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Tue 10 Jun 2008 05:11 PM

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Babies,bottles and Bisphenol A

Child health agencies have issued warnings about it; the FDA is reviewing its policy on it; and headlines worldwide have condemned it. What's the big deal with BPA?

Child health agencies have issued warnings about it; the FDA is reviewing its policy on it; and headlines worldwide have condemned it. What's the big deal with BPA?

My 11-month-old daughter loves her baby bottles and sippy cups (writes Rebecca Roberts). But as I sit and watch her drink from them, I cringe, because I happen to be a scientist who studies a chemical found in those bottles and cups.

I also know that some scientific research suggests that exposure to that compound, bisphenol A (BPA), is detrimental to good health - something I can't help but think about as I watch my daughter use her cup as a teething ring.

As a scientist, I depend on evidence, logic, and imagination to explain observations made in the laboratory. As a mother, I strive to raise a healthy and happy child. In both of my roles, I depend on evidence-based information.

But, like all people, I am not qualified, nor do I have the time, to understand all scientific issues. I must rely on others - on the brokers of information: other scientists, medical personnel, the government, regulatory agencies and the media, to name a few.

The purveyors of information are not necessarily as objective, however, as my scientific self would like them to be - influenced as they are by timing, money, convenience, politics, and countless other agendas.

I can only hope that the "facts" I receive are objective. Moreover, I hope that any regulations stemming from this science are established for the benefit of my family and society as a whole. But how is the information regarding the effect of BPA on human health being packaged and communicated to the general public?

Chain reaction

In 1952, chemists working with BPA discovered that it could help form a hard, clear plastic called polycarbonate. Polycarbonates make such products as compact discs, sunglasses, bicycle helmets, water and milk bottles and baby bottles, and some medical devices such as incubators, dialysis machines, and blood oxygenators.

BPA is also used to make certain resins that are commonly found in the linings of food cans to prevent corrosion, and it is present in some polyvinyl chloride (PVC) plastic products. BPA ranks among the highest-volume chemicals manufactured worldwide, with an annual production in 2003 of about 13 billion kilograms.

Regulation requiring a significant reduction in BPA use could have a dramatic economic impact and would likely require some changes in personal lifestyle.

BPA has been shown to leach from water bottles and food cans into the packaged foodstuffs. It then enters the body through the digestive tract when those foods are consumed.

The level of BPA released from plastic depends on the age and wear of the plastic and on exposure to heat. For example, one study showed that small levels of BPA leached from baby bottles subjected to simulated normal uses, including boiling, washing with a bottle brush, and dishwashing.

Plastic tableware was also found to release BPA into hot vegetable soup. Older, worn bottles and bowls released BPA more readily than newer products.

A survey by the Centers for Disease Control and Prevention found that approximately 95% of Americans have detectable levels of BPA in their bodies.

Naturally, the prevalence of human exposure leads to questions about safety and health. Although the plastic industry continues to assert that BPA is safe, the chemical's endocrine-disrupting properties raise concern about its potential to cause harm.

BPA exposure affects the hormonal system, in particular, the pathway involving oestrogen. In adult male mice and rats, effects of BPA exposure - abnormal sperm and reduced fertility - were reversed when exposure stopped.

Of the few human epidemiological studies, one revealed a relationship between BPA exposure and repeated miscarriage. Additionally, BPA causes a human breast cancer cell line to proliferate, indicating that oestrogen-sensitive tissues and cells in the body may react similarly.

Many animal studies focus on the effect of BPA exposure during fetal development, when cells and tissues are especially susceptible to hormonal alterations.

Not only does BPA disrupt proper functioning of the placenta during gestation, but it causes many deleterious health effects in offspring exposed in utero, including enlarged prostates, malformed urethra, and a higher risk of prostate cancer in male offspring, and genital tract alterations and earlier puberty in female offspring.

Exposure also affects brain development, causing behavioural differences between males and females to be lost in offspring exposed in the uterus.

A similar correlation to human development is plausible. BPA has been found in the bloodstream, placenta, cord blood, and fetal blood of humans at levels that are within the range studied in many of the animal models.

Hazardous substance

Although BPA was not used in plastics manufacturing until the 1950s, its hormonal activity was reported in 1936. For decades, products containing BPA were shown not to release the compound, and thus these products were deemed safe. In 1999, however, scientific techniques progressed such that very small levels of BPA could finally be measured accurately.

Levels as low as parts per billion (ppb) are now routinely detected in the laboratory. Unfortunately, the ability to detect such low levels in a laboratory environment is often not good enough, since tissues and cells can respond to levels of BPA that are 100 times lower.

