“Microplastics are pervasive in our environment. They are present in all environs, from the deepest ocean trenches to the highest mountains, and are being found to be ingested by more and more species. However, this area of research is still in its infancy and the sources, fate and impacts are not fully understood.”

Presented by Dr Grant Northcott, Director, Northcott Research Consultants Limited and Dr Olga Pantos, Research Scientist, Institute of Environmental Science and Research, the Microplastics Webinar was a huge success that created many follow-up questions. 

To hear Grant and Olga’s original discussion , listen to the webinar.

Read the Q& A below:

How applicable is this information to soil stabilisation polymers?  These are generally advertised as non-toxic and non-hazardous.  Is this accurate? 

Soil stabilisation polymers are different to the polymers used in plastics that produce microplastics. The SSPs are large but discrete molecules that react with sites on soil particles to bind them together. The potential toxicity of SSPs will depend on the properties of the particular molecules that are being used. However, the fact that they react and bind with soil indicates they will have very limited bioavailability, and hence the risk to organisms will generally be considered low. 


What can Territorial Authorities do now to address this issue? e.g. strategy plans, policies, contracts. 

A first step may be to look at integrating some MP monitoring into their environmental programmes. If they are not sure how to do this, we’d be happy to discuss an EnviroLink Tools grant in partnership other TAs to have an advisory report developed to address the protocols/methods to assess MPs in the different environments they are interested in, and  validate the sampling and analysis methods. 

Can compostable plastics be the answer?  Or do they create similar issues? 

There is great confusion between ‘biodegradable’ and ‘compostable’, and even what is meant by this: industrial vs. home compostable. This is exacerbated by the way companies have incorrectly used these terms either intentionally or unintentionally to indicate that their products are more environmentally friendly than others. They have used ‘biodegradable’ to mean those that simply make the item fall apart into smaller pieces, however the plastic polymers remain unaffected. This can have great implications for the contamination of waste streams, both green waste and plastic waste. Plastics that fully biodegrade and mineralise (i.e. turn to CO2, water and biomass) may still pose problems after 100% decomposition has occurred due to the additives that are used in their manufacturing. The effect is therefore dependent on the additives used. When these plastics are not exposed to the specific conditions, decomposition will not occur, and therefore may pose similar problems as traditional plastics (there is a still a huge knowledge gap here). For example, PLA compostable under commercial conditions where temperatures greater than 45 degrees are maintained as they promote chemical hydrolysis and cleavage of the polylactic molecules. The microorganisms in the compost are then able to biodegrade the smaller hydrolysed polymer by-products. However, the temperatures required to achieve hydrolysis of PLA are not achieved in natural waters or soil and consequently PLA does not biodegrade in these environments.  

A very good source of information and discussion of biodegradable and compostable plastics is available on the website of the Parliamentary Commissioner for the Environment: https://www.pce.parliament.nz/publications/biodegradable-and-compostable-plastics-in-the-environment 


With regard to the Fox River landfill disaster, has there been any study done of the microplastics released at that time into the river/sea? This is especially relevant given the number of landfills adjacent to rivers or the foreshore. There is one at St Kilda in Dunedin that is currently being slowly undermined. 

No, no samples were taken straight after the breach occurred. As there was no data for the area beforehand it is not possible for us to say what we see has come from the landfill. We are keen to look at sediments both N and S, and at the mouth of the river, but have not been able to get samples just yet.

You can see the recommendations around landfills with respect to them posing a source of plastics and MPs to the environment at the Rethinking Plastic in Aotearoa New Zealand report released on the 8th December: https://cpb-ap-se2.wpmucdn.com/blogs.auckland.ac.nz/dist/6/414/files/2019/11/Rethinking-Plastics-in-Aotearoa-New-Zealand_Full-Report_8-Dec-2019-PDF.pdf 


I noticed on Grant’s slide where he shows the areas around NZ that have been ‘trawled’, there was nothing for the West Coast of NZ. Was there a reason for this? Is it too dangerous? Seems a shame when there have now been 3 examples of landfills being opened up by seas/rivers. 

