Estimating dermal transfer of copper particles from the surfaces of pressure-treated lumber and implications for exposure

Everything falls apart: How solids degrade and release nanomaterials, composite fragments, and microplastics

To ensure the safe use of materials, one must assess the identity and quantity of exposure. Solid materials, such as plastics, metals, coatings and cements, degrade to some extent during their life cycle, and releases can occur during manufacturing, use and end-of-life. Releases (e.g., what is released, how does release happen, and how much material is released) depend on the composition and internal (nano)structures of the material as well as the applied stresses during the lifecycle. We consider, in some depth, releases from mechanical, weathering and thermal stresses and specifically address the use cases of fused-filament 3D printing, dermal contact, food contact and textile washing. Solid materials can release embedded nanomaterials, composite fragments, or micro- and nanoplastics, as well as volatile organics, ions and dissolved organics. The identity of the release is often a heterogenous mixture and requires adapted strategies for sampling and analysis, with suitable quality control measures. Control materials enhance robustness by enabling comparative testing, but reference materials are not always available as yet. The quantity of releases is typically described by time-dependent rates that are modulated by the nature and intensity of the applied stress, the chemical identity of the polymer or other solid matrix, and the chemical identity and compatibility of embedded engineered nanomaterials (ENMs) or other additives. Standardization of methods and the documentation of metadata, including all the above descriptors of the tested material, applied stresses, sampling and analytics, are identified as important needs to advance the field and to generate robust, comparable assessments. In this regard, there are strong methodological synergies between the study of all solid materials, including the study of micro- and nanoplastics. From an outlook perspective, we review the hazard of the released entities, and show how this informs risk assessment. We also address the transfer of methods to related issues such as tyre wear, advanced materials and advanced manufacturing, biodegradable polymers, and non-solid matrices. As the consideration of released entities will become more routine in industry via lifecycle assessment in Safe-and-Sustainable-by-Design practices, release assessments will require careful design of the study with quality controls, the use of agreed-on test materials and standardized methods where these exist and the adoption of clearly defined data reporting practices that enable data reuse, meta-analyses, and comparative studies.

Transformation of zinc oxide nanoparticles in synthetic lung fluids

Surface coatings, including paints, stains, and sealants, have recently become a focus of "nano-enabled" consumer product engineering. Specifically, zinc oxide (ZnO) nanoparticles (NPs) have been introduced to surface coatings to increase UV resistance. As more "nano-enabled" products are made available for purchase, questions arise regarding their long-term environmental and human health effects. This study tracked the transformation of NP additives commonly added to consumer paints and stains using ZnO NPs as a model system. During product application and use, there is a risk of inhalation of aerosolized ZnO NPs. To investigate the potential chemical interactions and transformations that would occur after inhalation, ZnO NPs were incubated in two synthetic lung fluids (SLFs). Initial studies utilized ZnO NPs dispersed in Milli-Q water (control), or a commercially available deck stain. Additionally, two commercially available products advertising the inclusion of ZnO NP additives were evaluated. Subsamples were taken throughout incubation and analyzed via atomic absorption spectroscopy to determine both the total (including particulate) zinc concentration and dissolved (non-particulate) zinc concentration. Results indicate that the vast majority of ZnO transformation takes place within the first 24 h of incubation and is primarily driven by SLF pH and composition complexity. Significant dissolution of ZnO NPs was observed when incubated in Gamble's solution (between 25 and 68% depending on the matrix. Additionally, all ZnO solutions saw near immediate dissolution (~ 98-100%) within 3 h of incubation in artificial lysosomal fluid. Results illustrate potential for NPs in consumer products to undergo significant transformation during use and exposure over short time periods.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11051-022-05527-y.

