Leaching of biocides from polymer renders under wet/dry cycles--Rates and mechanisms

Eluates from façades at the beginning of their service time affect aquatic and sediment organisms

Biocides are used in building materials to prevent microbial growth during storage (in-can preservatives) as well as after application (film preservatives). These compounds can leach out from the material into the environment and harm non-target organisms. In this study, the ecotoxicological effect of leachates at the beginning of a façade lifetime, on sediment and aquatic organisms was examined. For this purpose, leaching tests were carried out in the setting of a natural weathering experiment and a laboratory immersion with façade samples consisting of render/paint systems. The leaching experiments were performed with three different formulations, namely no biocides containing control, a formulation containing only in-can preservatives (benzisothiazolinone (BIT), methylchloroisothiazolinone (CMIT), and methylisothiazolinone (MIT)), and, as is common in organic building materials, containing both in-can and film preservatives (octylisothiazolinone (OIT) and terbutryn (TB)). In order to elucidate the effects of in-can and film preservative-containing eluates the toxicity of the generated leachables was evaluated on the model of several aquatic and sediment organisms, namely luminescent bacteria (Vibrio fischeri), green algae (Scenedesmus subspicatus), Salmonella typhimurium TA1535/pSK1002 (umu-test), fish-egg (Danio rerio), Chironomus riparius, and Lumbriculus variegatus. It was demonstrated that in-can preservatives leach out rapidly at the beginning of a façade lifetime and despite the short half-life of these compounds in aqueous solutions, they could be detected at high concentrations in the eluates. Furthermore, eluates from early sampling times, predominantly containing in-can preservatives, were found to cause toxic effects on sediment and aquatic organisms. The results demonstrate that in-can preservatives can impose a significant stress factor on the environment.

Emissions of the Urban Biocide Terbutryn from Facades: The Contribution of Transformation Products

Biocides are added to facade paints and renders to prevent algal and fungal growth. The emissions of biocides and their transformation products from building facades during wind-driven rain can contaminate surface waters, soil, and groundwater. Although the emissions of biocide transformation products may be higher than those of the parent biocide, knowledge of the emissions of transformation products over time is scarce. Combining field- and lab-scale experiments, we showed that solar irradiation on facades controls the formation of transformation products and can be used with runoff volume to estimate the long-term emissions of terbutryn transformation products from facades. The slow (t1/2 > 90 d) photodegradation of terbutryn in paint under environmental conditions was associated with insignificant carbon isotope fractionation (Δδ13C < 2 ‰) and caused 20% higher emission of terbutryn-sulfoxide than terbutryn in leachates from facades. This indicated continuous terbutryn diffusion toward the paint surface, which favored terbutryn photodegradation and the concomitant formation of transformation products over time. The emissions of terbutryn transformation products (77 mg m-2) in facade leachates, modeled based on irradiation and facade runoff, were predicted to exceed those of terbutryn (42 mg m-2) by nearly 2-fold after eight years. Overall, this study provides a framework to estimate and account for the long-term emissions of biocide transformation products from building facades to improve the assessment of environmental risks.

Transformation and stable isotope fractionation of the urban biocide terbutryn during biodegradation, photodegradation and abiotic hydrolysis

Terbutryn is a widely used biocide in construction materials like paint and render to prevent the growth of microorganisms, algae and fungi. Terbutryn is released from the facades into the environment during rainfall, contaminating surface waters, soil and groundwater. Knowledge of terbutryn dissipation from the facades to aquatic ecosystems is scarce. Here, we examined in laboratory microcosms degradation half-lives, formation of transformation products and carbon and nitrogen isotope fractionation during terbutryn direct (UV light with λ = 254 nm and simulated sunlight) and indirect (simulated sunlight with nitrate) photodegradation, abiotic hydrolysis (pH = 1, 7 and 13), and aerobic biodegradation (stormwater pond sediment, soil and activated sludge). Biodegradation half-lives of terbutryn were high (>80 d). Photodegradation under simulated sunlight and hydrolysis at extreme pH values indicated slow degradability and accumulation in the environment. Photodegradation resulted in a variety of transformation products, whereas abiotic hydrolysis lead solely to terbutryn-2-hydroxy in acidic and basic conditions. Biodegradation indicates degradation to terbutryn-2-hydroxy through terbutryn-sulfoxide. Compound-specific isotope analysis (CSIA) of terbutryn holds potential to differentiate degradation pathways. Carbon isotope fractionation values (ε_C) ranged from -3.4 ± 0.3‰ (hydrolysis pH 1) to +0.8 ± 0.1‰ (photodegradation under UV light), while nitrogen isotope fractionation values ranged from -1.0 ± 0.4‰ (simulated sunlight photodegradation with nitrate) to +3.4 ± 0.2‰ (hydrolysis at pH 1). In contrast, isotope fractionation during biodegradation was insignificant. Λ^N/C values ranged from -1.0 ± 0.1 (hydrolysis at pH 1) to 2.8 ± 0.3 (photodegradation under UV light), allowing to differentiate degradation pathways. Combining the formation of transformation products and stable isotope fractionation enabled identifying distinct degradation pathways. Altogether, this study highlights the potential of CSIA to follow terbutryn degradation in situ and differentiate prevailing degradation pathways, which may help to monitor urban biocide remediation and mitigation strategies.

