A guest post by Francisca Fernandez-Piñas, Miguel Gonzalez-Pleiter, and Roberto Rosal
The following post is one of a series previewing the research that will be presented at the SETAC Europe Annual Meeting in Rome, Italy (13-17 May 2018).
The use of plastic materials has been increasing since the mid-20th century to reach current production volumes of more than 300 million metric tons per year. The global flow of plastic materials is still linear, which means it is not “circular,” or a closed loop that results in sustainable re-use. From manufacturing to landfilling, more than 30% of plastic materials end up leaking into the environment in an uncontrolled manner. This is particularly evident in the aquatic environment where plastic debris has been detected in increasing amounts since the 1970s. Public concern skyrocketed with the spreading of news about the so-called “plastic islands” or “plastic continents” at the confluences of ocean currents. The denomination “plastic islands” for the accumulations observed in oceanic turns is misleading because the concentration of plastic particles on the surface of these areas is estimated at around 500,000 particles per square kilometer (100 to 10,000 times greater than in other parts of the ocean, but still less than one particle per square meter). In any case, although it is evident that you can’t walk on these “islands,” the total amount of waste released into the environment in the form of plastic debris is enormous and currently represents over five billion (European) floating particles, which is almost 300,000 metric tons or 0.1% of the world annual production of plastic materials. The ultimate cause of this new type of pollution is the poor waste management, which accounts for over 25 million metric tons of plastic materials lost due to improper disposal every year. The situation is so worrying that if no measures are taken it is estimated that the amount of plastic poured into the seas will double in 2030. And, it will double again by 2050 when plastic will outweigh fish. In fact, plastic is being considered as a relevant indicator of the so-called Anthropocene, the epoch of time characterized by the human impact in geological processes and ecosystems.
Most of the plastic particles found in the oceans correspond to the most used materials–polyethylene, polypropylene and polystyrene–the most frequently found in sampling campaigns. The polymeric materials entering the environment are susceptible to degradation via biotic or abiotic processes. The breakdown is supposed to lead to the formation of micro and nano-sized particles, which would behave differently from both the original material and from microplastics in view of their larger surface area. In fact, there is little doubt that nanoscale particles can be produced during the environmental ageing of plastics, but the nanoplastics have not yet been measured in actual aquatic systems. Due to practical reasons, sampling campaigns are restricted to sizes of 350 microns or larger, which correspond to particles captured in zooplankton nets with a higher limit is usually established in 5 mm. However, the size definition for microplastics is still under debate, with a lower cut-off not well established yet. Lower size particles are important by several reasons. First, there is increasing evidence indicating that the degradation of higher particles to smaller sizes, including nanoplastics (<100 nm or <1000 nm depending on the adopted definition), is responsible for their disappearance as it has been noticed that there are far fewer microplastics in samplings at the sea surface than expected.
Besides the aesthetic issue, the concern about plastic debris is on the biological effect and potential risk for the environment and human health. The bigger fractions may cause fatal entanglement for many organisms or impair their normal life cycles. Plastic debris may also be ingested by higher organisms, such as birds or whales, which may cause their death. Less is known about the smaller fractions, especially those in the range of nanoplastics which can pass more easily through cellular barriers, and in the case of higher organisms such as humans, through the epithelial tissues and enter the bloodstream reaching different tissues and organs and possibly causing damage not yet observed.
It has also been suggested, and is the subject of intense experimental study, that plastic materials can act as vectors of environmental contaminants or can cause an indirect toxic effect due to the release of the additives they contain (flame retardants or plasticizers, for example, which on average represent about 4% of the weight of plastic materials).
Finally, plastics in the ocean are known substrates for the adsorption of many microorganisms. The term plastisphere, first coined by Dr. Linda Amaral-Zettler from the Marine Biological Laboratory, Dr. Tracy Mincer from Woods Hole Oceanographic Institution, and Dr. Erik Zettler from Sea Education Association, is now recognized as a new ecosystem, which hosts many microorganisms able to form biofilms. It is troubling that these biofilm-covered plastics may drift through the ocean and become a vector or reservoir for the spreading of potential pathogens or antibiotic resistance genes at a global scale. The same might be true for plastic debris in wastewaters and receiving bodies.
Humans and the environment are now facing the effects of long-lasting materials, such as plastic debris, and efforts should be made to control their production, use, disposal, and recycling when possible.
Session information: Ecotoxicology of micro and nanoplastics: Mechanistic approaches to understand their risk for the environment and human health
17 May 2018 | 10:50 a.m.–12:25 p.m. | Room N