The surface water trawls that have been carried out by Woods Hole Oceanographic Institution have been mainly done as part of their Sea Semester programme. They come out to NZ on an annual basis, and spend about 6 weeks, going out from Auckland mid-February and ending in Christchurch. Due to the weather conditions at that time of year they have found that doing the NE-E coast route is more reliable. They have done the west coast on one occasion but found conditions weren’t at all favourable.  


The breakdown of plastic to a scale where it can pass through cell membranes suggests that it isn’t as durable as originally thought.  Is the use of plastic packaging on food of potential health concern?  i.e. could plastic packaging be degrading on a micro/nano scale and becoming incorporated into the food that it is containing?  I’m aware that this is a broad question, but would be interested if they are aware of any studies / papers around this. 

We don’t know too much about how much MP is in our food. If it’s big enough to notice we know it’s there, but it’s the smaller stuff we just don’t know. Regardless, these very small particles of MP remain stable and resistant to biodegradation as they’re composed of the same stable and persistent polymers as the original parent material they are sourced from. To date, MPs have been identified in a range of foods, including honey, beer, bottled water, table salt and multiple seafood species. Some of the plastics found have been attributed to the packaging of the food, but others are assumed to be a result of environmental contamination. In the case of seafood it is all environmental contamination. A PhD project has just got underway which will address the question of dietary exposure of MPs in New Zealand so over the next few years we’ll have further insight into the quantity of MPs New Zealanders are exposed to via food and the risk they may or may not pose to human health. 

The first human health studies began last year in the Netherlands. There has been some preliminary data showing potential detrimental health effects for humans. These included food packaging plastics. There is still a lot of work to be done before robust and meaningful conclusions can be made. More information can be found at: https://www.plasticsoupfoundation.org/en/2019/10/the-first-evidence-of-health-risks-from-micro-and-nano-plastics/ 


In the beginning, work with Northland Regional Council was mentioned. Could the extent of this work be expanded on? As a regional council, I am looking for ways that we can contribute the missing data and am thinking that microplastic data collection via citizen science opportunities might be a good fit.  

As part of the project we are interested in trying to gain a better understanding of the distribution of MPs in NZ’s environment by examining multiple sites around the country. As well as providing important baseline data that will help establish whether the MP situation is improving with changes in policy and land management strategies, or not. An example of how we are achieving this is the work being done with NRC. We are keen for our research program to partner with organisations to achieve these common aims. In this way we’re able to cover more sites than we’d otherwise be able to achieve on our own. In return we will provide our data back to our partners. NRC is assisting us  by collecting the samples which we will process and analyse to quantify the amount of MPs and identify the polymer type they are composed of. We will then provide the data back to NRC, and the data will go towards scientific publications, helping to fill the knowledge gaps around both New Zealand and globally. We are able to assist with the training of staff for the sampling, and in the NRC case we are also supporting training of a member of the local analytical lab they use, with the intention that this lab will be able to assist them with analysis in the future.

As there is a significant lack of data around the levels of MPs in NZ environments, regional councils can play a significant role in supporting the access to samples to fill this knowledge gap. In addition to the MP surveys it may be good to also understand the levels of macroplastic pollution. For riverine and marine environments this may be possible the engaging with Sustainable Coastline’s Litter Intelligence programme. https://sustainablecoastlines.org/litterproject/ 


Do Olga and Grant have any other suggestions as to what regional councils can do? There might possibly be some work we can do around classifying plastic pollution as POPs. 

Classifying plastic and MPs as POPs has been previously proposed by environmental scientists and is something we’re sure will continue to be pursued as our understanding of the wider impacts of plastic and MP pollution grows. 

In NZ there is a general absence of information on the distribution of MPs in our environment, so any assessments Regional Councils can complete will provide valuable data. Most Regional Councils have existing water and/or sediment contaminant monitoring programs which could be extended to include MPs to provide baseline data for future comparison and to assess the benefit of future mitigation initiatives. 

One option to consider for coordinating a strategic approach to obtaining further data on MPs across the regions in NZ is via an EnviroLink tools application.  


Have you encountered microplastics in groundwater in New Zealand?  If so, can you please provide the location and, if possible, further detail. 

