Indirect estimation of degradation time for zinc pyrithione and copper pyrithione in seawater

Environmental occurrence, biological effects, and health implications of zinc pyrithione: A review

Due to the detrimental effects on aquatic organisms and ecosystem, tributyltin as a antifouling agent have been banned worldwide since 1990s. As a replacement for tributyltin, zinc pyrithione (ZnPT) has emerged as a new environmentally friendly antifouling agent. However, the widespread use of ZnPT unavoidably leads to the occurrence and accumulation in aquatic environments, especially in waters with limited sunlight. Despite empirical evidence demonstrating the ecotoxicity and health risks of ZnPT to different organisms, there has been no attempt to compile and interpret this data. The present review revealed that over the past 50 years, numerous studies have documented the toxicity of ZnPT in various organisms, both in vitro and in vivo. However, long-term effects and underlying mechanisms of ZnPT on biota, particularly at environmentally realistic exposure levels, remain largely unexplored. In-depth studies are thus necessary to generate detailed ecotoxicological information of ZnPT for environmental risk assessment and management.

Male Reproductive Toxicity of Antifouling Chemicals: Insights into Oxidative Stress-Induced Infertility and Molecular Mechanisms of Zinc Pyrithione (ZPT)

Zinc pyrithione (ZPT), a widely utilized industrial chemical, is recognized for its versatile properties, including antimicrobial, antibacterial, antifungal, and antifouling activities. Despite its widespread use, recent research has shed light on its toxicity, particularly towards the male reproductive system. While investigations into ZPT's impact on male reproduction have been conducted, most of the attention has been directed towards marine organisms. Notably, ZPT has been identified as a catalyst for oxidative stress, contributing to various indicators of male infertility, such as a reduced sperm count, impaired sperm motility, diminished testosterone levels, apoptosis, and degenerative changes in the testicular tissue. Furthermore, discussions surrounding ZPT's effects on DNA and cellular structures have emerged. Despite the abundance of information regarding reproductive toxicity, the molecular mechanisms underlying ZPT's detrimental effects on the male reproductive system remain poorly understood. This review focuses specifically on ZPT, delving into its reported toxicity on male reproduction, while also addressing the broader context by discussing other antifouling chemicals, and emphasizing the need for further exploration into its molecular mechanisms.

Toxic effects and potential mechanisms of zinc pyrithione (ZPT) exposure on sperm and testicular injury in zebrafish

Zinc pyrithione (ZPT) is widely recognized for its beneficial properties as an antifouling, antibacterial, and antifungal agent. Despite its positive industrial contributions, ZPT has been proven to exhibit toxicity towards various ecosystems, particularly affecting marine life. However, there is still a dearth of comprehensive research on ZPT toxicity and its toxicological mechanism in reproductive systems of aquatic organisms. In our study, we conducted a thorough analysis and unveiled a multitude of abnormalities in zebrafish sperm and testicular tissue caused by ZPT exposure, including a dose-dependent diminishing of testosterone levels, various sperm deformities, decreased sperm concentration and motility, and ROS-induced testicular tissue DNA damage. In addition, our study suggested that ZPT-induced testicular damage is associated with heightened oxidative stress, apoptosis, and possible hyperpolarization of the mitochondrial membrane. Through RNA-seq analysis, a total of 409 DEGs associated with ZPT-induced testicular injury were identified, and the hub gene was determined using a protein-protein interaction network (PPI). The genes and pathways uncovered in this study point to potential mechanisms of ZPT exposure on sperm and testicular injury in zebrafish.

Copper pyrithione and zinc pyrithione induce cytotoxicity and neurotoxicity in neuronal/astrocytic co-cultured cells via oxidative stress

Previous studies on copper pyrithione (CPT) and zinc pyrithione (ZPT) as antifouling agents have mainly focused on marine organisms. Even though CPT and ZPT pose a risk of human exposure, their neurotoxic effects remain to be elucidated. Therefore, in this study, the cytotoxicity and neurotoxicity of CPT and ZPT were evaluated after the exposure of human SH-SY5Y/astrocytic co-cultured cells to them. The results showed that, in a co-culture model, CPT and ZPT induced cytotoxicity in a dose-dependent manner (~ 400 nM). Exposure to CPT and ZPT suppressed all parameters in the neurite outgrowth assays, including neurite length. In particular, exposure led to neurotoxicity at concentrations with low or no cytotoxicity (~ 200 nM). It also downregulated the expression of genes involved in neurodevelopment and maturation and upregulated astrocyte markers. Moreover, CPT and ZPT induced mitochondrial dysfunction and promoted the generation of reactive oxygen species. Notably, N-acetylcysteine treatment showed neuroprotective effects against CPT- and ZPT-mediated toxicity. We concluded that oxidative stress was the major mechanism underlying CPT- and ZPT-induced toxicity in the co-cultured cells.

How do biocidals affect the non-target marine organisms: the short-term effects of antifouling agent sodium pyrithione on Mediterranean mussels (Mytilus galloprovincialis, Lamark 1819)

The metallic pyrithiones are used as antifouling paints for marine vehicles against fouling organisms. However, they are dissolved in marine water and have negative impacts on marine non-target organisms. This study evaluated the adverse effects of sodium pyrithione (NaPT) on Mytilus galloprovincialis using total hemocyte counts (THCs), oxidative stress and antioxidant parameters, and histopathological observations. Mussels were exposed to 0.1 and 1 μg/L NaPT for 96 h. The THC values of the NaPT-exposed mussels significantly decreased (p < 0.05). Lipid peroxidation and advanced oxidative protein products of digestive gland and gill tissues were decreased but only the digestive gland tissues of 0.1 μg/L NaPT values were significantly decreased compared to control groups (p < 0.05). Histological alterations were observed in the gill and the digestive gland tissues revealing malformations and hyperplasia of gill lamella; degenerations and loss of tubules of digestive gland after exposure to NaPT for 96 h. As a result, biocidal sodium pyrithione has adverse effects on the mussels even in short-term exposures and low concentrations.

Comparison of the accumulation and effects of copper pyrithione and copper sulphate on rainbow trout larvae

Copper pyrithione (CuPT) is used as a co-biocide in new antifouling paints but its toxicity remains little known. To compare the toxicity of copper-based compounds, rainbow trout (Oncorhynchus mykiss) larvae were exposed for 8-day to CuPT and CuSO4 at equivalent copper concentrations. CuPT exposure led to the greatest accumulation of Cu in larvae. Exposure to 10 µg.L-1 CuPT induced 99% larval mortality but only 4% for CuSO4-exposed larvae. The larval development and growth were affected by CuPT (from 0.5 µg.L-1 Cu) but not by CuSO4. Lipid peroxidation was not induced by either contaminant. The expression of genes involved in oxidative stress defence, detoxification and copper transport was induced in larvae exposed to CuSO4 and CuPT but at higher concentrations for CuPT. This study highlights the marked toxicity of CuPT for early life stages of fish and raises the question of the possible environmental risks of this antifouling compound.

Chemical hazard of robotic hull in-water cleaning discharge on coastal embryonic fish

In-water cleaning (IWC) involves the removal of biofilms and foulants from the hull of a ship using brush or water jet. During IWC, several factors associated with the harmful chemical contaminants release to the marine environment, which can create "hotspots" of chemical contamination in coastal areas. To elucidate the potential toxic effects of IWC discharge, we investigated developmental toxicity in embryonic flounder, which are sensitive life stage to chemical exposure. Zinc and copper were the dominant metals, while zinc pyrithione was the most abundant biocide associated with IWC discharge in two remotely operated IWC. Discharge from IWC carried by both remotely operated vehicles (ROVs) produced developmental malformations including pericardial edema, spinal curvature, and tail-fin defects. In an analyses of differential gene expression profiles (fold-change of genes with a cutoff < 0.05) as assessed by high-throughput RNA sequencing, genes associated with muscle development were commonly and significantly changed. The gene ontology (GO) of embryos exposed to IWC discharge from ROV A activities highly enriched muscle and heart development, while cell signaling and transport were evident in embryos exposed to IWC discharge of ROV B. We analyzed the gene network by significant GO terms. In the network, TTN, MYOM1, CASP3, and CDH2 genes appeared to be key regulators of the toxic effects on muscle development. In embryos exposed to ROV B discharge, HSPG2, VEGFA, and TNF genes related to the nervous system pathway were affected. These results shed light on the potential impacts of muscle and nervous system development in non-target coastal organisms exposed to contaminants found in IWC discharge.

