Microplastics and shellfish aquaculture

I’m lead author on a new study published today in the journal Aquaculture Environment Interactions on microplastics and shellfish aquaculture. This study took place over the last three years as a collaborative effort between DFO’s Aquaculture Collaborative Research and Development Program, the BC Shellfish Growers Association, the University of Victoria, and Vancouver Island University. Our study’s findings suggest that microplastics concentrations in BC farmed shellfish are low, at less than 1 particle per shellfish, on average, and that the plastic equipment used in shellfish farming is not a significant source of that microplastic. Instead, the results indicate that fibres from textiles are the most common form of microplastic contamination in shellfish and their environment. These fibres likely find their way into the ocean via sewage after we wash our clothes, but could also be transferring through the air. Overall, consumers should not be concerned about consuming microplastics via BC shellfish, as these numbers are low relative to other sources of microplastics in our diet.

Human Consumption of Microplastics

I’m the second author on a paper published on June 5th in Environmental Science and Technology in which we have reviewed 26 studies to create a first estimate of human consumption of microplastics. This is based on concentrations of microplastics that have been measured in air, water, seafood, added sugars, salt, and beer. We estimate that the low end of consumption could be 39,000-52,000 microplastic particles per year for the average person, or 74,000-121,000 when inhalation is included. Drinking only bottled water could increase microplastic exposure from drinking water by 22 times.

Of course, it is still very early days in the field of microplastics research, and these numbers won’t mean much until we have an idea of the real risk that is presented by these particles. Currently we know that microplastics represent a hazard, meaning that they can cause harm under high enough concentrations, however we do not know whether the concentrations we are exposed to actually represent a risk to human health. We have also only accounted for 15% of caloric intake (based on recommendations from the US Department of Health and Human Services) because there are no data on the amount of microplastics that occur in red meat, poultry, grains, or fruits and vegetables. So while we know that our numbers are on the low end of the true amount of exposure that is likely occurring, we still have no idea whether microplastics represent a threat to human health or not.

Rather than alarming everyone with the amount of plastic that we’re consuming (although this is likely going to happen to some extent regardless), we’re hoping that this paper will be a wake up call in a number of ways. The first is to raise general awareness of how much plastic we are using and the degree to which we are contaminating the environment with it. We need to dramatically rethink our relationship with plastics, and the best way to start doing that is with plastic packaging. Currently, plastic packaging accounts for over 50% of global plastic production, and a lot of it is excessive, could be reduced by changes in industry practices and consumer habits, or at the very least could be replaced by materials that actually break down in the environment. We also hope that this paper will lead to researchers filling in the blanks on the amount of microplastics contained in other food groups, as well as conducting further research on the degree to which this could be affecting human health.

The media coverage of our paper has really surprised us with the degree to which it has take off, and we’ve received coverage around the world. In no particular order, here are some links to stories that have been published about our research:

TIME

CNN

The Guardian

CBC

VICE

National Geographic

New paper published in Science of the Total Environment

My first lead-author paper is out!

The paper is published in Science of the Total Environment and is co-authored by my supervisors Sarah Dudas and John Dower, as well as two of my committee members, and two researchers from the Ocean Wise plastics lab. It can be viewed for free here until April 19, 2019.

This paper has been several years in the making and began as an investigation into the best way to sample microplastics from the shore while I was conducting work on microplastics and shellfish. From there, it eventually evolved into a study of how different mesh sizes might bias the microplastic concentrations reported by studies that sample seawater. Currently, it is very common for researchers to use a towed Manta Trawl to separate microplastics from seawater, but the nets used in this trawl have a mesh size of about 0.3 mm, which tends to allow fibres to slip through the holes due to their narrow width. By statistically analyzing the microplastic concentrations that are reported in the literature and accounting for sampling technique, I was able to determine that studies that rely solely on these towed sampling methods might be underestimating the number of microplastics (especially fibres) present in seawater by roughly 10-10, 000 times. Obviously, this is a huge range and it’s impossible to exactly predict how much we’re currently underestimating microplastic concentrations in the ocean, but the findings suggest that in order to make claims about the risk of ingestion and potential health effects that organisms in the ocean are currently facing, we need to use smaller mesh sizes to accurately depict microplastic concentrations in seawater, and not routinely exclude fibres.