Where BPA ban came from

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BISPHENOL A

Yeast testing gave rise to health concerns

Accidental discovery in the early 1990s led to efforts to test the

chemical's safety MARTIN MITTELSTAEDT, ENVIRONMENT REPORTER

April 17, 2008

Like many of the most fascinating discoveries in science, the

possibility that bisphenol A might present a health problem emerged

completely by accident.

In the early 1990s, researchers at Stanford University School of

Medicine in California were investigating yeast to see whether it had

a primitive estrogen receptor, and were finding something wonky going

on in their laboratory. When they ran their yeast experiments, they

noted that some unknown substance was acting just like estrogen - a

main female hormone in humans - and was interfering with their tests.

They eventually published a paper in the journal Endocrinology in 1993

alerting other researchers that a synthetic chemical able to mimic

estrogen was leaching into water they were using - water that had been

stored in polycarbonate plastic flasks subjected to autoclaving, or

high-temperature heating. Using nuclear magnetic resonance

spectroscopy and other sophisticated techniques, they identified the

substance as bisphenol A, or BPA.

Although they found that BPA was far less potent than natural female

hormones in their experiments, the scientists issued a warning and a

challenge to other researchers.

" Our findings raise the possibility that unsuspected estrogenic

activity in the form of BPA may have an impact on experiments

employing media autoclaved in polycarbonate flasks. It remains to be

determined whether BPA derived from consumer products manufactured

from polycarbonate could significantly contribute to the pool of

estrogenic substances in the environment, " said the paper, whose lead

author was Feldman, a Stanford medicine professor.

This serendipitous discovery triggered the start of efforts to test

the safety of BPA. Fifteen years later, it is having stunning

resonance in Canada, as retailers rush to remove polycarbonate plastic

water bottles from their shelves and many parents revert to using

glass again for baby bottles.

Canada is poised to become the first country to take strong action on

BPA, by placing it on the country's list of toxic substances. Such a

designation would allow Health Canada or Environment Canada to take

actions to control use of the chemical for either human-health reasons

or to protect the environment.

Bisphenol A is one of the most widely used synthetic substances in the

world, with industry able to make about three billion kilograms a

year. There are no domestic BPA manufacturing plants; Canadian

companies that use the chemical import it.

Derived from petroleum, BPA was first identified around 1900 and

tested in the 1930s during the initial search for estrogen-like drugs.

The chemical would likely have languished in obscurity had it not been

for a discovery in the 1950s made independently by chemists in the

United States and Germany: that BPA could be used as the starting

material for polycarbonate, a remarkably durable, lightweight plastic

that resembles glass.

Although BPA is now in hundreds of products, from the plastic lenses

of glasses to the coverings of compact discs and DVDs, the uses that

have caused controversy are those, such as plastic baby bottles or the

lacquer linings inside tin cans, that allow it to come into contact

with food and beverages.

Under normal conditions, such as the heating of a tin can to sterilize

its contents, or high-temperature washing of plastic, trace amounts of

BPA are able to leach into the foods or drinks, and ultimately into

the people who consume them.

The amount leaking from containers is vanishingly small, typically in

the low parts per billion. One part per billion is equivalent to only

one second of elapsed time over a 32-year period, and until scientists

began investigating hormones and chemicals that act like them, this

was thought to be such a minute quantity that it couldn't possibly

have any biological effect.

However, some hormones, such as estrogen, are active in far lower,

parts per trillion, concentrations, and dozens of studies by

independent researchers have found that low doses of BPA have dramatic

impacts in animal experiments.

These studies have shown the chemical has effects such as increasing

the number of mammary ducts in rodents, as well as boosting the size

of prostates, particularly for trace exposures during fetal

development and early in life.

These findings, which began emerging in the late 1990s, prompted

worries the chemical could be linked to conditions such as cancer, the

earlier onset of puberty in girls, declining sperm counts and other

problems connected to hormone imbalances.

The Dose Debate

There has been worldwide interest in bisphenol A, but to date no major

regulator has taken strong action against the chemical.

The U.S. Food and Drug Administration has approved the use of BPA, as

has the European Food Safety Authority. Both have based their

decisions mainly on research funded by the chemical industry that has

found bisphenol A doesn't cause health problems in animals at low

doses, although it does at high exposures.

Contradicting these findings are a large number of studies, conducted

by independent scientists, that have found the chemical affects the

prostate, the mammary gland and brain development at tiny doses

similar to what humans are exposed to through consumer products,

particularly at key points during fetal development.

About 90 per cent of studies by independent scientists have detected

some adverse effects at low doses, according to a running tally

compiled by Frederick vom Saal, a researcher at the University of

Missouri.

Critics of BPA say one of the difficulties figuring out what to do

with the chemical is that hormonally active substances such as

bisphenol A, which mimics estrogen, present a special challenge for

scientists used to traditional toxicology studies.

The mantra among toxicologists is that " the dose makes the poison. " In

other words, the more of a dangerous substance people or animals are

exposed to, the more adverse effects will be observed - the way a

two-pack-a-day smoker faces more risk of lung cancer than a

one-pack-a-day user. Under this principle, extremely low doses are

assumed to pose very low or non-existent risks.

But hormonally active chemicals don't follow this commonsense rule and

exert their influence at the minute amounts typical of natural

hormones. Paradoxically, hormones can have more pronounced effects at

low doses than at high ones.

" Why did traditional toxicology miss the effects of bisphenol A for so

long? It turns out it's because ... it follows non-traditional dose

response curves, " said Pete Myers of Environmental Health Sciences, a

U.S.-based advocacy group. Mittelstaedt

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