Reuben Woodley, of Plimmerton, asks :-

When my grandma was young there were no plastics. Are foods sold in plastic containers and liquids that have been in plastic pipes, kettles or bottles bad for us? What would happen if I ate some plastic?

Ian Shaw, a toxicologist at the University of Canterbury's chemistry department, responded.

This is a very interesting and very topical question because there are concerns about what effects our exposure to plastics is having on our health.

As you say in your question, your grandma’s generation were not exposed to plastics. For this reason we can look at health effects since plastics were first used widely (e.g. in food packaging) and explore any effects that might be linked to exposure to plastics. This is exactly what has been done and the results are very interesting and rather worrying.

An American scientist observed that alligators from Lake Apopka in Florida had shorter penises and lower levels of the male hormone (testosterone) than alligators from nearby Lake Woodruff. He linked the effect to pollutants in Lake Apopka compared to the pollution-free Lake Woodruff. It turned out that the pollutants (e.g. DDT) have molecular structures similar to the female hormone (estradiol) and can mimic it in the body so persuading male’s to become slightly female (e.g. shorter penises in the alligators).

We have since seen many more similar effects in wildlife and in humans. For example, the human sperm count is declining; it is thought that this is due to exposure to plastic components that mimic estradiol (e.g. the polycarbonate plastics monomer bisphenol A – BPA).

Similarly, girls are entering puberty earlier than in the past, this might be because they need estradiol to stimulate the onset of puberty and estradiol mimics in food, and from the environment fool their bodies that it is time to commence sexual development.

These issues are now being taken very seriously worldwide and the World Health Organisation produced a report in 2012 which pointed to in excess of 800 estrogen mimics in the environment and acknowledged the link between them and environmental harm and human developmental effects.

The answer to your question about the effects of eating a piece of plastic illustrated an important point. The wildlife and human effects of estrogen mimics result from long-term exposure to very small amounts. A one off exposure is very unlikely to have any effect at all. Therefore, chewing a piece of plastic is unlikely to harm you because you would only get a one-off low dose of estrogen mimics. The problem is the complex cocktail of estrogen mimics we are all exposed to every day.