Combined effects of engineered nanoparticles and anthropogenic contaminants on a coastal environment

During the last years, the emergence of nanotechnology and the rapidly increasing number of nano-enabled products used in various applications are causing concern about the potential environmental impacts of engineered nanoparticles (ENP). This has given ENP a high priority as potential "emerging pollutants" that can affect the environment. In addition to their intrinsic toxic properties, NP can also potentially interact with other man-made pollutants, such as environmental toxicants. Because of the high surface to volume ratio and surface properties of ENP, contaminants can bind to ENP. This can lead to an altered distribution of pollutants in the natural environment, and a change in the contaminant bioavailability, and hence their toxic potential for organisms in the natural environment. The research project Nano Marine investigated toxic effects of two engineered metal nanoparticles (TiO2NP and AgNP) on marine organisms and the effects of mixtures of these NP and three selected anthropogenic organic pollutants compounds with different mechanisms of action. These compounds were the cancerogenic polyaromatic hydrocarbon (PAH) compound benzo(a)pyrene [B(a)P], the synthetic hormone 17?-ethinylestradiol (EE2) that acts as a hormone disturb the marine organisms and the water soluble fraction of crude oil from oil platform Troll in the North Sea. TiO2NP and AgNP are two of the most produced and used types NP and they therefore have a relatively large pollution potential. The effects were studied in three laboratory experiments on key species in the marine food chain: copepods (Calanus finmarchicus), mussels (Mytilus edulis) and turbot (Scophthalmus maximus). In addition, we conducted a field study in which we examined the levels of PAH and elements in wild fish at the discharge point of Høvringen waste water treatment plant in Trondheimsfjorden and at a reference area in Froan nature reserve. Høvringen treatment plant treats wastewater from 2/3 of Trondheim. In seawater NP agglomerated quickly, but AgNP, which was surface treated with poly (N-vinylpyrrolidone) (PVP) was more stable in solution than TiO2NP, which was not surface treated. Despite aggregation, the study showed that Ti and Ag were released from the nanoparticles and was bioavailable for uptake in the test species. The exposure caused toxic effects related to oxidative stress and immune function. Combined (mixed) exposure to Ti2NP and B(a)P decreased the bioavailability of B(a)P in mussels. However, increased frequencies of chromosomal damage by this mixture exposure indicate mixture toxicity, possibly because of additive stress responses. Combined exposure to AgNP and EE2 did not alter the bioavailability of EE2 in turbot. However, the results showed that this mixture exposure affected the synthesis of certain steroid hormones, which may indicate mixing toxicity. In the copepods, AgNP attached to the surface of the animals, and mixed exposure resulted in an increase of AgNP on surface of the animals. Exposure to AgNP induced oxidative stress in copepods, and this response was somewhat elevated by mixed exposure for AgNP and the water-soluble fractions of crude oil. The field survey showed that there were no elevated levels of PAHs in flatfish caught near the Høvringen treatment plant wastewater outlet. Exposure to NP caused effects related to oxidative stress, hormone disruption and immuneresponses. The project showed that exposure to combined mixtures of NP and the studied organic contaminants decreased bioavailability of contaminants, but caused similar or somewhat larger toxic effects. The effects of exposure to NP and the examined contaminants in combination (mixture exposures) indicate interactive (additive) stress responses.

This project seeks to enhance the knowledge on the effects of engineered nanoparticles (ENPs) on a coastal environment and their influence on the impacts of present pollutants of concern. In this study commercially available silver and TiO2 nanoparticles (AgNP, TiO2NP) featuring different surface stabilisation will be applied. Their behaviour and consequently their environmental fate in marine water with different salinity and content of natural organic matter (NOM), from the Trondheimsfjorden will be as sessed. In a broad range of laboratory studies, the uptake and effects of AgNP and TiO2NP and their influence of two contaminants of concern, benzo(a)pyrene (BaP) and 17a-ethynylestradiol (EE2), will be investigated. Exposure concentrations will be deri ved from concentrations in the environment and in biota. These concentrations will be evaluated by field sampling at anthropogenic impacted sites in the Trondheimsfjorden. The study will consist of subsequent laboratory experiments where filter feeders Mytilus edulis (benthic) and Calanus finmarchicus (pelagic), planctonic bacterial communities and the benthic fish Pleuronectes platessa will be exposed to BaP and EE2 in the presence and absence of ENPs. Uptake and bioavailability investigations will be followed by evaluation of potential toxic effects. This will include investigation of both, general stress biomarkers, such as oxidative stress, DNA damage and histological changes and also analysis of specific endpoints such as induction of cytochrome P4 50 enzymes and changes in sex hormone homeostasis. Analysis of ENP-chemical interaction and determination of contaminant specific effects should indicate the role of ENP presence on contaminant action - a Trojan horse type mechanism or additive effect.