Bisphenol A, or BPA, is a synthetic compound used to make plastic and epoxy resins. It is used to make plastic bottles and can lining. BPA tends to leak from the plastic and can lining into the liquid or food. BPA is very controversial because it is a synthetic estrogen linked to increased risks of birth defects, cancers, developmental disabilities, obesity and neurological problems. It has been shown to cause abnormal sexual effects in certain animals like in the case of exposed alligators that affected their egg quality and caused a decrease in the penis size of the males. But does BPA pose a real danger to humans?
How BPA disrupts the endocrine system
BPA is a non steroidal estrogen capable of mimicking, enhancing, or inhibiting the activity of endogenous estrogens (1). BPA also disrupts functioning of the thyroid hormone, affects the androgen system, influences the immune system and has diverse influences on the functioning of the central nervous system (1).
Products made with BPA
BPA is used in medical equipment, consumer electronics, eyeglass lenses, sports safety equipment, water pipes, toys in production of polycarbonate plastics and used to line metal cans (2). BPA can be found and measured in human serum, urine, amniotic fluid, placental tissue, umbilical cord blood and blood (2). The most well known BPA containing product is probably metal cans. Many companies are researching alternatives to BPA cans but finding a substance that is heat stable and that does not leach out into the can is proving to be very difficult.
BPA in glass versus plastic bottles
It was found that plastic bottles had higher estrogenic activity than glass bottles from the same water source (3). The average estrogenic activity of water in glass bottles was 1.48 while the same sourced water in plastic bottles had estrogenic activity of 4.68 (3). BPA is commonly found in baby bottles so be careful in when choosing a bottle.
BPA exposure in fetuses
BPA has been found in amniotic fluid and placental tissue. One study found BPA levels in amniotic fluid to reach 8.3 ng/mL at 15 weeks of pregnancy and an average of 1.1 ng/mL during late pregnancy (2). It has been suggested that BPA may accumulate in fetuses because their organs are still too immature to clear the BPA. Measurement in placental tissue found BPA levels to be 11.2 ng per gram of tissue with an upper range of 104.9 ng per gram of tissue (2). If accurate these levels are even higher than the levels found in the blood of adults.
BPA in breast milk
BPA has commonly been found in breast milk. One study of 23 healthy women found BPA concentrations of 0.28-0.97 ng/mL in breast milk (4). Another study detected free BPA in 60% of the breast milk samples and total BPA in 90% of the samples with a median levels of 1.1 ng/mL (5).
BPA in human urine
A study of 394 American adults found traces of BPA in 95% of the urine samples (6). This study found the average amounts of BPA in the urine of males to be 1.63 ng/mL and females 1.12 ng/mL. Another study found BPA in the urine of 95% of the female subjects (7). It has been estimated that the daily intake of BPA is about 0.6-71.4 ug/day (8).
BPA levels around the globe
One study measured the BPA in the urine from various countries in Asia and Europe (9). They found BPA in the urine of 94.3% of all people studied. The average concentration from all the countries was 1.20 ng/mL with Kuwait having the highest levels (3.05 ng/mL) and Japan having the lowest (0.95 ng/mL).
BPA levels in can lining
BPA has been shown to leach into food when the container is heated, as in the case with plastic Tupperware that is safe to microwave. BPA was also found in plastic stretch film used in food containers. A study found that 4 out of 5 stretch film wrappers contained BPA levels ranging from 43 to 483 mg/kg of film (10).
To protect the inside of cans from rust and corrosion companies line the can with epoxy resins. Canned food is heated to sterilize and prevent its contents from spoiling. When the can is heated to 100 C, the BPA concentration in the water increases 1.7-55.4 times more than the unheated concentration (11)
BPA levels of the most commonly bought cans in the US
BPA was detected in 71 of 78 canned food samples from this survey (12). Canned green beans had some of the highest levels, ranging from 22 to 730 ng/g depending on the brand and imported refried beans (one of my favorite foods, especially Ducal from Guatemala) ranged from 6.3 to 790 ng/g depending on the brand. Canned fruit had the lowest concentrations of BPA with six of fourteen cans showing no detectable BPA. These low levels are most likely from the manufacturers of fruit cans using tin instead of epoxy film lining. Generally the solid food in the cans contained higher levels of BPA than the liquid in the cans.
