Morphological Transformation of Silver Nanoparticles from Commercial Products: Modeling from Product Incorporation, Weathering through Use Scenarios, and Leaching into Wastewater

Chemical-analytical characterization and leaching of heavy metals associated with nanoparticles and microplastics from commercial face masks and the abundance of personal protective equipment (PPE) waste in three metropolitan cities of South America

In this study, we surveyed the presence of personal protective equipment (PPE) waste on the streets of Bogotá-Colombia, Lima-Perú, and Mar del Plata-Argentina. Furthermore, this work is also focused on the release capacity of Ag, Cu, and Zn metals associated with nanoparticles, and microplastics (MPs) from textile face masks (TFMs) and disposable face masks. According to our results, an association between low-income areas and PPE waste was found, which may be related to the periodicity of waste collection and economic activity. Polymers, like polypropylene, cotton-polyester, and additives, such as CaCO₃, MgO, and Ag/Cu as nanoparticles, were identified. TFMs released high levels of Cu (35,900-60,200 μg·L^-1), Zn (2340-2380 μg·L^-1), and MPs (4528-10,640 particles/piece). Metals associated with nanoparticles leached by face masks did not present any antimicrobial activity against P. aeruginosa. Our study suggests that TFMs may leach large amounts of polluting nano/micromaterials in aquatic environments with potential toxicological effects on organisms.

Binational survey of personal protective equipment (PPE) pollution driven by the COVID-19 pandemic in coastal environments: Abundance, distribution, and analytical characterization

In the present contribution, two nationwide surveys of personal protective equipment (PPE) pollution were conducted in Peru and Argentina aiming to provide valuable information regarding the abundance and distribution of PPE in coastal sites. Additionally, PPE items were recovered from the environment and analyzed by Fourier transformed infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX), and X-ray diffraction (XRD), and compared to brand-new PPE in order to investigate the chemical and structural degradation of PPE in the environment. PPE density (PPE m^-2) found in both countries were comparable to previous studies. FTIR analysis revealed multiple polymer types comprising common PPE, mainly polypropylene, polyamide, polyethylene terephthalate, and polyester. SEM micrographs showed clear weathering signs, such as cracks, cavities, and rough surfaces in face masks and gloves. EDX elemental mapping revealed the presence of elemental additives, such as Ca in gloves and face masks and AgNPs as an antimicrobial agent. Other metals found on the surface of PPE were Mo, P, Ti, and Zn. XRD patterns displayed a notorious decrease in the crystallinity of polypropylene face masks, which could alter its interaction with external contaminants and stability. The next steps in this line of research were discussed.

Critical review of the characteristics, interactions, and toxicity of micro/nanomaterials pollutants in aquatic environments

A wide range of contaminants of emerging concern such as micro/nanoplastics (MPs/PNPs) and metal-nanoparticles (Me-NPs) from anthropogenic activities have been identified in aquatic environments. The hazardous effects of these micro/nanomaterials as pollutants in organisms and the lack of knowledge about their behavior in aquatic environments have generated growing concern in the scientific community. The nanomaterials have a colloidal-type behavior due to their size range but with differences in their physicochemical properties. This review comprises the behavior of micro/nanomaterials pollutants and the physicochemical interactions between MPs/PNPs and Me-NPs in aquatic environments, and their potential toxicological effects in organisms. Moreover, this article describes the potential use of Me-NPs to remove MPs/PNPs present in the water column due to their photocatalytic and magnetic properties. It also discusses the challenge to determine harmful effects of micro/nanomaterials pollutants in organisms and provides future research directions to improve integrated management strategies to mitigate their environmental impact.

The Physical Modeling Analysis of Fate and Transport of Silver Nanoparticles Dispersed by Water Flow

The release of silver nanoparticles (AgNPs) from consumer products into an environment has become a central issue for many countries. Despite that the fate and behaviors of AgNPs incorporated into a wastewater have been investigated by building a model of wastewater treatment process, the transport and retention behaviors of AgNPs influenced by the water flow in a river must be understood. The physical model of simulated river to mimic a natural flow of river was proposed to investigate the behaviors of AgNP transport in the river. The results showed that the large amount of AgNPs deposited on the riverbed as Ag sediment with only 1.26% of AgNPs remained in the water flow. The elemental content of Ag freely dispersed across the riverbed increases from the upstream to downstream area of the simulated river. Verification of the spatial distribution of Ag dispersed along the water flow may contribute to a better understanding of the fate and transport of AgNPs in the aquatic environment.

