Polybrominated diphenyl ethers (PBDEs) have been used in a broad array of polymeric materials such as plastics, foams, resins and adhesives to inhibit the spread of fires since the 1970s. The widespread environmental contamination and well documented toxic effects of PBDEs have led to bans and voluntary withdrawals in many jurisdictions. Replacement novel brominated flame retardants (NBFRs) have, however, exhibited many of the same toxic characteristics as PBDEs and appear to share similar environmental fate. This paper presents a critical review of the scientific literature regarding PBDE and NBFR contamination of surface soils internationally, with the secondary objective of identifying probable pollution sources. An evaluation of NBFR distribution in soil was also conducted to assess the suitability of the newer compounds as replacements for PBDEs, with respect to their land contamination potential. Principle production of PBDEs and NBFRs and their consequent use in secondary polymer manufacture appear to be processes with strong potential to contaminate surrounding soils. Evidence suggests that PBDEs and NBFRs are also released from flame retarded products during disposal via landfill, dumping, incineration and recycling. While the land application of sewage sludge represents another major pathway of soil contamination it is not considered in this review as it is extensively covered elsewhere. Both PBDEs and NBFRs were commonly detected at background locations including Antarctica and northern polar regions. PBDE congener profiles in soil were broadly representative of the major constituents in Penta-, Octa- and Deca-BDE commercial mixtures and related to predicted market place demand. BDE-209 dominated soil profiles, followed by BDE-99 and BDE-47. Although further research is required to gain baseline data on NBFRs in soil, the current state of scientific literature suggests that NBFRs pose a similar risk to land contamination as PBDEs.

The aim of the present study was to link Pb toxicokinetics to toxicodynamics in Enchytraeus crypticus. The enchytraeids were exposed for 14 d to different Pb concentrations (uptake phase) in natural Lufa 2.2 soil, followed by a 14-d elimination phase in clean soil. Pb accumulation and enchytraeid mortality were determined at different time intervals. At each exposure concentration, internal Pb concentration increased with exposure time and achieved equilibrium in approximately 7 d. Median lethal concentration (LC50) based on total Pb concentration in soil decreased with exposure time, but did not reach a steady-state level. Pb toxicity, therefore, showed a delay compared to accumulation in E. crypticus. LC50s based on internal Pb concentrations in the surviving animals did reach steady state in approx.14 d, suggesting that linking toxicokinetics to toxicodynamics may reduce the effects of time. This study highlighted that exposure time, as an important factor in metal uptake and toxicity, should be taken into account in ecotoxicological tests for risk assessment.

Cadmium (Cd) is a toxic heavy metal and harmful to human health due to its ability to accumulate in organs. Previous studies have shown that Cd can induce DNA damage and autophagy. Autophagy can stabilize genetic material and DNA integrity. The aim of the present study was to determine the exact mechanism and role of autophagy induced by Cd in spermatozoa cells. Mouse spermatocyte-derived cells (GC-2) were treated with 20 μM Cd chloride for 24 h. The level of reactive oxygen species (ROS), DNA damage, autophagy and the expression of the molecular signaling pathway ATM/AMP-activated protein kinase (AMPK)/mTOR were determined. The results showed that Cd induced autophagy and DNA damage in GC-2 cells via ROS generation, and the autophagy signal pathway AMPK/mTOR was activated by ATM which is a DNA damage sensor. Melatonin, a well-known antioxidant, ameliorated DNA damage, and inhibited autophagy via the AMPK/mTOR signal pathway. Furthermore, after inhibition of autophagy by knockdown of AMPKα, increased DNA damage by Cd treatment was observed in GC-2 cells. These findings demonstrated the protective role of autophagy in DNA damage and suggested that the mechanism of autophagy induced by Cd was through the ATM/AMPK/mTOR signal pathway in spermatozoa cells.

Nano-aluminium oxide (nAl2O3) is one of the most widely used nanomaterials. However, nAl2O3 toxicity mechanisms and potential beneficial effects on terrestrial plant physiology remain poorly understood. Such knowledge is essential for the development of robust nAl2O3 risk assessment. In this study, we studied the influence of a 10-d exposure to a total selected concentration of 98 μM nAl2O3 or to the equivalent molar concentration of ionic Al (AlCl3) (196 μM) on the model plant Arabidopsis thaliana on the physiology (e.g., growth and photosynthesis, membrane damage) and the transcriptome using a high throughput state-of-the-art technology, RNA-seq. We found no evidence of nAl2O3 toxicity on photosynthesis, growth and lipid peroxidation. Rather the nAl2O3 treatment stimulated root weight and length by 48% and 39%, respectively as well as photosynthesis opening up the door to the use of nAl2O3 in biotechnology and nano agriculture. Transcriptomic analyses indicate that the beneficial effect of nAl2O3 was related to an increase in the transcription of several genes involved in root growth as well as in root nutrient uptake (e.g., up-regulation of the root hair-specific gene family and root development genes, POLARIS protein). By contrast, the ionic Al treatment decreased shoot and root weight of Arabidopsis thaliana by 57.01% and 45.15%, respectively. This toxic effect was coupled to a range of response at the gene transcription level including increase transcription of antioxidant-related genes and transcription of genes involved in plant defense response to pathogens. This work provides an integrated understanding at the molecular and physiological level of the effects of nAl2O3 and ionic Al in Arabidopsis.

