Search

The expanding production and use of engineered nanomaterials (ENMs) have raised concerns about the potential risk of those materials to food safety and human health. In a prior study, the accumulation of Zn, Cu, and Ce from ZnO, CuO, or CeO2, respectively, was examined in carrot (Daucus carota L.) grown in sand culture in comparison to accumulation from exposure to equivalent concentrations of ionic Zn2+, Cu2+, or Ce4+. The fresh weight concentration data for peeled and unpeeled carrots were used to project dietary intake of each metal by seven age-mass classes from child to adult based on consumption of a single serving of carrot. Dietary intake was compared to the oral reference dose (oral RfD) for chronic toxicity for Zn or Cu and estimated mean and median oral RfD values for Ce based on nine other rare earth elements. Reverse dietary intake calculations were also conducted to estimate the number of servings of carrot, the mass of carrot consumed, or the tissue concentration of Zn, Cu, or Ce that would cause the oral RfD to be exceeded upon consumption. The projections indicated for Zn and Cu, the oral RfD would be exceeded in only a few highly unrealistic scenarios of exceedingly high Zn or Cu concentrations in the substrate from ZnO or CuO or consumption of excessive amounts of unpeeled carrot. The implications associated with the presence of Ce in the carrot tissues depended upon whether the mean or median oral RfD value from the rare earth elements was used as a basis for comparison. The calculations further indicated that peeling carrots reduced the projected dietary intake by one to two orders of magnitude for both ENMand ionic-treated carrots. Overall in terms of total metal concentration, the results suggested no specific impact of the ENM form on dietary intake. The effort here provided a conservative view of the potential dietary intake of these three metals that might result from consumption of carrots exposed to nanomaterials (NMs) and how peeling mitigated that dietary intake. The results also demonstrate the potential utility of dietary intake projections for examining potential risks of NM exposure from agricultural foods. [ABSTRACT FROM AUTHOR]

Sonication and humic acids (HA) are known to disperse carbon nanotube (CNT) suspensions, but potential effects on sorption of chemicals to CNTs remain poorly understood. We applied a passive sampling method to investigate the influence of dispersion/aggregation on sorption of pyrene to CNTs. Sonication broke down CNT aggregates and increased pyrene sorption affinity by up to 1.39 orders of magnitude. Sorption surfaces newly exposed by sonication remained available to pyrene even after reaggregation occurred, suggesting an irreversible effect of sonication. The presence of HA decreased sorption of pyrene to CNTs, but at the highest HA concentration investigated (200 mg/L), sorption affinity was still 1.90 orders of magnitude larger than sorption of pyrene to HA alone. Specific interactions between pyrene and CNTs were thus still taking place, in spite of the presence of a HA coating on the CNTs' surface. A greater suppression of sorption by CNTs occurred when the HA addition was combined with a sonication pretreatment. Sorption isotherm fitting indicated that the maximum sorption capacity, sorption affinity, and heterogeneity of the CNT surface were all affected by sonication and the presence of HA at a concentration as low as 1 mg/L. The present results contribute to an improved understanding of the sorption behavior of CNTs in both natural and wastewater systems. [ABSTRACT FROM AUTHOR]

The octanol/water partition coefficient (Kow) for organic compounds is widely used in predictive environmental studies. A significant proportion of contaminants of surface and ground water are ionisable (e.g. many pesticides, pharmaceuticals, metabolites). Such compounds may be partially ionised dependent on the pH. Since the neutral and ionic species exhibit different polarities, the Kow value of ionisable pesticides is pH dependent. It is therefore essential to determine Kow values over the full range of pH that occurs in the environment in order to get appropriate predictors. Numerous methods are available to measure lipophilicity but only a few are appropriate for ionisable pesticides (e.g. pH metric and filter probe methods). Parameters such as pH and ionic strength need to be carefully controlled when working with ionisable compounds. Variation of these factors probably explains why literature can yield Kow values that differ by more than one order of magnitude for some compounds. In this article, Kow values obtained for six acidic pesticides with three different methods are compared as well (data from the literature, measured by pH metric method and calculated with five computer programs). The values used in predictive regression equations needs to be either measured with a suitable method or selected from the literature with great care. [Copyright &y& Elsevier]

