Plastics and chemicals

The United Nations Environment Program called marine plastics the “new toxic time bomb”.   Marine plastic is not only entangling and drowning wildlife, it is being mistaken for food and ingested along with its toxic contaminants. Marine plastics and in particular microplastics, provide a global transport medium for the most toxic chemicals into the marine food chain and ultimately, to humans.

Persistent bioaccumulative toxins (PBTs) contaminate all forms of marine plastics (eg resin pellets, microbeads, polystyreneand microplastic debris liketiny threads from ropes and nets.   Because microplastics have larger surface area to volume ratio,   they accumulate   and   concentrate PBTs   and   metals. Once   in   marine environments plastic polymers undergo some weathering and degradation, aiding the   adsorptionof   PBTs   from   the   seawater,   where   they exist at   very   low concentrations. The contaminants concentrate in microplastic fragments at several orders of magnitude higher than background levels in seawater.

By ingesting the minute pieces of plastic, marine species consume persistent organic pollutants (POPs) includingpesticides such as DDT, PCBs, lindane, as well as many toxic plastic additives (eg bisphenolA(BPA), phthalate plasticizers, brominated flame retardants(PBDE) and heavy metal stabilisers.)

Many of these contaminants are endocrine (hormone) disruptors capable of adverse effects at very low levels. Marine organisms are also exposed to the chemical intermediates from the plastics’ partial degradation like carcinogenic styrene and highly toxic, polycyclic aromatic hydrocarbons (PAHs). Perfluorinated compounds (PFCs) used to make fluoropolymers eg,Polytetrafluoroethylene (PTFE) have also been found in microplastics.

PBTs and POPs are highly bioaccumulative in animalsand can cause cancer, affect reproduction and development as well as impact on the immune system. Once in the digestive tract, these contaminantscan enter the bloodstream, by which they reach other organs resulting in physiologic damage. Microplastics are found in every marine habitat, including estuaries, the breeding areas for fish. Australian research detected POPs and other contaminants in plastic resin pellets in Australian waters and studies of Shearwaters from Lord Howe showed that their contaminant load was positively correlated the amount of plastic they had ingested.

Read the complete National Toxics Network report here.