The impact of sewage sludge processing on the safety of its use

Particular attention is devoted to pharmaceutical residues in sewage sludge caused by their potential ecotoxicological effects. Diclofenac, ibuprofen and carbamazepine, 17-α-ethinylestradiol, β-estradiol, were analysed in four types of fertilizers, based on sewage sludge commercial products, in compliance with Polish requirements. The release of active pharmaceutical compounds from fertilizers to water the phase after 24 h and 27 days was analysed. Solid-water partition coefficients (K_d) and partitioning coefficient values normalized on organic carbon content (log K_OC) were evaluated. The environmental risk to terrestrial ecosystems, due to the application of fertilizers onto soils, was estimated. Cumulative mass of pharmaceuticals emitted to water from fertilizers ranged from 0.4 to 30.8 µg/kg after 24 h contact. The greatest amount of the material that was released, over 70%, was observed for carbamazepine. No presence of compounds except ibuprofen was observed after 27 days of testing. The highest environmental risk in fertilizers is due to carbamazepine, risk quotation, RQ = 0.93 and diclofenac RQ = 0.17. The values of risk quotation estimated for soil were below RQ = 0.01. This fact means that no risk to terrestrial ecosystems is expected to occur. The important decrease of the concentrations of active compounds after passing from sewage sludge to fertilizers [and] to fertilized soil could be observed.

Environmental risk assessment of priority biocidal substances on Polish surface water sample

The EU directive 2013/39/EU has incorporated four biocidal compounds as priority substances: diuron, isoproturon, cybutryne, and terbutryn. The research was undertaken to determine the concentration of biocides in surface waters in three locations in southern Poland: the Wisła River in Kraków, the Wisłoka River in Mielec, and the drainage ditch draining water from arable fields located near Mielec. Environmental samples were taken in two series: winter (February) and spring (May and June). The analyses were carried out using gas chromatography with mass spectrometry. The seasonality of biocides in surface waters was observed. In winter samples, the concentrations were below MQL, while in spring, they ranged from a few to several dozen nanograms per liter. The highest concentrations of all analyzed compounds were recorded in water taken from the Wisła River. According to directive 2013/39/EU, the maximum allowable concentration was exceeded only in the case of cybutryne in water from the Wisła, both in May and in June. The assessment of the toxicity with the tested compounds was defined based on the Environmental Risk Assessment method. Low risk was estimated for diuron and isoproturon, while moderate risk for terbutryn and cybutryne.

Influence of façade orientation on the leaching of biocides from building façades covered with mortars and plasters

Biocides used in building façades to prevent potential growth of algae, fungi and bacteria are of major concern regarding the quality of stormwater runoff. The aim of the study was to analyze the influence of the façade orientation on the biocide release under real weather conditions to gain information for the development of on-site treatment systems. Field tests with model houses containing two different plaster compositions were carried out over a period of 18 months. The results of the analyzed rain events demonstrate that façade orientation plays an important role in the leaching loads of biocides. Biocide loads in the runoff decreased corresponding to the wind direction. High cumulated active substance discharges of diuron (149 mg/m²), carbendazim (43.5 mg/m²), terbutryn (9.3 mg/m²) and octylisothiazolinone (OIT) (31.9 mg/m²) were found in the runoff of the façades facing the predominant weather orientation. Meanwhile, the highest concentrations of diuron (2.8 mg/L) and OIT (0.7 mg/L) were observed in the runoff from façades with smaller runoff volumes. The obtained results demonstrate that treatment facilities have to be installed at all building sides. The hydraulic and the substance load is highest at the weather side, which has a strong influence on the dimension and the lifetime of the treatment system.