Effects of antifouling compounds on the growth of macroalgae Undaria pinnatifida

Seaweeds are some of the principal primary producers of marine environments, and they are important ecological elements of coastal ecosystems. The effects of harmful chemicals on seaweeds may adversely affect coastal ecosystems, hence we aimed to develop a new phytotoxicity test using the gametophytes of a common temperate kelp species, Undaria pinnatifida (KU-1630), for the widely used antifouling chemical substances Cybutryne, Diuron, Cu2+, and Zn2+. Toxicity to gametophytes of U. pinnatifida was assessed by comparing the relative growth rate (RGR) at the logarithmic growth phase. Fragmentation method, initial algal biomass, photon irradiance, and adhesive period were investigated for developing optimal test conditions. Cybutryne exposure tests were performed with seven replicates and control, the RGR ranging from 0.17 to 0.19, while mean 7-day EC50 and no observed effect concentration (NOEC) were 5.1 μg/L and 1.8 μg/L, respectively. The 7-day EC50 for other antifoulants was 14 μg/L for Diuron, 17 μg/L for Cu2+, and 1500 μg/L for Zn2+. This test method demonstrated high sensitivity and reproducibility, and it may be added to the routine methods used for toxicity evaluation of hazardous chemicals.

A novel thiourea derivative for preconcentration of copper(II), nickel(II), cadmium(II), lead(II) and iron(II) from seawater samples for Flame Atomic Absorption Spectrophotometry

A novel adsorbent, 3-phenyl-1-(2-pyridyl)thiourea (PPTU) was synthesized and its adsorption capabilities were studied for Cu(II), Cd(II), Ni(II), Pb(II) and Fe(II) cations in the waters such as tap and polluted seawaters. The kinetics, Langmuir and Freundlich isotherms were discussed related to the adsorptions. The adsorption capacities of PPTU were found 9.4; 12.6; 90.9; 57.1 and 30.4 mg g^-1 and preconcentration with PPTU including the FAAS step yielded the LOQ values 0.46; 2.65; 1.12; 2.65 and 1.72 ng mL^-1 for Cu(II), Cd(II), Ni(II), Pb(II) and Fe(II), respectively. The adsorbent after the elutions and washings could be reused three times in the next adsorptions. The interferences on the adsorptions arising from the major cations of the seawater and the usability of PPTU for interested metals in the seawater were discussed. The proposed method is simple with highly efficient and green preconcentration procedure for trace analysis of the target metal ions.

Effects of copper pyrithione (CuPT) on apoptosis, ROS production, and gene expression in hemocytes of white shrimp Litopenaeus vannamei

Copper pyrithione (CuPT) is used globally to prevent biofouling. However, it poses certain risks to aquatic ecosystems. To understand the effects of CuPT on Litopenaeus vannamei after exposure to different concentrations of CuPT (0, 64, and 128 μg/L), the apoptotic cell ratio, production of reactive oxygen species (ROS), and gene expression in the hemocytes were studied at 0, 3, 12, 24, and 48 h. The results revealed that ROS production was induced significantly at 3-48 h only in the 128 μg/L groups. The apoptotic cell ratio was increased significantly at 12 and 24 h in the 64 μg/L groups, and at 3-48 h in the 128 μg/L groups. Meanwhile, CuPT exposure changed gene expression in hemocytes at different levels. In the 64 μg/L groups, the expression of Mn-superoxide dismutase (MnSOD) was induced at 12 h, glutathione peroxidase (GPx) was induced at 24 and 48 h, caspase-3 induced at 24 h, metallothionein (MT) and HSP70 were increased at 3 h. In the 128 μg/L groups, MnSOD was increased at 3 h and then decreased at 12-48 h, GPx was up-regulated at 3, 24 h and then decreased at 48 h, caspase-3 was increased at 24 h, MT was increased at 3-48 h, HSP60 and HSP70 were up-regulated at 3-12 h. These results indicated that CuPT induced ROS production and the expression of caspase-3 in hemocytes, then caused hemocyte apoptosis. Expression levels of MnSOD, GPx, MT, HSP60, and HSP70 were up-regulated to protect the hemocyte against CuPT stress.

The degradation and environmental risk of camptothecin, a promising marine antifoulant

Given the adverse environmental impacts of the antifoulants currently used in marine antifouling paints, such as copper and booster biocides, it is urgent to identify potential substitutes that are environmentally benign. Here, we examined the degradation of camptothecin (a natural product previously identified as an efficient antifoulant in the laboratory and in the field) under various conditions and evaluated the environmental risks associated with its use as a marine antifoulant. We found that camptothecin was rapidly photolyzed in seawater: the half-life of camptothecin was less than 1 d under a light intensity of 1000-20,000 lx and was approximately 0.17 d under sunlight irradiation. At pH 4 and pH 7, camptothecin had half-lives of 30.13 and 16.90 d, respectively; at 4 °C, 25 °C, and 35 °C, the half-lives of camptothecin were 23.90, 21.66, and 26.65 d, respectively. Camptothecin biodegradation in seawater was negligible. The predicted no-effect concentration (PNEC) of camptothecin was 2.19 × 10^-1 μg L^-1, while the average predicted environmental concentrations (PECs) in open seas, shipping lanes, commercial harbors, and marinas were 6.14 × 10^-7, 9.39 × 10^-7, 6.80 × 10^-3, and 5.03 × 10^-2 μg L^-1, respectively. The PEC/PNEC ratio of camptothecin was much lower than 1 (i.e., 2.80 × 10^-6, 4.29 × 10^-6, 3.11 × 10^-2, and 2.30 × 10^-1 for open seas, shipping lanes, commercial harbors, and marinas, respectively), indicating that the use of camptothecin as a marine antifoulant posed little environmental risk.

Zinc pyrithione exposure compromises oocyte maturation through involving in spindle assembly and zinc accumulation

Zinc Pyrithione (ZPT), a Food and Drug Administration (FDA) approved chemical, is widely used for topical antimicrobials and cosmetic consumer products, including anti-dandruff shampoos. ZPT and its degraded byproducts have detected in large quantities in the environment, and identified to pose healthy risks on aquatic organisms and human. However, so far, knowledge about ZPT effects on female reproduction, particularly oocyte maturation and quality, is limited. Herein, we investigated the adverse impact of ZPT on mouse oocyte maturation and quality in vitro and found exposure to ZPT significantly compromises oocyte maturation. The results revealed that ZPT disturbed the meiotic cell cycle by impairing cytoskeletal dynamics, kinetochore-microtubule attachment (K-MT), and causing spindle assembly checkpoints (SAC) continuous activation. Further, we observed the microtubule-organizing centers (MTOCs) associated proteins p-MAPK and Aurora-A were disrupted in ZPT-treated oocytes, signified by decreased expression and abnormal localization, responsible for the severe cytoskeletal defects. In addition, ZPT exposure induced a significant increase in the levels of H3K9me2, H3K9me3, H3K27me1, and H3K27me3, suggesting the alterations of epigenetic modifications. Moreover, the accumulation of zinc ions (Zn2+) was observed in ZPT-treated oocytes, which was detrimental because overmuch intracellular Zn2+ disrupted oocyte meiosis. Finally, these above alterations impaired spindle organization and chromosome alignment in metaphase-II (MII) oocytes, indicative of damaged oocytes quality. In conclusion, ZPT exposure influenced oocyte maturation and quality via involvement in MTOCs-associated proteins mediated spindle defects, altered epigenetic modifications and zinc accumulation.

Comparative toxicity study of waterborne two booster biocides (CuPT and ZnPT) on embryonic flounder (Paralichthys olivaceus)

A new generation of booster biocides that include metal pyrithiones (PTs) such as copper pyrithione (CuPT) and zinc pyrithione (ZnPT) are being used as tributyltin alternatives. In the marine environment, ZnPT can easily transchelate Cu to form CuPT, and the environmental fate and persistence of these two metal pyrithiones are closely related. Although some data on the toxicity of biocides on marine fish are available, little is known about their toxicity and toxic pathway. We thus compared the toxic effects of CuPT and ZnPT on embryonic olive flounder (Paralichthys olivaceus) by investigating their adverse effects based on developmental morphogenesis and transcriptional variation. In our study, the toxic potency of CuPT was greater with respect to developmental malformation and mortality than ZnPT. Consistent with the developmental effects, the expression of genes related to tail fin malformation (including plod2, furin, and wnt3a) was higher in embryonic flounder exposed to CuPT than in those exposed to ZnPT. Genes related to muscle and nervous system development exhibited significant changes on differential gene expression profiles using RNA sequencing (cutoff value P < 0.05). Gene ontology analysis of embryos exposed to CuPT revealed affected cellular respiration and kidney development, whereas genes associated with cell development, nervous system development and heart development showed significant variation in embryonic flounder exposed to ZnPT. Overall, our study clarifies the common and unique developmental toxic effects of CuPT and ZnPT through transcriptomic analyses in embryonic flounder.

