Role of insulin signaling pathway in apoptosis induced by food chain delivery of nano-silver under the action of environmental factors.

OBJECTIVE: To investigate how the environmental factor affects the delivery of nano silver through food chain, we set up a two-stage food delivery chain model of Escherichia coli and Caenorhabditis elegans system. METHODS: Through a two-stage food delivery chain model of E. coli and C. elegans, the mRNA expression levels of DAF-2, age-1, PDK-1, Akt-1 and DAF-16 in the insulin growth factor 1 signaling pathway in nematode gonad cells which occurs AgNPs induced apoptosis were evaluated and the apoptosis of gonad cells in the mutant strains of the above key genes were detected. RESULTS: DAF-2, age-1, PDK-1 and Akt-1 could significantly negatively regulate the apoptosis of nematode cells induced by AgNPs, while DAF-16 could significantly promote the apoptosis induced by AgNPs. The DAF-16 up-regulated expression was a protective effect on the body and the phenomenon of DNA double-strand breaks was significantly increased. The damage effect induced by AgNPs was significantly enhanced in the presence of the environmental factor fulvic acid. CONCLUSION: The damage effect induced by AgNPs after food delivery involves the regulation of the insulin growth factor 1 signaling pathway and environmental factors have a significant impact on the biological effects.

Microplastic ingestion from atmospheric deposition during dining/drinking activities.

Human-health risks from microplastics have attracted considerable attention, but little is known about human-exposure pathways and intensities. Recent studies posited that inhalation of atmospheric microplastics was the dominant human-exposure pathway. Herein, our study identified that atmospheric microplastics ingested from deposition during routine dining/drinking activities represent another important exposure pathway. We measured abundances of atmospheric-deposited microplastics of up to 105 items m-2 d-1 in dining/drinking venues, with 90% smaller than 100 µm and a dominance of amorphous fragments rather than fibers. Typical work-life scenarios projected an annual ingestion of 1.9 × 105 to 1.3 × 106 microplastics through atmospheric deposition on diet, with higher exposure rates for indoor versus outdoor dining/drinking settings. Ingestion of atmospheric-deposited microplastics through diet was similar in magnitude to presumed inhalation exposure, but 2-3 orders of magnitude greater than direct ingestion from food sources. Simple mitigation strategies (e.g., covering and rinsing dishware) can substantially reduce the exposure of atmospheric deposition microplastics through diet.

Airborne Microplastic Concentrations in Five Megacities of Northern and Southeast China.

Airborne microplastics (MPs) are receiving increasing attention due to their ubiquitous nature and the potential human health consequences resulting from inhalation. The limited data for airborne MP concentrations vary widely among studies (∼4 orders of magnitude), but comparisons are tenuous due to the inconsistent collection and detection/enumeration methodologies among studies. Herein, we used uniform methodologies to obtain comparable airborne MP concentration data to assess MP exposure intensity in five Chinese megacities. Airborne MP concentrations in northern cities (358 ± 132 items/m3) were higher than those in southeast cities (230 ± 94 items/m3) but of a similar order of magnitude, unlike previous studies. The majority (94.7%) of MPs found in air samples were smaller than 100 µm, and the main shape of airborne MPs was fragments (88.2%). Polyethylene, polyester, and polystyrene were the dominant polymers comprising airborne MPs. No consistent relationships were detected between airborne MP concentration and typical socioeconomic indices, and the spatial and diurnal patterns for airborne MPs were different from various components of air quality indices (PM2.5, PM10, etc.). These findings reflect the contrasting source/generation dynamics between airborne MPs and other airborne pollutants. Maximum annual exposure of humans to airborne MPs was estimated in the range of 1-2 million/year in these megacities, highlighting the need for additional research examining the human health risks from the inhalation of airborne MPs.

A reaction density functional theory study of the solvent effect in prototype SN2 reactions in aqueous solution.

The bimolecular nucleophilic substitution (SN2) reaction is a fundamental and representative reaction in organic chemistry, and the reaction rate is sensitive to the choice of underlying solvents. Herein, we investigate the solvent effect on the free energy profiles of two paradigm reactions in aqueous solution, i.e., symmetric and asymmetric SN2 reactions, by using the proposed multiscale reaction density functional theory (RxDFT) method, which employs quantum density functional theory for calculating the intrinsic reaction free energy coupled with classical density functional theory for addressing solvation contribution. The solvent effect is quantitatively addressed with RxDFT by examining the changes in the free energy profile of the chemical reaction from the gas phase to the aqueous solution. The complete descriptions of the free energy profiles in aqueous solution for the SN2 reactions based on RxDFT agree well with the results from the Specific Reaction Parameterization (SRP) quantum model, QM/MM and the RISM/SCF method. Overall, the RxDFT method is an efficient tool to predict the free energy profile and address the solvent effect of chemical reactions with satisfactory accuracy and low computational cost.