Toronto Star

New science on microplast­ics suggests macro problems

- RICK SMITH AND CHELSEA ROCHMAN

One way to think about how science works is to imagine an onion: With each new research study, more is learned, and another layer of the onion is peeled away leading scientists closer to the answer they seek.

Climate change is an example of a debate that has followed this trajectory. Throughout the 1960s and 1970s scientists couldn’t agree whether the world was warming or cooling. Researcher­s persevered, more studies were completed, and by 1988 the first internatio­nal conference on global warming was hosted in Toronto.

In the same year, the Intergover­nmental Panel on Climate Change (IPCC) was establishe­d, which continues to co-ordinate investigat­ions by thousands of scientists around the world. The result of all this work? The scientific consensus that humans are the cause of global warming has now “grown to 100 per cent.”

Another large onion that the research community is in the process of peeling is that of microplast­ics. The science of microplast­ics is younger than that of climate change. In fact, the word itself was only coined in 2004.

With hundreds of millions of tonnes of plastic discarded into the environmen­t over the past few decades, scientists are now learning that what is visible is only the tip of the plastic waste iceberg.

Plastic bottles and bags, coffee cup lids, vehicle tires, and lint from polyester clothing gets broken down over time into tiny plastic particles that have become a permanent part of ecosystems globally.

Scientists have now shown that microplast­ics are cycling in global dust and water cycles, and can be found from the deepest ocean trenches to the highest mountain peaks, and from the most remote corners of the Arctic to the house dust in the corners of our homes. The threat is sufficient­ly clear that the United Nations has recently declared that plastics are “the second most ominous threat to the global environmen­t, after climate change.”

With microplast­ics ubiquitous in the environmen­t, and ubiquitous in food crops and meat, the next frontier of microplast­ics research is whether — and to what extent — microplast­ics are not just an environmen­tal problem but also a concern for human health.

Research demonstrat­ing measurable risk to wildlife offer some hints in this regard. Concentrat­ions that can lead to adverse effects in wildlife range from about 10-520 particles per litre in freshwater ecosystems. Although many places have lower levels than this threshold, such concentrat­ions are not unheard of in heavily urbanized areas and freshwater tributarie­s — including in Lake Ontario and its watersheds in the Greater Toronto Area.

As a result, legislatio­n has been adopted, for example in California, to begin to quantify microplast­ics in drinking water and determine adverse effect thresholds for human health.

Because microplast­ics can be both ingested and inhaled, scientists are beginning to estimate human exposure from all sources, with a recent calculatio­n pegging this at 39,000 to 52,000 particles a year. At the same time, the first studies have started to come out measuring microplast­ic levels in actual human bodies in Europe and Asia and in North America.

Microplast­ics have now been found to be released by baby bottles, they’ve now been found for the first time in human placentas and a study this month has shown that microplast­ics can disrupt the cells in human lungs.

Later this year, the federal government has served notice that it plans on banning a variety of single-use plastics, such as plastic grocery bags.

Its January 2021 scientific justificat­ion for doing so is largely based on the demonstrat­ed environmen­tal harm of visible and invisible plastic to the environmen­t.

The government notes that: “Humans may be exposed to microplast­ics via the ingestion of food, bottled water, and tap water, as well as through the inhalation of indoor and outdoor air. However, informatio­n on the human health effects of microplast­ics is limited.”

Given the pace at which microplast­ics researcher­s are now focused on probing human health impacts we doubt the available informatio­n will stay “limited” for very long.

 ??  ?? Chelsea Rochman is an assistant professor in the department of ecology and evolutiona­ry biology at the University of Toronto and a leading microplast­ics researcher.
Chelsea Rochman is an assistant professor in the department of ecology and evolutiona­ry biology at the University of Toronto and a leading microplast­ics researcher.
 ??  ?? Rick Smith is executive director of the Broadbent Institute and co-author of two bestsellin­g books on the effects of pollution on human health.
Rick Smith is executive director of the Broadbent Institute and co-author of two bestsellin­g books on the effects of pollution on human health.

Newspapers in English

Newspapers from Canada