Toxicological cross-check

in vitro culture of human nerve cells (yellow; nuclei: purple) exposed to various concentrations of different flame retardants: PBDE 99 is already in use and suspected to be harmful to health; the substance was thus used as a positive control. At a concentration of 100 µM, PBDE 99 as well as ETA-DOPO and EG-DOPO showed significant damage to the cells. In contrast, this was not observed for DOPO and EDA-DOPO.

The team, led by Cordula Hirsch, exposed both lung cells and macrophages (scavenger cells) to a number of flame retardants. The Empa researchers could only conclude that there were no toxic reactions for one of the three substances. However, the lungs are primarily affected by flame retardants during production and processing in powder form. Subsequently, the toxic substances enter the body by penetrating the skin and there can give rise to skin damage or even neurotoxic effects.

Hirsch, therefore, passed the samples on to Stephanie Mathes at the Zurich University of Applied Sciences (ZHAW) in Wädenswil, who examined the new flame retardants for skin tolerance with her team. Here, the researchers cultivated human skin and exposed it to varying concentrations of the flame retardant. Stefan Schildknecht and his colleagues at the University of Konstanz were responsible for the neurological investigations. He examined the direct impact of the substance on neural effects using tests involving brain cells.

The conclusion of the researchers: two of the three flame retardants failed the tests. Both of these resulted in damage to the test cells used and will thus not be developed further. However, the researchers also showed that the newly developed EDA-DOPO not only has better flame retardancy than previously available products, but also had no toxic effects at all in the tests that were conducted. EDA-DOPO is thus a good candidate to take forward to a next stage of development.