Due to their systemic character and high efficacy to insect controls, neonicotinoid insecticides (neonics) have been widely used in global agriculture since its introduction in early 1990. Recent studies have indicated that neonics may be ubiquitous, have longer biological half-lives in the environment once applied, and therefore implicitly suggested the increasing probability for human exposure to neonics. Despite of neonics’ persistent characters and widespread uses, scientific literature in regard of pathways in which human exposure could occur is relatively meager. In this review, we summarized results from peer-reviewed articles published prior to 2017 that address potential human exposures through ingestion and inhalation, as well as results from human biomonitoring studies. In addition, we proposed the use of relative potency factor approach in order to facilitate the assessment of concurrent exposure to a mixture of neonics with similar chemical structures and toxicological endpoints. We believe that the scientific information that we presented in this review will aid to future assessment of total neonic exposure and subsequently human health risk characterization.

Benzo[a]pyrene (BaP) is a bio-accumulative toxic compound found in the atmosphere, water, and soil that may affect the life cycle of amphibians. In this study, a few contamination biomarkers, such as hepatic melanomacrophages (MMs), mast cells, erythrocyte micronuclei (MN) and white blood cells were used to determine how BaP acts in these cells in the anurans Physalaemus cuvieri and Leptodactylus fuscus. Animals of both species were divided into three treatment groups: 1 day, 7 days and 13 days, subcutaneously injected 2 mg/kg BaP diluted in mineral oil and control group with only mineral oil. After 7 days, BaP caused the frequency of MN to increase in both species while reducing melanin area. The micronucleus frequency increased due to the genotoxicity of BaP, while the decreasing melanin area may be related to the inhibition of tyrosinase activity, an enzyme responsible for regulating melanogenesis, decreasing the synthesis of melanin. The mast cell density increased in all groups and in both species as a response to the inflammatory action of BaP. These cells respond to nonspecific inflammatory effects leading, therefore, to this response in all treatments. The percentage of leukocytes remained unchanged probably due to great intraspecific variability. Additionally, the leukocyte profiles of both species were characterized and the differences were attributed to extrinsic factors. In short, BaP can affect the integrity of several organs and tissues, and cell functions leading to the conclusion that this compound is hepatotoxic, genotoxic and immunotoxic for anurans.

The behaviour of arsenic (As) from geogenic soil exposed to aerobic conditions is critical to predict the impact of As on the environment, which processes remain unresolved. The current study examined the depth profile of As in geologically derived subsoil cores from Hong Kong and investigated the mobilization, plant availability, and bioaccessibility of As in As-contaminated soil at different depths (0–45.8 m). Results indicated significant heterogeneity, with high levels of As in three layers of soil reaching up to 505 mg/kg at a depth of 5 m, 404 mg/kg at a depth of 15 m, and 1510 mg/kg at a depth of 27–32 m. Arsenic in porewater samples was <11.5 μg/L in the study site. X-ray absorption spectroscopy (XAS) indicated that main As species in soil was arsenate (As(V)), as adsorbed fraction to Fe oxides (41–69% on goethite and 0–8% on ferrihydrite) or the mineral form scorodite (30–57%). Sequential extraction procedure demonstrated that 0.5 ± 0.4% of As was exchangeable. Aerobic incubation experiments exhibited that a very small amount (0.14–0.48 mg/kg) of As was desorbed from the soil because of the stable As(V) complex structure on abundant Fe oxides (mainly goethite), where indigenous microbes partly (59 ± 18%) contributed to the release of As comparing with the sterilized control. Furthermore, no As toxicity in the soil was observed with the growth of ryegrass. The bioaccessibility of As was <27% in the surface soil using simplified bioaccessibility extraction test. Our systematic evaluation indicated that As in the geogenic soil profile from Hong Kong is relatively stable exposing to aerobic environment. Nevertheless, children and workers should avoid incidental contact with excavated soil, because high concentration of As was present in the digestive solution (<0.1–268 μg/L).

Oligomeric organophosphate esters (OOPEs) like 2,2-bis(chloromethyl)-propane-1,3-diyltetrakis (2-chloroethyl) bisphosphate (V6), resorcinol bis(diphenylphosphate) (RDP) and bisphenol A bis(diphenylphosphate) (BDP), are widely used as alternatives of Deca-BDE in plastic and electronic consumer products. However, studies on the environmental occurrence and fate of OOPEs are very scarce. This work studied the occurrence, distribution and fate of V6, BDP and RDP during the different treatment stages of a sewage treatment plant (STP) in Beijing, China. To accomplish this, a method to analyze trace V6, BDP and RDP in suspended solids samples and aqueous samples of sewage and sludge was developed by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Using this method, BDP and RDP were detected for the first time in suspended solids of sewage and sludge with a concentration of 2.06–5.82 ng/g dry weight and 0.44–3.45 ng/g dry weight, respectively, whereas their concentration level in the aqueous phase of these samples were below the detection limits of the method. However, V6 was detected in all treatment stages of the STP, with concentrations in the range of 10.2–27.1 ng/L in aqueous phase and 0.40–1.73 ng/g dw in solid phase. Mass balance results indicated that 75.6% of the original V6 mass flow was discharged along with effluent, while 83.3% and 72.2% of the initial RDP and BDP mass flow were lost due to biodegradation, respectively. Nevertheless, compared to the 14 widely used monomeric organophosphate esters (MOPEs), the concentration levels of OOPEs in this studied STP were relatively low.