The first such study showing a detrimental effect of BPA at very low doses was published in 1997, and since then, over 100 other studies have been published.

Let's step back a moment and consider the roles of United States regulatory agencies such as the FDA and the EPA in determining the "safe" human exposure level for a chemical. Founded in 1970, the EPA is charged with determining the safe human exposure level for chemicals.

Since taking on this daunting task of monitoring the roughly 75,000 chemicals produced in or imported into the US, the EPA has taken action to reduce the risk of over 3,600 chemicals but has banned or limited the production or use of only five.

Currently, the EPA lists the "safe level" for BPA as being 50 micrograms (or 0.00005 grams) of BPA per kilogram of body weight per day.

At this point, you might be wondering why this is the first time you've ever heard of BPA. The information is out there but it is a puzzle to get through. Early studies indicated that BPA did not leach, or leached in very small amounts, from plastic products, including baby bottles.

However, since 1999 many studies have shown that BPA leaches from products at levels known to cause health effects in animals. Earlier studies on BPA exposure also tended to find little resulting adverse health effects, yet these studies were often using doses that were higher than those now regarded as being in an environmentally relevant range.

These were the main studies initially used by the EPA to determine the "safe" level of BPA exposure and that are often referenced to attest to the safety of BPA.

Chemicals and controversy

This ambiguity means findings can be obscured by those who inform the public. As a result, the media presents a confusing and unclear picture of the health risks of BPA exposure by giving equal weight to statements from independent scientists and those working for industry.

The resulting influence of this ambiguity was recently revealed in the spring of 2006 when US state legislators in California, Maryland, and Minnesota attempted to pass legislation that would ban the use of BPA in products aimed at children. None of them passed.

The bills focused on children because they are far more susceptible to adverse affects from chemical exposures than adults, even at very low doses. Moreover, children are more likely to be exposed to BPA orally because of their need to put things in their mouth - a purpose for which some BPA-containing products, such as some baby bottles and teething rings, are specifically designed.

The California bill (AB319) was introduced in February 2005, making it the first such legislation to be introduced in any state. It called for any BPA-containing products, including toys or childcare articles, intended for use by a child three years old or younger to be prohibited in the state.

Violators of the ban would face civil action, carried out by the Attorney General, and penalties of no less then US$10,000 for each day of violation.

The bill was energetically opposed by stakeholders in the chemical, plastics, baby products, and grocery industries. Under the umbrella organization Coalition for Consumer Choice, the NoAB319 campaign successfully fought the bill both in the media and in the Assembly hearing.

In a news release by NoAB319, Steve Hentges, executive director of the Polycarbonate Business Unit of the American Plastics Council, stated that the legislation was; "founded on insubstantial claims and unproven hypotheses that lack scientific rigor."

At a more local level, the first legislation to ban BPA from products aimed at children passed in the city of San Francisco. The "Stop Toxic Toys" bill was virtually identical to AB319 and was signed into law on June 16, 2006.

However, in April 2007, the clause limiting BPA in child-aimed products was repealed pending action at the state level. As a result, no action on BPA-containing products could occur in the city until January 2008, and only then if the state has not taken appropriate actions to reduce its use at the state level.

At the national level, the White House disputes the "low-dose theory" and has proposed funding cuts for EPA research on endocrine-disrupting chemicals such as BPA; however, the US Congress has maintained the funding level.

Currently, both the EPA and the European Food Safety Authority (EFSA) have set the "safe" level of exposure to BPA to 0.00005 grams per kilogram of body weight per day.

Although difficult to estimate accurately, humans are typically exposed to about 0.000001 grams of BPA per kilogram of body weight per day. This is 50 times lower than the EPA- and EFSA-deemed "safe" limit.

Unfortunately, this level of exposure is still significantly higher than the low doses that some studies have shown to cause adverse health effects. Moreover, the levels of BPA found by the Center for Disease Control and Prevention to be present in the bodies of Americans appear to be too high to be explained by exposure to known sources of BPA.

Policy review

There is a clear need for further health studies on BPA exposure and for regulatory agencies to continue to monitor the science behind the politics. In the meantime, what is the scientist-mother to do?

I have switched my brand of sippy cups to one that doesn't contain BPA (a quick internet search will yield many sites describing these and other BPA-free baby products).

Nevertheless, while I feel proactive as I watch my daughter happily drink her water, I still cringe a little bit when she drops the sippy cup, toddles over to her toy bin, and starts to gnaw on her plastic turtle instead.

2007 Quitmeyer and Roberts. First published online by journal PLoS Biology.

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