Efficacy and toxicity of self-polishing biocide-free antifouling paints

The ban on harmful substances in antifouling paints requires the development of new antifouling strategies. Alternatives should be as effective as conventional paints but of lower toxicity. In the present study two commercially available, self-polishing antifouling paints were examined in order to get information on their antifouling properties and toxicological potential. Efficacy was shown in settlement assays with the marine barnacle species Balanus amphitrite, however, efficacy was related to toxic effects observed on target and non-target organisms. Toxicity of the paint extracts was concentration-dependent and differed according to the paint and the species investigated. Toxicity could at least partially be attributed to zinc leached from the paints. Effects of a water-soluble paint were more pronounced in larvae of B. amphitrite, Artemia salina and in the green algae Dunaliella tertiolecta. Embryos of the freshwater species Danio rerio and Vibrio fisheri were more affected by a paint based on organic solvents.     

Spirotox--a new tool for testing the toxicity of volatile compounds.

A new method for estimating the toxicity of volatile compounds was developed. The test was carried out in the disposable polystyrene multiwells. After the organisms, protozoa Spirostomum ambiguum, were added to the wells, microplate was tightly closed using silicone grease and polyethylene film. The toxicities of 21 organic compounds were estimated. No control mortality was observed in all cases. Transparent PE film enabled good observation of test response. The toxicity of tested compounds varied over 4 orders of magnitude. Deformations were 2-4 more sensitive toxic response then lethality. The toxicity of tested compounds in Spirotox test correlates well with the log Kow and toxicity results from other bioassays: Microtox, D. magna and T. pyriformis.     

Bioassays and selected chemical analysis of biocide-free antifouling coatings

Over the years several types of biocide-free antifouling paints have entered the market. The prohibition of biocidal antifouling paints in special areas of some European countries such as Sweden, Denmark and Germany has favoured the introduction of these paints to the market.

Several types of biocide-free antifouling paints were subjected to bioassays and selected chemical analysis of leachate and incorporated substances. Both non-eroding coatings (silicones, fibre coats, epoxies, polyurethane, polyvinyl) and eroding coatings (SPCs, ablative) were tested to exclude the presence of active biocides and dangerous compounds. The paints were subjected to the luminescent bacteria test and the cypris larvae settlement assay, the latter delivering information on toxicity as well as on efficacy.

The following chemical analyses of selected compounds of dry-film were performed:

• leaching-rate of organotin compounds from silicones and of nonylphenol and bisphenol A from epoxy and vinyl based coatings,

• concentration and leaching rate of selected organic compounds in polyurethane,

• concentration of heavy metals in eroding coatings.

The results of the bioassays indicated that none of the coatings analysed contained leachable biocides. Nevertheless, some products contained or leached dangerous compounds. The analyses revealed leaching of nonylphenol (up to 74.7 ng/cm²/d after 48 h) and bisphenol A (up to 2.77 ng/cm²/d after 24 h) from epoxy resins used as substitutes for antifouling paints. The heavy metal, zinc, was measured in dry paint film in quantities up to 576 000 ppm in erodable coatings, not incorporated as a biocide but to control the rate of erosion. Values for TBT in silicone elutriates were mostly below the detection limit of 0.005 mg/kg. Values for DBT ranged between <0.005 and 6.28 mg/kg, deriving from catalysts used as curing agents. Some biocide-free paints contained leachable, toxic and dangerous compounds in the dry film, some of which may act as substitutes for biocides or are incorporated as plasticizers or catalysts. Implications to environmental requirements and legislation are discussed.     

Photodegradation of the antifouling compounds Irgarol 1051 and Diuron released from a commercial antifouling paint

The antifouling compound Irgarol 1051 and its degradation product M1 (also known as GS26575), along with another antifouling compound Diuron, have recently been found in Japanese coastal waters. This study was undertaken to find the origin of these chemicals and investigate their aquatic fate. Five glass plates, each coated with 1 g of antifouling paint containing Irgarol and Diuron, were submerged in 250 ml of five different test waters and the plates removed after several months. The aqueous solutions were divided into two groups: one exposed to natural sunlight, and the other kept in the dark as a control. Irgarol and Diuron were detected in all aqueous solutions, suggesting leaching from antifouling paints is the origin of these antifouling biocides found in Japanese coastal waters. Under sunlight conditions, Irgarol underwent a rapid degradation to produce M1, which remained even after Irgarol had disappeared from the system. These compounds were persistent in any aqueous solutions tested under dark conditions, indicating high stability to hydrolysis. Diuron and M1 were more persistent than Irgarol under sunlight irradiation. Since these compounds have high herbicidal activities, their ultimate impact on aquatic ecosystems is closely related to their aquatic fate.     

