Bisphenol A health risk

Those that learned the facts think they can. The evidence is convincing enough for California lawmakers to consider restriction of bisphenol A use in baby bottles and containers. If enacted, it would be the first law of this kind in the U.S. Similar bills are introduced in about a dozen other states. Abroad, Canada intends to ban it as a component in baby bottles, but Europe seems to be - at least officially - at ease with it, noting that their limit to acceptable daily intake for this chemical is 1/5 of that established by the FDA.

What is it that makes bisphenol A a concern, and should it be the only one?

Bisphenol A is industrial chemical with many uses: from production of hard (polycarbonate) plastics and resins, to the protective coating inside metal food containers and dental sealants. Billions pounds of it is produced every year. Pharmacologically, it is a hormonally active agent, specifically, environmental estrogen (xenoestrogen). That means it is a compound which activates estrogen hormonal receptors, disrupting endocrine function of the body.

Since 1997, well over 100 studies and scientific research papers provided plenty of evidence that it

can adversely affect the body in a number of ways.

From endocrine system disruption, not only limited to estrogen, to recurrent miscarriage, increased susceptibility to some cancers, alteration of brain development and sexuality, or contributing to the development of insulin resistance, obesity and hypertension.

Most of the research is based on the experiments on rodents, which means not directly applicable to humans. There is no direct evidence for its effect on humans.

However, whenever a substance is found to have significant detrimental effect on rodents at concentrations close to those of human exposure, it is a warning not to be taken lightly. And bisphenol A affects rodents often at the levels significantly bellow the official EPA/FDA estimated safe exposure level - so called reference dose -  of 50 µg/kg/day. 

This is why 38 scientists, including long-time bisphenol A researchers Soto and Newbold, have joined together this past year to warn lawmakers of the potential harm to human health inflicted by this particular chemical (the statement is published in the Reproductive Toxicology journal).

The emphasis is on protection during the early development - from unborn babies in mother's womb to about 3 year olds - where the chances of harm are the highest. The research indicates that

it is during early development - particularly the fetal stage -
that the most serious damage is initiated;

health conditions caused by these hormonal, enzymatic and epigenetic alterations surface much later in life, seemingly unrelated to their actual cause - or contributing factor - bisphenol A.

The bad news, as the researchers point out, is that we already have in our bodies significantly higher concentrations of this chemical than those capable of inflicting adverse health effects in animal experiments. Recent CDC (U.S. Centers for Disease Control, Calafat et al. 2004) publication puts the current average level of bisphenol A at 2.7 nanograms/milliliter (parts per billion), or 2.7µg/liter, with 93% of over 2500 participants tested having measurable levels.

Bisphenol A half-life in the body of 5.4 hours results in 95% daily intake being disposed of. With the average daily urine output of 2 liters (2,000 milliliters), it indicates the overall intake average of 5.4µg/person/day. However, average urine concentrations for children (over 6) and adolescents was higher, 4.5µg and 3µg/L, respectively.

Children younger than 6 have not being tested, but the trend indicates that they may be having the highest bisphenol A concentration of all.

Note that your individual value for bisphenol A half-life may differ from the average, since it is mainly determined by the efficacy of your detox system - specifically, glucuronic acid pathway, whose main enzyme is zinc-dependant.

The industry was quick to point out that this is still much bellow the FDA/EPA maximum acceptable intake of 50 µg/kg/day. But how sound is this criterion? It is based on studies back in 1980s where the effect of bisphenol A on rodents - specifically weight loss - was observed at the intake level of 50mg/kg/day. No other possible effects were monitored. The FDA/EPA official "safe" level for humans, established in 1993, is arrived at after applying 1/1000 safety factor.

In the meantime, a number of studies - nearly 40 - have come up with the evidence that bisphenol A has adverse health effect on rodents in

concentrations much lower than 50mg/kg/day.

Abnormal cell growth resulted at doses 20 million times lower (Murray et al. 2001), or 2.5 nanograms/kg/day. For comparison, infants can consume up to 13 µg/kg/day of bisphenol A leaching from baby food cans and polycarbonate bottles alone - over 500 times higher exposure (it is also higher than the official acceptable exposure limit for general population in Europe). 

In vitro cellular experiments, when the cells were directly exposed to the chemical, have observed significant effects of bisphenol A

down to 0.23 ppt (parts per trillion),

more than 10,000 times lower than its average urine concentration in the general population.

And where does FDA stands on this issue? As usual, on the side of the industry. It maintains that bisphenol A is safe, and doesn't intend to re-evaluate its approval which, by the way, was based on two industry funded studies. To them, the rest of research on bisphenol A is "inconclusive", with the final argument being that we don't know what the effect on humans is without a large controlled human study.

Since no such study is going to take place in the foreseeable future, don't expect from the government to take the action and ensure that your exposure to bisphenol A is reduced to reasonably safe. Since most of your bisphenol A (BPA) exposure comes from food consumption, you can have it significantly reduced by:

• avoiding polycarbonate ("PC" or "7") plastic food and drink containers, particularly while pregnant, as well as in feeding your infant or small child (Born Free makes BPA-free plastic baby bottles)

• avoiding canned foods (some, like most Eden Foods canned products, are BPA-free)

• opt for dental sealant type not containing this chemical

Remember, it is babies in mother's womb, infants and small children that are most vulnerable.

Of course, as important is it can be, bisphenol A is only the tip of the iceberg. Many other chemicals present in foods and the environment are endocrine disruptors, or have some other adverse health effect. They include dioxins, PCBs, BHA (food additive), large number of pesticides, other plasticizers (phthalates, chemicals used in plastic production), arsenic, cadmium, lead, mercury, and so on. They have become our xenobiotic inheritance. R