Since the introduction of plastics in 1907, they have transformed our world. However, their story doesn't end when we throw them away. Emeritus Professor Ian Shaw explores how plastics become microplastics, their journey through ecosystems and our bodies, and the emerging evidence associating them with environmental and human health impacts.
It all began in the USA in 1907 when Leo Baekerland created the first plastic. One hundred and eighteen years on and plastics are part of almost every bit of our lives. Our kitchen utensils, surgical equipment, mobile phones, computers and cars comprise huge amounts of plastics. To give an idea of the meteoric rise in plastic manufacture, in 1960 about 10 million tonnes were manufactured and by 2014 more than 300 million tonnes were produced. Plastics have a huge economic value because of their broad application to all aspects of our lives – this is their all-important life. But what happens when we have finished with them? What is their afterlife?
Most plastics end up in landfills or are discarded into the environment by careless users. While there are few bacteria that fully degrade plastics, constant erosion by the sea or earth abrasion breaks plastics into smaller and smaller fragments, eventually becoming microplastics (2 µm to 10 mm across) which persist in the environment.
The millions of tonnes of plastics in the environment are slowly being converted to microplastics. Now almost everywhere on earth is contaminated. They are filtered from marine environments by filter feeders (e.g., mussels) which affects their growth and development, and they are appearing in plants, including many vegetables consumed by humans. In addition, microplastics are light and can become airborne. All facets of the earth’s environment are now contaminated. We are constantly exposed to microplastics in our food, the water we drink, and the air we breathe.
Plastics also contain other chemicals. For example, plasticisers are used to modify the physical properties of everyday plastics – they make them soft, bendable and stretchy. When plastics enter the environment, these plasticisers leach out or are carried within microplastics. Many plasticisers are biologically active. Some mimic the female hormone, estrogen and have feminising effects on humans and animals. They might influence the incidence of some hormone-driven cancers (e.g., breast cancer) or confuse animal reproduction processes.
Further, as microplastics are transported around the earth on ocean currents, they adsorb environmental pollutants (e.g., pesticides) and carry them to their human and animal destinations. The implications of this can currently only be imagined.
The potential for plastics via plasticisers or microplastics to impact ecosystems or human health is becoming fact. The impact of estrogen mimics on ecosystems is well understood, their impact on human health is becoming understood, and there are the first inklings of associations between microplastics and human diseases such as early onset colorectal cancer.
In his talk, Professor Shaw will explore the mechanisms and effects that underpin the environmental and health impacts of plastics and speculate on where it is all leading.
YOUR SPEAKERS
Emeritus Professor of Toxicology, DSc, PhD, FRCPath