Comparing differential tolerance of native and non-indigenous marine species to metal pollution using novel assay techniques

Recent research suggests anthropogenic disturbance may disproportionately advantage non-indigenous species (NIS), aiding their establishment within impacted environments. This study used novel laboratory- and field-based toxicity testing to determine whether non-indigenous and native bryozoans (common within marine epibenthic communities worldwide) displayed differential tolerance to the common marine pollutant copper (Cu). In laboratory assays on adult colonies, NIS showed remarkable tolerance to Cu, with strong post-exposure recovery and growth. In contrast, native species displayed negative growth and reduced feeding efficiency across most exposure levels. Field transplant experiments supported laboratory findings, with NIS growing faster under Cu conditions. In field-based larval assays, NIS showed strong recruitment and growth in the presence of Cu relative to the native species. We suggest that strong selective pressures exerted by the toxic antifouling paints used on transport vectors (vessels), combined with metal contamination in estuarine environments, may result in metal tolerant NIS advantaged by anthropogenically modified selection regimes.     

Inputs of antifouling paint-derived dichlorodiphenyltrichloroethanes (DDTs) to a typical mariculture zone (South China): potential impact on aquafarming environment

Existing evidence indicated that dichlorodiphenyltrichloroethane (DDT)-containing antifouling paints were an important source of DDT residues to mariculture zones. However, the magnitude of the impact on aquafarming environment has remained largely unknown. In the present study, the concentrations of DDT and its metabolites (designated as DDXs) were determined in harbor sediment and antifouling paint samples collected from a typical mariculture zone in South China. Compositional and concentration correlation analyses implicated the DDT-containing antifouling paints for fishing boat maintenance as an important source of DDT in the mariculture zone. The annual emission of DDXs to the study region was estimated at 0.58 tons/yr. Furthermore, a comparison of the expected DDT loadings in pelagic fish and field measurements indicated that fish feed especially trash fish was a major source of DDTs in the fish body. Nevertheless, the use of DDT-containing antifouling paints should be limited to prevent further deterioration in aquafarming environment.     

Comparative environmental assessment of biocides used in antifouling paints

In response to increasing scientific evidence on the toxicity and persistence of organotin residues from antifouling paints in the aquatic environment, the use of triorganotin antifouling products was banned on boats of less than 25 m length in many countries during 1987. Alternatives to tributyltin (TBT) paint are mainly copper based coatings containing organic booster biocides to improve the efficacy of the formulation, and have been utilised on small boats for the last 10 years. With policies encouraging a total ban on TBT, it is expected that these biocides will be used to a greater extent in the future. Limited data and information are available on the environmental occurrence, fate, toxicity, and persistence of these biocides, and thus any decisions on policies regulating antifoulants cannot be fully informed. In this study, a multicriteria comparison of alternative biocides, based on a general assessment of available information in the literature, provided support for the use of the precautionary principle with respect to policies on antifouling products. This assessment was validated by a more detailed comparison of four selected biocides and TBT. Results indicate that TCMS pyridine and TCMTB demonstrate environmental characteristics similar to TBT and thus detail risk assessments are needed before their use is permitted. The widespread use of the other biocides should be allowed only after research to fill the gaps in knowledge with respect to their toxicity and persistence in aquatic environments.     

