Results from the Swedish Screening programme 2012

As an assignment from the Swedish Environmental Protection Agency, a screening study of pyrithiones and their major degradation products has been performed by IVL during 2012/2013. Zinc pyrithione (ZnPT) is a broad-spectrum biocide effective against bacteria, fungi and algae. ZnPT is commercially used as anti-dandruff agent in shampoos and as preservatives in cosmetics. Due to ZnPTs solubility in water it is suitable for use in outdoor and marine paints. Sodium pyrithione (HPT) is used as a preservative in cosmetics and as protective agent for fluids used in the metal industries. The objective of the present screening was to determine concentrations and to illuminate the fate of pyrithiones in sewage treatment plants and in small boat marinas by broadening the chemical analysis also to 2-pyridinesulfonic acid (PSA) and other pyrithione residues. ZnPT and/or cupper pyrithione (CuPT) were detected in 79% of influent and in 7% of effluent wastewaters from sewage treatment plants (STPs). A decrease in concentration from influent to effluent indicates that ZnPT and CuPT are degraded in the STPs. The absence of ZnPT and/or CuPT in sludge suggests that degradation will take place in contact with sludge. The degradation product PSA was the most abundant compound in the study. PSA was present in the majority of the wastewater samples and in all the sludge samples analysed. The concentration range of PSA in influents were 73 - 480 (median 240) ng/L (n=14), in effluents