Fate of the insecticide chlordecone under methanogenic conditions

International audience ; Chlordecone (CLD) is an organochlorine insecticide of raw formula C10Cl10O, used from 1972 to 1993 (date of its ban) to control the banana weevil populations in French West Indies (FWI). By the time of writing, i.e. three decades after its ban use, CLD is still present in the FWI soils and has led to widespread contamination of the other FWI environmental compartments and associated food resources, resulting in a widespread impregnation of the West Indian population, with proven health consequences. Despite a series of measures to prevent CLD from reaching the consumer's plate, it continues to circulate actively at least among the population living in the most contaminated areas. A definitive solution to the problem would be to destroy the stock of CLD still present in soil. Of all the options available to achieve this goal, microbial degradation is generally an economically attractive option, as well as being potentially applicable in situ. Until the late 2010’s, because of its structure, CLD was considered non-biodegradable but the work of Dolfing et al (2012, Environ Sci Technol, 46, 8131-8139) showed that there was no thermodynamic impediment to its partial transformation (e.g dechlorination) or ultimate mineralization, and that microorganisms capable of catalyzing these reactions should/could exist. Old literature data (Jablonski et al., 1996, FEMS Microbiol. Lett. 139, 169-173) suggested that all methanogens would be enzymatically equipped to attack CLD and that natural sources of these organisms such as anaerobic digesters could eventually be used for bioaugmentation in a soil remediation process. This possibility was reinforced by the monitoring of CLD concentrations at the inlet and outlet of 2 FWI industrial anaerobic digesters treating contaminated rum vinasses, which showed that 53 to 91% of the CLD present in the vinasses was not found at the outlet of the digesters and had apparently not accumulated in their biomass (Macarie et al., 2013, https://hal.science/hal-01648258). ...