Microbial Diversity and Activity During the Biodegradation in Seawater of Various Substitutes to Conventional Plastic Cotton Swab Sticks

The European Parliament recently approved a new law banning single-use plastic items for 2021 such as plastic plates, cutlery, straws, cotton swabs, and balloon sticks. Transition to a bioeconomy involves the substitution of these banned products with biodegradable materials. Several materials such as polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), poly(butylene succinate) (PBS), polyhydroxybutyrate-valerate (PHBV), Bioplast, and Mater-Bi could be good candidates to substitute cotton swabs, but their biodegradability needs to be tested under marine conditions. In this study, we described the microbial life growing on these materials, and we evaluated their biodegradability in seawater, compared with controls made of non-biodegradable polypropylene (PP) or biodegradable cellulose. During the first 40 days in seawater, we detected clear changes in bacterial diversity (Illumina sequencing of 16S rRNA gene) and heterotrophic activity (incorporation of ³H-leucine) that coincided with the classic succession of initial colonization, growth, and maturation phases of a biofilm. Biodegradability of the cotton swab sticks was then tested during another 94 days under strict diet conditions with the different plastics as sole carbon source. The drastic decrease of the bacterial activity on PP, PLA, and PBS suggested no bacterial attack of these materials, whereas the bacterial activity in PBAT, Bioplast, Mater-Bi, and PHBV presented similar responses to the cellulose positive control. Interestingly, the different bacterial diversity trends observed for biodegradable vs. non-biodegradable plastics allowed to describe potential new candidates involved in the degradation of these materials under marine conditions. This better understanding of the bacterial diversity and activity dynamics during the colonization and biodegradation processes contributes to an expanding baseline to understand plastic biodegradation in marine conditions and provide a foundation for further decisions on the replacement of the banned single-used plastics.

Exposure to sublethal concentrations of zinc pyrithione inhibits growth and survival of marine polychaete through induction of oxidative stress and DNA damage

Effects of zinc pyrithione (ZnPT) and inorganic Zn (ZnCl₂) were evaluated on a marine polychaete at sublethal concentrations for 14 days. ZnPT decreased the burrowing activity and AChE activity with higher acute toxicities, implying its cholinergic effect. Both ZnPT and ZnCl₂ increased MDA levels at higher concentrations, suggesting lipid peroxidation and oxidative stress. In the ZnPT-treated polychaete, enzymatic activities of CAT and SOD were elevated with an increase in DNA damage, whereas the levels of GSH, GPx, GR, and GST were decreased. However, in the ZnCl₂-treated polychaete, the level of GSH and enzymatic activities of CAT, SOD, GPx, GR, and GST were significantly elevated to resist cellular damage. During 97 days depuration experiment, significant mortality and growth retardation were observed in the ZnPT-exposed polychaete. Overall, ZnPT was found to be more toxic than ZnCl₂ with the harmful impact on antioxidant defense system and DNA stability in marine polychaete.

Rapid toxicity assessment of six antifouling booster biocides using a microplate-based chlorophyll fluorescence in Undaria pinnatifida gametophytes

Biocides of antifouling agents can cause problems in marine ecosystems by damaging to non-target algal species. Aquatic bioassays are important means of assessing the quality of water containing mixtures of contaminants and of providing a safety standard for water management in an ecological context. In this study, a rapid, sensitive and inexpensive test method was developed using free-living male and female gametophytes of the brown macroalga Undaria pinnatifida. A conventional fluorometer was employed to evaluate the acute (48 h) toxic effects of six antifouling biocides: 4,5-Dichloro-2-octyl-isothiazolone (DCOIT), diuron, irgarol, medetomidine, tolylfluanid, zinc pyrithione (ZnPT). The decreasing toxicity in male and female gametophytes as estimated by EC50 (effective concentration at which 50% inhibition occurs) values was: diuron (0.037 and 0.128 mg l-1, respectively) > irgarol (0.096 and 0.172 mg l-1, respectively) > tolylfluanid (0.238 and 1.028 mg l-1, respectively) > DCOIT (1.015 and 0.890 mg l-1, respectively) > medetomidine (12.032 and 12.763 mg l-1, respectively). For ZnPT, 50% fluorescence inhibition of U. pinnatifida gametophytes occurred at concentrations above 0.4 mg l-1. The Undaria method is rapid, simple, practical, and cost-effective for the detection of photosynthesis-inhibiting biocides, thus making a useful tool for testing the toxicity of antifouling agents in marine environments.

Waterborne zinc pyrithione modulates immunity, biochemical, and antioxidant parameters in the blood of olive flounder

In this study, potential immunological and hematological effects of different concentrations (0, 1, 10, and 50 μg L^-l) of waterborne zinc pyrithione (ZnPT) were studied in the blood of the olive flounder Paralichthys olivaceus over 30 days. Reduced alternative complement activity (ACH50) and lysozyme activity were measured in fish exposed to 10 and/or 50 μg L^-l of ZnPT for 20 days. Decreased levels of total Ig were also observed in response to 10 and/or 50 μg L^-l ZnPT during the exposure period. Levels of cortisol, a marker of stress, were significantly increased by 10 and 50 μg L^-l ZnPT from day 10, and by 1 μg L^-l exposure on day 30. The levels of red blood cells (RBCs) and white blood cells (WBCs) decreased following exposure to 10 and/or 50 μg L^-l ZnPT, while no significant change was observed in hemoglobin level. Concentrations of total protein and albumin were significantly reduced with 50 μg L^-l ZnPT at day 20. Alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activities were significantly increased following exposure to 10 and/or 50 μg L^-l ZnPT. Lipid peroxidation was induced by ZnPT, and higher concentrations (10 and 50 μg L^-l) significantly increased intracellular malondialdehyde levels during exposure. Regarding the subsequent antioxidant response, intracellular glutathione levels increased significantly in response to 10 and 50 μg L^-l ZnPT on days 20 and 30. Similarly, catalase and superoxide dismutase activity was significantly increased in response to 10 and 50 μg L^-l ZnPT after day 10. Taken together, changes in the studied parameters suggested the immunotoxicity of ZnPT, with modulations observed in hematological homeostasis and oxidative stress induction in the blood of olive flounder.

Behavioral and biochemical effects of the antifouler and antidandruff zinc pyrithione on the freshwater fish Gambusia holbrooki

The presence of pharmaceutical residues in the aquatic environment is receiving great attention since the levels of these substances have significantly increased in this compartment, potentially leading to adverse ecological effects. Zinc pyrithione (ZnPt) is a widely used organometallic biocide, which is incorporated into antifouling formulas, such as paints, to prevent the establishment of biofilms on surfaces exposed to the aquatic environment. It is also used in cosmetics, such as antidandruff shampoos and soaps. Considering this wide use, and the absence of a significant amount of data on the toxicity of ZnPt especially towards non-target organisms, the objective of this study was to characterize the toxicity of ZnPt, on several ecological relevant endpoints assessed in the fish Gambusia holbrooki. For this purpose, we measured traits related to feeding and aggressive behavior, as well as indicators of oxidative stress (CAT and GSTs), neurotoxicity (AChE), and anaerobic metabolism (LDH), after acute and chronic exposures to ZnPt. In terms of behavioral features, the feeding test showed the occurrence of significant differences between the control animals and those exposed to a concentration of ZnPt of 45 μg/L. In addition, ZnPt caused changes in terms of oxidative stress biomarkers (CAT and GSTs), for both exposure periods. ZnPt was also capable of causing changes in the cholinergic neurotransmission functioning and anaerobic metabolism, but only following the chronic exposure.

Effects of zinc pyrithione on biochemical parameters of the freshwater Asian clam Corbicula fluminea

Zinc pyrithione (ZnPT) is an organometallic biocide with bactericide, algaecide, and fungicide activity. Considering this biological activity, ZnPT has been used in anti-fouling paints, and also in human therapeutics and cosmetics, in shampoos to treat dandruff and seborrhoea. Despite its potential uses and consequent presence in the aquatic environment, the ecotoxicological effects of ZnPT are poorly understood. This work aims to characterise the effects of ZnPT in biochemical parameters of the Asian clam, one of the most invasive bivalves known for its biofouling action in hydro-dependent industries, using a classical (LC₅₀ determination) and a biomarker-based approach (quantification of the activities of catalase, GSTs, and acetylcholinesterase, and also the muscle glycogen content). The here determined LC₅₀-96 h for zinc pyrithione was 2.17 mg/L. ZnPT caused significant increases in the activity of catalase and of cholinesterases. These findings evidence the pro-oxidative effects caused by the metabolism of ZnPT. Despite the absence of clear effects, it is important to stress that the presence of ZnPT in the wild is usually accompanied by other pyrithiones, whose co-existence can contribute to the exertion of considerable toxic effects.