Nanopesticides are being introduced in agriculture, and the associated environmental risks and benefits must be carefully assessed before their widespread agricultural applications. We investigated the impacts of a commercial Cu(OH) 2 nanopesticide formulation (NPF) at different agricultural application doses (e.g., 0.5, 5, and 50 mg of Cu kg -1 ) on enzyme activities and bacterial communities of loamy soil (organic matter content of 3.61%) over 21 days. Results were compared to its ionic analogue (i.e., CuSO 4 ) and nano-Cu(OH) 2 , including both the commercial unformulated active ingredient of NPF (AI-NPF) and synthesized Cu(OH) 2 nanorods (NR). There were negligible changes in the activity of acid phosphatase, regardless of exposure dose, whereas significant ( p < 0.05) variations in activities of invertase, urease, and catalase were observed at a dose of 5 mg kg -1 or higher. Invertase activity decreased with an increasing bioavailable Cu concentration in soil under various treatments. In comparison to CuSO 4 , both Cu(OH) 2 nanopesticide (i.e., NPF) and nano-Cu(OH) 2 (i.e., AI-NPF and NR) caused a significant ( p < 0.05) inhibition of urease activity, wherein a significant ( p < 0.05) increase in the activity of catalase was observed, representing serious oxidative stress. Accordingly, NPF, AI-NPF, and NR differently affected soil bacterial abundance, diversity, and community compared to CuSO 4 , which could have resulted from the changes in the bioavailable Cu concentration as a result of the distinct nature of copper spiked (i.e., nano form versus salt). Moreover, minor differences in the soil enzyme activity and bacterial community were observed between NPF and AI-NPF, reflecting that the impact of the Cu(OH) 2 nanopesticide was primarily attributed to the presence of nano-Cu(OH) 2 . In total, the impacts of nano-Cu(OH) 2 on the soil bacterial community and enzyme activity tested in this study differed from CuSO 4 , shedding light on the environmental risks of the Cu(OH) 2 nanopesticide in the long run.

The surface area and pore volume of carbonaceous materials, which are commonly determined by N 2 and/or CO 2 gas-physisorption, are important parameters when describing environmental processes such as adsorption. Their measurement requires prior degassing of samples, which can change the nature of the material. Current guidelines for biochar characterization recommend different degassing temperatures. To investigate how degassing temperatures affect gas-physisorption we systematically degassed a range of materials (four biochars, carbon nanotubes, and Al 2 O 3 reference material) at different temperatures (105, 150, 200, 250 and 300°C; for ≥14h each). Degassing temperatures had no effect on Al 2 O 3 or carbon nanotubes but the measured surface areas and pore volumes of biochars increased by up to 300% with degassing temperature. An equation is presented for predicting surface area obtained at different degassing temperatures. Elemental analysis and results from sorption batch experiments suggest that surface area and pore volume may increase as biochar components volatilize during degassing. Our results showed that degassing temperatures change material properties and influence gas-physisorption measurements, and therefore need to be standardized. These results may also apply to the characterization of other complex materials, including carbon nanotubes coated with natural organic matter and fouled activated carbon., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A review of the epidemiological literature on the potential effects of land contamination shows that the largest body of contaminant-specific research relates to cadmium (Cd). First, a brief outline of the key issues related to the study of health impact of land contamination is presented. The recent literature is then reviewed for evidence of associations and possible causal relationships between exposure to Cd from land contamination and health impact. A large number of studies focusing on Cd arise because of the ready availability of biomarkers of exposure and effect and the demonstrated link between soil Cd and itai-itai disease (severe renal and bone disorders) via dietary exposure in Japan and China. Where dietary differences yield lower exposures, links have been established between Cd in soil and biomarkers of renal or bone dysfunctions, but not to health impacts per se. Potential effects of Cd exposure were also investigated for other health outcomes, including hypertension, cancer incidence, preterm delivery, and semen parameters. In contrast to renal and bone disorders, results are generally inconsistent and require further lines of evidence. Residence in locations with elevated concentrations of Cd in soil is a poor surrogate for exposure, and there are examples where residents in locations with elevated concentrations of Cd in soil did not appear to suffer serious health consequences.