DES- synthetic estrogen and cancer risk
DES was a synthetic estrogen developed in 1940 as a drug to prevent premature labor, miscarriage, and related complications of pregnancy (13). In 1971 researchers found that the use of DES was associated with a rare type of cancer called clear cell adenocarcinoma, which affects the cervix and vagina. After this finding the FDA told doctors to no longer prescribe this medication. DES is an endocrine disrupting chemical that negatively affects the endocrine system leading to birth defects, cancer and other developmental abnormalities. Research has shown that endocrine disrupting chemicals have the largest impact on developing fetuses.
Males exposed to DES in the womb urogenital tract developed abnormalities such as epidydimal cysts, hypospadias, and hypoplatic testes compared to those not exposed (30% compared to 8%) (14)
High intake of contaminated fish and developmental problems in offspring
In the 1970s health problems were observed in fish from the Great Lakes region that had been contaminated with PCB’s (PCB’s cause cancer and are used in automobile coolant). Researchers measured the blood levels of PCB’s in healthy pregnant mothers (15). Within 2 years of birth there were significant delays in neurological and neuromuscular development observed in the children from mothers who ate the most PCB contaminated fish. At four years of age children from mothers who had the highest levels of PCB at birth showed short term memory problems compared to other children. At 11 years of age these same children showed significantly reduced academic skills and a slightly lower IQ.
Why BPA leeches from products
BPA molecules are linked together by bonds (ester bonds) that are subject to breaking apart with the addition of water molecules which is accelerated by an increase in temperature or when coming into contact with an acid or base (16). This means that the canning of an acidic food (tomatoes), a basic food (certain fruits and vegetables), the heating of canned foods to sterilize them, the washing of plastic with hot water and leaving your plastic in the sun can all cause BPA to leach out.
Scientists determined the levels of free circulating estradiol that were active during normal development (16). They then figured out how much of an increase in free circulating estradiol was needed to disrupt development of the male reproductive system. With this information they determined the dose of BPA that would cause the same type of developmental effects in the system.
It was found that the estradiol concentration during development of the male urine reproductive tract was 0.21 pg/mL in fetal serum and that an increase of only 0.10 pg/mL (0.31 pg/mL) in free estradiol was enough to cause developmental changes (an increase in the number and hyperplasia of prostate gland ducts) and permanent enlargement of the prostate and upregulation of prostatic androgen receptors in the resulting adults for months after exposure. This shows that introduction of an endocrine disruptor at a level of only 0.10 pg/mL may be enough to be biologically active
BPA from non food sources
Besides through food there are other ways to be exposed to BPA. Free BPA is found in carbonless copy paper and thermal paper. Examples of products printed on thermal paper include receipts, labels, airline tickets and cinema tickets. One study found 8-17 g/kg of BPA on 11 of 13 thermal printing papers. Touching the thermal paper receipt with a bare hand resulted in the transfer of 1 μg BPA which was still on the finger 2 hours after exposure. Newspapers, napkins and toilet paper also become contaminated with BPA during the recycling process. BPA can be transferred through the skin into the body.
The effects of BPA in Green Monkeys
Since this study uses monkeys which is the closest thing we can get to humans without using humans (aside from chimps and bonobos) I will talk about it in some detail. The most important part of the study was that researchers used BPA levels that are considered safe for humans to take daily. The researchers used female monkeys that had their ovaries removed (this was done since ovaries produce estrogen and it would be easier to measure the effects of BPA if they were the only estrogens in the bodies).
Researchers found that BPA completely eliminates the synaptogenic response to estradiol (17). Why is this important? As remodeling of spine synapses in the brain may play a vital role in cognition and mood and as BPA eliminates this response areas in the brains dealing with cognition and mood may be affected.
Change in the patterns of synaptogenesis may play critical roles in neurological/neuropsychiatric disorders including: Alzheimer’s Disease, developmental disorders and mental retardation, mood disorders and schizophrenia. Interfering with spinal synapses likely causes negative changes in learning and memory.