Revealing the structural and chemical properties of copper-based nanoparticles released from copper treated wood

Copper-based preservatives consisting of micronized and nanoscale copper particles have been widely used in applications for wood protection. The widespread use of these preservatives along with the potential release of copper-containing nanoparticles (Cu NPs) during the life cycle of treated wood, has raised concerns over the impacts on the environment and occupational exposure. Along with assessing the potential hazards of these materials, a critical step is determining the chemical and morphological characteristics of the copper species released from copper-treated wood. Therefore, a combination of scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) was utilized to characterize and differentiate the released copper-containing particles based on their structures, sizing, and chemical properties. Airborne wood dust samples were collected during the abrasion and sawing of micronized copper (MC) treated wood in a laboratory testing system. Based on the signature Cu L_2,3 edge of EEL spectra, three different copper species (i.e., basic copper carbonate, copper, and copper–wood complex) were identified as major components of the embedded particles in wood dust. In addition, two types of individual Cu NPs consisting of basic copper carbonate and copper were identified. The variation of morphologies and chemical properties of copper-containing particles indicates the importance of copper–wood interactions to determine the formation and distribution of copper species in wood components. Our findings will advance the fundamental understanding of their released forms, potential transformation, and environmental fate during the life cycle.

A combination of analytical electron microscopy and electron energy loss spectroscopy enables effective speciation and characterization of airborne copper nanoparticles released from copper-treated wood.

Food contact of paper and plastic products containing SiO2, Cu-Phthalocyanine, Fe2O3, CaCO3: Ranking factors that control the similarity of form and rate of release

The paper industry is an important sector annually consuming kilotons of nanoforms and non-nanoforms of fillers and pigments. Fillers accelerate the rate of drying (less energy needed) and product cost (increasing the load of low-cost fillers). The plastic industry is another use sector, where coloristic pigments can be in nanoform, and many food containers are made of plastic. Use of paper to wrap both wet and dry food is consumer practice, but not always intended by producers. Here we compare the release behavior of different nano-enabled products (NEPs) by changing a) nanoform (NF) characteristics, b) NF load, c) the nano-enabled product (NEP) matrix, and d) food simulants. The ranking of these factors enables an assessment of food contact by concepts of analogy, specifically via the similarities of the rate and form of release in food during contact. Three types of matrices were used: Paper, plastic ((Polylactic Acid (PLA), Polyamide (PA6), and Polyurethane (PU)), and a paint formulation. Two nanoforms each of SiO₂, Fe₂O₃, Cu-Phthalocyanine were incorporated, additionally to the conventional form of CaCO₃ that is always contained in paper to reduce cellulose consumption. Tests were guided by the European Regulation EC 1935/2004 and EU 10/2011. No evidence of particle release was observed: the qualitative similarity (the form of release) was high regarding the food contact of all NEPs with embedded NFs. Quantitative similarity of releases depended primarily on the NEP matrix, as this controls the penetration of the simulant fluid into the NEP. The solubility of the NF and impurities in the simulant fluid was the second decisive factor, as dissolution of the NF inside the NEP is the main mechanism of release. This led to complete removal of CaCO₃ in acidic medium, whereas Fe and Si signals remained in the paper, consistent with the low release rates in an ionic form. In our set of 16 NEPs, only one NEP showed a dependence on the REACH NF descriptors (substance, size, shape, surface treatment, crystallinity, impurities), specifically attributed to differences in soluble impurities, whereas for all others the substance of the nanoform was sufficient to predict a similarity of food contact release, without influences of size, shape, surface treatment and crystallinity.

Focused Microbiome Shifts in Reconstructed Wetlands Correlated with Elevated Copper Concentrations Originating from Micronized Copper Azole-Treated Wood

Micronized copper (Cu) azole (MCA) wood preservative formulations include Cu in nano form, and relatively little is known about longer term effects of Cu leached from MCA into wetland ecosystems. We tested the hypothesis that changes in soil microbiomes within reconstructed freshwater wetlands will be associated with exposure to elevated Cu concentrations originating from immersed MCA-treated wood stakes. Eight replicate communities were assembled with Willamette Valley (OR, USA) flood plain soil and clonally propagated wetland plants within mesocosms. Inundated communities were equilibrated for 5 months before installation of MCA or control southern yellow pine stakes (n = 4 communities/experimental group). Soil samples were collected for 16S and internal transcribed spacer amplicon sequencing to quantify responses in prokaryotes and eukaryotes, respectively, at 15 time points, spanning two simulated seasonal dry downs, for up to 678 days. Physiochemical properties of water and soil were monitored at 20 and 12 time points respectively, over the same period. For both taxonomic groups of organisms, phylogenetic diversity increased and was positively correlated with elapsed days. Furthermore, there was significant divergence among eukaryotes during the second year based on experimental group. Although the composition of taxa underwent succession over time, there was significantly reduced relative abundance of sequence variants from Gomphonema diatoms and Scutellinia fungi in communities where MCA wood stakes were present compared with the controls. These focused microbiome shifts were positively correlated with surface water Cu and soil Cu concentrations, which were significantly elevated in treated communities. The reconstructed communities were effective systems for assessing potential impacts to wetland microbiomes after exposure to released copper. The results further inform postcommercialization risk assessments on MCA-treated wood. Environ Toxicol Chem 2021;40:3351-3368. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Variation in zinc release from surface coatings as a function of methodology