Metal leaching from antimicrobial cloth face masks intended to slow the spread of COVID-19

Global health organizations recommend the use of cloth face coverings to slow the spread of COVID-19. Seemingly overnight, companies whose primary business is in no way related to healthcare or personal protective equipment-from mattresses manufacturers to big box stores-transitioned into the "mask business." Many companies advertise antimicrobial masks containing silver, copper, or other antimicrobials. Often, the techniques used to load such antimicrobials onto mask fibers are undisclosed, and the potential for metal leaching from these masks is yet unknown. We exposed nine so-called "antimicrobial" face masks (and one 100% cotton control mask) to deionized water, laundry detergent, and artificial saliva to quantify the leachable silver and copper that may occur during mask washing and wearing. Leaching varied widely across manufacturer, metal, and leaching solution, but in some cases was as high as 100% of the metals contained in the as-received mask after 1 h of exposure.

Cradle-to-grave environmental impact assessment of silver enabled t-shirts: Do nano-specific impacts exceed non nano-specific emissions?

Consumption of silver nanoparticles (nAg) is increasing due to their use in various industries. A comprehensive analysis is needed to elucidate the potential environmental and human health benefits and costs of the silver-enabled consumer products. For this purpose, four commercially available silver/nanosilver enabled polyester textiles with different initial silver/nanosilver loadings (1.07-4030 μg Ag/g textile) are included in the current research and cradle-to-grave life cycle assessments (LCA) are conducted to identify hotspots associated with production and use of these products throughout their lifetimes (100 cycles). Both non nano-specific and nano-specific impacts are calculated using nano-specific ecotoxicity characterization factors for nAg, instead of the commonly utilized ionic silver (Ag⁺) surrogate. Additionally, four different laundering scenarios were modeled to analyze the impacts resulting from using conventional and high efficiency machines. In the majority of environmental impact categories, either polyester textile manufacturing (regardless of Ag/nAg enabling) or laundering were identified as hotspots. Non nano-specific ecotoxicity impacts ranged from 1.58 × 10¹-2.91 × 10¹ CTUe/textile (CTUe: comparative toxic units for ecosystems) and nano-specific ecotoxicity impacts ranged from 2.01 × 10^-4-3.10 × 10^-3 CTUe/textile for the lowest and the highest Ag/nAg containing textiles, respectively. It is also found that unless the initial silver loading per textile is significantly high (in this case 4030 μg Ag/g textile comparing to the lowest load of 1.07 μg Ag/g textile), ecotoxicity and human health impacts of released silver species would be lower than ecotoxicity and human health impacts resulting from raw materials acquisition and manufacturing of the antibacterial textiles.

Transformation of silver nanoparticles released from skin cream and mouth spray in artificial sweat and saliva solutions: particle size, dissolution, and surface area

The use of silver nanoparticles (Ag NPs) in consumer products can result in diffuse environmental dispersion of both NPs and ionic silver. This study investigated the transformation of Ag NPs present in two consumer products (skin cream, mouth spray) in terms of release of Ag NPs and ionic silver and changes in particle size in artificial sweat and saliva solutions. Large differences in silver release were observed with the smaller sized Ag NPs in mouth spray releasing more silver compared with the Ag NPs of the skin cream. Substantial particle agglomeration took place in both artificial sweat and saliva, forming large-sized agglomerates (> 100 nm). The amount of dissolved silver in solution after 24 h was less than 10% of the total amount of Ag NPs for both products. The results show that the Ag NPs of these consumer products will largely remain as NPs even after 24 h of skin or saliva contact. The use of normalization by geometric surface area of the particles was tested as a way to compare dissolution for Ag NPs of different characteristics, including pristine, bare, as well as PVP-capped Ag NPs. Normalization of silver dissolution with the geometric surface area was shown promising, but more extensive studies are required to unambiguously conclude whether it is a way forward to enable grouping of the dissolution behavior of Ag NPs released from consumer products.

