Despite increasing interest in and use of nanoparticles (NP), the environmental consequences of using NP are poorly understood because most relevant studies have not taken the effects of natural coatings on NP into consideration. The aim of this study was to improve our understanding of the fates of NP in aquatic systems. The fates of silver NP (AgNP) capped with citrate and polyethylene glycol dispersed in ecotoxicological matrices in the presence of environmentally relevant components of natural water (humic substances and extracellular polymeric substances) were investigated. Interactions between AgNP and natural organic matter were evaluated by ultracentrifugation and electrophoretic mobility measurements to assess AgNP dissolution. Humic substances and extracellular polymeric substances both decreased the dissolution rate. The natural organic matter (humic substances and extracellular polymeric substances) provided conditions in which the medium stabilized the NP. The dissolution rate depended on the coating type (citrate or polyethylene glycol), dissolved organic carbon concentration, and particle concentration. The presence of algae and Daphnia affected AgNP conversion, demonstrating the value of research that takes environmentally relevant matrices into consideration. The results improve our understanding of the factors that affect the bioavailabilities of AgNP and therefore improve our ability to evaluate AgNP toxicity. Studies of other NP using the same strategy will improve our understanding of the fates of nanomaterials in the environment and biota.

Highlights

• Natural organic matter controls silver nanoparticle environmental dissolution/fate;

• Exopolysaccharides and aquatic humic substances both promote AgNP stabilization;

• Capping agents (citrate or polyethylene glycol) change the AgNP dissolution rate;

• AgNP behave differently when considering media for algae and Daphnia bioassays.

Triclosan (TCS), triclocarban (TCC), parabens, bisphenols (BPAs), tetrabromobisphenol A and its alternatives (TBBPAs), and phthalate esters (PAEs) are typical endocrine-disrupting chemicals (EDCs), which have received increasing attention due to their potential adverse effects on ecological and human health. Human exposure to these EDCs is widespread. However, data regarding the distribution and related health risks of multiple EDCs in chemical parks are relatively scarce. In this study, 28 EDCs were determined in surface soil, sediment, and sludge samples collected from the Yangkou Chemical Industrial Park (Jiangsu, China). With the exception of TBBPAs, the distributions of Σ(TCS + TCC), Σ₆parabens, Σ₈BPAs, and Σ₉PAEs in environmental media were as follows: sludge > sediment ≥ soil. No obvious differences were found regarding the concentrations of Σ₉PAEs within the soil samples. Higher levels of Σ(TCS + TCC) (186 μg kg^-1 dw) and Σ₃TBBPAs (154 μg kg^-1 dw) were found in the soil near a chemical manufacturer and the main sewage outlet of a wastewater treatment plant, respectively. The non-carcinogenic risks of EDCs from soil were estimated, and the risk levels were found to be a few orders of magnitude lower than the reported reference dose (RfD) values. The hazard indexes for all the samples were smaller than one, suggesting that the chemical industrial park posed a low risk to the workers. Additionally, the mass inventories of Σ(TCS + TCC), Σ₆parabens, Σ₈BPAs, Σ₃TBBPAs, and Σ₉PAEs were estimated to be 507, 90.6, 133, 20.7, and 1090 kg, respectively. These findings help to establish baseline concentrations for EDCs in soil, sediment, and sludge in a chemical industrial park.

Exposure to high levels of benzene, toluene, ethylbenzene, and xylenes (BTEX) poses health risks in high-traffic urban areas. BTEX exposure at two microenvironments, the roadside and along the traveling routes, within urban and suburban areas of the Bangkok Metropolitan Region was examined to assess cancer and noncancer risks. The lifetime cancer risk (LCR) for benzene and noncancer hazard index (HI) for all BTEX compounds were evaluated for adult male and female groups (drivers, passengers, and street vendors) in two scenarios: average case and worst case. With the assumption of negligible exposure outside the two considered microenvironments, the pickup drivers had the highest LCR and HI. Higher exposure risks were found in urban areas than in the suburbs and among men than females. Higher toluene levels were found at all monitoring sites in two microenvironments, but benzene was the most important in causing noncancer risk. The HI for all target groups ranged from 8.5E-03 to 4.0E-01, indicating a low noncancer risk from BTEX exposure (HI < 1). The LCR caused by benzene exposure ranged from 1.7E-06 to 7.2E-05, which is higher than the United States EPA most health-protective limit (1E-06). Further research should include other microenvironments by assessing the 24-hour exposure of all considered groups.

The growing popularity of electronic cigarettes (e-cig) has raised questions about the health effects of e-cig use, or vaping. Previous studies have reported on the potential of exposure to arsenic (As) and other metal(loid)s from vaping, but little is known about the speciation of As in the inhaled aerosols, an important determinant of toxicity. Inorganic As (iAs) species As^III and As^V are generally more hazardous than organic As species. This study aimed to investigate total and speciated As in condensed aerosols of popular commercial e-cig products and to compare them with regulatory exposure limits. High-performance liquid chromatography and inductively-coupled plasma mass spectrometry were used for As measurements of e-cig aerosol condensates. The analysis included samples from three types of e-cig devices: MODs, PODs, and disposable pod (d-POD) devices. iAs species were identified in all 23 analyzed e-cig aerosol condensate samples, with the highest aerosol concentrations measured in MODs. The geometric mean (range) iAs concentration of 2.3 (1.2-5.1) µg/m³ observed in MOD devices in this study exceeded the recommended exposure limit of 2 µg/m³ for 15-min or shorter inhalation exposures set by the United States National Institute for Occupational Safety and Health. These preliminary results suggest that iAs species are present in inhalable aerosols of some MOD products at levels above regulatory limits for iAs inhalation.

The worldwide production and usage of novel flame retardants increase their exposure to non-human fauna. Animals can accumulate and metabolize these novel flame retardants including novel halogenated flame retardants (NHFRs) and organophosphate flame retardants (OPFRs), which is of considerable significance to their internal exposure and final toxicities. In this review, recent studies on the metabolic pathways and kinetics of the two classes of novel flame retardants and the internal exposure and toxicity of their major metabolites are summarized. The results showed that the metabolic pathways of OPFRs were similar among various animals, while the metabolism kinetics (or toxicokinetics) were variable among species. O-dealkylation, hydroxylation and phase II conjunction were the most likely pathways for OPFRs. NHFRs might be metabolized through the pathways of debromination, hydroxylation, dealkylation, and phase II conjunction. We also suggested that di-alkyl phosphates (DAPs) and hydroxylated OPFRs (OH-OPFRs) were the predominant metabolites in the animal body. DAPs, 2,3,4,5-tetrabromobenzoic acid (TBBA) and 2-ethylhexyl tetrabromophthalate (TBMEHP) have relatively higher internal exposure levels in fauna, which might attribute to their high conversion rate and stability in the body. The metabolism of OPFRs and NHFRs in non-human animals may eliminate their acute toxicity but not their chronic toxicities (especially for endocrine-disrupting effects), which suggests attention should also be paid to the major metabolites. Based on the issues mentioned above, we proposed that the metabolic processes in multitrophic organisms, the transfer of major metabolites across the food web, and the co-exposure of the novel flame retardants and their metabolites in fauna are worth studying in the future.