Over the last decade the growth of "nano-enabled" products have exploded in both industrial and direct to consumer applications. One area of interest is surface coatings, including paints, stains and sealants. Large scale applications of the products raise questions about both short- and long-term effects to both human and environmental health. Release of nanoparticles (NPs) from surfaces as a function of dermal contact is recognized as a potential human exposure route. Several standardized methods to quantify nanomaterial release have been previously used. In the current study, two standardized method were used to quantify the total mass of NPs released during sampling. ZnO (NPs) were used as a case study as they are commonly added to surface coatings to increase UV resistance. Particles were dispersed in Milli-Q water or a deck stain and applied to sanded plywood surfaces. Total release of Zn due to simulated dermal contact was evaluated using the Consumer Product Safety Commission (CPSC) and National Institute for Occupational Safety and Health (NIOSH) wipe methods. Additionally, three different sampling materials were tested. The total quantity of Zn released between the two methods was dependent upon the material used and how the ZnO was applied to the surface. Critically, less than 3% of the ZnO NPs applied to test surfaces was removed using either method. The results of this study demonstrate how different testing methodologies may result in varying estimates of human and environmental risk from NPs in surface coatings.

Release and transformation of nanoparticle additives from surface coatings on pristine & weathered pressure treated lumber

As the market for "nano-enabled" products (NEPs) continues to expand in commercial and industrial applications, there is a critical need to understand conditions that promote release of nanomaterials and their degradation products from NEPs. Moreover, these studies must aim to quantify both the abundance and form (aggregates, ions, hybrids, etc.) of material released from NEPs to produce reasonable estimates of human and environmental exposure. In this work ZnO nanoparticles (NPs), a common additive in NEP surface coatings, were dispersed in Milli-Q water and a commercially available wood stain before application to pristine and weathered (outdoor 1 year) micronized copper azole pressure treated lumber (MCA). Coated lumber surfaces were sampled consecutively eight times using a method developed by the Consumer Product Safety Commission (CPSC) to track potential human exposure to ZnO NPs and byproducts through simulated dermal contact. Surprisingly, the highest total release of Zn was observed from aged lumber coated with ZnO NPs dispersed in wood stain, releasing 233 ± 26 mg Zn/m² over the course of all sampling events. Alternatively, separate leaching experiments using a synthetic precipitation solution to simulate environmental release found aged lumber released significantly less Zn than pristine lumber when using the same coating formulation. Zinc speciation analysis also demonstrates that transformation of crystalline ZnO to Zn-organic complexes shortly after application to aged lumber. Regardless of experimental treatment, the majority of applied zinc (>75%) remains on the MCA surface. Finally, this work highlights how the nature of the screening technique (dermal contact vs. leaching) may result in different interpretations of exposure and risk.

Evaluating performance, degradation, and release behavior of a nanoform pigmented coating after natural and accelerated weathering

Pigments with nanoscale dimensions are added to exterior coatings to achieve desirable color and gloss properties. The present study compared the performance, degradation, and release behavior of an acrylic coating that was pigmented by a nanoform of Cu-phthalocyanine after both natural (i.e., outdoor) and accelerated weathering. Samples were weathered outdoors in three geographically distinct locations across the United States (Arizona, Colorado, Maryland) continuously for 15 months. Identically prepared samples were also artificially weathered under accelerated conditions (increased ultraviolet (UV) light intensity and elevated temperatures) for three months, in one-month increments. After exposure, both sets of samples were characterized with color, gloss, and infrared spectroscopy measurements, and selectively with surface roughness measurements. Results indicated that UV-driven coating oxidation was the principal degradation pathway for both natural and accelerated weathering samples, with accelerated weathering leading to an increased rate of oxidation without altering the fundamental degradation pathway. The inclusion of the nanoform pigment reduced the rate of coating oxidation, via UV absorption by the pigment, leading to improved coating integrity compared to non-pigmented samples. Release measurements collected during natural weathering studies indicated there was never a period of weathering, in any location, that led to copper material release above background copper measurements. Lab-based release experiments performed on samples weathered naturally and under accelerated conditions found that the release of degraded coating material after each type of exposure was diminished by the inclusion of the nanoform pigment. Release measurements also indicated that the nanoform pigment remained embedded within the coating and did not release after weathering.

