Despite its widely known health effects, BPA is still used in a variety of consumer products containing epoxy resins, polyester styrene, and polycarbonate plastics. It is added to various plastics in many different consumer products including plastic bottles while epoxy resins are used as protective coatings for metal food and beverage cans. It is found in every can and most plastic bottles unless they are labelled BPA- free.
Bisphenol A is extensively used in the food-packaging industry so even food take away wrappers may be contaminated with BPA. It is also found in thermal paper for receipts and fax, however, human exposure occurs mainly from the direct contact of food with Bisphenol A containing plastics.
Other exposure routes that are of particular concern are Bisphenol A leaching from babies’ feeding bottles, and Bisphenol A BPA leaching from dental fillings and sealants. In one study, BPA was detected in 15 conventional samples, including dish and laundry detergent, tub and tile cleaner, soaps, lotions, shampoo, conditioner, shaving cream, nail polish, and sunscreen.
90% exposure rate
Overall, human exposure to BPA is frequent and widespread, and more than 90% of individuals have detectable amounts of BPA in urine as reported by studies around the world.
In a study in the USA, BPA was found in 92.6% of urine samples from 2,517 people across the country.
BPA was first reported to impact the reproductive system of female rats in the 1930s. Since then there have been hundreds of published studies showing BPA effects in animals even at very low levels (μg/kg/d) and at levels we would normally be exposed to on a daily basis.
It appears that these low levels may even be more of problem on health than much higher levels.
Pregnant mothers exposed to BPA are also at risk of exposing their unborn child to the chemical. The developing foetus is tremendously sensitive to the effects of BPA, which has been found to cross the human placenta during gestation, exposing the unborn baby to the BPA levels in the mother’s system. The study found that in the space of three hours, 27% of the BPA has crossed the maternal barrier and was found in the foetal compartment where the foetus is continuously exposed to BPA.
BPA is somewhat fat loving (lipophilic), allowing it to move and accumulate into fat and breast milk and has been measured in the breast milk of healthy women. In a large study, BPA was found in 100% of the 101 samples of human colostrum, the milk produced within the first three days of giving birth.
Due to their small size, infants ingest larger amounts of BPA per body weight than older children and adults and have a highly restricted diet.
Even infants on infant formula are likely to be exposed to BPA (usually held within a container lined with epoxy resins) and water which is fed from a bottle most likely containing BPA. Exposure during pregnancy has also shown to be linked with increased negative birth outcomes including miscarriage and even Downs Syndrome. When mice were exposed on a low‑dose short‑term basis they suffered from successive miscarriages and retardation in the offspring.
Exposure to BPA has been linked to a disorder known as ‘precocious puberty’ in females which is an unusually early onset of puberty. BPA alters the action of Luteinizing Hormone and Follicle Stimulating Hormone which control menarche in girls.
Breast cancer link
Many studies have linked exposure to BPA with the development of breast cancer. A study on female rats showed that exposure to BPA at levels typically found in human studies affected development of the mammary gland. Even low doses of BPA have been observed to cause premalignant (pre‑cancerous) changes to the mammary gland in mice, rats and humans. A number of other studies reported rats exposed to BPA as newborns increased the susceptibility of mammary tissue to carcinomas later in life.
In women, other findings include an inverse relation between BPA and peak estradiol and the number of oocytes with the absence of pregnancy, and implantation failure. Follow on research has found BPA concentrations associated with lower serum estradiol, oocyte yield, mature oocyte count, and the number of normally fertilising oocytes.
BPA has also been linked with androgen (male hormone) receptors and is associated with a reduced proportion of male births in the populations and increased the risk of absence of testicles, defects of the penis, and reduced semen quantity and quality in males. This is widely supported in animal studies including infertility and sub fertility in males.
