Biodegradation of PVC microplastics outside the laboratory environment

Sammanfattning

Polyvinyl chloride (PVC) is a major global plastic and the dominant anthropogenic sink for chlorine, yet its environmental fate as microplastic and the potential formation of chlorinated degradation products remain poorly understood. This thesis synthesizes current knowledge on PVC microplastic biodegradation, with a particular focus on the identity and environmental implications of chlorinated intermediates and end-products. A systematic literature review was conducted following PRISMA guidelines, complemented by quantitative analysis of reported biodegradation experiments, comparison of analytical methods, and compilation of organisms and enzymes implicated in PVC transformation. Environmental monitoring reveals a pronounced “missing PVC” problem: despite large production volumes and high density, PVC rarely exceeds 5% of identified polymers in marine sediment datasets. Possible reasons are spectral changes, analytical bias, fragmentation, biodegradation. At the same time, field and laboratory studies indicate that soil and aquatic microbiomes can partially depolymerize and dechlorinate PVC, generating a range of chlorinated organic by-products. Bioinformatic searches in global ocean metagenomes reveal widespread homologs of recently characterized PVC-degrading enzymes, indicating a broad environmental potential for PVC transformation, though current data do not permit robust correlations with PVC pollution. Together, these findings challenge the traditional view of the PVC-backbone as environmentally inert and highlight the need to evaluate PVC biodegradation as a potentially significant source of chlorinated organic pollutants.