Over the past couple of decades, premature human births have risen as has the number of people experiencing the early onset of puberty. It has been suggested that one contributing factor is the widespread use of endocrine-disrupting chemicals, such as bisphenol A (BPA), which mimics the effects of estradiol.
BPA has been used to harden plastics for more than 40 years and is found in a wide range of products, including polycarbonate baby bottles, food storage boxes and the linings of canned foods and drinks. It can leach into food and beverages, particularly when containers are heated. As a result, almost all of us have BPA in our bodies. One study found it in 95% of urine samples tested.
In recent years BPA has been linked to a variety of health problems. Evidence from animal studies has led to particular concern about its potential effects on foetuses, infants and young children. Some experts believe it could disrupt normal hormone levels and affect children’s brains and behaviour. In both children and adults it may also increase the risk of cancer and heart problems. It has also been connected with many other conditions, including obesity, diabetes and attention deficit hyperactivity disorder.
Because BPA’s toxicity has resulted in public concern and some government-imposed restrictions, many manufacturers have replaced it with bisphenol S (BPS). Yet the new products, often boldly labelled “BPA-free”, may be no safer, because BPA and BPS are similar. The BPS molecule simply replaces BPA’s central dimethylmethylene group with a sulfone group, but it still has the two phenol rings that allow BPA to mimic estradiol.
A study led by researchers at the University of California in Los Angeles (and reported in the 1 February 2016 issue of Endocrinology) has confirmed that BPS may be as worrying as BPA. Using zebrafish (because their transparent embryos make it relatively easy to study cell growth), the researchers examined the effects of BPA and BPS on brain cells and on the genes that control the growth and function of reproductive organs. When the fish were exposed to either chemical at levels no higher than the traces found in polluted river waters, their physiology at the embryonic stage changed in as little as 25 hours. Embryos developed much faster than normal, leading to premature egg-hatching.
The researchers also found that low-level exposure to either chemical led to an overstimulation of the endocrine neurons that regulate reproduction. This could lead to premature puberty and disruption of the reproductive system. Furthermore, the research showed that BPA and BPS both affect the thyroid hormone system. Since thyroid hormone has a significant influence on brain development during gestation, the research could have important implications for understanding general embryonic and foetal development.
All in all, it seems that we may face a health hazard from any plastics that come into contact with our food and drinks. But how do we reduce the risk? Here are some suggestions:
- Use food containers made of glass, porcelain or stainless steel rather than plastic.
- Buy more fresh, frozen or bottled foods.
- Don’t heat plastic containers in the microwave or pour boiling water into them, and don’t put plastic items in the dishwasher.
- Throw out chipped or cracked plastic products, which are more likely to leach chemicals.
- Replace liquid baby formulae with powdered products, which are less likely to absorb chemicals from container linings.
The main action needs to be taken by national and international health bodies. They should investigate all chemicals used in food and drink containers and force manufacturers to use only those that have been proven to be safe.