Impact of anaerobically digested silver and copper oxide nanoparticles in biosolids on soil characteristics and bacterial community

This study investigated whether 2 and 30 mg AgNPs or CuONPs/g TS present in treated sludge (biosolids) may impact the soil health by monitoring the soil characteristics and soil bacterial community for 105 days after the application of biosolids. AgNPs or CuONPs/g TS were first anaerobically digested with mixed primary and secondary sludge rather than adding pristine nanoparticles to biosolids directly. Both environmentally relevant (under the USEPA ceiling concentration limits) and high concentrations of AgNPs and CuONPs were tested. Soil tests included TOC, TN, TP, pH, cell viability and heterotrophic plate counts (HPC). Metagenomic data was generated by high-throughput sequencing of the 16S rRNA gene to explore bacterial populations and diversity. AgNPs and CuONPs at 2 and 30 mg NPs/g TS of sludge could impact soil health factors such as bacterial diversity, community structure, and the population of plant growth-promoting rhizobacteria (PGPR). The population of the highly abundant bacteria that have important physiological roles in soil decreased, while the less important bacteria for soil function were able to thrive. CuONPs exhibited a higher level of toxicity than the AgNPs at both phylum and genus taxonomic levels, and the HPC decreased with higher concentrations of AgNPs and CuONPs. Initially, most of the studied phyla abundance was affected, but the control and other reactors approached similar levels by the end of the experiments, which may be explained by the decrease in toxicity due to the transformation of nanoparticles and the defence mechanisms of bacteria, and indicates the need for long-term field studies.

Organic amendments exacerbate the effects of silver nanoparticles on microbial biomass and community composition of a semiarid soil

Increased utilization of silver nanoparticles (AgNPs) can result in an accumulation of these particles in the environment. The potential detrimental effects of AgNPs in soil may be associated with the low fertility of soils in semiarid regions that are usually subjected to restoration through the application of organic amendments. Microbial communities are responsible for fundamental processes related to soil fertility, yet the potential impacts of low and realistic AgNPs concentrations on soil microorganisms are still unknown. We studied the effects of realistic citrate-stabilized AgNPs concentrations (0.015 and 1.5 μg kg^-1) at two exposure times (7 and 30 days) on a sandy clay loam Mediterranean soil unamended (SU) and amended with compost (SA). We assessed soil microbial biomass (microbial fatty acids), soil enzyme activities (urease, β-glucosidase, and alkaline phosphatase), and composition of the microbial community (bacterial 16S rRNA gene and fungal ITS2 sequencing) in a microcosm experiment. In the SA, the two concentrations of AgNPs significantly decreased the bacterial biomass after 7 days of incubation. At 30 days of incubation, only a significant decrease in the Gram+ was observed at the highest AgNPs concentration. In contrast, in the SU, there was a significant increase in bacterial biomass after 30 days of incubation at the lowest AgNPs concentration. Overall, we found that fungal biomass was more resistant to AgNPs than bacterial biomass, in both SA and SU. Further, the AgNPs changed the composition of the soil bacterial community in SA, the relative abundance of some bacterial taxa in SA and SU, and fungal richness in SU at 30 days of incubation. However, AgNPs did not affect the activity of extracellular enzymes. This study demonstrates that the exposure time and organic amendments modulate the effects of realistic concentrations of AgNPs in the biomass and composition of the microbial community of a Mediterranean soil.

Fates of Au, Ag, ZnO, and CeO2 Nanoparticles in Simulated Gastric Fluid Studied using Single-Particle-Inductively Coupled Plasma-Mass Spectrometry

The increasing use of engineered nanoparticles (ENPs) in many industries has generated significant research interest regarding their impact on the environment and human health. The major routes of ENPs to enter the human body are inhalation, skin contact, and ingestion. Following ingestion, ENPs have a long contact time in the human stomach. Hence, it is essential to know the fate of the ENPs under gastric conditions. This study aims to investigate the fate of the widely used nanoparticles Ag-NP, Au-NP, CeO2-NP, and ZnO-NP in simulated gastric fluid (SGF) under different conditions through the application of single-particle inductively coupled plasma-mass spectrometry (SP-ICP-MS). The resulting analytical methods have size detection limits for Ag-NP, Au-NP, ZnO-NP, and CeO2-NP from 15 to 35 nm, and the particle concentration detection limit is 135 particles/mL. Metal ions corresponding to the ENPs of interest were detected simultaneously with detection limits from 0.02 to 0.1 μg/L. The results showed that ZnO-NPs dissolved completely and rapidly in SGF, whereas Au-NPs and CeO2-NPs showed apparent aggregation and did not dissolve significantly. Both aggregation and dissolution were observed in Ag-NP samples following exposure to SGF. The size distributions and concentrations of ENPs were affected by the original ENP concentration, ENP size, the contact time in SGF, and temperature. This work represents a significant advancement in the understanding of ENP characteristics under gastric conditions.