Carbon nanotubes (CNTs) are currently incorporated into various consumer products, and numerous new applications and products containing CNTs are expected in the future. The potential for negative effects caused by CNT release into the environment is a prominent concern and numerous research projects have investigated possible environmental release pathways, fate, and toxicity. However, this expanding body of literature has not yet been systematically reviewed. Our objective is to critically review this literature to identify emerging trends as well as persistent knowledge gaps on these topics. Specifically, we examine the release of CNTs from polymeric products, removal in wastewater treatment systems, transport through surface and subsurface media, aggregation behaviors, interactions with soil and sediment particles, potential transformations and degradation, and their potential ecotoxicity in soil, sediment, and aquatic ecosystems. One major limitation in the current literature is quantifying CNT masses in relevant media (polymers, tissues, soils, and sediments). Important new directions include developing mechanistic models for CNT release from composites and understanding CNT transport in more complex and environmentally realistic systems such as heteroaggregation with natural colloids and transport of nanoparticles in a range of soils.

Decabromodiphenyl ether (BDE 209), the major congener in the high volume industrial flame retardant mixture "DecaBDE", has recently been shown to be metabolized by carp. To further explore this phenomenon, juvenile rainbow trout were exposed to BDE 209 via the diet for a five month period. Analysis of the whole body homogenate, liver, serum, and intestinal tissues revealed that BDE 209 accumulated in rainbow trout tissues and was most concentrated in the liver. In addition to BDE 209, several hepta-, octa-, and nonaBDE congeners also accumulated in rainbow trout tissues over the same period as a result of BDE 209 debromination. Based on the total body burden of the hepta- through decaBDE congeners, uptake of BDE 209 was estimated at 3.2%. Congener profiles were different among whole body homogenate, liver, and serum, with the whole body homogenates having a greater contribution of the debrominated biotransformation products. Extracts of the rainbow trout whole body homogenates were compared with extracts from a previous experiment with common carp. This comparison revealed that BDE 202 (2,2',3,3',5,5',6,6'-octabromodiphenyl ether) was a dominant debromination product in both studies. To determine whether the observed debromination was metabolically driven, liver microsomal fractions were prepared from both common carp and rainbow trout. Analysis of the microsomal fractions following incubation with BDE 209 revealed that rainbow trout biotransformed as much as 22% of the BDE 209 mass, primarily to octa- and nonaBDE congeners. In contrast, carp liver microsomes biotransformed up to 65% of the BDE 209 mass, primarily down to hexaBDE congeners. These microsomal incubations confirm a metabolic pathway for BDE 209 debromination.

Engineered nanoparticles, due to their unique electrical, mechanical, and catalytic properties, are presently found in many commercial products and will be intentionally or inadvertently released at increasing concentrations into the natural environment. Metal- and metal oxide-based nanomaterials have been shown to act as mediators of DNA damage in mammalian cells, organisms, and even in bacteria, but the molecular mechanisms through which this occurs are poorly understood. For the first time, we report that copper oxide nanoparticles induce DNA damage in agricultural and grassland plants. Significant accumulation of oxidatively modified, mutagenic DNA lesions (7,8-dihydro-8-oxoguanine; 2,6-diamino-4-hydroxy-5-formamidopyrimidine; 4,6-diamino-5-formamidopyrimidine) and strong plant growth inhibition were observed for radish (Raphanus sativus), perennial ryegrass (Lolium perenne), and annual ryegrass (Lolium rigidum) under controlled laboratory conditions. Lesion accumulation levels mediated by copper ions and macroscale copper particles were measured in tandem to clarify the mechanisms of DNA damage. To our knowledge, this is the first evidence of multiple DNA lesion formation and accumulation in plants. These findings provide impetus for future investigations on nanoparticle-mediated DNA damage and repair mechanisms in plants.

