PCBs found on nurdles from Balnakeil Beach

Plastic@Bay sent one hundred nurdles from Balnakeil Beach to International Pellet Watch (IPW), a program designed to monitor the pollution status of the oceans. Nurdles are small plastic pellets about the size of a lentil. Nurdles and other plastics are known to attract and concentrate toxic chemicals such as polychlorinated biphenyls (PCBs). The IPW results [1] show from 100 nurdles collected, the average PCBs concentration was 82 ppb (82 ng/g of nurdle sample).

Nurdles or plastic pellets are used each year to make nearly all our plastic products. Billions of nurdles get spilled during transportation and leak into the environment (Figure 1). Across the UK it is estimated that as many as 53 billion pellets could enter our oceans each year [2]. Like other microplastics, nurdles are ingested by many marine animals, entering the food chain.

Nurdles and other plastics are hydrophobic (repel water). They sorb (take up) and concentrate other hydrophobic chemicals like persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and DDT from sea water, onto their surface. Plastic recovered from the ocean have been found to contain pollutant concentrations orders of magnitude higher than the surrounding water [3]. PCBs, are now banned due to the risks they pose to the environment and human health. Long-term exposure to PCBs has been shown to cause a range of adverse effects on the nervous, immune and endocrine systems. They impair reproductive function and also cause cancer [4].

The IPW results show that the 100 nurdles collected are moderately polluted, with an average PCB concentration of 82 ppb. Moderately polluted nurdles have PCB concentrations ranging from 50-200 ppb, while highly to extremely polluted nurdles exhibit PCB concentrations in excess of 200 ppb [1].

The problem is that plastic particles such as nurdles acts as a vector for PCBs when ingested by marine animals. PCBs take a long time to degrade, and concentrate or bioaccumulate [5][6] in fatty tissues of animals. They then enter the food chain, eventually concentrating in dangerously high levels higher up the food chain in top predators such as orca whales, dolphins and porpoises, in a process called biomagnification [5] (Figure 2). Biomagnification; a herring eats small larvae, its mistakes nurdles for larvae and ingests ten from our sample, a salmon eats one hundred of these herrings, and an orca whale eats 100 salmon. A human eating salmon regularly has the potential to biomagnify PCBs levels in their fatty tissues by 1000 times greater than the original nurdle. While the killer whale now has the potential to biomagnify PCBs levels in their fatty tissues by 100000 times greater than the original nurdle. This is indeed an over-simplification of biomagnification which is a complex biological process that should include the actual mass of contaminated fat transferred from organism to organism. Notice that biomagnification in mammals exist through generations and offspring will be more contaminated then their mother.

Figure 2Biomagnification of PCBs in the food chain

Evidence of the harmful effects of biomagnification of PCBs are documented in a study of a killer whale called Lulu, was found dead on the Isle of Tiree in Scotland in 2016. Scottish Marine Animal Stranding Scheme reported the level of PCBs in the whales blubber to be 957 ppm (957 ng per mg fatty tissue) [7], making her the most contaminated find of this species in the Eastern Atlantic. Work, undertaken by Scotland’s Rural College in collaboration with the University of Aberdeen, found that Lulu was at least 20 years old. Based on analysis of the ovaries, it appears that she never reproduced, despite being much older than the average age for maturity in killer whales. One of the factors considered in killer whale which fail to reproduce is high levels of organic pollutants, such as PCBs [8].

Plastic@Bay took part in The Great Nurdle Hunt in 2017, 2019, and 2020. In 2017 and 2019 we found an average of 30-50 nurdles on Balnakeil Beach after 1.5 hours. Regrettably the quantity of nurdles has drastically increased in 2020 to 230 nurdles collected in 1.5 hours. Nurdles concentrate and transport dangerous toxic chemical through the environment. The harmful and toxic nature of nurdles needs to be highlighted and monitored. For this reason Plastic@Bay will continue to send samples to IPW. It takes one year to get the results back, so bear with us and click here to subscribe to our website to get future updates.

If you find lots of nurdles on your local beach and you are concerned about the concentrations of toxic chemicals concentrated on them you can send a sample into the International Pellet Watch. Click here for instructions. Nurdles are toxic so remember to wear gloves when collecting them.


  1. http://www.pelletwatch.org/gmap/
  2. https://www.nurdlehunt.org.uk/the-problem.html
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4314237/#!po=0.666667
  4. http://www.efsa.europa.eu/en/topics/topic/dioxins-and-pcbs
  5. https://science.jrank.org/pages/854/Bioaccumulation.html
  6. https://www.nature.com/articles/srep03263?source=post_page—————————
  7. https://strandings.org/smass/publications/reports/SMASS_Annual_Report_2016.pdf
  8. https://www.sruc.ac.uk/news/article/1860/scottish_killer_whale_contained_one_of_the_highest_concentrations_of_pcb_pollutants_ever_recorded_in_marine_mammals

Further Reading Effects Persistent Organic Chemicals on humans