Halocycles – Toxicological evaluation of acetal-like electrolysis products generated during the electrochemical treatment of lindane waste

The environmental persistence of lindane creates severe risks to the environment and human health. Consequently, many research groups are developing strategies for the sustainable degradation of this substance. However, most groups focus solely on dehalogenation or complete destruction, with no effort to preserve and reuse molecular structures such as the carbon skeleton or halogens as reactive intermediates. Within the Halocycles project, sustainable electrochemical methods have been developed to degrade lindane into various new acetal-like substances. The Halocycles project is an initiative funded by the Carl-Zeiss foundation with the aim of recycling contaminated sites containing various persistent halogenated substances, such as lindane, in a highly sustainable way. To ensure the safety of five of these products (ClADA, DnPrACA, DnBuACA, DiBuACA, DBnACA), their cytotoxicity and mutagenicity were evaluated in a series of toxicological assays. Experiments using three different cytotoxicity (resazurin reduction assay, neutral red assay, Celltiter-Glo® assay) assays revealed the acetal with the shortest carbon chain to be the most cytotoxic of the five substances but indicated no correlation between chain length and cytotoxicity. In addition, the products' mutagenic potential was assessed using the Ames fluctuation test with two bacterial strains (TA98 and TA100) to evaluate different endpoints. None of the substances significantly increased the frequency of frameshift mutations in the TA98 strain. However, in the absence of metabolic activation using the rat liver S9-mix, the short-chain acetals significantly increased the frequency of base-pair substitution mutations. Metabolic activation reduced the rate of base-pair substitution mutations following exposure to short chain acetals but increased that for the long chain acetal DBnACA. These findings provide an initial overview of the toxicity of electrolysis products produced within the Halocycles project for sustainable recycling of lindane waste.