Twenty-six megatonnes of chemicals were illegally traded between 2004 and 2019, despite UN treaties meant to limit their transport and use. The substances, that can have harmful impacts on people and the environment, ranged from tetraethyl lead for fuels to tributyltin compounds for anti-fouling paint.

The new Swiss study has highlighted that there is a highly organised global trade of chemicals known to be hazardous to people and the environment. The researchers made their discovery by analysing over 66,000 trade records from the UN Comtrade database to identify the illicit trade taking place. Environmental experts are concerned as this new data shows that many chemicals that were previously thought to have been phased out globally are still being traded. These include pesticides such as 1,2-dibromoethane (EDB), a known carcinogen, and fuel additives, such as tetraethyl and tetramethyl lead, despite their neurotoxic effects.

Zhanyun Wang from Empa-Swiss Federal Laboratories for Material Science and Technology worked on the study with Hongyan Zou, Tao Wang and Zhong-Lang Wang. He says that the highly toxic chemicals being traded and transported globally ‘are hampering the protection of human and environmental health’. This is despite a UN treaty, the Rotterdam Convention, that was formulated to provide transparency on the trade of harmful chemicals.

Katharina Kummer Peiry, an expert in international law and waste and chemicals policy, says the Rotterdam Convention was ‘being brought in as developed countries realised the effect on the health and environment due to harmful chemicals, banned their use, but the same chemicals were still being exported to developing countries with less knowledge of their impact’. Peiry notes that the Rotterdam Convention ‘establishes a system by which states can decide to allow or not allow the import of the chemicals listed in the annexes of the convention’.

The Rotterdam Convention does not ban any chemical. It simply requires all states who are party to the convention to publicly list the chemicals they want to block from import. The UN shares this information and import bans should be respected by states that are participants in the convention. Transporting listed chemicals to a country that has signed up to the Rotterdam Convention is illegal under international law. However, the treaty has no formal enforcement mechanisms, and it is up to individual states to determine consequences for breaches.

Accurate records for these types of trades are often hard to come by so the study took a conservative approach in their estimations. Data quality had to be taken into account too as there were examples of countries trading with countries who kept no record of their exports. The group worked to fill in the gaps to give the best possible estimation of the scale of the illegal trade.

The study highlights that trade in 54 chemicals listed in the Rotterdam Convention has fallen around 70% since the convention was signed in 1998. However, the researchers uncovered that several thousand tonnes of tetraethyl and tetramethyl lead were traded in 2019. These chemicals were destined for fuel for aircraft, farm equipment and high-performance competition vehicles. However, the traded volumes of them in 2019 were 10 times lower than in 2012. Leaded petrol was banned worldwide in 2021 but there is no up to date data on whether or not it is still traded.

Tributyltin compounds are also still widely traded and around 4500 tonnes have been shipped every year since 2012, despite being banned internationally in 2008. They are often used in anti-fouling paints for ships but can accumulate in the environment and harm humans and wildlife. The study showed that these two classes of chemicals were primarily being exported by China to the US and Europe. Trade in ethylene dichloride, a carcinogen used in the production of PVC, has actually increased over the 15 years the study focused on, with the US exporting 7 megatonnes between 2015 and 2019 alone. The figures are conservative estimates of global trade and don’t include chemicals that are smuggled or sold on the black market.

While the study doesn’t include the very latest data, Wang points out that more can be done in terms of enforcement to limit the impact of this trade in the future. ‘Other treaties, such as the Montreal Protocol that phased out ozone depleting chemicals, worked well because they had strong punishment mechanisms. Work needs to be done to improve compliance, as well as looking at expanding the list of chemicals that are listed in the convention.’