Transformation and release of nanoparticle additives & byproducts from commercially available surface coatings on pressure treated lumber via dermal contact

Production and marketing of "nano-enabled" products for consumer purchase has continued to expand. However, many questions remain about the potential release and transformation of these nanoparticle (NP) additives from products throughout their lifecycle. In this work, two surface coating products advertised as containing ZnO NPs as active ingredients, were applied to micronized copper azol (MCA) and aqueous copper azol (ACA) pressure treated lumber. Coated lumber was weathered outdoors for a period of six months and the surface was sampled using a method developed by the Consumer Product Safety Commission (CPSC) to track potential human exposure to ZnO NPs and byproducts through simulated dermal contact. Using this method, the total amount of zinc extracted during a single sampling event was <1 mg/m² and no evidence of free ZnO NPs was found. Approximately 0.5% of applied zinc was removed via simulated dermal contact over 6-months, with increased weathering periods resulting in increased zinc release. XAFS analysis found that only 27% of the zinc in the as received coating could be described as crystalline ZnO and highlights the transformation of these mineral phases to organically bound zinc complexes during the six-month weathering period. Additionally, SEM images collected after sampling found no evidence of free NP ZnO release during simulated dermal contact. Both simulated dermal contact experiments, and separate leaching studies demonstrate the application of surface coating solutions to either MCA and ACA lumber will reduce the release of copper from the pressure treated lumber. This work provides clear evidence of the transformation of NP additives in consumer products during their use stage.

Release and transformation of ZnO nanoparticles used in outdoor surface coatings for UV protection

A major area of growth for "nano-enabled" products has been the addition of nanoparticles (NPs) to surface coatings including paints, stains and sealants. Zinc oxide (ZnO) NPs, long used in sunscreens and sunblocks, have found growing use in surface coating formulations to increase their UV resistance, especially on outdoor products. In this work, ZnO NPs, marketed as an additive to paints and stains, were dispersed in Milli-Q water and a commercial deck stain. Resulting solutions were applied to either Micronized-Copper Azole (MCA) pressure treated lumber or a commercially available composite decking. A portion of coated surfaces were placed outdoors to undergo environmental weathering, while the remaining samples were stored indoors to function as experimental controls. Weathered and control treatments were subsequently sampled periodically for 6 months using a simulated dermal contact method developed by the Consumer Product Safety Commission (CPSC). The release of ZnO NPs, and their associated degradation products, was determined through sequential filtration, atomic spectroscopy, X-Ray Absorption Fine Structure Spectroscopy, and electron microscopy. Across all treatments, the percentage of applied zinc released through simulated dermal contact did not exceed 4%, although transformation and release of zinc was highly dependent on dispersion medium. For MCA samples weathered outdoors, water-based applications released significantly more zinc than stain-based, 180 ± 28, and 65 ± 9 mg/m² respectively. Moreover, results indicate that the number of contact events drives material release.

Copper release and transformation following natural weathering of nano-enabled pressure-treated lumber

Commercially available lumber, pressure-treated with micronized copper azole (MCA), has largely replaced other inorganic biocides for residential wood treatment in the USA, yet little is known about how different outdoor environmental conditions impact the release of ionic, nano-scale, or larger (micron-scale) copper from this product. Therefore, we weathered pressure treated lumber for 18 months in five different climates across the continental United States. Copper release was quantified every month and local weather conditions were recorded continuously to determine the extent to which local climate regulated the release of copper from this nano-enabled product during its use phase. Two distinct release trends were observed: In cooler, wetter climates release occurred primarily during the first few months of weathering, as the result of copper leaching from surface/near-surface areas. In warmer, drier climates, less copper was initially released due to limited precipitation. However, as the wood dried and cracked, the exposed copper-bearing surface area increased, leading to increased copper release later in the product lifetime. Single-particle-ICP-MS results from laboratory prepared MCA-wood leachate solutions indicated that a) the predominant form of released copper passed through a filter smaller than 0.45 micrometers and b) released particles were largely resistant to dissolution over the course of 6 wks. Toxicity Characteristic Leaching Procedure (TCLP) testing was conducted on nonweathered and weathered MCA-wood samples to simulate landfill conditions during their end-of-life (EoL) phase and revealed that MCA wood released <10% of initially embedded copper. Findings from this study provide data necessary to complete a more comprehensive evaluation of the environmental and human health impacts introduced through release of copper from pressure treated lumber utilizing life cycle assessment (LCA).