An integrated approach to assess the impacts of zinc pyrithione at different levels of biological organization in marine mussels

The mechanisms of sublethal toxicity of the antifouling biocide, zinc pyrithione (ZnPT), have not been well-studied. This investigation demonstrates that 14-d sublethal exposure to ZnPT (0.2 or 2 μM, alongside inorganic Zn and sea water controls) is genotoxic to mussel haemocytes but suggests that this is not caused by oxidative DNA damage as no significant induction of oxidised purines was detected by Fpg-modified comet assay. More ecologically relevant endpoints, including decreased clearance rate (CR), cessation of attachment and decreased tolerance of stress on stress (SoS), also showed significant response to ZnPT exposure. Our integrated approach was underpinned by molecular analyses (qRT-PCR of stress-related genes, 2D gel electrophoresis of proteins) that indicated ZnPT causes a decrease in phosphoenolpyruvate carboxykinase (PEPCK) expression in mussel digestive glands, and that metallothionein genes are upregulated; PEPCK downregulation suggests that altered energy metabolism may also be related to the effects of ZnPT. Significant relationships were found between % tail DNA (comet assay) and all higher level responses (CR, attachment, SoS) in addition to PEPCK expression. Principal component analyses suggested that expression of selected genes described more variability within groups whereas % tail DNA reflected different ZnPT concentrations.

The influence of seawater properties on toxicity of copper pyrithione and its degradation product to brine shrimp Artemia salina

Copper pyrithione (CuPT) is a biocide, used worldwide to prevent biofouling on submerged surfaces. In aquatic environments it rapidly degrades, however, one of the degradation products (HPT) is known to react with cupric ion back to its parent compound. Not much is known about the behavior and toxicity of CuPT and its degradation product HPT in different water systems. Hence, our aim was to investigate the ecotoxicity of CuPT, HPT as well as Cu²⁺ to the brine shrimp Artemia salina in natural seawater and organic matter-free artificial seawater. Moreover, in order to elucidate the influence of ionic strength of water on CuPT toxicity, tests were performed in water media with modified salinity. The results showed that CuPT was the most toxic to the exposed crustaceans in a seawater media with the highest salinity and with no organic matter content. HPT in a presence of cupric ion converted to CuPT, but the measured CuPT concentrations and the mortality of A. salina in natural water were lower than in artificial water. The toxicity of CuPT to A. salina was significantly influenced by the organic matter content, salinity, and proportions of constituent salts in water. In a combination with cupric ion, non-hazardous degradation product HPT exhibits increased toxicity due to its rapid transformation to its parent compound.

Copper pyrithione, a booster biocide, induces abnormal muscle and notochord architecture in zebrafish embryogenesis

The metal pyrithiones, principally zinc (ZnPT) and copper (CuPT), are replacing tributyltin (TBT) as antifouling agents. Zebrafish embryos were exposed within the first hour after fertilization to 12 and 64 µg/L of CuPT for 24 h. Morphological abnormalities in notochord and muscle architecture were observed at 96 h post fertilization (hpf). TEM revealed abnormal electron dense deposits in the notochord sheath and muscle fiber degeneration in animals treated with 12 µg/L of CuPT. Embryos that were exposed to 64 µg/L of CuPT displayed severe muscle fiber degeneration including abnormal A and I band patterning and altered z disk arrangement. Abnormalities in the notochord sheath, swelling of the mitochondria and numerous lipid whorls were also noted. Total antioxidant capacity was significantly decreased in embryos exposed to 12 and 64 µg/L of CuPT. Acridine orange staining revealed an increase in apoptosis particularly in the brain, eye, heart and tail regions of both treatment groups. Apoptosis was confirmed with an increase in caspase 3/7 activity in both treatment groups. Severe alternations in primary motor neuron axon extensions, slow tonic muscle fibers and fast twitch fibers were observed in CuPT treated embryos. There was a significant upregulation in sonic hedgehog and myod1 expression at 24 hpf in the 12 µg/L treatment group. Exposed zebrafish embryos showed ultra-structural hallmarks of peroxidative injury and cell death via apoptosis. These changes question the use of copper pyrithione as an antifouling agent.

Comparison of Toxicities of Metal Pyrithiones Including Their Degradation Compounds and Organotin Antifouling Biocides to the Japanese Killifish Oryzias latipes

Japanese killifish Oryzias latipes were exposed to three levels (0, 1, and 10 µg l^-1) of copper pyrithione (CuPT₂), zinc pyrithione (ZnPT₂), six of their degradation products, and the organotin compounds tributyltin (TBT) and triphenyltin (TPT) for 48 h at 20 °C. All individual fish exposed to 1 and 10 µg l^-1 of CuPT₂ or 10 µg l^-1 of ZnPT₂ were dead within 12 h, respectively, and at 24 h the survival rate of the fish exposed to 1 µg l^-1 of ZnPT₂ was 50%. All fish exposed to 10 µg l^-1 of ZnPT₂ showed morphological abnormalities in the form of vertebral deformity. None of the fish exposed to six of the degradation products of PTs, TBT, and TPT died during a 48-h exposure period, but various biological effects were observed in the fish exposed to these chemicals: abnormalities of respiration and swimming behavior, and decreased hatchability. Our findings suggest that O. latipes has a higher ecological risk of CuPT₂ and ZnPT₂ exposure than of TBT and TPT exposure during their life history. Because these antifouling biocides have been used in both freshwater and marine environments, our results highlight these biocides' deleterious effects on the freshwater fish as well as marine fish, and they indicate freshwater and marine pollution.

Efficacy and Ecotoxicity of Novel Anti-Fouling Nanomaterials in Target and Non-Target Marine Species

Biofouling is a global problem that affects virtually all the immersed structures. Currently, several novel environmentally friendly approaches are being tested worldwide to decrease the toxicity of biocides in non-fouling species, such as the encapsulation/immobilization of commercially available biocides, in order to achieve control over the leaching rate. The present study addresses the toxicity of two widely used booster biocides, zinc pyrithione (ZnPT) and copper pyrithione (CuPT), in its free and incorporated forms in order to assess their toxicity and anti-fouling efficacy in target and non-target species. To achieve this goal, the following marine organisms were tested; the green microalgae Tetraselmis chuii (non-target species) and both target species, the diatom Phaeodactylum tricornutum and the mussel Mytilus edulis. Organisms were exposed to both biocides, two unloaded nanostructured materials and nanomaterials loaded with biocides, from 10 μg/L to 100 mg/L total weight, following standard protocols. The most eco-friendly and simultaneously efficient anti-fouling solution against the two photosynthetic species (nanoclays loaded with ZnPT) was then tested on mussels to assess its lethal efficacy (LC₅₀ = 123 μg/L) and compared with free biocide (LC₅₀ = 211 μg/L) and unloaded material (LC₅₀ > 1000 μg/L). A second exposure test with sub-lethal concentrations (lower than 100 μg/L), using mussels, was carried out to assess biochemical changes caused by the tested compounds. Oxidative stress, detoxification and neurotransmission markers were not responsive; however, different antioxidant patterns were found with free ZnPT and loaded nanoclay exposures. Thus, the immobilization of the biocide ZnPT into nanoclays proved to be a promising efficient and eco-friendly anti-fouling strategy.

The effects of copper pyrithione, an antifouling agent, on developing zebrafish embryos

A substitute for the organotins has been the use of metal pyrithiones, principally zinc and copper (CuPT) as antifouling agents. Zebrafish, Danio rerio, embryos were exposed after fertilization to increasing concentrations of CuPT (2, 4, 8, 12, 16, 32 and 64 μg/L) for 24 h. Morphological abnormalities at 30, 96 and 120 hours post fertilization (hpf) were recorded. Abnormalities at concentrations of 12 μg/L and higher were observed. Notochords became severely twisted as concentrations increased. These distortions of the notochord originated in the tail at the lower concentrations and proceeded rostrally with increasing dose. Edema was observed in the cardiac and yolk sac regions at the 12 and 16 μg/L CuPT concentrations. Light microscopy showed disorganization of muscle fibers, disruption and distortion of the transverse myoseptum and vacuolization of the myocyte. Hatching was measured every 12 h for 5 days following the 24 h exposure. Hatching decreased in a dose dependent manner. At 120 hpf, 47 % of the 64 μg/L CuPT treated embryos hatched. Inductively coupled plasma atomic absorbance spectrophotometry (ICPAAS) revealed copper bioaccumulation in whole embryo tissue and was significantly elevated in 32 and 64 μg/L CuPT treatment groups as compared to controls. Lipid peroxidation end products were significantly increased in animals exposed to 32 and 64 μg/L of CuPT. These data demonstrate that oxidative stress may play a role in the toxicity. The abnormalities and deformities observed in fish larvae would significantly decrease survival in polluted aqua-systems and question the use of this product as an antifouling agent.