Soil pH effects on the interactions between dissolved zinc,non-nano- and nano-ZnO with soil bacterial communities

Zinc oxide nanoparticles (ZnO NPs) are used in an array of products and processes, ranging from personal care products to antifouling paints, textiles, food additives, antibacterial agents and environmental remediation processes. Soils are an environment likely to be exposed to manmade nanoparticles due to the practice of applying sewage sludge as a fertiliser or as an organic soil improver. However, understanding on the interactions between soil properties, nanoparticles and the organisms that live within soil is lacking, especially with regards to soil bacterial communities. We studied the effects of nanoparticulate, non-nanoparticulate and ionic zinc (in the form of zinc chloride) on the composition of bacterial communities in soil with a modified pH range (from pH 4.5 to pH 7.2). We observed strong pH-dependent effects on the interaction between bacterial communities and all forms of zinc, with the largest changes in bacterial community composition occurring in soils with low and medium pH levels (pH 4.8 and 5.9). The high pH soil (pH 7.2) was less susceptible to the effects of zinc exposure. At the highest doses of zinc (2500 mg/kg dw soil), both nano and non-nano particulate zinc applications elicited a similar response in the soil bacterial community, and this differed significantly to the ionic zinc salt treatment. The results highlight the importance of considering soil pH in nanotoxicology studies, although further work is needed to determine the exact mechanisms controlling the toxicity and fate and interactions of nanoparticles with soil microbial communities.     

Toxicity of anti-fouling paints for use on ships and leisure boats to non-target organisms representing three trophic levels

Leachates of anti-fouling paints for use on ships and leisure boats are examined for their ecotoxicological potential. Paint leachates were produced in both 7‰ artificial (ASW) and natural seawater (NSW) and tested on three organisms, the bacterium Vibrio fischeri, the macroalga Ceramium tenuicorne, and the crustacean Nitocra spinipes. Generally, leaching in ASW produced a more toxic leachate and was up to 12 times more toxic to the organisms than was the corresponding NSW leachate. The toxicity could be explained by elevated concentrations of Cu and Zn in the ASW leachates. Of the NSW leachates, those from the ship paints were more toxic than those from leisure boat paints. The most toxic paint was the biocide-free leisure boat paint Micron Eco. This implies that substances other than added active agents (biocides) were responsible for the observed toxicity, which would not have been discovered without the use of biological tests.     

Two new growth inhibition tests with the filamentous algae Ceramium strictum and C. tenuicorne (Rhodophyta)

Two growth inhibition tests using the red marine macroalgae Ceramium strictum and the brackish water relative C. tenuicorne have been developed. Besides using phenol as a reference substance, the toxicity of a metal, a flame retardant and a complex effluent water were assayed. The two methods are reliable and repeatable bioassays for salinities between 4 and 30 per thousandth. The coefficients of variation (CV) for toxicity of the reference substance phenol were 15% for the Stereo Microscope Analysis test and between 24 and 51% for the Computer Image Analysis test (n=5). Ceramium spp. are common and important primary producers in temperate coastal waters and are thus relevant as test organisms. Both algae grow well in laboratorial conditions and tests can be performed all year around.     

A study on dynamic volatile organic compound emission characterization of water-based paints

Volatile organic compounds (VOCs) emitted from surface coatings have caused growing public concern for air quality. Even the low-emitted VOC impact from water-based paints on indoor air quality in urban areas has caused concern. This paper presents experimental data using a mathematical model to simulate dynamic VOC emissions from water-based paints that is based on mass transfer and molecular diffusion theories. A series of field-analogous experiments were carried out to continuously measure the VOCs emitted from two typical water-based paints using a gas chromatography-flame-ionization detector monitor in an artificial wind tunnel system. In the study cases, the mass flux of VOCs emitted from the water-based paints was up to 50 microg/m2sec. It was found that the time needed to completely emit VOCs from water-based paints is just hundreds of seconds. However, the order of magnitude of the VOC emission rate from water-based paints is not lower than that from some dry building materials and solvent-based paints. The experimental data were used to produce a useful semiempirical correlation to estimate the VOC emission rates for water-based paints. This correlation is valid under appropriate conditions as suggested by this work with a statistical deviation of +/- 7.6%. With this correlation, it seems feasible to predict the dynamic emission rates for VOCs during a painting process. This correlation is applicable for assessing the hazardous air pollutant impact on indoor air quality or for environmental risk assessment. Associated with the dynamic VOC emission characterization, the air-exchange rate effect on the VOC emission rates is also discussed.     

