Pesticides Are Corroding History

Scientists discover that a modern pesticide accelerated the corrosion of an ancient Roman relic.

Chlorobenzenes, a chemical that was once used in pesticides and is known to accumulate in soil and water sources, have been detected in traces on a corroded Roman bowl that dates to the Late Iron Age (between 43 and 410 AD). According to the study, which was published in the journal Scientific Reports, soil contaminated with chlorobenzenes may continue to be a threat to the preservation of archaeological artifacts buried under the earth.

Chlorobenzenes are synthetic compounds that may be harmful in high concentrations, and most have been banned from usage in the UK due to environmental concerns. However, it is believed that these compounds accumulated in the environment as a result of earlier industrial and agricultural activities. A copper-alloy Roman bowl was discovered in 2016 on a farm in Kent (UK), a site that has been used for agriculture since at least 1936.

The recent history of the Roman Bowl–(A) the area where the bowl was found in relation to other Roman sites, exact findspot cannot be shown to protect the site (B) the interior and (C) exterior of the bowl during conservation and (D) the bowl on display at Sandwich Museum. Credit: Scientific Reports, Carvalho et al., map created by Luciana da Costa Carvalho using heritage maps.

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Luciana da Costa Carvalho and colleagues analyzed the green and brown-colored corrosion on the bowl to identify their different components. They found elements that were indicative of the changes over time in the soil caused by human activities. In the green-colored corrosion, the authors found chlorobenzenes were present. The authors also found diethyltoluamide (also known as DEET) in the brown-colored corrosion, a modern compound that is still used in insect repellents.

The authors suggest that the chlorobenzenes were associated with increased corrosion in the Roman bowl. They conclude that even though chlorobenzenes are no longer used in the UK, polluted soil may still threaten the preservation of archaeological material still buried and more research needs to be undertaken to better understand the processes involved.

Reference: “The influence of pesticides on the corrosion of a Roman bowl excavated in Kent, UK” by Luciana da Costa Carvalho, Dana Goodburn-Brown, James S. O. McCullagh and A. Mark Pollard, 6 October 2022, Scientific Reports.
DOI: 10.1038/s41598-022-17902-9