Ecotoxicological effect of zinc pyrithione in the freshwater fish Gambusia holbrooki

Currently diverse biocidal agents can be used for distinct applications, such as personal hygiene, disinfection, antiparasitic activity, and antifouling effects. Zinc pyrithione is an organometallic biocide, with bactericidal, algicidal and fungicidal activities. It has been recently incorporated in antifouling formulas, such as paints, which prevent the establishment of a biofilm on surfaces exposed to the aquatic environment. It has also been used in cosmetics, such as anti-dandruff shampoos and soaps. Previously reported data has shown the presence of this substance in the aquatic compartment, a factor contributing to the potential exertion of toxic effects, and there is also evidence that photodegradation products of zinc pyrithione were involved in neurotoxic effects, namely by inhibiting cholinesterases in fish species. Additional evidence points to the involvement of zinc pyrithione in alterations of metal homeostasis and oxidative stress, in both aquatic organisms and human cell models. The present work assesses the potential ecotoxicity elicited by zinc pyrithione in the freshwater fish Gambusia holbrooki after an acute (96 h) exposure. The oxidative stress was assessed by the quantification of the activities of specific enzymes from the antioxidant defense system, such as catalase, and glutathione-S-transferases; and the extent of peroxidative damage was quantified by measuring the thiobarbituric acid reactive substances levels. Neurotoxicity was assessed through measurement of acetylcholinesterase activity; and a standardized method for the description and assessment of histological changes in liver and gills of was also used. Zinc pyrithione caused non-specific and reversible tissue alterations, both in liver and gills of exposed organisms. However, histopathological indices were not significantly different from the control group. In terms of oxidative stress biomarkers, none of the tested biomarkers indicated the occurrence of pro-oxidative effects, suggesting that the oxidative pathway is not the major toxicological outcome of exposure to zinc pyrithione.

Immunotoxicity in ascidians: antifouling compounds alternative to organotins-IV. The case of zinc pyrithione

New biocides such as the organometallic compound zinc pyrithione (ZnP) have been massively introduced by many countries in formulations of antifouling paints following the ban on tributyltin (TBT). The effects of sublethal concentrations (LC50=82.5 μM, i.e., 26.2 mg/l) on cultured haemocytes of the ascidian Botryllus schlosseri have been investigated and compared with TBT. The percentage of haemocytes with amoeboid morphology and containing phagocytised yeast cells were significantly (p<0.05) reduced after exposure to 0.1 (31.7 μg/l) and 0.5 μM (158 μg/l), respectively. An antagonistic interaction in inducing cytoskeletal alterations was observed when ZnP and TBT were co-present in the exposure medium. ZnP affected only the actin component. As caused by TBT, ZnP induced apoptosis and inhibited both oxidative phosphorylation and lysosomal activities. In contrast to the case of TBT, a decrement in Ca(2+)-ATPase activity and a decrease in cytosolic Ca(2+) were detected after incubation at the highest concentration (1 μM, i.e., 317.7 μg/l) used. In comparison with other antifouling compounds, ZnP shows as much toxicity as TBT to cultured haemocytes at extremely low concentrations interfering with fundamental cell activities.

Degradation kinetics of a potent antifouling agent, butenolide, under various environmental conditions

Here, we investigated the degradation kinetics of butenolide, a promising antifouling compound, under various environmental conditions. The active ingredient of the commercial antifoulant SeaNine 211, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), was used as positive control. The results showed that the degradation rate increased with increasing temperature. Half-lives of butenolide at 4 °C, 25 °C and 40 °C were>64 d, 30.5 d and 3.9 d, respectively. Similar half-lives were recorded for DCOIT: >64 d at 4 °C, 27.9 d at 25 °C and 4.5d at 40 °C. Exposure to sunlight accelerated the degradation of both butenolide and DCOIT. The photolysis half-lives of butenolide and DCOIT were 5.7 d and 6.8 d, respectively, compared with 9.7 d and 14.4 d for the dark control. Biodegradation led to the fastest rate of butenolide removal from natural seawater, with a half-life of 0.5 d, while no obvious degradation was observed for DCOIT after incubation for 4 d. The biodegradative ability of natural seawater for butenolide was attributed mainly to marine bacteria. During the degradation of butenolide and DCOIT, a gradual decrease in antifouling activity was observed, as indicated by the increased settlement percentage of cypris larvae from barnacle Balanus amphitrite. Besides, increased cell growth of marine diatom Skeletonema costatum demonstrated that the toxicity of seawater decreased gradually without generation of more toxic by-products. Overall, rapid degradation of butenolide in natural seawater supported its claim as a promising candidate for commercial antifouling industry.

Acute and chronic toxicities of zinc pyrithione alone and in combination with copper to the marine copepod Tigriopus japonicus

Zinc pyrithione (ZnPT) is a widely used booster biocide in combination with copper (Cu) in antifouling paints as a substitute for tributyltin. The co-occurrence of ZnPT and Cu in coastal marine environments is therefore very common, and may pose a higher risk to marine organisms if they can result in synergistic toxicity. This study comprehensively investigated the combined toxicity of ZnPT and Cu, on the marine copepod Tigriopus japonicus, for the first time, based on both 96-h acute toxicity tests using adult copepods and chronic full-life cycle tests (21 d) using nauplii <24-h old. As ZnPT has been reported to be easily trans-chelated to copper pyrithione (CuPT) in the presence of Cu, the acute toxicities of CuPT alone and in combination with Cu on adult copepods were also assessed. Our results showed that ZnPT and Cu exhibited a strong synergistic toxic effect on the copepod in both acute and chronic tests. During the acute test, the mortalities of adult copepods increased dramatically even with an addition of Cu at concentrations as low as 1-2 μg/L compared with those exposed to ZnPT alone. Severe chronic toxicities were further observed in the copepods exposed to ZnPT-Cu mixtures, including a significant increase of naupliar mortality, postponing of development from naupliar to copepodid and from copepodid to adult stage, and a significant decrease of intrinsic population growth when compared with those of copepods exposed to ZnPT or Cu alone. Such synergistic effects might be partly attributable to the formation of CuPT by the trans-chelation of ZnPT and Cu, because CuPT was found to be more toxic than ZnPT based on the acute toxicity results. Mixtures of CuPT and Cu also led to synergistic toxic effects to the copepod, in particular at high Cu concentrations. A novel non-parametric response surface model was applied and it proved to be a powerful method for analysing and predicting the acute binary mixture toxicities of the booster biocides (i.e., ZnPT and CuPT) and Cu on the copepod. To better protect precious marine resources, it is necessary to revise and tighten existing water quality criteria for biocides, such as ZnPT and CuPT, to account for their synergistic effects with Cu at environmentally realistic levels.

Current and emerging environmentally-friendly systems for fouling control in the marine environment

Following the ban in 2003 on the use of tributyl-tin compounds in antifouling coatings, the search for an environmentally-friendly alternative has accelerated. Biocidal TBT alternatives, such as diuron and Irgarol 1051®, have proved to be environmentally damaging to marine organisms. The issue regarding the use of biocides is that concerning the half-life of the compounds which allow a perpetuation of the toxic effects into the marine food chain, and initiate changes in the early stages of the organisms' life-cycle. In addition, the break-down of biocides can result in metabolites with greater toxicity and longevity than the parent compound. Functionalized coatings have been designed to repel the settlement and permanent attachment of fouling organisms via modification of either or both surface topography and surface chemistry, or by interfering with the natural mechanisms via which fouling organisms settle upon and adhere to surfaces. A large number of technologies are being developed towards producing new coatings that will be able to resist biofouling over a period of years and thus truly replace biocides as antifouling systems. In addition urgent research is directed towards the exploitation of mechanisms used by living organisms designed to repel the settlement of fouling organisms. These biomimetic strategies include the production of antifouling enzymes and novel surface topography that are incompatible with permanent attachment, for example, by mimicking the microstructure of shark skin. Other research seeks to exploit chemical signals and antimicrobial agents produced by diverse living organisms in the environment to prevent settlement and growth of fouling organisms on vulnerable surfaces. Novel polymer-based technologies may prevent fouling by means of unfavourable surface chemical and physical properties or by concentrating antifouling compounds around surfaces.