Polymer coating of copper oxide nanoparticles increases nanoparticles uptake and toxicity in the green alga Chlamydomonas reinhardtii

Copper oxide nanoparticles (CuO NPs) are frequently used in a polymer-coated form, to be included in paints or fabrics for antimicrobial properties. Their application in antifouling paints may lead to the contamination of aquatic ecosystems. However, the toxicological risk of NPs in the environment is hard to evaluate due to a lack of knowledge on the mechanisms of NP interaction with biological systems. In this study, we investigated the effect of polymer coating on CuO NP toxicity in the green alga Chlamydomonas reinhardtii by comparing bare and polymer-coated CuO NPs prepared from the same CuO nanopowder. Both CuO NP suspensions were toxic to C. reinhardtii after 6 h treatment to concentrations of 0.005-0.04 g L⁻¹. Bare and polymer-coated CuO NPs induced a decrease of Photosystem II activity and the formation of reactive oxygen species. Polymer-coated CuO NP was found to be more toxic than the uncoated CuO NP. The higher toxicity of CS-CuO NP was mainly associated with the increased capacity of polymer-coated CuO NP to penetrate the cell compared to bare CuO NPs. These results indicates that the high toxicity of polymer-coated CuO NPs in algal cells results of intracellular interactions between NPs and the cellular system.     

Survey for the occurrence of antifouling paint booster biocides in the aquatic environment of Greece

Since the restriction imposed by European Union regulations on the use of TBT-based antifouling paints on boats below 25 m in length, new terms have been introduced in the 'small boat' market. Replacement products are generally based on copper metal oxides and organic biocides. Several studies have demonstrated the presence of these biocides in European ports and marinas of Spain, France, Germany and the United Kingdom. An extended survey of the antifouling biocides chlorothalonil, dichlofluanid, irgarol 1051 and sea-nine 211 was carried out in Greek ports and marinas of high boating activities from October 1999 to September 2000. The sampling sites were: Piraeus, Elefsina, Thessaloniki, Patras, Chalkida, Igoumenitsa, and Preveza (Aktio). The extraction of these compounds from the seawater samples was performed off-line with C18 solid phase extraction (SPE) disks while the determination was carried out with gas chromatography coupled to electron capture (ECD), thermionic (FTD) and mass spectroscopy (MS) detectors. The concentration levels of biocides were higher during the period from April to October. This seasonal impact depends on the application time of antifouling paints and mimic trends in the seasonal distribution of biocides in other European sites.     

Coral skeletal tin and copper concentrations at Pohnpei, Micronesia: possible index for marine pollution by toxic anti-biofouling paints

We present 40 year-long skeletal chronologies of tin (Sn) and copper (Cu) from an annually-banded coral (Porites sp.) collected from Pohnpei Island, Micronesia (western equatorial Pacific). Both the elements are present in antifouling marine paints and are released inadvertently into ambient seawater. Especially, Sn has often been used in the form of tributyltin (TBT). Based on a stepwise pretreatment examination, Sn and Cu both inside and outside the aragonite lattice of the coral skeleton show a potential for providing marine pollution indicators. High values of extra-skeletal Cu/Ca and Sn/Ca atomic ratios were found between late 1960s and late 1980s during a period of active use of TBT-based antifouling paints worldwide. However, a significant decrease in both the ratios in the beginning of 1990s can be attributed to regulation of the use of TBT on cargo ships by countries such as the USA, Japan and Australia.     

Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C(12)-2-LAS to Corophium volutator

The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C₁₂-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment-water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments.     

Gyrineum natator: a potential indicator of imposex along the Indian coast

Imposex related studies have used neogastropods as sentinel organism. In this effort, we elucidate the potential of a mesogastropod, Gyrineum natator, for imposex monitoring on the central west coast of India. Observations were made with specimens collected from Mumbai (three stations), Ratnagiri (two stations), Goa (one station) and Mangalore (one station). The analyzed populations at all four sites were affected by imposex. The six different stages of imposex in this organism are illustrated through schematic and scanning electron micrographs. In view of the anticipated ban on TBT based antifouling paints this baseline information can serve as an indicator for environmental monitoring in this region.     