Preparation, Test, and Analysis of a Novel Aluminosilicate-Based Antimildew Agent Applied on the Microporous Structure of Wood

Fungi play a considerable role in the deterioration of lignocellulose materials, as their activities either affect the esthetic properties or lead to decay of the host materials. The new generation of organic-inorganic preservatives, which are copper-based but chrome- and arsenic-free, is a subject of many research works. Mildew fungus prevention, treatment of affected materials, and their successive conservation are essential to the woodworkers. To prevent degradation and prolong the service life of wood, a sol-gel organic-inorganic procedure was employed in this study. Aluminum sulfate (Al₂(SO₄)₃), copper sulfate (CuSO₄·5H₂O), and boric acid (H₃BO₃) were introduced into phosphoric acid (H₃PO₄) and water glass as an antimildew agent, with different treatment concentrations (0.7, 1.4, and 2%). Wood was inoculated with Aspergillus niger and Trichoderma viride after new treatment based on the inorganic preservative. The changes in wood surface, structural chemistry, and the crystalline structure of the treated wood were examined by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD), respectively. The growth of the two mildew fungi showed distribution, and evidence of mildew covering only the untreated wood surfaces and an increase in the crystallinity of wood was observed after the process. The study suggests that the two mildew fungi investigated herein could be prevented by sol-gel coating with a Si-Al-Cu-P antimildew agent.

Biocide emissions from building materials during wet weather: identification of substances, mechanism of release and transfer to the aquatic environment

Biocides are added to or applied on building materials to prevent microorganisms from growing on their surface or to treat them. They are leached into building runoff and contribute to diffuse contamination of receiving waters. This review aimed at summarizing the current state of knowledge concerning the impact of biocides from buildings on the aquatic environment. The objectives were (i) to assess the key parameters influencing the leaching of biocides and to quantify their emission from buildings, (ii) to determine the different pathways from urban sources into receiving waters and (iii) to assess the associated environmental risk. Based on consumption data and leaching studies, a list of substances to monitor in receiving water was established. Literature review of their concentrations in the urban water cycle showed evidences of contamination and risk for aquatic life, which should put them into consideration for inclusion to European or international monitoring programs. However, some biocide concentration data in urban and receiving waters is still missing to fully assess their environmental risk, especially for isothiazolinones, iodopropynyl carbamate, zinc pyrithione and quaternary ammonium compounds, and little is known about their transformation products. Although some models supported by actual data were developed to extrapolate emissions on larger scales (watershed or city scales), they are not sufficient to prioritize the pathways of biocides from urban sources into receiving waters during both dry and wet weathers. Our review highlights the need to reduce emissions and limit their transfer into rivers and reports several solutions to address these issues.

The extent of tebuconazole leaching from unpainted and painted softwood

Exposure to water and high air humidity may affect the preservation of wood products as many preservatives are water-soluble and thus likely to leach. In this study, depletion of a common fungicide, tebuconazole (TAZ), from treated wood was investigated using a ¹⁴C-labeled tracer. The wood species and treatment technique were chosen to be representative of products such as windows and doors; specifically, ponderosa pine was dip treated with a solvent-based, metal-free formulation. The impact of different aqueous settings including high air humidity, and either simulated continuous or intermittent rain was evaluated over a period of two months. Along with the exposure type, the effect of end-grain sealing on TAZ loss was explored. Despite the exposure of treated wood to laboratory-simulated harsh environmental conditions, more than 60% of the originally sorbed TAZ remained in the wood under all scenarios. While high air humidity did not lead to TAZ depletion, simulated continuous rain led to a TAZ leaching mainly from the end grain. TAZ leaching was found to be higher for unpainted wood, where up to 40% of the originally sorbed TAZ was prone to depletion from an end grain. End-grain sealing with water-based primer and paint led to a substantial two-fold reduction of TAZ leaching. Unexpectedly, wood exposure to intermittent rain caused additional TAZ loss that could not be explained only by water leaching.

Ecotoxicological Assessment of Immersion Samples from Facade Render Containing Free or Encapsulated Biocides

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.

