Understanding the translocation of nanoparticles (NPs) into plants is challenging because qualitative and quantitative methods are still being developed and the comparability of results among ...different methods is unclear. In this study, uptake of titanium dioxide NPs and larger bulk particles (BPs) in rice plant (Oryza sativa L.) tissues was evaluated using three orthogonal techniques: electron microscopy, single-particle inductively coupled plasma mass spectroscopy (spICP-MS) with two different plant digestion approaches, and total elemental analysis using ICP optical emission spectroscopy. In agreement with electron microscopy results, total elemental analysis of plants exposed to TiO2 NPs and BPs at 5 and 50 mg/L concentrations revealed that TiO2 NPs penetrated into the plant root and resulted in Ti accumulation in above ground tissues at a higher level compared to BPs. spICP-MS analyses revealed that the size distributions of internalized particles differed between the NPs and BPs with the NPs showing a distribution with smaller particles. Acid digestion resulted in higher particle numbers and the detection of a broader range of particle sizes than the enzymatic digestion approach, highlighting the need for development of robust plant digestion procedures for NP analysis. Overall, there was agreement among the three techniques regarding NP and BP penetration into rice plant roots and spICP-MS showed its unique contribution to provide size distribution information.
U.S. regulatory and research agencies use ecotoxicity test data to assess the hazards associated with substances that may be released into the environment, including but not limited to industrial ...chemicals, pharmaceuticals, pesticides, food additives, and color additives. These data are used to conduct hazard assessments and evaluate potential risks to aquatic life (e.g., invertebrates, fish), birds, wildlife species, or the environment. To identify opportunities for regulatory uses of non-animal replacements for ecotoxicity tests, the needs and uses for data from tests utilizing animals must first be clarified. Accordingly, the objective of this review was to identify the ecotoxicity test data relied upon by U.S. federal agencies. The standards, test guidelines, guidance documents, and/or endpoints that are used to address each of the agencies’ regulatory and research needs regarding ecotoxicity testing are described in the context of their application to decision-making. Testing and information use, needs, and/or requirements relevant to the regulatory or programmatic mandates of the agencies taking part in the Interagency Coordinating Committee on the Validation of Alternative Methods Ecotoxicology Workgroup are captured. This information will be useful for coordinating efforts to develop and implement alternative test methods to reduce, refine, or replace animal use in chemical safety evaluations.
•This review summarizes the ecotoxicity data needs of six U.S. federal agencies.•It identifies 87 tests utilizing vertebrate and invertebrate species.•It identifies challenges related to cross-taxa and interspecies extrapolation.•This review will inform development and implementation of non-animal methods.
The health implications and remediation obligations of contaminated urban soils are significant issues in many North American cities. Remediation guidance for soils is evolving and shifting from ...values based on geochemical background approximations to values based on health risks. This analysis examines residential-soil guidance variability among the states and provinces of North America for Cd, Cr, Cu, Ni, Pb, and Zn. For some metals, values vary by as much as 5 orders of magnitude. Nonparametric comparisons are used to illustrate the degree to which current standards differ and to examine the spatial distribution of differences. Parametric statistical analysis is used to examine the significance of variations, and to determine if correlations exist in the structure of guidance values. Hazard index analysis is also used to examine how guidance value differences impact site risk assessments. Results indicate that most of the current variation can be explained as plausible randomness if determining maximum acceptable soil exposures is a random process. Differences between the statistical properties of Cd, Cr, Cu, Ni, and Zn guidance and that of Pb also demonstrate the influence that national leadership can have on stabilizing guidance. Key words: heavy metals, remediation guidance values, residential soil contamination, risk analysis, hazard index analysis.
Understanding the phase distribution of nanoparticles between soils or sediments and water is a critical factor in determining their fate in environmental systems. As such, we examined the ...interactions of ...-labeled multiwalled carbon nanotubes (MWNTs) in aqueous systems with peat as a model solid organic material. MWNTs that had been treated with strong oxidative acids possessed negative charges on their surfaces and were relatively stable in deionized water. In the absence of peat, MWNTs aggregated when the concentration of sodium cations was above 4.0 mM or at a solution pH of 4.0. Dissolved organic matter (DOM) from peat effectively stabilized MWNTs in solution by making the suspended nanotubes less sensitive to changes in sodium concentration or solution pH. Direct sorption interactions between MWNTs and solid peat were not observed in the absence of sodium cations, whereas they became apparent when the ionic strength was sufficiently high to reduce electrostatic repulsion between peat and MWNTs. (ProQuest: ... denotes formulae/symbols omitted.)
Air-liquid interface (ALI) systems have been widely used in recent years to investigate the inhalation toxicity of many gaseous compounds, chemicals, and nanomaterials and represent an emerging and ...promising
method to supplement
studies. ALI exposure reflects the physiological conditions of the deep lung more closely to subacute
inhalation scenarios compared to submerged exposure. The comparability of the toxicological results obtained from
and
inhalation data is still challenging. The robustness of ALI exposure scenarios is not yet well understood, but critical for the potential standardization of these methods. We report a cause-and-effect (C&E) analysis of a flow through ALI exposure system. The influence of five different instrumental and physiological parameters affecting cell viability and exposure parameters of a human lung cell line
(exposure duration, relative humidity, temperature, CO
concentration and flow rate) was investigated. After exposing lung epithelia cells to a CeO
nanoparticle (NP) aerosol, intracellular CeO
concentrations reached values similar to those found in a recent subacute rat inhalation study
. This is the first study showing that the NP concentration reached
using a flow through ALI system were the same as those in an
study.
Carbon nanotubes are often modified to be stable in the aqueous phase by adding extensive hydrophilic surface functional groups. The stability of such CNTs in water with soil or sediment is one ...critical factor controlling their environmental fate. We conducted a series of experiments to quantitatively assess the association between water dispersed multi-walled carbon nanotubes (MWCNTs) and three soil minerals (kaolinite, smectite, or shale) in aqueous solution under different sodium concentrations. super(14)C-labeling was used in these experiments to unambiguously quantify MWCNTs. The results showed that increasing ionic strength strongly promoted the removal of MWCNTs from aqueous phase. The removal tendency is inversely correlated with the soil minerals' surface potential and directly correlated with their hydrophobicity. This removal can be interpreted by the extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory especially for kaolinite and smectite. Shale, which contains large and insoluble organic materials, sorbed MWCNTs the most strongly.
The effect of gold nanoparticles (AuNPs) and ciprofloxacin on the catabolism of microbial communities was assessed. This was accomplished through an ex situ methodology designed to give a priori ...knowledge on the potential for nanoparticles, or other emerging contaminants, to affect the catabolic capabilities of microbial communities in the environment. Microbial communities from a variety of sources were incubated with 31 prespecified carbon sources and either National Institute of Standards and Technology reference material 10-nm AuNPs or ciprofloxacin on 96-well microtiter plates. From the ciprofloxacin study, dose-response curves were generated and exemplified how this method can be used to assess the effect of a toxicant on overall catabolic capabilities of microbial communities. With 10-nm AuNPs at concentrations ranging from 0.01 mu g/mL to 0.5 mu g/mL, rhizosphere communities from Typha roots were only slightly catabolically inhibited at a single concentration (0.05 mu g/mL); no effects were seen on wetland water communities, and a minor positive (i.e., enhanced catabolic capabilities) effect was observed for loamy soil communities. This positive effect might have been because of a thin layer of citrate found on these AuNPs that initiated cometabolism with some of the carbon sources studied. Under the conditions considered, the possible adverse effects of AuNPs on the catabolic capabilities of microbial communities appears to be minimal.