Species sensitivity distribution approach to primary risk analysis of the metal pyrithione photodegradation product, 2,2'-dipyridyldisulfide in the Inland Sea and induction of notochord undulation in fish embryos

To carry out a primary risk assessment in the Inland Sea of Japan for 2,2'-dipyridyldisulfide [(PS)(2)], a metal pyrithione photodegradation product, we used a methodology based on the species sensitivity distribution (SSD) estimated with a Bayesian statistical model. We first conducted growth inhibition tests with three marine phytoplankton species, Tetraselmis tetrathele, Chaetoceros calcitrans, and Dunaliella tertiolecta. We also performed acute and early life stage toxicity (ELS) tests with a teleost fish, the mummichog (Fundulus heteroclitus). The algal growth inhibition tests revealed that the 72-h EC(50) ranged from 62 to 1100 μg/L. Acute toxicity tests with larval mummichogs revealed that the 96-h LC(50) was approximately 500 μg/L based on the actual toxicant concentrations. ELS testing of (PS)(2) under continuous flow-through conditions for 50 days revealed that growth was the most sensitive endpoint, and both total length and body weight were significantly lower in the groups exposed to 27 μg/L (PS)(2) compared to the solvent control group. We determined a lowest observed effect concentration of 17 μg/L and a NOEC of 5.9 μg/L based on the actual toxicant concentrations. By using the ecotoxicity data (LC(50) and EC(50)) from this study and previous work, we calculated a hazardous concentration that should protect 95% and 99% of species (HC(5) and HC(1)) based on the SSD derived with a Bayesian statistical model. The medians with 90% confidence intervals (parentheses) of the HC(5) and HC(1) were 31.0 (3.2, 101.8) μg/L and 10.1 (0.5, 44.2) μg/L, respectively. In the ELS test, about 80% of hatched larvae exposed to 243-μg/L (PS)(2) displayed a notochord undulation. To elucidate the cause of the notochord undulation, we carried out embryo toxicity tests by exposing embryos at various developmental stages to (PS)(2). Exposure to (PS)(2) through the entire gastrulae stage was important to induction of the morphological abnormality. Lysyl oxidase activity was significantly decreased in these embryos compared to the control group, a suggestion that lysyl oxidase-mediated collagen fiber organization, which is essential for notochord formation, is disrupted because of (PS)(2) toxicity. We also investigated the occurrence of (PS)(2) in water from several coastal sites of the Inland Sea and detected (PS)(2) at concentrations of <0.1-0.4 ng/L. Comparison of environmental concentrations to the HC values suggests that the current ecological risk posed by (PS)(2) in the Inland Sea is low. This is the first report of the detection of a metal pyrithione degradation product in the natural marine environment.

Nanomolar concentrations of zinc pyrithione increase cell susceptibility to oxidative stress induced by hydrogen peroxide in rat thymocytes

Zinc pyrithione is used as an antifouling agent. However, the environmental impacts of zinc pyrithione have recently been of concern. Zinc induces diverse actions during oxidative stress; therefore, we examined the effect of zinc pyrithione on rat thymocytes suffering from oxidative stress using appropriate fluorescent probes. The cytotoxicity of zinc pyrithione was not observed when the cells were incubated with 3 μM zinc pyrithione for 3 h. However, zinc pyrithione at nanomolar concentrations (10 nM or more) significantly increased the lethality of cells suffering from oxidative stress induced by 3 mM H(2)O(2). The application of zinc pyrithione alone at nanomolar concentrations increased intracellular Zn(2+) level and the cellular content of superoxide anions, and decreased the cellular content of nonprotein thiols. The simultaneous application of nanomolar zinc pyrithione and micromolar H(2)O(2) synergistically increased the intracellular Zn(2+) level. Therefore, zinc pyrithione at nanomolar concentrations may exert severe cytotoxic action on cells simultaneously exposed to chemicals that induce oxidative stress. If so, zinc pyrithione leaked from antifouling materials into surrounding environments would be a risk factor for aquatic ecosystems. Alternatively, zinc pyrithione under conditions of oxidative stress may become more potent antifouling ingredient.

Toxicity and metabolism of copper pyrithione and its degradation product, 2,2'-dipyridyldisulfide in a marine polychaete

We conducted acute toxicity tests and sediment toxicity tests for copper pyrithione (CuPT) and a metal pyrithione degradation product, 2,2'-dipyridyldisulfide [(PS)2], using a marine polychaete Perinereis nuntia. The acute toxicity tests yielded 14-d LC50 concentrations for CuPT and (PS)2 of 0.06 mg L(-1) and 7.9 mg L(-1), respectively. Sediment toxicity tests resulted in 14-d LC50 concentrations for CuPT and (PS)2 of 1.1 mg kg(-1) dry wt. and 14 mg kg(-1) dry wt., respectively. In addition to mortality, sediment avoidance behavior and decreases in animal growth rate were observed; growth rate was the most susceptible endpoint in the sediment toxicity tests of both toxicants. Thus, we propose lowest observed effect concentrations of 0.3 mg kg(-1) dry wt. and 0.2 mg kg(-1) dry wt. for CuPT and (PS)2, respectively, and no observed effect concentrations of 0.1 mg kg(-1) dry wt. for both CuPT and (PS)2. The difference in the toxicity values between CuPT and (PS)2 observed in the acute toxicity test was greater than the difference in these values in the sediment toxicity test, and we attribute this to (PS)2 being more hydrophilic than CuPT. In addition to the toxicity tests, we analyzed conjugation activity of several polychaete enzymes to the toxicants and marked activity of palmitoyl coenzyme-A:biocides acyltransferase and UDP-glucuronosyl transferase was observed.

Novel antifouling agent zinc pyrithione: determination, acute toxicity, and bioaccumulation in marine mussels (Mytilus galloprovincialis)

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.

Acute toxicity and synergism of binary mixtures of antifouling biocides with heavy metals to embryos of sea urchin Glyptocidaris crenularis

Acute toxicity and synergism of four antifouling biocides (Irgarol 1051, dichlofluanid, tolylfluanid and Sea-Nine 211) and five heavy metals (Ni, Pb, Zn, Cd and Cu) are investigated using the sea urchin embryos of Glyptocidaris crenularis (G. crenularis) at six typical developmental stages, that is, 2-cell, 4-cell, 8-cell, blastula, gastrula and 4-arm pluteus. Our results show that the toxicity of the four biocides is in an order of Sea-Nine 211 > tolylfluanid > dichlofluanid > Irgarol 1051 and their -log EC(50) values at all stages are strongly linearly correlated with the 1-octanol/water partition coefficient (log P) values (correlation coefficients R > 0.72) indicating the importance of hydrophobicity for the embryonic toxicity. For the five heavy metals, the EC(50) ranges from 0.36 to 30.78 μM and the toxicity follows an order of Cu > Pb > Zn > Cd >Ni. The significant correlation (R > 0.79) between the -log EC50 and the bioconcentration factor (log BCF) values of metals also indicate that the bioaccumulation property of metals contributes to their aquatic toxicity. In addition, the joint effects of the biocides with the heavy metals in embryonic development are assessed by using a concentration addition model. Synergistic effects are observed in almost all 25 mixtures, showing that Cu yields the strongest while Ni the weakest synergistic toxic effects on the embryos development.

Toxicity of metal pyrithione photodegradation products to marine organisms with indirect evidence for their presence in seawater

We evaluated the acute toxicities of the metal pyrithiones (MePTs)--copper pyrithione (CuPT) and zinc pyrithione (ZnPT)--to four species of marine algae and a marine crustacean (Tigriopus japonicus). We also performed acute toxicity tests using six of the main MePT photodegradation products: pyridine-N-oxide (PO); 2-mercaptopyridine (HPS); pyridine-2-sulfonic-acid (PSA); 2-mercaptopyridine-N-oxide (HPT); 2,2'-dithio-bis-pyridine ([PS](2)); and 2,2'-dithio-bis-pyridine-N-oxide ([PT](2))-and three marine organisms representing three trophic levels: an alga (Skeletonema costatum), a crustacean (T. japonicus), and a fish (Pagrus major). The acute toxicity values (72-h EC(50)) of CuPT, ZnPT, HPT, (PT)(2), (PS)(2), HPS, PO, and PSA for S. costatum, which was the most sensitive of the test organisms to the chemicals tested, were 1.5, 1.6, 1.1, 3.4, 65, 730, >100,000, and >100,000 microg l(-1), respectively. CuPT was detected in the growth media used for S. costatum tests and in seawater containing HPT or (PT)(2); the concentration of CuPT in seawater containing HPT was highly dependent on the Cu(2+) concentration. These results indicate that in the presence of sufficient Cu(2+), the toxicities of HPT and (PT)(2) should be assessed as CuPT because in Japan MePTs are most frequently used as antifouling booster biocides in conjunction with cuprous oxide.

