergo

a new risk assessment. Previous assessments were done more than 15

years ago, when the technology to screen for health risks was

immature. Most of the research pointing to its potential for harm has

come out in the past five years.

 

BPA is a synthetic plasticizer used to make polycarbonates (clear,

shatter-resistant plastics), epoxy resins (coatings that line food

containers) and white dental sealants, but this is not what it was

originally intended for.

 

In 1936, British chemist Charles Edward Dodds found that BPA could

mimic estrogen, and he proposed that it be produced as a synthetic

hormone. But it was never used for that purpose because Dr. Dodds

abandoned it when he discovered the now-banned synthetic estrogen DES.

 

Scientists later found that BPA had another property -- the ability to

produce strong plastics and smooth coatings.

 

" Materials made from BPA have unique attributes, including shatter

resistance, optical clarity and chemical resistance, " says Steve

Hentges, executive director of the polycarbonate business unit of the

American Plastics Council.

 

However, the BPA molecules are bound by " ester bonds, " which can be

disrupted by heat and by acidic or basic conditions to release the

chemical.

 

This has prompted many researchers to worry that the chemical may pose

a risk to human health.

 

Any hormone can harm you if you receive too much of it, and estrogen

is no exception. It normally stimulates cells to grow and divide,

making it integral to the development of the sex organs. But too much

of it can cause cell division to spiral out of control.

 

For this reason, estrogen-only hormone-replacement therapy may

increase a woman's chances of developing breast cancer. Estrogen

overload can also lead to lowered sperm counts, malformed testicles

and penises, prostate cancer and a host of other problems.

 

Although it is well established that BPA can bind to the body's

natural estrogen receptors, the plastics industry contends that

exposure to the chemical through food poses no threat.

 

" In the intestine and liver, BPA is completely metabolized into

BPA-glucuronide, a different form of BPA that is not estrogenic, " Dr.

Hentges says. " Essentially, none of the estrogenic compound reaches

the blood. "

 

However, research by Ana Soto, a Tufts University professor who has

spent the past decade studying BPA, suggests otherwise. In 2002, she

conducted a study in which the chemical was attached to radioactive

labels in order to see where it went when given to mice. " We found

unchanged BPA and BPA-glucuronide in the fetuses, " Dr. Soto wrote.

" This shows that BPA was able to cross the placenta. "

 

Fetal development is of greatest concern to those worried about BPA.

Embryos have not yet developed their adult detoxification systems so

they are much more vulnerable to chemical pollutants. (This explains

why a woman eating mercury-contaminated fish can give birth to a

deformed fetus, yet remain healthy herself.)

 

Many studies have found adverse effects from prenatal exposure to BPA.

 

Male mice can develop prostate cancer and females breast cancer. Mice

also can grow into larger animals (suggesting a link to the rise in

obesity) and tend to be hyperactive and slow to learn (implying a link

to ADHD in children).

 

The chemical has also been shown in mice to lower sperm quality, cause

brain damage, alter the immune system, lead to early puberty in

females and damage chromosomes.

 

However, Dr. Hentges plays down the studies. " The level of BPA that

causes adverse effects in lab animals is more than millions of times

higher than what people are typically exposed to -- there's a huge

margin of safety, " he says.

 

A number of studies have found the typical concentration of BPA in

human urine to be in the part-per-billion range. However, many

experiments in lab animals have documented effects in the part-per-

trillion range.

 

" But that's not totally surprising, given that that's the level where

hormones have effects, " says Frederick vom Saal, a biologist who

researches BPA at the University of Missouri.

 

In a recent paper in the journal Environmental Health Perspectives,

Dr. vom Saal compared studies on BPA that were funded by industry, all

11 of which found no effect, with studies funded by governments, of

which 94 out of 104 documented harmful effects. " The chances of 100

per cent of industry studies being negative, and over 90 per cent of

government studies being positive is about one in two billion, " he said.

 

Although few studies have been done on humans, ones conducted in Japan

have suggested that women with high levels of BPA in their blood are

more likely to experience frequent miscarriages and to suffer from

polycystic ovaries.

 

Given the animal studies, some scientists are calling on federal

regulatory agencies to perform new risk assessments on BPA.

 

Health Canada is re-evaluating all 23,000 chemicals in use in this

country, but the work is not expected to be complete by 2006. The U.S.

Environmental Protection Agency has not performed a risk assessment on

BPA since 1988 (when estrogenicity was not even considered), and has

no current plans to re-evaluate it.

 

Zoe Cormier is a former science editor of The Varsity at the

University of Toronto.

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