Triclosan (TCS) is a broad-spectrum antimicrobial agent that is found extensively in natural aquatic environments. Enzyme-catalyzed oxidative coupling reactions (ECOCRs) can be used to remove TCS in aqueous solution, but there is limited information available to indicate how metal cations (MCs) and natural organic matter (NOM) influence the environmental fate of TCS during laccase-mediated ECOCRs. In this study, we demonstrated that the naturally occurring laccase from Pleurotus ostreatus was effective in removing TCS during ECOCRs, and the oligomerization of TCS was identified as the dominant reaction pathway by high-resolution mass spectrometry (HRMS). The growth inhibition studies of green algae (Chlamydomonas reinhardtii and Scenedesmus obliquus) proved that laccase-mediated ECOCRs could effectively reduce the toxicity of TCS. The presence of dissolved MCs (Mn²⁺, Al³⁺, Ca²⁺, Cu²⁺, and Fe²⁺ ions) influenced the removal and transformation of TCS via different mechanisms. Additionally, the transformation of TCS in systems with NOM derived from humic acid (HA) was hindered, and the apparent pseudo first-order kinetics rate constants (k) for TCS decreased as the HA concentration increased, which likely corresponded to the combined effect of both noncovalent (sorption) and covalent binding between TCS and humic molecules. Our results provide a novel insight into the fate and transformation of TCS by laccase-mediated ECOCRs in natural aquatic environments in the presence of MCs and NOM.

Various toxic chemicals used in hydraulic fracturing fluids may influence the inherent health risks associated with these operations. This study investigated the possible occupational inhalation exposures and potential risks related to the volatile organic compounds (VOCs) from chemical storage tanks and flowback pits used in hydraulic fracturing. Potential risks were evaluated based on radial distances between 5 m and 180 m from the wells for 23 contaminants with known inhalation reference concentration (RfC) or inhalation unit risks (IUR). Results show that chemicals used in 12.4% of the wells posed a potential acute non-cancer risks for exposure and 0.11% of the wells with may provide chronic non-cancer risks for exposure. Chemicals used in 7.5% of the wells were associated with potential acute cancer risks for exposure. Those chemicals used in 5.8% of the wells may be linked to chronic cancer risks for exposure. While eight organic compounds were associated with acute non-cancer risks for exposure (>1), methanol the major compound in the chemical storage tanks (1.00–45.49) in 7,282 hydraulic fracturing wells. Wells with chemicals additives containing formaldehyde exhibited both acute and chronic cancer risks for exposure with IUR greater than 10⁻⁶, suggesting formaldehyde was the dominant contributor to both types of risks for exposure in hydraulic fracturing. This study also found that due to other existing on-site emission sources of VOCs and the geographically compounded air concentrations from other surrounding wells, chemical emissions data from storage tanks and flowback pits used in this study were lower than reported concentrations from field measurements where higher occupational inhalation risks for exposure may be expected.

The potential toxic impacts of different crystal phases of titania nanoparticles (TNPs) on freshwater biofilms, especially under ultraviolet C irradiation (UVC), are unknown. Here, adverse impacts of three phases (anatase, rutile, and P25, 50 mg L−1 respectively) with UVC irradiation (An-UV, Ru-UV, and P25-UV) on freshwater biofilms were conducted. Characterization experiments revealed that rutile TNPs had a higher water environment stability than anatase and P25 TNPs, possessing a stronger photocatalytic activity under UVC irradiation. Phase-dependent inhibition of cell viability and significant decreases of four- and five-fold in algal biomass at 12 h of exposure were observed compared with unexposed biofilms. Moreover, phase-dependent oxidative stress resulted in remarkably significant reductions (P < 0.01) of the photosynthetic yields of the biofilms, to 40.32% (P25-UV), 48.39% (An-UV), and 46.77% (Ru-UV) of the plateau value obtained in the unexposed biofilms. A shift in community composition that manifested as a strong reduction in diatoms, indicating cyanobacteria and green algae were more tolerant than diatoms when exposed to TNPs. In terms of the toxic mechanisms, rutile TNPs resulted in apoptosis by inducing excessive intracellular reactive oxygen species (ROS) production, whereas P25 and anatase TNPs tended to catalyze enormous acellular ROS lead to cell necrosis under UVC irradiation.

This study aimed at assessing the effects of increased air temperature and reduced soil moisture content on the multi-generation toxicity of a soil polluted by metal/metalloid mining wastes. Enchytraeus crypticus was exposed to dilution series of the polluted soil in Lufa 2.2 soil under different combinations of air temperature (20 °C and 25 °C) and soil moisture content (50% and 30% of the soil water holding capacity, WHC) over three generations standardized on physiological time. Generation time was shorter with increasing air temperature and/or soil moisture content. Adult survival was only affected at 30% WHC (∼30% reduction at the highest percentages of polluted soil). Reproduction decreased with increasing percentage of polluted soil in a dose-related manner and over generations. Toxicity increased at 30% WHC (>50% reduction in EC50 in F0 and F1 generations) and over generations in the treatments at 20 °C (40–60% reduction in EC50 in F2 generation). At 25 °C, toxicity did not change when combined with 30% WHC and only slightly increased with 50% WHC. So, higher air temperature and/or reduced soil moisture content does affect the toxicity of soils polluted by metal/metalloid mining wastes to E. crypticus and this effect may exacerbate over generations.