Assessing the release of copper from nanocopper-treated and conventional copper-treated lumber into marine waters II: Forms and bioavailability

One application of nanocopper is as a wood-preserving pesticide in pressure-treated lumber. Recent research has shown that pressure-treated lumber amended with micronized copper azole (MCA), which contains nanosized copper, releases copper under estuarine and marine conditions. The form of copper released (i.e., ionic, nanocopper [1-100 nm in size]) is not fully understood but will affect the bioavailability and toxicity of the metal. In the present study, multiple lines of evidence, including size fractionation, ion-selective electrode electrochemistry, comparative toxicity, and copper speciation were used to determine the form of copper released from lumber blocks and sawdust. The results of all lines of evidence supported the hypothesis that ionic copper was released from MCA lumber and sawdust, with little evidence that nanocopper was released. For example, copper concentrations in size fractionations of lumber block aqueous leachates including unfiltered, 0.1 μm, and 3 kDa were not significantly different, suggesting that the form of copper released was in the size range operationally defined as dissolved. These results correlated with the ion-selective electrode data which detects only ionic copper. In addition, comparative toxicity testing resulted in a narrow range of median lethal concentrations (221-257 μg/L) for MCA lumber blocks and CuSO4 . We conclude that ionic copper was released from the nanocopper pressure-treated lumber under estuarine and marine conditions. Environ Toxicol Chem 2018;37:1969-1979. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Assessing the release of copper from nanocopper-treated and conventional copper-treated lumber into marine waters I: Concentrations and rates

Little is known about the release of metal engineered nanomaterials (ENMs) from consumer goods, including lumber treated with micronized copper. Micronized copper is a recent form of antifouling wood preservative containing nanosized copper particles for use in pressure-treated lumber. The present study investigated the concentrations released and the release rate of total copper over the course of 133 d under freshwater, estuarine, and marine salinity conditions (0, 1, 10, and 30‰) for several commercially available pressure-treated lumbers: micronized copper azole (MCA) at 0.96 and 2.4 kg/m3 , alkaline copper quaternary (ACQ) at 0.30 and 9.6 kg/m3 , and chromated copper arsenate (CCA) at 40 kg/m3 . Lumber was tested as blocks and as sawdust. Overall, copper was released from all treated lumber samples. Under leaching conditions, total release ranged from 2 to 55% of the measured copper originally in the lumber, with release rate constants from the blocks of 0.03 to 2.71 (units per day). Generally, measured release and modeled equilibrium concentrations were significantly higher in the estuarine conditions compared with freshwater or marine salinities, whereas rate constants showed very limited differences between salinities. Furthermore, organic carbon was released during the leaching and demonstrated a significant relationship with released copper concentrations as a function of salinity. The results indicate that copper is released into estuarine/marine waters from multiple wood treatments including lumber amended with nanoparticle-sized copper. Environ Toxicol Chem 2018;37:1956-1968. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Quantitative human health risk assessment along the lifecycle of nano-scale copper-based wood preservatives

