Potential arsenic exposures in 25 species of zoo animals living in CCA-wood enclosures

Occurrence, fate, and potential impacts of wood preservatives in the environment: Challenges and environmentally friendly solutions

Wood preservation has gained global prevalence in recent years, primarily owing to the renewable nature of wood and its capacity to act as a carbon sink. Wood, in its natural form, lacks intrinsic resilience and is prone to decay if left untreated; hence, wood preservatives (WPs) are used to improve wood's longevity. The fate and potential hazards of wood preservatives to human health, ecosystems, and the environment are complex and depend on various aspects, including the type of the preservative compounds, their physicochemical properties, application methods, exposure pathways, environmental conditions, and safety measures and guidelines. The occurrence and distribution of WPs in environmental matrices such as soil and water can result in hazardous pollutants seeping into surface water, groundwater, and soil, posing health hazards, and polluting the environment. Bioremediation is crucial to safeguarding the environment and effectively removing contaminants through hydrolytic and/or photochemical reactions. Phytoremediation, vermicomposting, and sustainable adsorption have demonstrated significant efficacy in the remediation of WPs in the natural environment. Adsorbents derived from biomass waste have been acknowledged for their ability to effectively remove WPs, while also offering cost-efficiency and environmental sustainability. This paper aims to identify wood preservatives' sources and fate in the environment and present a comprehensive overview of the latest advancements in environmentally friendly methods relevant to the removal of the commonly observed contaminants associated with WPs in environmental matrices.

Environmental and Health Hazards of Chromated Copper Arsenate-Treated Wood: A Review

Copper chrome arsenate (CCA) water-borne solution used to be widely used to make timber highly resistant to pests and fungi, in particular, wood products designed for outdoor use. Nowadays, CCA is a restricted chemical product in most countries, since potential environmental and health risks were reported due to dermal contact with CCA residues from treated structures and the surrounding soil, as well as the contamination of soils. However, large quantities of CCA-treated timber are still in use in framings, outdoor playground equipment, landscaping, building poles, jetty piles, and fencing structures around the world, thus CCA remains a source of pollutants to the environment and of increasing toxic metal/metalloid exposure (mainly in children). International efforts have been dedicated to the treatment of materials impregnated with CCA, however not only does some reuse of CCA-treated timber still occur, but also existing structures are leaking the toxic compounds into the environment, with impacts on the environment and animal and human health. This study highlights CCA mechanisms and the documented consequences in vivo of its exposure, as well as the adverse environmental and health impacts.

Microbial remediation for the removal of inorganic contaminants from treated wood: Recent trends and challenges

Owing to the seriousness of the ecological risk and human hazard of inorganic wood preservatives, their effective removal was gradually recognized. This paper details different types of wood preservatives, their perniciousness, and their potential removal alternatives, while the wood treatment process is briefly described. Among decontamination methods, microbial remediation is considered as an environmentally friendly approach with enormous potentialities over the conventional treatments. In the current review, the mechanism of bioremediation is summed up and recent advances, challenges, and future perspectives of microbial remediation are discussed. The removal of heavy metals from treated wood requires a combination of various technologies to obtain higher performance. Meanwhile, the decontaminated wood generated through bioremediation can be effectively reused.

Comparative Cr, As and CCA induced Cytostaticity in mice kidney: A contribution to assess CCA toxicity

CCA (Chromium Copper Arsenate) treated wood, widely used in outdoor residential structures and playgrounds, poses considerable dangers of leaching of its components to the environment. In this study, mouse kidney samples were used to evaluate the effects of CCA, chromium trioxide (CrO₃) and arsenic pentoxide (As₂O₅) on cell pathophysiology by flow cytometry. Samples were collected after 14, 24, 48 and 96 h of animal exposure. While Cr had no statistically significant cytostatic effects, As₂O₅ induced a S-phase delay in animals exposed for 24 h, and over time a G0/G1 phase blockage. The effects of CCA in S-phase were similar, but more severe than those of As₂O₅. Since environmental and public health hazards due to the long durability of CCA-treated wood products, these data confirm that CCA has profoundly toxic effects on cell cycle, distinct from the compounds themselves. These cytostatic effects support cell cycle dynamics as a valuable endpoint to assess the toxicity of remaining CCA-treated infrastructures, and the expected increased waste stream over the coming decades.

