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To protect house facades from fouling by microorganisms, biocides can be added to a render or paint before it is applied. During driving rain events, these biocides gradually leach out and have the potential to pollute soil or aquatic ecosystems. We studied the leaching behavior of biocides and toxicity of leachates from renders with either free or encapsulated biocides. Both render types contained equal amounts of terbutryn, 2-octyl-3(2H)-isothiazolinone (OIT), and 4,5-dichloro-2-n-octyl-4-isothiazolino-3-one (DCOIT). Nine leachate samples were generated over 9 immersion cycles according to a European standard, and biocides were quantified. The first and ninth leachate samples were tested using bioassays with algae, bacteria, and water fleas, the first sample was also tested with earthworms and springtails. Encapsulation reduced leaching of terbutryn, OIT, and DCOIT by 4-, 17-, and 27-fold. For aquatic organisms, the toxicity of water from render containing encapsulated biocides was always lower than that of render with free biocides. Furthermore, toxicity decreased by 4- to 5-fold over the 9 immersion cycles. Inhibition of photosynthesis was the most sensitive endpoint, followed by algal growth rate, bacterial bioluminescence, and water flea reproduction. Toxicity to algae was due to terbutryn and toxicity to bacteria was due to OIT. None of the samples affected soil organisms. Results demonstrate that combining standardized leaching tests with standardized bioassays is a promising approach to evaluate the ecotoxicity of biocides that leach from facade renders. Environ Toxicol Chem 2018;37:2246-2256. © 2018 SETAC.

Surface sediments can accumulate contaminants that affect microorganisms and invertebrates and disturb benthic ecological functions. However, effects of contaminants on ecological functions supported by sediment communities are understudied. Here, we tested the relevance of two simple tools to assess the ecotoxicological effects of metal contamination on natural sediment communities using particulate organic matter breakdown and decomposition as a functional descriptor. To this aim, we performed a 21-day laboratory microcosm experiment to assess the individual and combined effects of Cu and As (nominal concentration of 40 mg kg−1 dw each) using the bait-lamina method (cellulose, bran flakes, and active coal in PVC strips) as well as artificial tablets (cellulose, bran flakes and active coal embedded in an agar matrix). Sediment toxicity was also evaluated using the standardized ostracod toxicity test. Both the bait-lamina and artificial tablet methods showed low effects of As on organic matter breakdown and decomposition but strong effects of Cu on this important ecological function. Both also showed that the presence of Cu and As in mixture in the sediment induced total inhibition of organic matter breakdown and decomposition. The ostracod toxicity test also showed high toxicity of Cu-spiked and Cu-plus-As-spiked sediments and low toxicity of As-spiked sediments. Besides confirming that artificial organic matter substrates are relevant and useful for assessing the functional effects of contaminants on sediment micro-and macro-organism communities, these results suggest that the proposed methods offer promising perspectives for developing tools for use in assessing functional ecotoxicology in the sediment compartment.