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Citrate-coated AgNPs (c-AgNPs) have negatively charged surfaces and their surface interactions with heavy metals can affect metal toxicity in aquatic environments. This study used Daphnia magna to compare the acute toxicities and bioaccumulation of As(V), Cd, and Cu when they interact with c-AgNPs. The 24-h acute toxicities of As(V) and Cu were not affected by the addition of c-AgNPs, while bioaccumulation significantly decreased in the presence of c-AgNPs. In contrast, both the 24-h acute toxicity and bioaccumulation of Cd increased in the presence of c-AgNPs. These toxicity and bioaccumulation trends can be attributed to the interactions between the AgNP surface and the heavy metals. As(V) and c-AgNPs compete by negative charge, decreasing As(V) toxicity. Copper adheres readily to c-AgNP citrate, decreasing Cu bioavailability, and thus reducing Cu toxicity and bioaccumulation. Citrate complexes with divalent cations such as Ca and Mg reduce the competition between divalent cations and Cd on biotic ligand, increasing toxicity and bioaccumulation of Cd. This study shows that surface properties determine the effect of c-AgNPs on heavy metal toxicities and bioaccumulations; hence, further studies on the effect of nanoparticle by it surface properties are warranted. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that the toxicity of fine dust particles (PM 2.5) is linked to specific components rather than their mass. However, research on the chemical composition and health risk of PM 2.5 is insufficient. This study analyzed the metals, polycyclic aromatic hydrocarbon (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) present in PM 2.5 and evaluated their risk to health during outdoor activities. The concentration of metals was one order of magnitude higher than that of PAHs and the concentration and detection frequency of OCPs and PCBs were considerably lower than those of metals and PAHs. The lifetime excess cancer risk (LECR) for carcinogens in PM 2.5 exceeded de minimis risk (1 × 10−6) as 1.33–3.44 × 10−6 (at 5th–95th percentile) as Cr(VI), As, and Cd showed high contributions. Children in the 2 < years <18 age group had a high risk of cancer due to early-life susceptibility. The proportion of ∑Metals to LECR was approximately 95%, while ∑PAHs attributed to 5% of total LECR. The effects of ∑OCPs and 2,3′,4,4′,5′-Pentachlorobiphenyl (PCB-123) on LECR were negligible. The hazard quotient (HQ) for non-carcinogens was <1, and non-carcinogenic effects were not expected. Mn, BaP, Pb, As, and Cd were the key determinants of the HQ values and among the identified PM 2.5 sources they are closely related to industrial activities, oil combustion, and gasoline exhaust. Therefore, control strategies for these sources can effectively reduce PM 2.5 risk. This study measured the concentrations of toxic compounds in ambient PM 2.5 and considered only PM 2.5 exposure during outdoor activities. PM 2.5 health risk during the entire day would be higher than the PM 2.5 risk determined in this study, and further research is required for this evaluating this risk. Unlabelled Image • LECR was 1.33–3.44 × 10−6 (5th–95th percentile); this cannot be ignored. • Non-carcinogenic effects are not expected by acute exposure of PM2.5 (HQ < 1). • The major contributors to PM 2.5 risk were As, Cr(VI), Cd, Mn, BaP, and Pb. • Related sources were industrial activities, combustion of oil, and vehicle exhaust. [ABSTRACT FROM AUTHOR]