Toxicity of chlorophenols to Pseudokirchneriella subcapitata under air-tight test environment

A closed-system algal toxicity test with no headspace was applied to evaluate the toxicity of chlorophenols to Pseudokirchneriella subcapitata. The dissolved oxygen production and the growth rate based on cell density were the response endpoints. Phenol and seven chlorophenols were tested using the above test technique. Median effective concentrations (EC50) range from 0.004 to 25.93 mg/l (based on DO production) and 0.0134 to 20.90 mg/l (based on growth rate). No-observed-effect concentration (NOEC) is within the range of 0.001-8.19 mg/l. In general, growth rate is a more sensitive response endpoint than the oxygen production, except for the case of pentachlorophenol. However, the differences in sensitivity between the two parameters were marginal. Furthermore, quantitative structure-activity relationships (QSAR's) based on the n-octanol/water partition coefficient (log P) and the acid dissociation constant (pK(a)) values were established with R(2) ranged from 0.90 to 0.96. From literature data also based on P. subcapitata, the new test method is 1.65-108 times more sensitive than the conventional algal batch tests. A completely different relative-sensitivity relationship among various aquatic organisms was thus observed. The results of this study indicate that the toxicity data of volatile organic chemicals derived by conventional algal toxicity tests may severely underestimate the impact of these toxicants. Our results show that alga is very sensitive to chlorophenols compared to other aquatic organisms such as the luminescent bacteria (the Microtox test), Daphnia magna, and rainbow trout.     

Toxicity of tributyltin to willow trees

BACKGROUND: Tributyltin is an organotin compound, used as an antifouling agent in ship paint, with heavy impact on the marine environment. Contaminated dredged harbor sludge is now dumped on land. The toxicity of tributyltin (TBT) to trees has not yet been quantified. Eventually, a vegetation cover on the dumped sludge could be established for the purpose of non-food cash crop production and phytoremediation. METHODS: The phytotoxicity of tributyltin chloride (TBTCl) and tributyltin hydride (TBTH) was measured at pH 4 and at pH 7 using the willow tree transpiration test. Different pH levels of the nutrient solutions were achieved by adding ammonium salt (low pH) or nitrate (high pH) as nitrogen source. RESULTS AND DISCUSSION: At low pH (pH 4), all trees showed symptoms of poor health. Transpiration decreased at concentrations above or equal to 0.1 mg TBTCl/l and 1 mg TBTH/L. The TBT toxicity was more pronounced at pH 7. The trees survived even the highest dose of 10 mg/l TBTCl or TBTH, although their growth and transpiration was strongly reduced. CONCLUSION: In contrast to other organisms, TBTCl and TBTH were less toxic to higher plants. RECOMMENDATIONS AND OUTLOOK: The toxicity of TBT is no hindrance for establishing vegetation on TBT-contaminated sludge. Phytoremediation and cash crop production could be possible with suitable plants.     

Evaluation of the Hormosira banksii (Turner) desicaine germination and growth inhibition bioassay for use as a regulatory assay

A germination and growth inhibition bioassay using the marine macroalga, Hormosira banksii, was evaluated for use as a standard method for direct toxicity assessment testing in the Australasian region. H. banksii is the dominant macroalga and an important primary producer in temperate coastal zones of Australasia and is therefore relevant as a test organism. Moreover, it releases gametes readily under laboratory conditions, therefore allowing tests to be conducted year round. The test endpoints' variability and sensitivity was evaluated using ammonia, a common constituent of waste waters. The two test endpoints of germination and growth proved to be both reliable and repeatable bioassay endpoints. The coefficients of variation (CV's) for toxicity to germination and growth by ammonia ranged from 25% to 38% (n=18).     

Toxicity evaluation of new antifouling compounds using suspension-cultured fish cells

A simple, rapid toxicity test was developed using the suspension-cultured fish cell line CHSE-sp derived from chinook salmon Oncorhynchus tshawytscha embryos in order to assess the toxicity of new marine antifouling compounds. The compounds tested were copper pyrithione, Diuron, Irgarol 1051, KH101, Sea-Nine 211, and zinc pyrithione, all of which have been nominated in Japan as possible replacements for organotin compounds. The in vitro acute toxicity (24-h EC50) of the six compounds to these fish cells was evaluated using the dye Alamar Blue to determine cell viability, and then correlated with the results of in vivo chronic toxicities (28-day LC50) to juvenile rainbow trout Oncorhynchus mykiss. The suspension-cultured fish cells were found to be suitable for the screening of such chemicals before performing an in vivo test. The toxicities of the test compounds obtained from both tests, shown in decreasing order, were as follows: copper pyrithione > zinc pyrithione > KH101 > or = Sea-Nine 211 > Diuron > Irgarol 1051. The herbicides Diuron and Irgarol 1051 showed the least toxicity, while the pyrithiones had the greatest toxicity.