Additionally, decreased testosterone levels have been observed in rodents exposed to BPA during the prepubertal and pubertal period. In a study of 308 young men from the general population they found that 98% of the men had detectable urinary levels of BPA and reported effects on the hypothalamic–pituitary–gonadal hormone feedback system. They reported significantly higher concentrations of serum Lutenising hormone, testosterone and estradiol and a lower percentage of progressive motile sperm in healthy, young men. BPA has been shown to induce prostrate problems linked to prostate cancer in rodents.
Effect on sexual development
Infant exposure to BPA has been shown to have ongoing effects on the structure, function and behaviour of the brain in rats and mice throughout their adult life. Several studies found that exposure to BPA as an infant can negatively affect the regions of the brain involved with sexual development. This leads to a reduction in the characteristics that differentiate between the male and female individuals of a species. A study conducted with mice also showed a decrease in the maternal function. The mother mice were observed to spend less time in the nest feeding their young and more time on their own grooming. Studies in both humans and rats show exposure in the womb to BPA may cause behaviour and emotional problems in young girls, including hyperactive, anxious, aggressive and depressed behaviour. As the chemical levels increased, so did behaviour problems in the girls.
Low doses of BPA impair triiodothyronine (T3), one of the thyroid hormones which is essential for normal brain development. It is linked with producing different cognitive deficits in both humans and animals and is required for a developing brain and proper cognitive functions in animals. BPA exposure has also been shown to cause a reduction in memory retention and retrieval processes and interfere with brain processes associated with learning.
Exposure to BPA during foetal and infant development, which are critical periods in cell differentiation, can lead to a process called epigenetic programming. This is a process where BPA can change the programming of genes, leading to metabolic diseases and cancers later in life. Disturbances of hormones during infant development can also influence the likelihood of the development of diseases or dysfunctions later in life. Epidemiological studies showed relationships between BPA exposure and increased body mass index (BMI), cardiovascular disease and metabolic syndrome. BPA causes hyperinsulinemia or insulin resistance, a forerunner for Type‑2 diabetes, hypertension, and dyslipidemia. BPA imitates human estrogen, estradiol causing pancreatic cells to secrete insulin. The chemical binds with estrogen receptors on pancreatic cells to boost insulin secretion. Therefore, repeated exposure to BPA causes insulin resistance and eventually diabetes.
In a study of 1,326 children, girls between ages 9 and 12 with high BPA levels had double the risk of being obese than girls with low BPA levels, validating previous animal and human studies. The chemical can alter the body’s metabolism and make it harder to lose weight. Girls with high levels of BPA, two micrograms per litre or more, were twice as likely to be obese as girls with lower levels of BPA in the same age group. Girls with very high levels of BPA, more than 10 micrograms per litre, were five times more likely to be obese.
Similar results have also been shown in animal studies. When pregnant rats are exposed to BPA it increased the fat mass in offspring, even later in life. In animal experiments, a mother’s exposure to BPA has produced the same outcomes that we see in humans born light at birth: an increase in abdominal fat and glucose intolerance.
The challenge we now face is that BPA has now become a chemical found in so many products.
And as Australian regulatory authorities are so far behind the science, the onus is on consumers to determine which products are safe. Best to use ceramic, glass and metal containers and avoid plastics for food and water as well as reduce your exposure to foods in cans as there are no safe levels.
Peter Dingle’s March-April Wellness Presentations.
7.00 -9.00 PM. Wednesday nights
445 Charles St North Perth Western Australia
$15 online/$20 at the door
March 22, 2017: Probiotics, People and Poo
March 29, 2017: 7 Steps To Permanent Weight Loss
April 12, 2017: Eat Your Way To Health
April 19, 2017: Reducing Toxic Overload in our Kids
Dr Peter Dingle (PhD) has spent the past 30 years as a researcher, educator, author and advocate for a common sense approach to health and wellbeing. He has a PhD in the field of environmental toxicology and is not a medical doctor. He is Australia’s leading motivational health speaker and has 14 books in publication.