For hundreds of years the Firth of Forth and the streams and rivers feeding it have been exposed to heavy industrial pollution. A succession of water quality regulations means that the Forth is now much cleaner than it has been for generations. However some of the harmful toxins used in industries like chemical manufacture, paper mills, dye works, agriculture, mining, construction and oil refining do not break down easily in the environment and so have left a permanent legacy.
These harmful industrial chemicals known as 'Persistent Bioaccumulating Toxins' (PBTs) can accumulate in animal and human tissue causing long term damage. Although lots of PBTs are now banned many can still be found in the sediment and water in the Forth.
In the marine environment plastics attract and absorb PBTs and can concentrate them to levels millions of times higher than in the surrounding water. A sample of nurdles collected in the Firth of Forth has been scientifically analysed for a variety of these chemicals, the results show significant levels of DDTs and PCBs and extremely high levels of PAHs (Polycyclic aromatic hydrocarbons).
To see how these results from the Forth compare globally please follow this link to the International Pellet Watch website