Persistent Organic Pollutants on Plastic Resin Pellets from Foul Bay Western Australia

Plastic resin pellets collected at Foul Bay Western Australia in August 2007 have been tested for sorbed persistent organic pollutants. The tests were carried out at the University of Agriculture and Technology in Tokyo, Japan as part of the International Pellet Watch programme (1) which aims to use beached resin pellets as a means for monitoring the global distribution of Persistent Organic Pollutants (POPs). These are long lasting carbon containing chemicals circulating in all major ecosystems and come from both manmade and natural sources.

Levels of these chemicals found on the Foul Bay pellets are given in table 1.

Table 1 – Foul Bay PRP Test Results.

*1ng/g-pellet is 1 billionth of 1 gram of pollutant per 1 gram of pellet.

Based on the results the International Pellet Watch categorises Foul Bay as a clean beach in terms of persistent organic pollutants as compared with other sites so far tested around the world.

Questions Raised

Are Low Levels of POPs (Sorbed to Pellets) Harmful?

The origin of pellets varies and some will have spent longer in the ocean than others. Resulting from this, some pellets have higher concentrations of POPs than others. These pellets may have come from, or spent time circulating in, more heavily polluted areas before eventually being beached. International Pellet Watch endeavours to reflect the regional POPs concentrations for its purpose so the tests are designed to achieve a median level where a small number of peak concentration levels are excluded. (4) The actual level of POPs on individual pellets will vary below and in some cases significantly above the median level. There are two things to consider regarding levels. First, some plastic resin pellets can accumulate high concentrations of POPs as they pass through heavily polluted waters before washing ashore on local beaches. The degree of staining on pellets is an indicator of the length of time the pellet has been in the sea and hence its length of exposure to pollutants. Some pellets with very pronounced staining are found on local beaches and suggest pellets with higher concentrations of POPs are arriving on our beaches from remote locations. Second, if the results indicate low regional levels of POPs is there a problem? Four of the chemicals identified in the Foul Bay sample are endocrine disruptors. Endocrine disrupting effects can be triggered at “extraordinarily” low concentrations. (5) In what is known as the non monotonic dose response observed in the study of endocrine systems, very low concentrations – e.g. parts per trillion and less – begin to trigger a response in a given system and continue until, at high concentrations e.g. parts per billion and above a system begins to shut off and events in the cell that should occur do not occur. (6, 7) Ingestion of pellets with low concentrations of POPs by marine organisms is expected to present a problem for marine organisms. Very little research, however, has been carried out to test for chemicals sorbed to pellets becoming bio available once ingested, but much data is available that ingestion by a range of species occurs.

Where do the POPs come from?

This cannot yet be answered in detail but generally the most significant input for POPs is atmospheric deposition. For West Australian waters part of the input will be during summer when prevailing Easterly winds pick up chemical molecules, dust and other particles contaminated with pesticides and industrial chemicals and carry these out to sea. Here a number of processes will cause them to settle on the sea surface. During the wet season chemicals can be flushed from the land and deposited in the ocean by flood waters resulting in high local concentrations. Stormwater, treated sewage water and industrial waste water all contribute POPs when discharged directly into the ocean. From many disparate sources POPs tend to settle and concentrate into the surface skin of the sea known as the Sea Surface Micro Layer. (8) It is here that POPs are gathered up by plastic resin pellets.

Where do the Pellets come from?

Again only a general answer can be given and that is that there is a mix of pellets from local land sources and from ocean current borne pellets from other parts of the globe.

What Happens to the Pellets?

Pellets may persist in the marine environment for a number of years. (9) Equally it may take a number of years for the sorption of chemicals to reach equilibrium on the pellets. Our observations in the capes region of South Western Australia suggest that once caught in a dynamic coastal environment many pellets undergo weathering processes which reduce them to micro plastic particles. This micro plastic will continue to either circulate in local coastal systems or find its way back to the open ocean.

Are There other Chemicals Involved in this process?

Plastic resin pellets have two sets of chemicals, those absorbed while in the ocean and those incorporated during production. As to the first there are many persistent organic pollutants with a growing number of these being identified as endocrine disruptors. Scientific study of sorption of chemicals onto pellets in seawater has only recently begun and data is limited. There are hundreds of endocrine disrupting chemicals and thousands of persistent organic pollutants amongst the nearly one hundred thousand chemicals currently in production. As to their makeup, pellets will contain a number of different chemicals depending on the requirements of the plastic fabricator. Nonylphenyls (4) and Phthalates (10) are two chemicals incorporated in pellets which are endocrine disruptors.

What species are exposed to this process?

Turtles, seabirds, crustaceans and fish are known to ingest plastic resin pellets in the Northern hemisphere. (11) There is now considerable data on ingestion of marine plastic debris amongst Australian species across a similar range of organisms but little data on ingestion of plastic resin pellets. Ingestion of micro plastic particles by marine organisms is being studied in the UK where detritivores, deposit feeders and filter feeders have been observed to ingest micro plastics. (12) A wide range of local smaller marine organisms will be exposed to plastic pollution at a range of sizes that make ingestion probable. All living organisms are now contaminated with traces of persistent organic pollutants and within the food web some POPs can “biomagnify” as they are passed up the food chain resulting in top predator species accumulating levels at tens of thousands of times the levels in the surrounding sea. (13) Contaminated pellets add another dimension to this exposure process.

Discussion

Global oceans are receiving ever increasing quantities of garbage and chemical pollutants. The sea surface micro layer is now populated with micro plastic particles and thousands of manmade chemicals. This layer is the single most important marine ecosystem in that it is where the majority of sea organisms either spend their lives or begin their lives. Much plastic debris is now thought to migrate to the sea floor by way of the actions of marine organisms. This process distributes all the effects of plastic and chemical pollution throughout the ocean. Local West Australian waters may have been relatively clean in one respect within a whole ocean system which is rapidly declining in health under the impacts of marine debris, chemical pollution and a range of effects from global warming. Our local seas are becoming increasingly affected by these global pollution processes. Locally there is little understanding about the transport and transfer of toxic chemicals to marine organisms via plastic resin pellets and post consumer plastic debris. There are (in so far as we are aware) no monitoring systems for endocrine disrupting chemicals entering local waters and accumulating in marine organisms. The impact globally of marine plastic debris on large marine organisms has reached horrific proportions and yet the area of greatest impact from marine plastic and chemical pollution is now thought to be amongst the micro organisms at the basic levels of the marine food web.

This report prepared for Tangaroa Blue Foundation by Wally Smith wally@tangaroablue.org