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What are microplastics?
The term "microplastics" is commonly used to describe synthetic plastic particles less than 5 millimeters in size. That’s about the size of an eraser on the end of a pencil. There are two types of microplastics, primary and secondary. Primary microplastics are plastics that are made to be 5 millimeters or smaller. Primary microplastics include microbeads which, up until the Microbead Free Waters Act in 2015 , were commonly found in health care products like face washes and toothpastes. Secondary microplastics occur when larger pieces of plastic like bottles and fishing line break down through photodegradation until the plastics become 5 millimeters or smaller.
Are microplastics a problem in the ocean?
Plastics are an emerging marine pollutant around the world. 80% of marine debris is plastic, and it makes up 90% of the particles floating on the ocean surface (read Setala et al. 2014 for more information). Plastic particles can also be hazardous to aquatic life. Many marine organisms, such as fish, oysters and plankton, are known to ingest plastics instead of their normal food. This can cause the animals to feel full without getting the energy they would normally get from food. Since plastics contain many chemicals, plastic particles can leach out these chemicals into the ocean, disrupting animal processes. These plastics include polypropylene, which is known to irritate eyes and the respiratory system, Bisphenol A, which affects hormone levels, behavior, and increases the risk of cancer and heart disease, and phenanthrene, which affects growth. Plastics also are very sorbent, meaning organic toxins in the water can latch on to them, making the plastics even more harmful to the organisms that swallow them.
Our work on microplastics has three objectives: (1) to develop methods for microplastics analysis in water and beach sediments that includes the smallest plastic size classes, which are often overlooked; (2) utilize these procedures to quantify microplastics in water samples and beaches along Delaware Bay; and (3) consider implications of these data for public policy pertaining to aquatic animal health and watershed management.
To collect the plastic samples used in this study, we conduct net tows at 16 sites along the Delaware Bay (link to project info page). The plastics are removed from the samples, weighed, and observed under a microscope to determine the number and types of plastics present.
The figure below illustrates the results of a tow conducted in Fall of 2016. The largest circle on this figure is located in a highly populated area. These results suggest that the mass of microplastics 1-5 mm in size is correlated with areas of high urbanization.
Are you a classroom teacher or non-formal educator looking to incorporate microplastics information into your classroom? Please have a look at our Education page for some great microplastics resources.