Toxicity and bioaccumulation of the booster biocide copper pyrithione, copper 2-pyridinethiol-1-oxide, in gill tissues of Salvelinus fontinalis (brook trout)

This investigation studied the acute effects of copper pyrithione (CuPT) exposure on juvenile brook trout, Salvelinus fontinalis. Morphologic changes, copper bioaccumulation, and markers of oxidative stress in gill tissue were studied. Juvenile brook trout were treated with one of six experimental doses of CuPT (2-64 microg/L) for 2 hours. A seventh group served as a control population. Inductively coupled plasma atomic absorbance spectrophotometry (ICPAAS) analysis demonstrates significantly increased levels of copper in gill tissue (p < 0.001). Results from scanning electron microscopy and histological analysis demonstrate the formation of club-shaped lamella, edema, fusion of secondary lamella, loss of microridge structures and epithelial exfoliation. Transmission electron microscopy revealed altered morphology of chloride cells, including the swollen appearance of mitochondria with disruption of internal cristae and lipid membrane disruption. Thiobarbituric acid reactive substance (TBARS) assays demonstrated increased levels of lipid peroxidation products in gill tissue. Assays for the total antioxidant capacity of gill tissue revealed significantly lowered antioxidant levels. This data indicates that CuPT is potentially harmful to nontarget aquatic organisms at environmentally relevant doses.

Toxicity of fungicides to natural bacterial communities in wetland water and sediment measured using leucine incorporation and potential denitrification

We assessed potential toxicity of fungicides to natural bacterial communities from a constructed wetland, located in southern Sweden, and compared the sensitivity of two endpoints indicating bacterial activity, leucine incorporation, and potential denitrification, in detecting toxicity. The effects of eight fungicides (benomyl, carbendazim, carboxin, captan, cycloheximide, fenpropimorph, propiconazole, and thiram), two bactericides (bronopol and chlortetracycline) as controls, and one reference compound (3,5-dichlorophenol), were tested in a water-sediment microcosm set-up. Leucine incorporation was measured in both the water and sediment column, while potential denitrification was measured for the entire microcosm. The bactericides and the reference compound gave sigmoid concentration-response curves for both endpoints in all but one case. The fungicides thiram, captan, and benomyl, and to a lesser extent fenpropimorph and propiconazole had quantifiable toxic effects on leucine incorporation, with EC(50) values ranging from 3 to 70 mg l(-1), while carbendazim, carboxin, and cycloheximide had little effect at the investigated concentrations. Only thiram and captan inhibited potential denitrification; the other fungicides showed no quantifiable effect. A greater toxic effect on leucine incorporation was recorded for bacterial communities associated with the water column, compared to the sediment column, for all tested compounds. Leucine incorporation was the more sensitive method for toxicity assessment of bacterial communities, and also allowed for a rapid and simple way of comparing exposure in the sediment and water column, making it an attractive standard method for community based toxicological assays in aquatic environments.

Variation in toxicity of copper pyrithione among populations and families of the barnacle, Balanus amphitrite

Inter- and intra-population variation in the toxicity of the antifouling biocide copper pyrithione (CuPT) was examined for nauplius larvae of the barnacle Balanus amphitrite. Nauplii were collected from brooding adults from four sites within the Newport River estuary (NC), chosen based on an initial estimation of recent and historical human activities that affect local contamination levels. Each site was characterized for the presence of polycyclic aromatic hydrocarbons and for the frequency of gastropod imposex, an indicator of contamination by organotins. Sensitivity of nauplii to CuPT varied significantly across the sites/populations, with LC(50) values ranging from 4.0 microg l(-1) to 6.1 microg l(-1). Larvae from the most contaminated site were the most sensitive to CuPT. Intrapopulation variation in toxicity was investigated by exposing nauplius larvae from 15 maternal families to a fixed concentration of CuPT (6.1 microg l(-1)). Variation in larval mortality among the families was significant, ranging from 15.1% to 98.9%.

Leaching of hydrophobic Cu and Zn from discarded marine antifouling paint residues: evidence for transchelation of metal pyrithiones

Leaching of Cu and Zn from a composite of discarded antifouling paint residues ([Cu] = 288 mg g(-1); [Zn] = 96 mg g(-1)) into natural sea water has been studied over a period of 75 h. Total Cu and Zn were released according to a pseudo first-order reaction, with rate constants on the order of 0.3 and 2.5 (mg L(-1))(-1) h(-1), respectively, and final concentrations equivalent to the dissolution of about 8 and 2% of respective concentrations in the composite. Time-distributions of hydrophobic metals, determined by solid phase extraction-methanol elution, were more complex. Net release of hydrophobic Cu was greater in the absence of light than under a sequence of light-dark cycles; however, hydrophobic Zn release was not detected under the former conditions but contributed up to 50% of total aqueous Zn when light was present. These observations are interpreted in terms of the relative thermodynamic and photolytic stabilities of biocidal pyrithione complexes.

DNA microarray analysis suggests that zinc pyrithione causes iron starvation to the yeast Saccharomyces cerevisiae

Zinc pyrithione has been used in anti-dandruff shampoos and in anti-fouling paint on ships. However, little is known of its mode of action. We characterized the effects of sub-lethal concentrations of zinc pyrithione (Zpt) on Saccharomyces cerevisiae using DNA microarrays. The majority of the strongly upregulated genes are related to iron transport, and many of the strongly downregulated genes are related to the biosynthesis of cytochrome (heme). These data suggest that Zpt induces severe iron starvation. To confirm the DNA microarray data, we supplemented cultures containing Zpt with iron, and the growth of the yeast was restored significantly. From these results, we propose that the principal toxicity of zinc pyrithione arises from iron starvation.

Inhibition of acetylcholinesterase by metabolites of copper pyrithione (CuPT) and its possible involvement in vertebral deformity of a CuPT-exposed marine teleostean fish

In a previous study, we demonstrated that exposure to an antifouling biocide, copper pyrithione (CuPT), early during life induced vertebral deformity in the larvae of a marine fish, the mummichog (Fundulus heteroclitus). Skeletal deformities may be caused by inhibition by of acetylcholiensterase (AChE) activity, and to elucidate the mechanism underlying the CuPT-associated vertebral deformity, we first examined whether CuPT, zinc pyrithione (ZnPT), and their degradation products could inhibit AChE activity in the fish. Two of the degradation products, 2,2'-dipyridyldisulfide [(PS)(2)] and 2,2'-dithiobispyridine-N-oxide [(PT)(2)], but neither CuPT nor ZnPT, exhibited prominent AChE-inhibiting activity. Secondly, thin-layer chromatography revealed that mummichog hepatic microsomes metabolized CuPT to produce (PS)(2) in a microsome-dependent manner. The AChE inhibition induced in CuPT-exposed fish is likely due to (PS)(2) that was produced through metabolism of acquired CuPT. (PS)(2) may cause therefore skeletal deformity in CuPT-exposed fish by means of its neuromuscular blocking properties, through a mechanism similar to that proposed for animals exposed to organophosphorous pesticides.

Trace metals in antifouling paint particles and their heterogeneous contamination of coastal sediments

Antifouling paint residues collected from the hard-standings of a marine leisure boat facility have been chemically characterised. Scanning electron microscopy revealed distinct layers, many containing oxidic particles of Cu and Zn. Quantitative analysis indicated concentrations of Cu and Zn averaging about 300 and 100 mg g(-1), respectively, and small proportions of these metals (<2%) in organometallic form as pyrithione compounds. Other trace metals present included Ag, Cd, Cr, Ni, Pb and Sn, with maximum concentrations of about 330, 75, 1200, 780, 1800 and 25,000 microg g(-1), respectively. Estuarine sediment collected near a boatyard contained concentrations of Cu and Zn an order of magnitude greater than respective concentrations in "background" sediment, and mass balance calculations suggested that the former sample was contaminated by about 1% by weight of paint particles. Clearly, antifouling residues represent a highly significant, heterogeneous source of metallic contamination in the marine environment where boating activities occur.