Politicians calling for reduced BPA in a variety of products
I found an interesting article written in the Washing Post in 2008 about BPA. The article mentions two politicians that want a reduction in BPA use (18). Canada wants to ban BPA from baby bottles while Sen. Charles E. Schumer (D-N.Y.) is sponsoring a bill to prohibit BPA from children’s products, and Rep. Edward J. Markey (D-Mass.) wants to bar it from all food and drink packaging. A few major retailers including Walmart and Toys R Us pledged to drop all BPA products from their stores while many baby bottle and sports bottle companies have switched to BPA free products. The main purpose of this Washington Post article was actually to highlight a new study measuring the long term effects of BPA on green monkeys. That was the study I mentioned in the previous paragraph
The opinion of the FDA regarding BPA
Despite the previously mentioned study along with countless other studies showing the negative effects BPA can have in animals and likely humans the FDA declared BPA safe for use in food packaging and bottles. From their website updates this year:
“FDA’s current perspective is that BPA is safe at the current levels occurring in foods. Based on FDA’s ongoing safety review of scientific evidence, the available information continues to support the safety of BPA for the currently approved uses in food containers and packaging.”
All of their evidence comes from a handful of studies on rats which are mostly funded by companies producing BPA. They mention toxicity studies but not long term low dosage effects. I hope I made the point that just because something is not immediately toxic does not mean that there is no long term danger. I am disappointed that all chemicals are considered safe if they occur at levels that do not result in toxicity. Chemicals should be measured for their ability to activate certain receptors in the body and brain such as estrogen receptors. If they can activate these receptors they likely have some kind of long term influence perhaps even in ways that we would not think to measure so hence would not discover.
Of note is that the FDA recently removed BPA from baby bottles and as coating in the packaging of infant formulas. Great yes, but what is not great is that they did this based on the recommendation of the American Chemistry Council (ACC). Reading the ACC website I found this:
“The Polycarbonate/BPA Global Group promotes the business interests and general welfare of the polycarbonate and bisphenol A (BPA) industry through relevant technical, communications, and public policy activities. The membership consists of most of the major manufacturers of polycarbonate plastic and BPA worldwide.”
A real unbiased source that the FDA relies on for information! But enough about the FDA, I just want you to be critical of recommendations from government sources which rely on information from certain special interest groups.
How to limit your intake of BPA
There are steps you can take to limit your intake of BPA. If you tend to use canned vegetables, beans or pasta sauce switch to dry beans, glass pasta sauce, and fresh or frozen vegetables. This will help lower your sodium intake as well. Dry beans are less convenient than canned beans since you have to boil them but they have higher nutritional value (fiber & protein) than the canned beans. If you drink plastic water bottles never reuse them and never leave any plastic bottles in the heat. I would suggest buying a steel canteen water bottle. They are very durable and easy to clean.
It is clear that BPA poses a danger to all human beings that consume it. It may not be toxic, but it is potent enough to negatively affect our organ and endocrine systems resulting in DNA damage, increased cancer risk and other maladies that we cannot predict as of now. The FDA will admit that BPA poses a danger to babies but still refuses to acknowledge that BPA can harm adults as well. We must move away from testing chemicals such as BPA for toxicology and move towards testing them for the ability to stimulate estrogen receptors. The hormones in our body are strictly regulated and kept within a narrow range and we do not need any estrogen from external sources. Our bodily systems have not evolved to handle additional estrogenic chemicals that we get from the environment.
Look at it this way. There are probably safe hormone levels for everybody which differ slightly. Some people naturally have higher levels than others. For the people that naturally have dangerously high levels, any additional estrogen will put them over the top and increase their risk from the effects of excess estrogen.
Think of sugar. We get all the sugar we need from complex carbohydrates and do not need any simple sugars from fruit or table sugar. Eating table sugar everyday will not result in any immediate harm. But over time you may develop diabetes. In susceptible people this can even result from eating tiny amounts of processed sugar everyday. So if sugar were a chemical scientists produced it would be approved by the FDA as it is not immediately toxic. Whether or not it caused long term harm like diabetes would not factor into the FDA approval. This highlights the problem with the method the FDA uses to approve chemical substances.
I am not sure why there is so much disagreement about whether or not small amounts of dietary estrogen that we have no need for may increase our circulating estrogen and have negative effects on estrogen dependent bodily systems. We can never accurately assess its long term effects by using rats. Personally I do not feel safe consuming any amount of dietary estrogen.
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