Experimental modeling of the acute toxicity and cytogenotoxic fate of composite mixtures of chromate, copper and arsenate oxides associated with CCA preservative using Clarias gariepinus (Burchell 1822)

Concurrent occurrence of chromium (Cr), copper (Cu) and arsenic (As) from chromated copper arsenate (CCA) wood preservative in aquatic ecosystems demands that their joint-actions in eliciting toxic effects be assessed for adequate understanding of the health risk they may pose to biota. Clarias gariepinus was exposed to As₂O₃ , CrO₃ and CuO and their composite mixtures (1:1 and 1:1:1) at various concentrations (0 – 600 mg/L) for 96-h to determine the acute toxicity using OECD (1992) protocol. C. gariepinus was then exposed to sub-lethal concentrations corresponding to 6.25, 12.5, 25.0, 50.0 and 100% of the 96-h LC₅₀ for 7 days to assess the cytogenotoxic effects using piscine micronucleus (MN) test. The 96-h LC₅₀ showed that the metals/metalloid demonstrated differential interactions in a concentration dependent pattern. The 96-h LC₅₀ showed that Cr was the most toxic while Cu and As:Cu were indeterminate (Cr > Cr:Cu > As:Cr > As > As:Cr:Cu > Cu = As:Cu indeterminate). Isobologram and synergistic ratio (SR) models predicted antagonistic interaction between Cu:Cr and As:Cr and synergism between As:Cu in the causation of morbidity and mortality of C. gariepinus. Interaction factor model predicted antagonism as common interactive mechanism among the metal/metalloid mixtures in the induction of MN and abnormal nuclear erythrocytes in C. gariepinus. Predicted interactions among the three metals/ metalloid were largely antagonism and synergism towards the induction of acute toxicity and cytogenotoxicity. The models employed herein may be useful in establishing environmental safe limits for mixtures of metals/metalloids against the induction of acute toxicity and DNA damage in lower aquatic vertebrates.

Anaerobic digestion to reduce biomass and remove arsenic from As-hyperaccumulator Pteris vittata

The lack of efficient methods to treat As-rich biomass is a drawback for phytoremediation technology. In this study, we applied anaerobic digestion to reduce biomass and remove As from As-rich Pteris vittata biomass. P. vittata biomass including control (3.1 mg kg^-1 As) and As-rich (2665 mg kg^-1 As), together with positive and negative controls, was anaerobically digested at 35 °C for 35 d. Arsenic partitioning among gas, liquid and solid phases after anaerobic digestion was determined. Methane index potential assay was used to assess methane yields whereas liquid-displacement method was used to measure methane gas production. After 35 d, As partitioning in the liquid, solid and gas phases was 79, 30 and 1%, respectively. Besides, volatile solid was decreased from 91 to 12-17% total solid, while P. vittata biomass was decreased by 73-83%. Moreover, anaerobic digestion solubilized 76% As from P. vittata biomass, with 90% soluble As at 4.95 mg L^-1 being recovered by As-Mg precipitation. Finally, methane production after 35 d was 197-212 L_NCH₄/kg volatile solid, showing slight As inhibition. Effective As removal from P. vittata biomass prior to disposal can improve the phytoremediation process.

Arsenic removal and biomass reduction of As-hyperaccumulator Pteris vittata: Coupling ethanol extraction with anaerobic digestion

Improper disposal of arsenic-rich biomass and the lack of efficient methods to treat it may cause contamination in the environment. We developed an efficient method for arsenic (As) removal and biomass reduction of As-rich biomass of the As-hyperaccumulator Pteris vittata by coupling ethanol extraction with anaerobic digestion. This study assessed As partitioning among the three phases (gas, liquid and solid) after anaerobic digestion of P. vittata biomass. Biomass with and without As was first extracted with ethanol. Ethanol extraction removed ~93% As, with remaining As concentration at 197 mg kg^-1. The extracted biomass was then digested at 35 °C under anaerobic conditions for 35 d. Arsenic in the digested biomass was reduced by 89%, with remaining As concentration at 60 mg kg^-1. In addition, anaerobic digestion reduced the biomass by 64-71% and decreased the volatile solids content from 94 to 15-18%. Methane production was 145 and 160 L_NCH₄/kgVS after 35 d for As-rich and control biomass, respectively. As a final step, As concentration in anaerobic digestate supernatant was reduced to 0.26 mg L^-1 by As-Mg precipitation. Overall, coupling ethanol extraction with anaerobic digestion decreased As concentration in P. vittata biomass from 2665 to 60 mg kg^-1, or by 98%. At this level (<100 mg As kg^-1), P. vittata biomass can be considered a safe material based on USEPA regulations. Effective As removal from P. vittata biomass prior to disposal improves the phytoremediation process and lowers biomass transport and landfill disposal costs.