Fate of triazoles in softwood upon environmental exposure

Determining the fate of preservatives in commercial wood products is essential to minimize their losses and improve protective impregnation techniques. The fate of triazole fungicides in ponderosa pine wood was investigated in both outdoor and controlled-environment experiments using a representative triazole, tebuconazole (TAZ), which was accompanied by propiconazole (PAZ) in selected experiments. The study was designed to mimic industrial settings used in window frame manufacturing. To investigate the TAZ fate in detail, loosely and strongly bound fractions were differentiated using a multi-step extraction. The loosely bound TAZ fraction extracted through two sonications accounted for 85± 5% of the total TAZ, while the strongly bound TAZ was extracted only with an exhaustive Soxhlet extraction and corresponded to the remaining 15± 5%. A significant fraction (∼80%) of the original TAZ remained in the wood despite a six-month exposure to harsh environmental conditions, maintaining wood preservation and assuring minimal environmental impact. Depletion of loosely bound TAZ was observed from cross-sectional surfaces when exposed to rain, high humidity and sunlight. Water leaching was deemed to be the major route leading to triazole losses from wood. Leaching rate was found to be slightly higher for TAZ than for PAZ. The contribution of bio-, photo- and thermal degradation of triazoles was negligible as both PAZ and TAZ sorbed in wood remained intact. Triazole evaporation was also found to be minor at the moderate temperature (20-25 °C) recorded throughout the outdoor study.

Photodegradation of octylisothiazolinone and semi-field emissions from facade coatings

Amongst others, 2-octyl-isothiazol-3(2 H)-one (OIT) is used as film preservative in water-based polymer resin paints and renders to prevent the growth of moulds and bacteria. It is known that biocides leach from facades with rainwater and end up in the environment via stormwater runoff. In the present study the leaching and fate of OIT used in facade coatings was determined under natural conditions. Potential phototransformation products were initially identified in laboratory experiments using UV-light. Afterwards, the leaching of OIT and seven degradation products were studied on artificial walls equipped with organic top coatings formulated with OIT. A mass balance, including the leached and remaining amounts of OIT and its seven transformation products, can explain up to 40% of the initial amount of OIT. The OIT remaining in the material after 1.5 yr is by far the largest fraction. The study shows that in the assessment of biocides in coating material, transformation products need to be taken into account both in leachate and remaining in the material. Furthermore, in case of volatile degradation products, the emissions to air might be relevant.

Determination of diffusion coefficients of biocides on their passage through organic resin-based renders

In this study the diffusion coefficients of isoproturon, diuron and cybutryn in acrylate and silicone resin-based renders were determined. The diffusion coefficients were determined using measuring concentrations of biocides in the liquid phase after being in contact with renders for specific time intervals. The mathematical solution of the transient diffusion equation for an infinite plate contacted on one side with a limited volume of water was used to calculate the diffusion coefficient. The diffusion coefficients through the acrylate render were 8.10·10(-9) m(2) s(-1) for isoproturon, 1.96·10(-9) m(2) s(-1) for diuron and 1.53·10(-9) m(2) s(-1) for cybutryn. The results for the silicone render were lower by one order of magnitude. The compounds with a high diffusion coefficient for one polymer had likewise high values for the other polymer.

Biocide leaching during field experiments on treated articles

BACKGROUND

Biocidal products can be sources of active substances in surface waters caused by weathering of treated articles. Marketing and use of biocidal products can be limited according to the European Biocidal Products Regulation if unacceptable risks to the environment are expected. Leaching of active substances from treated articles was observed in field experiments to obtain information on leaching processes and investigate the suitability of a proposed test method.

RESULTS

Leaching under weathering conditions proceeds discontinuously and tends to decrease with duration of exposure. It does not only mainly depend on the availability of water but is also controlled by transport processes within the materials and stability of the observed substances. Runoff amount proved to be a suitable basis to compare results from different experiments. Concentrations of substances are higher in runoff collected from vertical surfaces compared to horizontal ones, whereas the leached amounts per surface area are higher from horizontal surfaces. Gaps in mass balances indicate that additional processes such as degradation and evaporation may be relevant to the fate of active substances in treated articles. Leached amounts of substances were considerably higher when the materials were exposed to intermittent water contact under laboratory conditions as compared to weathering of vertically exposed surfaces.

CONCLUSIONS

Experiences from the field experiments were used to define parameters of a procedure that is now provided to fulfil the requirements of the Biocidal Products Regulation. The experiments confirmed that the amount of water which is in contact with exposed surfaces is the crucial parameter determining leaching of substances.