Marine sediment analysis confirms effectiveness of pollution control legislation

This study used samples from a dated sediment core taken from the North Sea to track levels of 90 chemicals over the last century.  The researchers report that, following legislative restrictions, pollution levels fell for many substances, but residual levels remain much higher than before contamination in several cases.

Chemical pollution is a major environmental concern globally and within the EU. In Europe, the issue has typically been characterised by cycles of development and utilisation of new chemicals followed by the identification of contamination levels and risks – leading to implementation of restrictions on use, often through national, European and international legal instruments. Data on the long-term impact of such regulations on widespread environmental concentrations of target pollutants are valuable in understanding and justifying such actions.

Persistent pollutants build up in marine areas, which they may enter either directly from shipping and coastal activities or indirectly through rivers, precipitation and atmospheric deposition. As marine sediments are laid down, these chemicals are held within them at concentrations proportional to the level of contamination at that point in time. This allows scientists to estimate historic pollution levels from samples taken from different depths in a sediment.

This study analysed sediment cores taken in 2017 at Skagerrak, an area of the North Sea known to accumulate high levels of sediment. The researchers determined the ages of the layers within the cores through analysis of lead and caesium isotopes. They analysed levels of 90 pollutants over a timescale of around 100 years. These included:

• eight trace metals of toxicological relevance – arsenic, cadmium, chromium, copper, nickel, lead, titanium and zinc;
• 21 per- and poly-fluoroalkyl substances (PFASs – a diverse group with applications in clothing, food processing and construction);
• 61 hydrophobic organic compounds (HOCs – another diverse group of substances including combustion products, pesticides and flame retardants).

They then considered the results in the context of the history of use and regulations of each substance or group.

Among the trace metals analysed, the researchers report that levels of lead in the sediment increased steadily from around 1958 to around 1981 and continuously decreased thereafter. They say that this corresponds to the use of lead in fuel additives, which was subjected to increasing restrictions in Europe through the 1970s and 1980s.

Of the 21 PFASs analysed, only six were repeatedly detected at high enough concentrations to allow analysis, they report, and all of these were found at increasing levels from the 1980s to the early 2010s, after which they declined sharply. They say that this aligns with regulatory measures that were brought in from the late 2000s, under the EU Persistent Organic Pollutants Regulation and the UN Stockholm Convention on Persistent organic pollutants, to control the use of PFASs.

Most of the HOCs measured showed a similar pattern of steady increase followed by consistent decrease, according to the researchers. However, they note that three of the four groups of chemicals within this category declined in concentration far more slowly than they had accumulated. For instance, they say that although the level of polychlorinated biphenyls (PCBs – probable human carcinogens, which were used as coolants and lubricants in transformers, capacitors, and other electrical equipment) began to decline in the 1980s following widespread restrictions, levels were still around six times higher in the 2010s than they had been 100 years previously.

The researchers assert that these findings confirm the importance, effectiveness and justification of regulatory regimes in reducing environmental pollution. However, they note that pollutants can continue to enter the environment even after bans, for instance from disposal and degradation of existing products or release of trapped chemicals when sea ice, glaciers or permafrost melt. They highlight that relatively short periods of chemical use prior to restrictions can lead to an accumulation of contamination that requires much longer periods to reverse. In conclusion they propose that future governmental pollution-monitoring schemes should cover known, emerging and novel contaminants and be flexible and more responsive to identify threats over short timeframes. They add that pollution-monitoring schemes should find ways to track mixtures of substances, both old and new, as interactions between them can increase toxicity to organisms.

Source:

Logemann, A., Reininghaus, M., Schmidt, M., Ebeling, A., Zimmermann, T., Wolschke, H., Friedrich, J., Brockmeyer, B., Pröefrock, D. and Witt, G. (2022) Assessing the chemical anthropocene – Development of the legacy pollution fingerprint in the North Sea during the last century. Environmental Pollution 302: 119040.

Available from: https://doi.org/10.1016/j.envpol.2022.119040

To cite this article/service:

“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.