Although the presence of polybrominated diphenyl ethers (PBDEs) in house dust has been linked to consumer products, the mechanism of transfer remains poorly understood. We conjecture that volatilized PBDEs will be associated with dust particles containing organic matter and will be homogeneously distributed in house dust. In contrast, PBDEs arising from weathering or abrasion of polymers should remain bound to particles of the original polymer matrix and will be heterogeneously distributed within the dust. We used scanning electron microscopy and other tools of environmental forensic microscopy to investigate PBDEs in dust, examining U.S.A. and U.K. dust samples with extremely high levels of BDE 209 (260-2600 µg/g), a non-volatile compound at room temperature. We found that the bromine in these samples was concentrated in widely scattered, highly contaminated particles. In the house dust samples from Boston (U.S.), bromine was associated with a polymer/organic matrix. These results suggest that the BDE 209 was transferred to dust via physical processes such as abrasion or weathering. In conjunction with more traditional tools of environmental chemistry, such as gas chromatography-mass spectrometry (GC/MS), environmental forensic microscopy provides novel insights into the origins of BDE 209 in dust and their mechanisms of transfer from products.

The unique chemical and physical properties of engineered nanomaterials that make them attractive for numerous applications also contribute to their unexpected behaviour in the environment and biological systems. The potential environmental risks, including their impact on aquatic organisms, have been a central argument for regulating the growth of the nanotechnology sector. Here we show in a simplified food web that carboxylated and biotinylated quantum dots can be transferred to higher trophic organisms (rotifers) through dietary uptake of ciliated protozoans. Quantum dot accumulation from the surrounding environment (bioconcentration) was limited in the ciliates and no quantum dot enrichment (biomagnification) was observed in the rotifers. Our findings indicate that dietary uptake of nanomaterials should be considered for higher trophic aquatic organisms. However, limited bioconcentration and lack of biomagnification may impede the detection of nanomaterials in invertebrate species.

The estrogen receptor agonist fate of hexane extracts from various locations and phases (liquid and solid) within one pilot-scale and two full-scale wastewater treatment facilities were examined by use of the receptor-binding yeast estrogen screen (YES assay). Estrogenic activity was found in samples that contained a high concentration of biological solids and was particularly high in the suspended solid fraction from biosolids treatment facilities. Mass balances revealed that the estrogenic activity associated with the processed biosolids constituted between 5 and 10% of the influent estrogenic activity, while the treated liquid effluent prior to disinfection contained between 26 and 43%. Overall, this suggests that between 51 and 67% of the estrogenic activity contained in the influent wastewater was either biodegraded during the wastewater or biosolids treatment processes or was unavailable to the extraction/detection procedure. In both aerobic and anaerobic digestion, mass balances revealed an increase in estrogenic activity as treatment progressed and biosolids destruction occurred. The estrogenic activity associated with the solid phase decreased during mesophilic aerobic digestion. A correlation was observed between the estrogenicity of mixed liquor suspended solids and aerobic sludge age and suggests that wastewater treatment facilities can be designed and operated to enhance the sorption and removal of estrogenic compounds from the liquid phase.

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Sorption coefficients (K(COC)) between 17beta-estradiol (E2), 17alpha-ethinylestradiol (EE2) and size-fractionated colloidal organic carbon (COC) derived from two biological wastewater treatment facilities were quantified by fluorescence quenching. The two wastewater treatment systems included a full-scale activated sludge system (FSAS) and a membrane bioreactor (MBR). The K(COC) coefficients were highly variable and ranged between (<1 to 179) x 10(3) L/kgCOC for E2 and (<1 to 430) x 10(3) L/kgCOC for EE2 and were higher than expected from the analytes octanol-water partition coefficient. Correlations between the molar extinction coefficients measured at 280 nm (e280) and K(COC) coefficients were weak but stronger for E2 compared to EE2. Attempts at correlating sorption behavior with colloidal protein and polysaccharide concentrations were only marginally successful (r2 approximately 0.4). These low correlations suggest that aromatic content, protein, or polysaccharide concentration can not adequately explain E2 and EE2 sorption behavior to COC and that other fractions of the organic matter pool play an important role in binding. A substantial portion of the aqueous E2 and EE2 concentrations (up to 60%) may be associated with colloidal material, suggesting that COC may play a role in the fate and transport of E2 and EE2 during the activated sludge process.