The use of nano-scale copper oxide (CuO) and basic copper carbonate (Cu₂(OH)₂CO₃) in both ionic and micronized wood preservatives has raised concerns about the potential of these substances to cause adverse humans health effects. To address these concerns, we performed quantitative (probabilistic) human health risk assessment (HHRA) along the lifecycles of these formulations used in antibacterial and antifungal wood coatings and impregnations by means of the EU FP7 SUN project's Decision Support System (SUNDS, www.sunds.gd). The results from the risk analysis revealed inhalation risks from CuO in exposure scenarios involving workers handling dry powders and performing sanding operations as well as potential ingestion risks for children exposed to nano Cu₂(OH)₂CO₃ in a scenario involving hand-to-mouth transfer of the substance released from impregnated wood. There are, however, substantial uncertainties in these results, so some of the identified risks may stem from the safety margin of extrapolation to fill data gaps and might be resolved by additional testing. Our stochastic approach successfully communicated the contribution of different sources of uncertainty in the risk assessment. The main source of uncertainty was the extrapolation from short to long-term exposure, which was necessary due to the lack of (sub)chronic in vivo studies with CuO and Cu₂(OH)₂CO₃. Considerable uncertainties also stemmed from the use of default inter- and intra-species extrapolation factors.

Transformations of Nanoenabled Copper Formulations Govern Release, Antifungal Effectiveness, and Sustainability throughout the Wood Protection Lifecycle

Here we compare the standard European benchmark of wood treatment by molecularly dissolved copper amine (Cu-amine), also referred to as aqueous copper amine (ACA), against two nanoenabled formulations: copper(II)oxide nanoparticles (CuO NPs) in an acrylic paint to concentrate Cu as a barrier on the wood surface, and a suspension of micronized basic copper carbonate (CuCO₃·Cu(OH)₂) for wood pressure treatment. After characterizing the properties of the (nano)materials and their formulations, we assessed their effects in vitro against three fungal species: Coniophora puteana, Gloeophyllum trabeum, and Trametes versicolor, finding them to be mediated only partially by ionic transformation. To assess the use phase, we quantify both release rate and form. Cu leaching rates for the two types of impregnated wood (conventional and nanoenabled) are not significantly different at 172 ± 6 mg/m², with Cu being released predominantly in ionic form. Various simulations of outdoor aging with release sampling by runoff, during condensation, by different levels of mechanical shear, all resulted in comparable form and rate of release from the nanoenabled or the molecular impregnated woods. Because of dissolving transformations, the nanoenabled impregnation does not introduce additional concern over and above that associated with the traditional impregnation. In contrast, Cu released from wood coated with the CuO acrylate contained particles, but the rate was at least 100-fold lower. In the same ranking, the effectiveness to protect against the wood-decaying basidiomycete Coniophora puteana was significant with both impregnation technologies but remained insignificant for untreated wood and wood coated by the acrylic CuO. Accordingly, a lifecycle-based sustainability analysis indicates that the CuO acrylic coating is less sustainable than the technological alternatives, and should not be developed into a commercial product.

Dermal transfer and environmental release of CeO2 nanoparticles used as UV inhibitors on outdoor surfaces: Implications for human and environmental health

A major area of growth for "nano-enabled" consumer products have been surface coatings, including paints stains and sealants. Ceria (CeO₂) nanoparticles (NPs) are of interest as they have been used as additives in these these products to increase UV resistance. Currently, there is a lack of detailed information on the potential release, and speciation (i.e., ion vs. particle) of CeO₂ NPs used in consumer-available surface coatings during intended use scenarios. In this study, both Micronized-Copper Azole pressure-treated lumber (MCA), and a commercially available composite decking were coated with CeO₂ NPs dispersed in Milli-Q water or wood stain. Coated surfaces were divided into two groups. The first was placed outdoors to undergo environmental weathering, while the second was placed indoors to act as experimental controls. Both weathered surfaces and controls were sampled over a period of 6months via simulated dermal contact using methods developed by the Consumer Product Safety Commission (CPSC). The size and speciation of material released was determined through sequential filtration, total metals analysis, X-Ray Absorption Fine Structure Spectroscopy, and electron microscopy. The total ceria release from MCA coated surfaces was found to be dependent on dispersion matrix with aqueous applications releasing greater quantities of CeO₂ than stain based applications, 66±12mg/m² and 36±7mg/m², respectively. Additionally, a substantial quantity of CeO₂ was reduced to Ce(III), present as Ce(III)-organic complexes, over the 6-month experimental period in aqueous based applications.