Toxic cyanobacterial blooms have been implicated for their negative consequences on many terrestrial and aquatic organisms. Water birds belong to the most common members of the freshwater food chains and are most likely to be affected by the consumption of toxic cyanobacteria as food. However, the contribution of cyanotoxins in bird mortalities is under-studied. The aim of the study was to investigate the likely role of cyanotoxins in a mass mortality event of the Dalmatian pelican (Pelecanus crispus) in the Karla Reservoir, in Greece. Water, scum, tissues and stomach content of dead birds were examined for the presence of microcystins, cylindrospermopsins and saxitoxins by an enzyme-linked immunosorbent assay. High abundances of potential toxic cyanobacterial species and significant concentrations of cyanotoxins were recorded in the reservoir water. All examined tissues and stomach content of the Dalmatian pelicans contained significant concentrations of microcystins and saxitoxins. Cylindrospermopsin concentrations were detected in all tissues except from the brain. Our results suggest that cyanotoxins are a plausible cause for this bird mass mortality episode in the Karla Reservoir.

This study tested the hypothesis that different diets could modulate mercury (Hg) trophic transfer by concurrently altering the transfer of energy (in terms of growth) and transfer of Hg (in terms of biodynamic process). Firstly, we conducted a 40-d laboratory bioaccumulation experiment, in which tilapia (Oreochromis niloticus) was exposed to inorganic mercury (Hg[II]) and methylmercury (MeHg) via feeding on three distinct diets (macrophyte, freshwater shrimp, and commercial pellets) at a fixed ingestion rate of 0.065 g g⁻¹ d⁻¹. During the dietary exposure period, tilapia exhibited Hg species- and diet-dependent Hg trophic transfer patterns and diet-specific growth rates. We then employed a biokinetic model to assess how diet-specific biodynamics and/or diet-specific growth rates modulated the overall Hg bioaccumulation and trophic transfer. The diet-specific assimilation efficiencies (AEs) were monitored using radioisotope technique, and the determined AEs of Hg(II) (8.6%–29.7%) varied by 3.5 times among diets whereas the MeHg AEs (94.4%–97.1%) were not affected. The biokinetic modeling further revealed that Hg(II) trophic transfer in tilapia was controlled by the diet-specific AEs, while MeHg trophic transfer was governed by the diet-specific growth rates. Specifically, a diet-derived high growth rate reduced the MeHg trophic transfer in pellets-fed tilapia, and the overall accumulated MeHg level in fish was under the control of both somatic growth dilution and dietary MeHg influx. Moreover, we observed that the Hg levels (mainly as MeHg) in fast-growing farmed tilapia were significantly lower than wild-living tilapia after 100 d exposure in the field, attributed to somatic growth dilution (SGD). Both the laboratory and field study therefore demonstrated the importance of diet-derived SGD in modulating mercury trophic transfer in aquatic food webs.

This study reports a spatiotemporal characterization of formaldehyde and acetaldehyde in the summer and winter of 2017 in the urban area of Shiraz, Iran. Sampling was fulfilled according to EPA Method TO-11 A. The inverse distance weighting (IDW) procedure was used for spatial mapping. Monte Carlo simulations were conducted to evaluate carcinogenic and non-cancer risk owing to formaldehyde and acetaldehyde exposure in 11 age groups. The average concentrations of formaldehyde/acetaldehyde in the summer and winter were 15.07/8.40 μg m⁻³ and 8.57/3.52 μg m⁻³, respectively. The formaldehyde to acetaldehyde ratios in the summer and winter were 1.80 and 2.43, respectively. The main sources of formaldehyde and acetaldehyde were photochemical generation, vehicular traffic, and biogenic emissions (e.g., coniferous and deciduous trees). The mean inhalation lifetime cancer risk (LTCR) values according to the Integrated Risk Information System (IRIS) for formaldehyde and acetaldehyde in summer and winter ranged between 7.55 × 10⁻⁶ and 9.25 × 10⁻⁵, which exceed the recommended value by US EPA. The average LTCR according to the Office of Environmental Health Hazard Assessment (OEHHA) for formaldehyde and acetaldehyde in summer and winter were between 4.82 × 10⁻⁶ and 2.58 × 10⁻⁴, which exceeds recommended values for five different age groups (Birth to <1, 1 to <2, 2 to <3, 3 to <6, and 6 to <11 years). Hazard quotients (HQs) of formaldehyde ranged between 0.04 and 4.18 for both seasons, while the HQs for acetaldehyde were limited between 0.42 and 0.97.

