Ecologist Katrina McDermott explains why she returned from her recent holiday with a heightened concern for the extent of microplastic pollution.
Tropical islands normally conjure up images of sunbathing on beautiful white sand beaches with a cocktail in hand. However, a recent trip to the east coast of Hawaii left me with memories of multi-coloured sand and a hand full of plastic fragments. It was hard to overlook the multitude of coloured fragments in the sand surrounding us. The extent of the pollution was a sobering sight.
We couldn’t stop thinking, why was plastic pollution so prolific on this beach? We later realised we were staring right out at the Great Pacific Garbage Patch — the largest accumulation of ocean plastic in the world. The size of the Patch is quite hard to comprehend; it covers 1.6 million km² and has enough plastic for 250 pieces for each person on earth. This is just one of five major patches of ocean plastic!
We know that plastic in the ocean and in the wider environment is bad. Turtles mistake plastic bags for jellyfish; seabirds ingest plastic fragments thinking its food. But what happens when these larger plastics break down even further, into microplastics less than 5 mm in size? What impacts do these tiny microplastics have on the environment?
Microplastic pollution comes from either primary or secondary sources. Primary sources include microbeads and nurdles (raw plastic pellets used in manufacture of plastic products). Polluting plastic fibres are also generated when washing clothing such as fleeces. Secondary sources are generated by the physical, chemical or biological breakdown of larger plastic debris, like water bottles and plastic bags. Car tyres are also a huge contributor of microplastics — tyres contain plastics, which wear off as microplastic-laden dust. The sources of microplastic are numerous, ranging from large industrial manufacturers to individual consumers.
With such varied and numerous sources, it’s easy to agree that microplastic pollution is a big problem. It is everywhere in the world. Every continent. Every ocean. Microplastics have been discovered in some of the deepest oceans in the world, like the Mariana Trench, and in recently deposited Arctic snow. What’s really concerning is that these locations are a considerable distance away from potential sources.
Microplastics are also abundant on our own clean, green shores. A 2019 Scion study identified microplastics at 85% of sites surveyed across the Auckland Region. The highest densities of microplastics were found in the Manukau Harbour — textile fibres discharged from the Mangere Waste Water Treatment Plant were the probable primary sources. Auckland is not alone; a study of sediment along Canterbury’s coastline identified microplastics in 80% of survey locations. These studies may reflect the conditions along much of New Zealand’s coastline.
We know that microplastics are present in marine food chains. Fish, turtles and other animals mistake microplastics for food; shellfish filter these out of the plastic-riddled water. The health implications from microplastics within the food chain are relatively unknown. Recent research suggests that much of the microplastics ingested is likely to be passed intact through organisms. But there is still a lot to learn about the pieces that are left behind. There is evidence to suggest that chemicals within plastic might leach out, and that this could lead to reproductive toxicity, carcinogenicity and mutagenicity. Microplastics can also absorb or adsorb and concentrate additional organic contaminants from the water column, which may be taken up by animals upon ingestion. Not only can the microplastics themselves bioaccumulate, but the associated contaminants can also bioaccumulate when ingested.
Cetaceans are apex predators at the top of the food chain and are particularly susceptible to bioaccumulation of microplastics and their associated toxins. These toxins have been shown to accumulate in their blubber and are passed onto young in high concentrations through milk. A resident pod of Orca in the United Kingdom has not had a single calf in 23 years of monitoring. A recent post-mortem on a female pod member showed extreme levels of toxins in her blubber, far above the level at which damage to the health of marine mammals is known to occur. The high concentrations of toxins are thought to be the cause of the pod’s apparent infertility.
Research into the effects of microplastic pollution is being undertaken globally, with scientists trying to understand what the implications of this worldwide phenomenon might be. In New Zealand, the Institute of Environmental Science and Research (ESR) and Northcott Research Consultants are undertaking a five-year study on the impact of microplastics on New Zealand’s ecosystems, animals and people. It is highly unlikely that the results will be good news.
So, what can we do about this? How do we clean up pollution that is barely visible to the human eye? We can’t. Not entirely anyway. Microplastics are spread so far and so wide that it’s impossible to remove them entirely from the environment with current technology. However, this technology is changing at a rapid pace, with large organisations testing innovative methods of cleaning up microplastic pollution.
But this isn’t enough. Not only do we need to remove what we can, but we also need to reduce the volume of virgin plastic being manufactured and stop it entering the environment in the first place. While recent changes in New Zealand legislation banning microbeads and single-use plastics bags are a step in the right direction, these aren’t nearly enough — we need to do more. Legislative and behavioural changes need to happen on a global scale. We are seeing some manufacturers and industry taking responsibility for reducing plastic material in their products, but we have a long way to go to reduce the cumulative global impact of plastic on the environment. As consumers, we all need to stop choosing convenience, start taking accountability and use our purchasing power to demand changes from industry!
Plastic is fantastic — it’s a highly versatile material when used responsibly, and there will always be a place for some plastic products. However, our love affair has gotten out of hand. Our frantic consumerism of all things plastic may be one of humankind’s longest-lasting legacies. The full implications of this, we still don’t know.
For further information please contact Katrina McDermott
14 October 2019