12The bioavailability of organic contaminants adsorbed to carbon nanotubes (CNTs) remains 13 unclear, especially in complex natural freshwaters containing natural organic matter (NOM). reduced phenanthrene toxicity to algae (EC50; 528.4) compared to phenanthrene-only (EC50; 27 438.3), while the presence of MWCNTs had no significant effect on phenanthrene toxicity. 28However, phenanthrene adsorbed to NOM-dispersed CNTs proved to be bioavailable and 29 contribute to exert toxicity to P. subcapitata. 30 31
Background: Exposure to persistent organic pollutants (POPs) during fetal development can increase the risk of adverse health effects during childhood. Maternal characteristics and physiological changes during gestation, such as gestational weight gain (GWG), may have an influence in the overall burden of POPs in neonates. However, the associations between GWG and POP concentrations are still not well established.Objective: We examined the association of GWG with cord serum POPs concentrations after adjusting for prepregnancy maternal body mass index (BMI) and other potential determinants of the transfer of POPs into newborns. The GWG values were evaluated after grouping by the reference guidelines of the Institute of Medicine (IOM).Methods: We measured levels of 14 organochlorine pesticides, 7 polychlorobiphenyls (PCBs), and 14 polybrominated diphenyl ethers (PBDEs) in 325 cord serum samples from a Spanish birth cohort. Multivariable models were used to estimate associations of GWG, prepregnancy BMI, and other maternal determinants on cord serum concentrations of POPs.Results: Neonatal concentrations of POPs were inversely associated with GWG after adjustment for age, prepregnancy BMI, educational level, and fish consumption. On average, neonates of women with IOM-recommended GWG have lower POP concentrations than do neonates of mothers with inadequate GWG.Conclusions: The present findings suggest an association between neonatal exposure to POPs and inadequate GWG during pregnancy. Encouraging pregnant women to meet the recommended IOM guidelines for GWG may reduce the accumulation of POPs in newborns.Citation: Vizcaino E, Grimalt JO, Glomstad B, Fernández-Somoano A, Tardón A. 2014. Gestational weight gain and exposure of newborns to persistent organic pollutants. Environ Health Perspect 122:873–879; http://dx.doi.org/10.1289/ehp.1306758
The dispersion behavior of carbon nanotubes (CNTs) is influenced by both their physicochemical properties and by the aqueous media properties (e.g. ionic strength, presence of divalent cations and natural organic matter) in which they are dispersed. In the current study, the dispersibility and dispersion stability of four multi-walled CNTs (MWCNT) and a single walled CNT (SWCNT) with different physicochemical properties were investigated in three freshwater growth media (with and without natural organic matter; NOM) used in algae and daphnia ecotoxicity studies. CNT dispersion behavior was also investigated in a natural freshwater for comparison. SWCNTs and non-functionalized MWCNTs showed similar dispersibility irrespective of the media type (SWCNTs = 0.5-0.9 mg/L; MWCNTs = 1.5-2.8 mg/L). Functionalized MWCNTs exhibited higher dispersion concentrations, but were more dependent upon the ionic strength and divalent cation concentration of each media (MWCNT-COOH = 3.0-6.6 mg/L). In contrast, CNT surface oxygen content had no influence on CNT dispersibility in the natural water (all MWCNTs = 0.9-1.4 mg/L). Functionalized MWCNTs were affected more by the differences in media properties than non-functionalized MWCNTs. The dispersed CNT concentration decreased over time for all CNT types and in all media due to sedimentation, but was influenced by both CNT and media properties. The study shows how a complex interplay between CNT and media properties can influence the environmental fate of CNTs. Furthermore, the study demonstrates how different CNT types and/or ecotoxicological media in aquatic tests influences the dispersion behavior of the CNTs, and thus their exposure and toxicity to aquatic organisms.
Studies investigating the effect of carbon nanotubes (CNTs) on the bioavailability and toxicity of hydrophobic organic compounds in aquatic environments have generated contradictory results, and the influence of different CNT properties remains unknown. Here, the adsorption of the polycyclic aromatic hydrocarbon phenanthrene (70−735 μg/L) to five types of CNTs exhibiting different physical and chemical properties was studied. The CNTs were dispersed in the presence of natural organic matter (nominally 20 mg/L) in order to increase the environmental relevance of the study. Furthermore, the bioavailability and toxicity of phenanthrene to Daphnia magna in the absence and presence of dispersed CNTs was investigated. Both CNT dispersion and adsorption of phenanthrene appeared to be influenced by CNT physical properties (diameter and specific surface area). However, dispersion and phenanthrene adsorption was not influenced by CNT surface chemical properties (surface oxygen content), under the conditions tested. Based on nominal phenanthrene concentrations, a reduction in toxicity to D. magna was observed during coexposure to phenanthrene and two types of CNTs, while for the others, no influence on phenanthrene toxicity was observed. Based on freely dissolved concentrations, however, an increased toxicity was observed in the presence of all CNTs, indicating bioavailability of CNT-adsorbed phenanthrene to D. magna.
A number of methods have been reported for determining hydrophobic organic compound adsorption to dispersed carbon nanotubes (CNTs), but their accuracy and reliability remain uncertain. We have evaluated three methods to investigate the adsorption of phenanthrene (a model polycyclic aromatic hydrocarbon, PAH) to CNTs with different physicochemical properties: dialysis tube (DT) protected negligible depletion solid phase microextraction (DT-nd-SPME), ultracentrifugation, and filtration using various types of filters. Dispersed CNTs adhered to the unprotected polydimethylsiloxane (PDMS)-coated fibers used in nd-SPME. Protection of the fibers from CNT adherence was investigated with hydrophilic DT, but high PAH sorption to the DT was observed. The efficiency of ultracentrifugation and filtration to separate CNTs from the water phase depended on CNT physicochemical properties. While non-functionalized CNTs were efficiently separated from the water phase using ultracentrifugation, incomplete separation of carboxyl functionalized CNTs was observed. Filtration efficiency varied with different filter types (composition and pore size), and non-functionalized CNTs were more easily separated from the water phase than functionalized CNTs. Sorption of phenanthrene was high (< 70%) for three of the filters tested, making them unsuitable for the assessment of phenanthrene adsorption to CNTs. Filtration using a hydrophilic polytetrafluoroethylene (PTFE) filter membrane (0.1 μm) was found to be a simple and precise technique for the determination of phenanthrene adsorption to a range of CNTs, efficiently separating all types of CNTs and exhibiting a good and highly reproducible recovery of phenanthrene (82%) over the concentration range tested (70-735 μg/L).
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