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People spend increasing amounts of time at home, yet the indoor home environment remains understudied in terms of potential exposure to toxic trace metals. We evaluated trace metal (and metalloid) concentrations (As, Cu, Cr, Mn, Ni, Pb, and Zn) and health risks in indoor dust from homes from 35 countries, along with a suite of potentially contributory residential characteristics. The objective was to determine trace metal source inputs and home environment conditions associated with increasing exposure risk across a range of international communities. For all countries, enrichments compared to global crustal values were Zn > Pb > Cu > As > Cr > Ni; with the greatest health risk from Cr, followed by As > Pb > Mn > Cu > Ni > Zn. Three main indoor dust sources were identified, with a Pb-Zn-As factor related to legacy Pb sources, a Zn-Cu factor reflecting building materials, and a Mn factor indicative of natural soil sources. Increasing home age was associated with greater Pb and As concentrations (5.0 and 0.48 mg/kg per year of home age, respectively), as were peeling paint and garden access. Therefore, these factors form important considerations for the development of evidence-based management strategies to reduce potential risks posed by indoor house dust. Recent findings indicate neurocognitive effects from low concentrations of metal exposures; hence, an understanding of the home exposome is vital.

The development of nanopesticides has recently received an increased level of attention. However, there are very few data about the environmental fate of these new products, and it is not known whether nanoformulations can be evaluated within the current pesticide regulatory framework. Sorption and degradation parameters of the insecticide bifenthrin were measured in two soils for (i) the pure active ingredient, (ii) three nanoformulations, and (iii) a commercially available formulation. In most cases, fate parameters derived for the nanopesticides were significantly different from those derived for the pure active ingredient (factors of up to 10 for sorption and 1.8 for degradation), but discrepancies were not easy to relate to the characteristics of the nanocarriers. In some cases, differences were also observed between the commercial formulation and the pure active ingredient (factors of up to 1.4 for sorption and 1.7 for degradation). In the regulatory context, the common assumption that formulations do not influence the environmental fate of pesticide active ingredients after application seems therefore not always adequate. In the absence of direct measurement, an inverse modeling approach was successfully applied to evaluate the durability of the formulations in soil (release half-life ranged between 11 and 74 days). Predicted groundwater concentrations very much depended on the modeling approach adopted but overall suggest that the nanoformulations studied could reduce losses to groundwater.

Approaches based on the octanol-water partition coefficient are commonly used to describe sorption of neutral organic compounds in environmental systems, but they are not suitable for organic acids, which can dissociate to form anions. We here investigate the applicability of an alternative approach based on the pH-dependent distribution ratio (DOW) to describe sorption of aromatic acids to sorbents representing different degrees of carbonization. Sorption isotherms for four structurally similar acids ((2,4-dichlorophenoxy)acetic acid (2,4-D), 4-chloro-2-15 methylphenoxy)acetic acid (MCPA), 4-(2,4-dichlorophenoxy)butanoic16 acid (2,4-DB), and 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan)) were measured for 15 sorbents: fresh and carbonized wood shavings, pig manure, sewage sludge, carbon nanotubes, and activated carbon. Dissociation greatly affected the sorption of all acids. Sorption coefficients measured in the high pH range indicated that sorption of the anions ranged over several orders of magnitude and should not be neglected. Sorption trends for all sorbates and carbonized sorbents could be very well described by a single regression equation that included DOW of the sorbate and the specific surface area of the sorbent (R(2) > 0.89).

Surface properties, dispersion state, and sorption behavior of carbon-based nanomaterials will change after being released into the environment. To study these processes, five different scenarios were considered to probe the impact of changes in surface properties of dispersed fullerenes (nC60) on their sorption potential due to irradiation and presence of oxygen. Sorption isotherms of pyrene by nC60 were determined at environmentally relevant concentrations applying a passive sampling method. Isotherms of all dispersion scenarios were best fit with the Dubinin-Ashthakov model. Sorption was strongest for nC60 kept under anoxic condition. Both the presence of oxygen and irradiation significantly decreased the sorption capacity of nC60, while commercially available polyhydroxy fullerenes had the smallest sorption. In addition, competition for sorption sites was never observed in multiple sorbate experiments with four polycyclic aromatic hydrocarbons at small concentration. A strong relationship between sorption coefficients and hydrophobic properties of sorbates suggests that hydrophobic interactions are of major importance. The results emphasize that aging of released fullerenes results in a reduced strength of interactions with nonpolar compounds and, thus, reduces the impact on the environmental transport of hydrophobic pollutants.

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.

Understanding the interactions between organic contaminants and carbon nanomaterials is essential for evaluating the materials' potential environmental impact and their application as sorbent. Although a great deal of work has been published in the past years, data are still limited in terms of compounds, concentrations, and conditions investigated. We applied a passive sampling method employing polyoxymethylene (POM-SPE) to gain a better understanding of the interactions between polycyclic aromatic hydrocarbons (PAHs) and multiwalled carbon nanotubes (CNTs) over a 6 orders of magnitude wide concentration range. In the low-concentration range (pg-ng L(-1)), sorption of phenanthrene and pyrene was linear on a nonlogarithmic scale. Here, sorption could thus be described using a single sorption coefficient. Isotherm fits over the entire concentration range showed that (i) monolayer sorption models described the data very well, and (ii) the CNTs sorption capacity was directly related to their surface area. Sorption coefficients for 13 PAHs (11 of which have not been reported to date) were also measured at environmentally relevant low concentrations. No competition seemed to occur in the low-concentration range and sorption affinity was directly related to the solubility of the subcooled liquid of the compounds.