Arsenic removal by As-hyperaccumulator Pteris vittata from two contaminated soils: A 5-year study

The ability of As-hyperaccumulator Pteris vittata to remove As from two contaminated soils (CCA from an As-treated wood facility and DVA from a cattle-dipping vat) over 5 years was investigated for the first time. The goal was to evaluate P. vittata's ability to continuously remove As during 10 harvests and identify how soil As was affected by P. vittata under P-sufficient (P-fertilizer) and P-limiting (phosphate rock) conditions. Sequential extraction was used to determine changes in metal distribution among different soil fractions. The high frond biomass production occurred on the 9th (62.1-63.9 and 35.6-63.5 g plant^-1) and 10th harvest (58.6-60.7 and 51.9-57.1 g plant^-1) for CCA and DVB soils, though frond As concentration decreased. Soil arsenic removal averaged 7-10% per harvest during the 1-6th harvests and was reduced to 0-3% during the 7-10th harvests for DVA and CCA soils. Arsenic from all fractions, excluding the residual fraction, was affected by plant uptake. The largest reduction occurred in the amorphous fraction of CCA-soil at 64-66% (61.2-61.5 to 20.8-21.8 mg kg^-1) and in the crystalline fraction of DVA-soil at 50-86% (2.18-4.35 to 0.61-1.10 mg kg^-1). Soil As concentrations were reduced by 37-47% from 26.7 to 129 to 15.6-16.8 and 68.9-70.1 mg kg^-1 for the DVA and CCA soils, respectively. Our data indicated that P. vittata efficiently solubilized non-labile As under P-limiting conditions without impacting its As depletion.

Arsenic removal from As-hyperaccumulator Pteris vittata biomass: Coupling extraction with precipitation

Proper disposal of As-hyperaccumulator Pteris vittata biomass (Chinese brake fern) enhances its application in phytoremediation. The goal of this study was to optimize As removal from P. vittata (PV) biomass by testing different particle sizes, extractants, extraction times and solid-to-liquid ratios. PV biomass was extracted using different extractants followed by different Mg-salts to recover soluble As via precipitation. Water-soluble As in PV biomass varied from 6.8% to 61% of total As depending on extraction time, with 99% of As being arsenate (AsV). Extraction with 2.1% HCl, 2.1% H₃PO₄, 1 M NaOH and 50% ethanol recovered 81, 78, 47 and 14% of As from PV biomass. A follow-up extraction using HCl recovered 27-32% with ethanol recovering only 5%. Though ethanol showed the lowest extractable As, residual As in the biomass was also the lowest. Among the extractants, 35% ethanol was the best to remove As from PV biomass. Approximately 90% As was removed from PV biomass using particle size <1 mm at solid:liquid ratio 1:50 and pH 6 for 2 h. Adding MgCl₂ at As:Mg ratio of 1:400 with pH 9.5 was effective to precipitate soluble As, resulting in 98% removal. Effective removal of As from PV biomass prior to disposal helps make phytoremediation more feasible.

Arsenic concentrations and speciation in wild birds from an abandoned realgar mine in China

Birds are at a higher level in the food chain; however, the potential bioaccumulation and biotransformation of arsenic (As) in birds in As mines has rarely been studied. In this study, four passerine bird species (tree sparrow [Passer montanus], light-vented bulbul [Pycnonotus sinensis], Garrulax canorus [Leucodioptron canorus], and magpie [Pica pica]) were collected from an abandoned As mine in China. The highest recorded As concentrations were 4.95 mg/kg and 51.65 mg/kg in muscles and feathers, respectively. Detection using high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) revealed six As species, including arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenobetaine (AsB) and arsenocholine (AsC), with the former three species as the dominant (>92%) and the latter three as the minor As species (<6.17%). Further analysis of the selected bird samples using the X-ray absorption near edge structure (XANES) technique revealed the existence of As(III)-tris-glutathione (As(III)-GSH), which can be regarded as equivalent to the non-extractable and unidentified As form in the HPLC-ICP-MS data. Both methods revealed similar patterns of As species in the birds from the As mine, with muscles containing mainly inorganic As and DMA and feathers containing mainly inorganic As. The results of this study contribute to the knowledge regarding As accumulation and speciation in terrestrial organisms.