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Emerging contaminants such as nanoplastics and nanoparticles likely experience similar environmental behaviours, fate and effects but our knowledge of their combined toxicity is scanty. This study, therefore, investigated the joint toxicity of polystyrene nanoplastics (PNPs) and zinc oxide nanoparticles (ZnO-NPs) to an ecologically important rotifer Brachionus koreanus, and compared with the joint toxicity of PNPs and Zn ions (Zn-IONs from ZnSO

Coated zinc oxide nanoparticles (ZnO-NPs) are more commonly applied in commercial products but current risk assessments mostly focus on bare ZnO-NPs. To investigate the impacts of surface coatings, this study examined acute and chronic toxicities of six chemicals, including bare ZnO-NPs, ZnO-NPs with three silane coatings of different hydrophobicity, zinc oxide bulk particles (ZnO-BKs), and zinc ions (Zn-IONs), toward a marine copepod, Tigriopus japonicus. In acute tests, bare ZnO-NPs and hydrophobic ZnO-NPs were less toxic than hydrophilic ZnO-NPs. Analyses of the copepod's antioxidant gene expression suggested that such differences were governed by hydrodynamic size and ion dissolution of the particles, which affected zinc bioaccumulation in copepods. Conversely, all test particles, except the least toxic hydrophobic ZnO-NPs, shared similar chronic toxicity as Zn-IONs because they mostly dissolved into zinc ions at low test concentrations. The metadata analysis, together with our test results, further suggested that the toxicity of coated metal-associated nanoparticles could be predicted by the hydrophobicity and density of their surface coatings. This study evidenced the influence of surface coatings on the physicochemical properties, toxicity, and toxic mechanisms of ZnO-NPs and provided insights into the toxicity prediction of coated nanoparticles from their coating properties to improve their future risk assessment and management.

The current hazard assessment of the emerging chemical contaminant, zinc oxide nanoparticles (ZnO-NPs), seldom considers the influence of environmental factors. However, under seasonal variation and global climate change, marine organisms are exposed to a changing environment with different regimes of temperature and salinity. This study, therefore, investigated the toxicity of ZnO-NPs, zinc oxide bulk-particles and zinc ions, to the marine copepod Tigriopus japonicus under the combined influence of temperature and salinity. The toxicity of ZnO-NPs generally increased with increasing temperature. At 15 °C, ZnO-NPs were less toxic because they generated fewer reactive oxygen species (ROS) and the copepods entered dormancy. At 35 °C, ZnO-NPs became more toxic because of their increased ROS production and potential physical impairments associated with the agglomerated particles, in addition to the thermal stress faced by the copepods. Their toxicity generally increased with decreasing salinity, due to their enhanced ion dissolution and osmotic pressure faced by the copepods at low salinity. Hence, ZnO-NPs were most toxic to the copepods at high temperature and low salinity, though temperature was a more influential factor than salinity. Based on the effect thresholds generated from the response surface model with consideration of the joint effect of temperature and salinity, the current marine water quality criteria may not provide adequate protection to marine organisms against ZnO-NPs. Our results provide new insights into the toxicity and modes of action of ZnO-NPs, and highlight the current deficiency of regulations under different regimes of temperature and salinity.

Coated zinc oxide nanoparticles (ZnO-NPs) are more commonly applied in commercial products but current risk assessments mostly focus on bare ZnO-NPs. To investigate the impacts of surface coatings, this study examined acute and chronic toxicities of six chemicals, including bare ZnO-NPs, ZnO-NPs with three silane coatings of different hydrophobicity, zinc oxide bulk particles (ZnO-BKs), and zinc ions (Zn-IONs), toward a marine copepod

In early August 2017, a serious palm stearin pollution accident occurred in the Pearl River Estuary, South China. While there were already several palm oil related spills around the world, the ecological effects and risks of such accidents to coastal marine environments remain largely unknown. In this study, we found that all seawater and sediment samples collected from six coastal sites were heavily contaminated by palm stearin within 1 week of the accident, and their levels significantly decreased to preaccident levels after four months. Waterborne exposure to palm stearin resulted in growth inhibition to four microalgal species (range of EC50: 9.9-212.6 mg/L) and acute mortality to four invertebrate species (range of LC50: 4.6-409.3 mg/L), while adverse chronic effects of palm stearin on the survival, development, and fecundity of Tigriopus japonicus and on the growth of Oryzias melastigma were observed. On the basis of these results, its interim-predicted no effect concentration was determined as 0.141 mg/L. The hazard quotient of palm stearin greatly exceeded 1 at all sites in August 2017 but returned to

Located within the tropics, Hong Kong has diverse marine habitats which host a rich marine biodiversity (∼6000 known species). Its marine environment is, however, under considerable anthropogenic pressure and continuous deterioration from rapid population growth and constant coastal development. This review summarizes the present status of the marine environment of Hong Kong from the perspectives of habitat loss and fragmentation, pollution, biological invasion, over-exploitation and climate change, which are the major threats identified by the IUCN to marine ecosystems. The Chinese white dolphin population (Sousa chinensis; one of the two resident marine mammals in Hong Kong) is at a historic low and continues to decline due to habitat loss through land reclamation, pollution, and intense marine traffic. Much of Hong Kong’s coastal water is degraded by both substantial local and transboundary pollution from the Pearl River Delta, leading to eutrophication and harmful algal blooms. Exposure risk to introduced exotic species is high, as Hong Kong is both the fourth busiest harbour in the world and release of animals into the marine environment during religious ceremonies is a common practice of local Buddhists and Taoists. The high consumption of seafood has stressed fishery stocks in Hong Kong and its supplying countries. All these impacts are compounded by the often insidious, but pressing, challenges of climate change, with warming temperatures and increasing acidity of coastal waters. Given these known and emerging threats, Hong Kong serves as a living laboratory to investigate the impacts of both global and local activities and, where possible, develop solutions which could be implemented globally.

Substantial production and wide applications of engineered nanomaterials (ENMs) have raised concerns over their potential influences on the environment and humans. However, regulations of products containing ENMs are scarce, even in countries with the greatest volume of ENMs produced, such as the United States and China. After a comprehensive review of life cycles of ENMs, five major challenges to regulators posed by ENMs are proposed in this review: (a) ENMs exhibit variable physicochemical characteristics, which makes them difficult for regulators to establish regulatory definition; (b) Due to diverse sources and transport pathways for ENMs, it is difficult to monitor or predict their fates in the environment; (c) There is a lack of reliable techniques for quantifying exposures to ENMs; (d) Because of diverse intrinsic properties of ENMs and dynamic environmental conditions, it is difficult to predict bioavailability of ENMs on wildlife and the environment; and (e) There are knowledge gaps in toxicity and toxic mechanisms of ENMs from which to predict their hazards. These challenges are all related to issues in conventional assessments of risks that regulators rely on. To address the fast-growing nanotechnology market with limited resources, four ENMs (nanoparticles of Ag, TiO2, ZnO and Fe2O3) have been prioritized for research. Compulsory reporting schemes (registration and labelling) for commercial products containing ENMs should be adopted. Moreover, to accommodate their potential risks in time, an integrative use of quantitative structure-activity relationship and adverse outcome pathway (QSAR-AOP), together with qualitative alternatives to conventional risk assessment are proposed as tools for decision making of regulators.