Effects of micronized and nano-copper azole on marine benthic communities

The widespread use of copper nanomaterials (CuNMs) as antibacterial and antifouling agents in consumer products increases the risk for metal contamination and adverse effects in aquatic environments. Information gaps exist on the potential toxicity of CuNMs in marine environments. We exposed field-collected marine meio- and macrobenthic communities to sediments spiked with micronized copper azole (MCA) using a novel method that brings intact benthic cores into the laboratory and exposes the organisms via surface application of sediments. Treatments included field and laboratory controls, 3 spiked sediments: low-MCA (51.9 mg/kg sediment), high-MCA (519 mg/kg sediment), and CuSO₄ (519 mg/kg sediment). In addition, single-species acute testing was performed with both MCA and CuSO_4. Our results indicate that meio- and macrofaunal assemblages exposed to High-MCA and CuSO₄ treatments differed significantly from both the laboratory control and the low-MCA treatments. Differences in macrofauna were driven by decreases in 3 Podocopa ostracod species, the bivalve Gemma gemma, and the polychaetes Exogone verugera and Prionospio heterobranchia relative to the laboratory control. Differences in the meiofaunal community are largely driven by nematodes. The benthic community test results were more sensitive than the single-species test results. Findings of this investigation indicate that CuNMs represent a source of risk to marine benthic communities comparable to that of dissolved Cu. Environ Toxicol Chem 2018;37:362-375. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

In vitro bioaccessibility of copper azole following simulated dermal transfer from pressure-treated wood

Micronized copper azole (MCA) and micronized copper quaternary (MCQ) are the latest wood preservatives to replace the liquid alkaline copper and chromated copper arsenate preservatives due to concerns over the toxicity or lack of effectiveness of the earlier formulations. Today, the use of MCA has become abundant in the wood preservative industry with approximately 38millionlbs of copper carbonate being used to treat lumber each year. Despite this widespread usage, little information is available on the bioaccessibility of this preservative upon gastrointestinal exposure. Using a simulated hand-to-mouth/gastric system exposure study we investigated several types of commercially available copper-treated lumber products as-purchased and after exposure to outdoor weathering conditions. Soluble and particulate fractions of copper were measured after transfer to and release from surface wipes passed along copper-treated lumber and exposed to synthetic stomach fluid (SSF, pH1.5) or deionized (DI) water. Wipes passed along new boards contained greater amounts of copper than wipes from weathered boards. The total copper recovered from the wipes after microwave extraction varied among the different wood types. For all wood types the copper released into SSF was more soluble than what was soluble in DI water. The data suggest that copper from treated wood is highly bioaccessible in SSF regardless of wood type and weathering condition.

The changing face of nanomaterials: Risk assessment challenges along the value chain

Risk assessment (RA) of manufactured nanomaterials (MNM) is essential for regulatory purposes and risk management activities. Similar to RA of "classical" chemicals, MNM RA requires knowledge about exposure as well as of hazard potential and dose response relationships. What makes MNM RA especially challenging is the multitude of materials (which is expected to increase substantially in the future), the complexity of MNM value chains and life cycles, the accompanying possible changes in material properties over time and in contact with various environmental and organismal milieus, and the difficulties to obtain proper exposure data and to consider the proper dose metric. This article discusses these challenges and also critically overviews the current state of the art regarding MNM RA approaches.

Release of copper-amended particles from micronized copper-pressure-treated wood during mechanical abrasion

Background

We investigated the particles released due to abrasion of wood surfaces pressure-treated with micronized copper azole (MCA) wood preservative and we gathered preliminary data on its in vitro cytotoxicity for lung cells. The data were compared with particles released after abrasion of untreated, water (0% MCA)-pressure-treated, chromated copper (CC)-pressure-treated wood, and varnished wood. Size, morphology, and composition of the released particles were analyzed.

Results

Our results indicate that the abrasion of MCA-pressure-treated wood does not cause an additional release of nanoparticles from the unreacted copper (Cu) carbonate nanoparticles from of the MCA formulation. However, a small amount of released Cu was detected in the nanosized fraction of wood dust, which could penetrate the deep lungs. The acute cytotoxicity studies were performed on a human lung epithelial cell line and human macrophages derived from a monocytic cell line. These cell types are likely to encounter the released wood particles after inhalation.

Conclusions

Our findings indicate that under the experimental conditions chosen, MCA does not pose a specific additional nano-risk, i.e. there is no additional release of nanoparticles and no specific nano-toxicity for lung epithelial cells and macrophages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-016-0232-7) contains supplementary material, which is available to authorized users.