Five Descriptors (D) of Marine Strategy Framework Directive (MSFD): marine litter (D10), non-indigenous species (D2) and organic and inorganic pollutants (D8), were estimated in a coastal area of GSA 16 (Augusta harbour, Central Mediterranean Sea) in order to study their effects on the biodiversity (D1) of the benthic community D6) and to improve data for the MSFD. Investigation of plastic debris had led to the identification of 38 fragments divided into four categories, among which microplastics resulted as the most abundant. Six non-indigenous species, belonging to Polychaeta (Kirkegaardia dorsobranchialis, Notomastus aberans, Pista unibranchia, Pseudonereis anomala, Branchiomma bairdi) and Mollusca (Brachidontes pharaonis) were found. Biodiversity and benthic indices suggested a generalised, slightly disturbed ecological status. Anthracene, Zinc and Chrome were the most abundant chemical compounds in analysed sediments. Significant correlations were found between the abundance of trace elements vs biotic indices and between plastic debris vs biodiversity and benthic indices. This study represents the first report about the abundance of plastic debris and its relationship to contaminants and infauna in Augusta harbour. Our results can provide useful information for national and international laws and directives.

Heavy metal pollution of urban stormwater poses potential risks to human and ecosystem health. The design of reliable pollution mitigation strategies requires reliable stormwater modelling approaches. Current modelling practices do not consider the influence of urbanisation characteristics on stormwater quality. This could undermine the accuracy of stormwater quality modelling results. This research study used a database consisting of over 1000 datasets to compare the characteristics of heavy metal build-up (one of the most important stormwater pollutant processes) on urban surfaces under the influence of anthropogenic and natural factors specific to different urban regions from China (Shenzhen) and Australia (Gold Coast), using Bayesian Networks. The outcomes show that the differences in heavy metals build-up loads between the two regions (mean value for Shenzhen – mean value for Gold Coast)/mean value for Shenzhen) were 0.45 (Al), 0.88 (Cr), 0.99 (Mn), 0.68 (Fe), 0.98 (Ni), 0.24 (Cu), 0.47 (Zn) and 0.13 (Pb), respectively. The research outcomes also confirmed that the influence of traffic on the build-up of different sized particles varies between Shenzhen and Gold Coast, and traffic plays distinct roles as a source and as a factor that drives heavy metal re-distribution. The road surface roughness was also found to influence build-up process differently between the two regions. More importantly, the assessment of inherent process uncertainty revealed that heavy metal build-up between different road sites in Shenzhen varies over a wider range than in Gold Coast. The study highlighted a clear distinction in the influence of sources and key anthropogenic factors on the variability of particle-bound heavy metals build-up between geographically different urban regions. The study outcomes provide new knowledge to enhance the accuracy of urban stormwater quality modelling.

Microplastics may lose buoyancy and occur in deeper waters and ultimately sink to the sediment and this may threaten plankton inhabiting in various water layers and benthic organisms. Here, we conduct the first survey on microplastics in the water column and corresponding sediment in addition to the surface water in the Bohai Sea. A total of 20 stations covering whole Bohai Sea were selected, which included 6 stations specified for water column studying. Seawater was sampled every 5 m, with maximal depth of 30 m in the water column using Niskin bottles coupled with a ship-based conductivity, temperature and depth sensor (CTD) system and surface sediment samples were collected using box corer. The results indicated that higher microplastic levels accumulated at a depth range of 5–15 m in the water column in some stations, suggesting the surface water survey was not sufficient to reflect microplastics loading in a water body. Fibers predominated microplastic types in both seawater and sediment of the Bohai Sea, which accounted for 75%–96.4% of the total microplastics. However the relatively proportion of the fibers in the deeper water layers and sediment was lower than that in the surface water. Microplastic shapes are more diverse in the sediment than in the seawater in general. The microplastic sizes changed with depth in the water column and the proportion of the size-fraction < 300 μm increased with depth, probably as a result of rapid biofouling on the small microplastics due to their higher specific surface area. Such depth distribution also implied that sampling with manta net (>330 μm) that commonly used in the oceanographic survey might underestimate microplastics abundance in the water column. Further studies are recommended to focus on the sinking behavior of microplastics and their effects on marine organisms.