After the severe explosion in the Chempark Leverkusen, the big question for the population is: What was in the cloud of smoke that formed during the fire in the disposal center, and in what quantities were the substances distributed in the area? Soot particles settled in the city of Leverkusen after the accident.
What is certain is that the burned tanks contained chlorinated solvents, among other things. On this basis, the State Office for Nature, Environment and Consumer Protection North Rhine-Westphalia (Lanuv) currently assumes that “dioxin, PCB and furan compounds” could have entered the environment.
“If chlorine compounds come into contact with great heat, there is always the risk that dioxin-like substances can arise,” says a spokesman for the State Environment Agency. So far it has been a suspicion as to which substances are involved and how high their concentration is, is now being determined in the dioxin laboratory. According to Lanuv, the results should be available on Friday.
“What matters is how the external exposure is made up.”
Dioxins are more than 200 chemical compounds with several chlorine atoms. What they have in common is that they are usually highly toxic and long-lived, so they only decompose slowly. The most toxic dioxin, called TCCD, contaminated the environment on a large scale after the chemical accident in Seveso in 1976. Due to their molecular structure, polychlorinated biphenyls (PCB) have properties similar to dioxins.
“The decisive factor is how the affected person is exposed,” says Martin Wilks, Director of the Swiss Center for Applied Human Toxicology. Was the toxic smoke inhaled by local residents? Or did the majority of the substances come down as soot flakes and settle on plants, for example? From the route of distribution and the concentration of the substances, it can then be concluded how high the risk to health is.
Dioxides accumulate mainly in the fatty tissue of living things. In particular, TCCD is considered to be carcinogenic when exposed to prolonged exposure, other dioxins also to a lesser extent. Effects similar to hormones are also conceivable. However, experts see a good chance that the affected areas can be decontaminated. There are limit values for the pollution of areas such as playgrounds; if the concentration is higher, a few centimeters of the soil would probably have to be removed and disposed of as hazardous waste.
Avoid skin contact with soot particles
“You shouldn’t try to wash off residues on food or garden vegetables,” warns Wilks. Instead, they would have to be disposed of properly. In general, residents should avoid skin contact with the soot particles, advises the toxicologist. For example, you shouldn’t wash garden furniture yourself if you notice suspicious soot particles on it, but seek advice from the hotlines that have been set up.
For decontamination, “the prevailing wind direction must first be determined,” says Daniel Dietrich, head of the human and environmental toxicology working group at the University of Konstanz. In this way, zones with high or low contamination could be determined. Dietrich suspects, however, that the explosion in Leverkusen released significantly fewer dioxins than, for example, the chemical accident in Seveso. This is indicated by the different course of the two accidents.
In the chemical plant near Seveso, Italy, a failed, self-sufficient chemical reaction caused an explosion. However, the temperatures were relatively low at the time and the raw materials in Seveso also promoted the formation of larger amounts of dioxins. Everything went much faster in Leverkusen. “It didn’t cook, there was a deflagration,” says Dietrich. This is indicated by the first large white cloud, which was later replaced by the striking black cloud of smoke.
For the time being, the warnings of the authorities continue to apply: do not touch any surfaces covered with soot or dust, do not carry anything into the house. “That applies until the laboratory results are available,” emphasized the spokesman for the State Environment Agency.