Prediction and assessment of mixture toxicity of compounds in antifouling paints using the sea-urchin embryo-larval bioassay

The ecotoxicological assessment of alternative "booster" biocides is urgently needed in order to develop environmentally acceptable antifouling paints. However, research has focused mainly on single compounds, and there is still a lack of data on their mixture toxicity. The present study investigated the single and mixture toxicity of three of the most widely used antifouling biocides: zinc pyrithione, chlorothalonil and Sea-Nine, using the sea-urchin (Paracentrotus lividus) embryo-larval bioassay. Also, the predictive ability of the concentration addition (CA) and independent action (IA) concepts for antifouling mixtures was evaluated. Both concepts failed to accurately predict the toxicity of the antifouling mixtures, with the exception of the zinc pyrithione and Sea-Nine mixture, which was accurately predicted by the IA concept, suggesting a dissimilar mode of action of those substances. In general, CA predicted consistently higher toxicity than IA; however, CA overestimated the toxicity of the studied mixtures by a factor of only 1.6, representing a reasonable worst-case approach to be used in the predictive hazard assessment of antifouling mixtures. Finally, the present study demonstrates that the risk of antifouling mixtures for the early developmental stages of sea urchin is higher than the risk of each single substance, and therefore, the inclusion of mixture considerations in the development of water quality criteria for antifouling compounds is strongly recommended.

Synergistic toxic effects of zinc pyrithione and copper to three marine species: Implications on setting appropriate water quality criteria

Zinc pyrithione (ZnPT) is widely applied in conjunction with copper (Cu) in antifouling paints as a substitute for tributyltin. The combined effects of ZnPT and Cu on marine organisms, however, have not been fully investigated. This study examined the toxicities of ZnPT alone and in combination with Cu to the diatom Thalassiosira pseudonana, polychaete larvae Hydroides elegans and amphipod Elasmopus rapax. Importantly, ZnPT and Cu resulted in a strong synergistic effect with isobologram interaction parameter lambda>1 for all test species. The combined toxicity of ZnPT and Cu was successfully modelled using the non-parametric response surface and its contour. Such synergistic effects may be partly due to the formation of copper pyrithione. It is, therefore, inadequate to assess the ecological risk of ZnPT to marine organisms solely based on the toxicity data generated from the biocide alone. To better protect precious marine resources, it is advocated to develop appropriate water quality criteria for ZnPT with the consideration of its compelling synergistic effects with Cu at environmentally realistic concentrations.

Aqueous phototransformation of zinc pyrithione

The photochemical behavior of the antifouling agent zinc pyrithione (ZnPT) was studied in aqueous media of different composition under simulated solar irradiation using a xenon light source. The influence of important constituents of natural water (dissolved organic matter and nitrate) was also examined using a multivariate kinetic model. It was found that photodegradation proceeds via a pseudo first-order reaction. Kinetic experiments were monitored by LC-MS and photolytic half-lives ranging between 9.2 and 15.1 min have been observed. The increasing concentration of dissolved organic matter (DOM) accelerates the photolysis reaction, while the effect of nitrate ions was also positive since it increased the degradation rate, but to a lesser extent. Irradiation of the aqueous ZnPT solutions gave rise to several transformation products that were isolated by means of solid-phase extraction using poly(styrene-divinylbenzene) extraction disks. These byproducts were identified using liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry. Besides 2-pyridinesulfonic-acid, other degradation products formed included pyridine-N-oxide, 2-mercaptopyridine, 2,2'-dithiobis(pyridine-N-oxide), 2,2-dipyridyl disulfide and the pyridine/pyrithione mixed disulfide, 2,2'-dithiobispyridine mono-N-oxide (PPMD).

Improved method for the determination of zinc pyrithione in environmental water samples incorporating on-line extraction and preconcentration coupled with liquid chromatography atmospheric pressure chemical ionisation mass spectrometry

A method has been developed for the determination of zinc pyrithione (ZnPT) in environmental water samples using monolithic reversed-phase silica columns for rapid on-line large volume solid phase extraction in tandem with on-line matrix removal using sacrificial strong anion exchange (SAX) columns. This is coupled with reversed-phase liquid chromatography with atmospheric pressure chemical ionisation mass spectrometric detection. Limits of detection in spiked river water samples, using a 200 mL preconcentration volume, were determined as 18 ng L(-1), with a limit of quantitation of 62 ng L(-1). The percentage recovery from spiked river water was found to be 72+/-9 (n=3 extractions), whilst overall method precision, following 10 repeat complete analyses was found to be 27% RSD at 1 microg L(-1). Linearity was determined over the concentration range of 0.25-10 microg L(-1) and the calculated regression coefficient was R(2)=0.9802. The method was used to investigate the environmental fate of zinc pyrithione in waters and its partition coefficient between sediment and water phases.

Toxicity reduction of metal pyrithiones by near ultraviolet irradiation

Zinc pyrithione (ZnPT) or copper pyrithione (CuPT) have been effectively used as ship-antifouling agents, as an alternative to organotin compounds. Because of their instability in light and a lack of suitable analytical procedures, there is little data on their residue levels in environmental matrices. It is possible to investigate the fate of such compounds by toxicity alteration with certain treatments. The purpose of this study was to evaluate the degradation of pyrithiones through toxicity reduction by near ultraviolet (UV-A) irradiation. Metal pyrithiones dissolved in acetonitrile were irradiated with a UV-A lamp for 0, 0.5, 1, and 2 h, and were subjected to UV spectral measurement and toxicity evaluation using both sea urchin and freshwater rotifer bioassays. For the bioassays, photolyzed samples were dissolved in dimethyl sulfoxide after evaporation of the acetonitrile. The changes in UV spectra of photolyzed ZnPT or CuPT showed a time-dependent degradation, and the UV spectra at 2 h irradiation suggested substantial decomposition. Toxicities of ZnPT and CuPT were 12 and 5 microg/L as 24 h LC50 to the survival of rotifers and 10(-6) ng/L and 2.3 ng/L as 27 h EC50 to normal pluteus formation, respectively. By evaporation of the acetonitrile, the EC50 of ZnPT was 2.2 ng/L, which was the same as that of CuPT. The EC50s of ZnPT or CuPT for both species increased with longer irradiation times. Photolyzed ZnPT or CuPT demonstrated substantial degradation in the UV spectra, but possessed marked toxicity, which is probably due to toxic degradation products. One reason why photolyzed CuPT was toxic to rotifers was explained by the high toxicity of copper ions formed by UV-A irradiation.

Effects on the function of three trophic levels in marine plankton communities under stress from the antifouling compound zinc pyrithione

This study aimed to investigate functional responses of natural marine planktonic communities to stress from the antifouling compound zinc pyrithione (ZPT). Isotope labelling techniques (14C) were applied to study bacterial incorporation of leucine, photosynthetic activity of phytoplankton and grazing of labelled prey by zooplankton communities for 6 days after exposures to nominal concentrations of 0, 5, 25, 50 nM ZPT in a mesocosm experiment in Isefjord, Denmark. Significant direct effects were visible on chlorophyll a concentrations, which decreased in all exposed communities, to between 48 and 36% of control concentrations on Day 3, 1 day after the last exposure. Phytoplankton activities were also significantly affected on Day 3 with activities between 9 and 26% of control levels, as was zooplankton activities in the 25 and 50 nM exposures. In the 50 nM exposure the total community zooplankton activity was reduced to 25+/-4%, and per individual to 46+/-11% of control levels. Bacterial communities showed positive indirect effects with high activities (up to 183+/-40%) due to higher amounts of available substrate from algal death. Pollution induced community tolerance analyses performed on phytoplankton and bacterial communities at the end of the experiment indicated a development of increased tolerance for phytoplankton in the 50 nM exposed communities, whereas there were no changes in tolerance in the bacterial communities. Multivariate analysis of the integrated functional response by the plankton communities revealed a significant difference (p<0.05) between exposed communities compared to controls in the first 3 days after last exposure and in the end of the experiment. The study provides evidence of diverse effects on the functions of marine plankton communities under stress from a pollutant. Direct effects lead to cascading indirect effects throughout the community, eventually causing different developments. Continuous exposure to ZPT could lead to severe long-term effects, causing more permanent changes in structure and function than observed here. The study demonstrates that it is possible to assess the functional effects of a stressor in a complex mesocosm system, and to determine effects in a complex plankton community, which were not predictable from laboratory studies.