Question:
My teenagers drink a lot of bottled water. A recent article stated researchers had found millions of plastic particles in bottled water. Is that bad for our health?
Answer:
Bottled water is a convenient on-the-go drink. New Zealanders consume about 140 million litres a year, or about 28 litres per person a year.
But plastic pollution in our environment and food supply is a concern worldwide. And that unease has increased recently with more evidence that microplastics and nanoplastics pollute our environment and food supply.
A study published in January revealed the disturbing news that bottled water contains nearly a quarter of a million plastic particles per litre of water, orders of magnitude higher than previous studies have reported. The research, published in the Proceedings of the National Academy of Sciences, found that 90% of those particles were nanoplastics, defined as less than 1 micrometre in size. The remaining 10% were microplastics, between 1 micrometre and 5 millimetres. A micrometre, or micron, is just 0.001mm.
This study adds to others, such as one in 2019 that found many teabags contain a common thermoplastic called polypropylene, which leaches billions of microplastics into our cups of tea.
In a world-first study in 2022, New Zealand researchers found microplastics in snow samples in Antarctica’s Ross Island region. They found an average concentration of 29 particles of 13 different types of microplastics per litre of melted snow. The most prevalent plastic was PET, commonly used to make soft drink bottles and clothing. Modelling suggests these microplastics could have originated up to 6000km away.
But how do plastic fragments in our food supply affect human health? Research on microplastics has increased rapidly in recent years because of a growing awareness of the potential for negative effects on health, noted a review in the journal Toxics.
Regulators are trying to quantify the risk to health by measuring exposure. In 2021, the California State Water Resources Control Board became the first regulatory authority to announce standard methods for quantifying microplastic concentrations in town drinking water. It plans to monitor microplastics in drinking water over the coming years.
The other piece of the puzzle is evaluating the effects of plastic fragments on health. Microplastic pieces have been found in human lung tissue and placentas, and toxicological studies involving human cell cultures have found that high concentrations of certain microplastics (such as polystyrene) harm human cells.
We also know that polyester and polypropylene-containing sutures used in medicine cause a low-level inflammatory reaction, and the human body treats these plastic-containing threads as foreign bodies, encapsulating them in fibrous material.
Nano-sized polyethylene particles generated from hip and knee replacements can also induce an inflammatory response.
Hundreds of studies investigating effects in animals have found that certain microplastics may lead to reproductive issues or physical damage in the organisms. However, the findings are challenging to interpret, given plastic fragments come in many different shapes, sizes and chemical compositions, all of which may alter their effects.
There is genuine concern that nanoplastics, such as those found in bottled water, may be more toxic to our health than microplastics, as their size makes it easier for them to enter the human body.
Some nanoplastics may be so small they can even enter human cells, interfering with cellular functions. Unfortunately, most of these fragments are so small that scientists cannot see them.
Without the complete picture, it is impossible to say whether the nanoplastics present in bottled water are particularly harmful, add substantially to the burden of micro- and nanoplastics we consume daily through other sources, or if they accumulate in our bodies over time, causing more harm.
All we do know is that the more plastics we create, the more micro- and nanoplastics we will find in our food, water and bodies.
