The term microplastic is used to describe pieces of plastic whose largest dimension is less than 5mm. Two kinds of microplastic are encountered in the environment: microplastic produced for a specific purpose, and fragments that have become detached from larger plastic objects. The first group includes plastic pellets, the basic material for the production of plastic, which are lost on their way to the factory to be processed, as well as plastic particles used in scouring and abrasive agents or in cosmetic articles such as peeling lotions that enter the environment through waste water. The second group, which is encountered above all in the sea, is made up of microplastic pieces that have been abraded from larger objects by the weather and mechanical influences.

Plastic in the Food Chain
The effect of ingesting plastic along with food on the various levels of the food chain is currently unforeseeable. As plastics may contain dangerous additives, and certain pollutants can concentrate on plastic, it is thought that the consequences could be far-reaching. Research work on mussels has already shown that microplastic parts can also be absorbed by the tissue of filter organisms.

Harmful Substances
A dangerous group of substances that concentrate on plastic are POPs – persistent organic pollutants). POPs are produced through chemical processes and are degradable only with great difficulty. As they are almost insoluble in water but easily soluble in fats, they are deposited in the fatty tissue of living organisms. With every further level in the food chain their concentration increases exponentially (bio-accumulation). A number of these substances are suspected of having undesirable effects on the hormone systems of living creatures, or of being carcinogenic. There is good reason to believe that they can have a negative impact on fertility, cause behavioral disorders and lead to defects in the immune system.

International Pellet Watch
With his organization «International Pellet Watch» at the Laboratory of Organic Geochemistry in Tokyo, Professor Hideshige Takada (Tokyo University of Agriculture and Technology, JP) studies the worldwide occurrence of long-lived pollutant in plastic pellets. A network of volunteer collectors sends him samples of around 200 pellets found on local beaches. The information thus acquired provides an indication of the global distribution of POPs, which can differ considerably from region to region.