Synergistic effects of engineered nanoparticles and organics released from laser printers using nano-enabled toners: potential health implications from exposures to the emitted organic aerosol.

Recent studies have shown that engineered nanoparticles (ENPs) are incorporated into toner powder used in printing equipment and released during their use. Thus, understanding the functional and structural composition and potential synergistic effects of this complex aerosol and released gaseous co-pollutants is critical in assessing their potential toxicological implications and risks. In this study, toner powder and PEPs were thoroughly examined for functional and molecular composition of the organic fraction and the concentration profile of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAH) using state of the art analytical methods. Results show significant differences in abundance of non-exchangeable organic hydrogen of toner powder and PEPs, with a stronger aromatic spectral signature in PEPs. Changes in structural composition of PEPs are indicative of radical additions and free-radical polymerization favored by catalytic reactions, resulting in formation of functionalized organic species. Particularly, accumulation of aromatic carbons with strong styrene-like molecular signatures on PEPs is associated with formation of semivolatile heavier aromatic species (i.e., PAHs). Further, the transformation of low molecular weight PAHs in the toner powder to high molecular weight PAHs in PEPs was documented and quantified. This may be a result of synergistic effects from catalytic metal/metal oxide ENPs incorporated into the toner and the presence/release of semi-volatile organic species (SVOCs). The presence of known carcinogenic PAHs on PEPs raises public health concerns and warrants further toxicological assessment.

Polycyclic Aromatic Hydrocarbon Contamination in Soils of San Mateo Ixtatán, Guatemala: Occurrence, Sources, and Health Risk Assessment.

Exposure to high concentrations of carcinogenic pollutants in soils and sediments can result in increased health risks. Determining the levels and sources of contamination in developing communities is important for helping to reduce pollution and mitigate the risk of exposure. In the Mayan community of San Mateo Ixtatán, Guatemala, 24 samples of topsoil from urban, peri-urban, and agricultural sites and six samples of river sediment were collected and analyzed for 17 polycyclic aromatic hydrocarbons (PAHs). The sum of the concentrations of these PAHs at the urban and peri-urban sites ranged from 460 to 3251 µg kg (mean, 1401 µg kg), whereas at agricultural sites the range was 350 to 2087 µg kg (mean, 1038 µg kg). Analysis to identify and apportion the source showed that the PAHs emitted from wood stoves contributed 71 and 76% of the total PAHs in urban and agricultural areas soils, respectively. The calculated incremental lifetime cancer risk due to the ingestion of soil, dermal contact, and dietary intake through corn consumption was greater than the acceptable level of 10 established by the USEPA. Our findings suggest that the residents of rural communities can be at increased cancer risk despite little or no industrial activity in the local area. Alternate domestic fuel sources should be considered to reduce the health risk in local communities.

New Antimicrobially Amended Media for Improved Nonpoint Source Bacterial Pollution Treatment.

Nonpoint source pollution (NPS) such as stormwater runoff may introduce high loads of bacteria, impairing surface water bodies. The existing filter materials in stormwater best management practices (BMP) are typically not designed to inactivate bacteria. Herein, novel filtration media were extensively tested for microbial load reduction in stormwater runoff. Red cedar wood chips (RC) were amended with different loadings of either 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA) or silver nanoparticles (AgNP). Under batch conditions at 25 °C, log10 removal values (LRV) up to 3.71 ± 0.38 (mean ± standard error) for TPA-RC and 2.25 ± 1.00 for AgNP-RC were achieved for Escherichia coli (E. coli), whereas unmodified RC achieved less than 0.5 LRV. Similar trends were observed at 17.5 °C, however at low temperature (10 °C) no statistically significant difference in E. coli inactivation between modified and unmodified RC was detected. Inactivation kinetic studies show that TPA-RC has higher inactivation rate constants compared to AgNP-RC. Under dynamic flow conditions a mass balance approach indicates that even after remobilization up to 99.8% of E. coli removal using 9 mg/g TPA-RC compared to 64.8% for unmodified RC. This study demonstrates that RC wood chips amended with antimicrobial compounds show promising applications as filtration material for the reduction of microbiological contamination load in stormwater runoff.