Groundwater MPs are not within the remit of out project. MPs have been found in groundwater elsewhere around the world but it is possible that some of it may have come from the PVC pipe casing the wells are typically constructed of. It’s only been relatively recently that people have started considering the levels and fate of nano- and microplastics in terrestrial systems. The studies to date have shown that they are mobile in the soils, and that biological processes such as the movement of fauna through the soils may facilitate their migration. As far as I’m aware there haven’t been any studies looking at the movement from surface soils into gravel aquifers, or the impacts on the stygofauna and aquifer ecosystem health. This is an area that we are interested in exploring further with our groundwater team at ESR.


 Would it be possible to get a reference list from the webinar?  

Here is a list of the referenced papers and studies. 


References and information resources: 






Bosker et al,. 2019. Microplastics accumulate on pores in seed capsule and delay germination and root growth of the terrestrial vascular plant Lepidium sativum. Chemosphere. 226: 774-781. https://doi.org/10.1016/j.chemosphere.2019.03.163 

Clunies-Ross et al, 2016. Synthetic shorelines in New Zealand? Quantification and characterisation of microplastic pollution on Canterbury’s coastlines. NZ Journal of Marine and Freshwater Research. 50:2, 317-325. https://doi.org/10.1080/00288330.2015.1132747

De Sousa Machado et al. 2018. Impacts of Microplastics on the Soil Biophysical Environment. Environmental Science and Technology. 52(17): 9656-9665. https://doi.org/10.1021/acs.est.8b02212

Dikareva and Simon. 2019. Microplastic pollution in streams spanning an urbanisation gradient. Environmental Pollution. 250: 292-299. https://doi.org/10.1016/j.envpol.2019.03.105

Eriksen et al., 2014. Plastic Pollution in the World’s Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111913

Rillig et al. 2019. Microplastic effects on plants. New Phytologist. 223(3): 1066-1070.  


Ruffle, H. (2019). Wastewater treatment plants as a source of microplastics to the environment. (MSc thesis, University of Canterbury)

Wenqing et al,. 2014. Plastic-film mulch in Chinese agriculture: Importance and problems. World Agriculture. http://www.world-agriculture.net/article/plastic-film-mulch-in-chinese-agriculture-importance-and-problems 





This webinar aims to outline the current state of knowledge around microplastics (and nanoplastics), exploring the knowledge gaps and potential solutions to this pollution problem.


About the presenters:

Olga Pantos is a marine biologist with a passion for understanding the impacts of anthropogenic effects on ecosystems and organisms. After completing an undergraduate degree in Marine and Environmental Biology at the University of St Andrews, UK, she went on to do a PhD at the University of Newcastle, UK. This project investigated the microbial communities associated with healthy and diseased reef-building corals. After completing her PhD she moved to San Diego State University for two years, and then to the University of Queensland, where she investigated the impacts of rising sea temperature, eutrophication and ocean acidification on the microbial communities associated with tropical coastal ecosystems, and the subsequent impacts on both ecosystem function and organism health.

When she moved to New Zealand in 2015, her research focus changed to looking at the impacts of microplastics, in particular how they affect microbial communities and ecosystem function. She is co-lead of a 5-year MBIE Endeavour Fund project looking at the levels and impacts of microplastics on New Zealand’s marine, freshwater and terrestrial environments, and the investigation of mitigation and microbial remediation options. The project team is made up of 16 researchers from 5 organisations, with expertise ranging from environmental chemistry to microbiology.

Grant Northcott is an environmental and analytical chemist and expert on the fate and effects of organic contaminants in the environment. Grant completed his BSc in chemistry at Waikato University and PhD at the Institute of Environmental and Biological Science, Lancaster University, UK. Grant began his career working for NIWA in Hamilton before moving to the UK to complete his PhD, followed by a two-year postdoc project funded by Unilever.

Grant returned to NZ in 2002 where he worked for HortResearch and subsequently, Plant and Food Research. Since 2012 Grant has operated his own research consulting business. He leads the contaminant chemistry research within the 5-year MBIE Endeavour Funded Emerging Organic Contaminants research program, provides organic contaminant expertise in ESRs Centre for Integrated Biowaste Research program and co-leads the 5-year MBIE Endeavour Funded Microplastics Research Program, for which he leads the contaminant chemistry research objective.