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Antifouling biocide zinc pyrithione (ZnPT) and its biological fate have received little attention because this compound was assumed not to be persistent in marine ecosystems. An analytical procedure was developed that has proved to be efficient and very sensitive in extracting ZnPT and its main secondary products, Zn and ionized pyrithione (PT-), from both seawater and biological samples, namely in the gills and digestive gland of the bioindicator species Mytilus galloprovincialis. Short-term experiments were carried out to investigate ZnPT toxicity and bioaccumulation. The effects on survival and tissue bioaccumulation of ZnPT and its secondary products were studied on adult mussels from a natural population, collected in the harbor area of Porto Santo Stefano (Italy) and exposed to sublethal doses of the biocide for up to 7 d. Zinc pyrithione was shown to be persistent in the experimental seawater in the short term. A basal level of ZnPT and ionized PT- was detected in the mussels, indicating that ZnPT availability in the sampling site is already high enough to induce a detectable accumulation in individuals of the native population. Zinc pyrithione rapidly accumulated in the tissues of the exposed mussels, proportionately to both exposure concentration and time, identifying the gills and digestive gland as important targets in the biological pathway of the contaminants. Even though the 7-d median lethal concentration (LC50) = 8.27 µM established here appears high with respect to reported ZnPT environmental concentrations, the results indicate that this biocide could represent a threat for marine organisms in coastal environments and that further investigations on its biological effects at sublethal doses are needed. Environ. Toxicol. Chem. 2010;29:2583-2592. © 2010 SETAC [ABSTRACT FROM AUTHOR]

Abstract: The anti-fouling biocide zinc pyrithione (ZnPT) was recently demonstrated to be more persistent than expected in the coastal environment, and to have a potential for bioaccumulation. We investigated the occurrence of adverse effects in the marine mussel Mytilus galloprovincialis when exposed to non-lethal concentrations of the contaminant (0.2 and 0.4μM ZnPT), through the use of a battery of biomarkers from the molecular to the individual level. In particular, the expression of HSP27, HSP60, HSP70 and the presence of genotoxic damage were investigated in the gills and digestive gland of mussels by means of Western blot and TUNEL procedures, respectively. In addition, a stress on stress response test was performed in order to highlight a possible general stress conditions in the exposed bivalves. A concentration of 0.2μM ZnPT was found sufficient to trigger a marked stress response in gills and digestive gland, and a concentration-dependent HSP expression was highlighted. Moreover, at the tested concentrations, ZnPT was found able to induce genotoxic effects, as demonstrated by an amplified DNA fragmentation (up to +37% of TUNEL positive cells in comparison to the control group) and by an increased frequency of apoptotic cells (up to +5%) in the tissues of the exposed mussels. In addition, the stress on stress response test demonstrated a heavily decreased tolerance to anoxic conditions in mussels exposed to the higher tested concentration of the biocide (LT50 =5.4 days) compared to the control individuals (LT50 =10.7 days). Multivariate analyses highlighted a strong correspondence between the observed biological effects in M. galloprovincialis, HSP over-expression and DNA damage in the gills and digestive gland, and the bioaccumulation levels of the biocide. Data presented here indicate the need for further investigations on the ZnPT effects on the key species of marine coastal communities, with the aim of obtaining the necessary information for a sound risk assessment of the impact of this new antifoulant on marine ecosystems. [Copyright &y& Elsevier]

Abstract: The recent ban on TBT in boat antifouling paints has resulted in a large employment of the biocide zinc pyrithione (ZnPT) as substitute. Despite concerns of its environmental toxicity at ultra-trace concentrations, ZnPT has received little attention, as it was assumed to photo-degrade easily. However, recent evidence has suggested that ZnPT degrades only partially, and persists in the marine environment, especially where the influence of light is limited, such as in harbours. Short-term acute toxicity tests and life table response experiments (LTREs) were performed to evaluate the effects of ZnPT on the polychaete Dinophilus gyrociliatus at both individual and population level. The 96h-LC50 values for ZnPT on D. gyrociliatus were 7.8 and 11.5nM under dark and 12h light/12h dark conditions, respectively. In LTREs, laboratory cultured cohorts of D. gyrociliatus were exposed to sublethal concentrations of ZnPT (0.5 and 1nM) and compared to a control cohort. The survival among individuals exposed to the highest concentration decreased already during the 2nd week of life with respect to the control. The effects of the biocide on fecundity were even more evident: ZnPT caused a considerable reduction in both the exposed groups. The demographic approach applied here succeeded in identifying ZnPT effects both on the biological cycle and on the growth potential of polychaete D. gyrociliatus. The net growth rate (R 0) appeared to be the demographic parameter most sensitive to ZnPT, as the biocide exposure was associated with a sharp decline of R 0 in both the 0.5 and the 1nM groups (−41% and −63%, respectively) in comparison to the control cohort. The population growth rate λ (often used as an index of population fitness) and the life expectancy e 0 were also significantly reduced, while ZnPT exposure did not affect the generation time T. These results highlight the potential ecological threat posed by the biocide ZnPT, even at the very low tested concentrations, which are already detectable in some European marinas. [Copyright &y& Elsevier]