Identification and assessment of ecotoxicological hazards attributable to pollutants in urban wet weather discharges.

Urbanization has led to considerable pressure on urban/suburban aquatic ecosystems. Urban Wet Weather Discharges (UWWD) during rainfall events are a major source of pollutants leached onto and into urban surfaces and sewers, which in turn affect aquatic ecosystems. We assessed the ecotoxicity of the different compounds identified in UWWD and identified the hazard represented by each of them. To this end, hazard quotient (HQ) values were calculated for each compound detected in UWWD based on their predicted no effect concentration (PNEC) values and their maximum measured effluent concentrations (MECmax) found in the dissolved part of UWWD. For the 207 compounds identified in UWWD, sufficient data existed for 165 of them to calculate their PNEC. The ecotoxicity of these compounds varied greatly. Pesticides represented a high proportion of the wide variety of hazardous compounds whose HQ values were calculated (94 HQ values), and they were among the most hazardous pollutants (HQ > 1000) transported by stormwater. The hazard of combined sewer overflows (CSO) was linked mainly to heavy metals and pharmaceutical compounds. Consequently, the monitoring of these pollutants should be a priority in the future. The hazard level of certain pollutants could have been underestimated due to their adsorption onto particles, leading to their low concentration in the dissolved phase of UWWD. Hence, an in-depth study of these pollutants will be required to clarify their effects on aquatic organisms.

A posteriori assessment of ecotoxicological risks linked to building a hospital.

Hospital wastewater (HWW) contain a large number of chemical pollutants such as disinfectants, surfactants, and pharmaceutical residues. A part of these pollutants is not eliminated by traditional urban wastewater treatment plants (WWTP), leading to a risk for the aquatic ecosystems receiving these effluents. In order to assess this risk, we formulated a specific methodology based on the ecotoxicological characterisation of the hospital wastewater using a battery of three chronic bioassays (Pseudokirchneriella subcapitata, Heterocypris incongruens and Brachionus calyciflorus). We used it for the posteriori risk assessment of a hospital recently built in south-east France, and we studied the evolution of this risk during two years. We also used it to assess the decrease of the ecotoxicological risk after treatment of the effluent in a specific line of the local WWTP. Lastly, we compared these results with the risk assessment made before the building of the hospital in the context of a priori risk assessment. The results obtained showed an important evolution of the risk overtime, according to the hospital activities and the river flows, and a real decrease of the risk after treatment in the dedicated line. They also showed that the a priori assessment of ecotoxicological risks, made previously, was overstated, mainly because of the application of the precautionary principle.

Respective contributions of diet and medium to the bioaccumulation of pharmaceutical compounds in the first levels of an aquatic trophic web.

Nowadays, pharmaceuticals (PCs) are ubiquitous in aquatic ecosystems. It is known that these compounds have ecotoxic effects on aquatic organisms at low concentrations. Moreover, some of them can bioaccumulate inside organisms or trophic webs exposed at environmental concentrations and amplify ecotoxic impacts. PCs can bioaccumulate in two ways: exposure to a medium (e.g., respiration, diffusion, etc.) and/or through the dietary route. Here, we try to assess the respective contributions of these two forms of contamination of the first two levels of an aquatic trophic web. We exposed Daphnia magna for 5 days to 0, 5, and 50 µg/L (15)N-tamoxifen and then fed them with control and contaminated diets. We used an isotopic method to measure the tamoxifen content inside the daphnids after several minutes' exposure and every day before and after feeding. We found that tamoxifen is very bioaccumulative inside daphnids (BCF up to 12,000) and that the dietary route has a significant impact on contamination by tamoxifen (BAF up to 22,000), especially at low concentrations in medium.

Bioconcentration of (15)N-tamoxifen at environmental concentration in liver, gonad and muscle of Danio rerio.

Pharmaceutical compounds (PCs) are ubiquitous in aquatic ecosystems. In addition to the direct ecotoxicological risk presented by certain PCs, others can accumulate inside organisms and along trophic webs, subsequently contaminating whole ecosystems. We studied the bioconcentration of a bioaccumulative PC already found several times in the environment: tamoxifen. To this end, we exposed Danio rerio for 21d to (15)N-tamoxifen concentrations ranging from 0.1 to 10µg/L and used an analytic method based on stable isotopes to evaluate the tamoxifen content in these organisms. The evolution of the (15)N/(14)N ratio was thus measured in liver, muscle and gonads of exposed fish compared to control fish. We succeeded in quantifying (15)N-tamoxifen bioconcentrations at all the exposure concentrations tested. The highest bioconcentration factors of tamoxifen measured were 14,920 in muscle, 73,800 in liver and 85,600 in gonads of fish after 21d exposure at a nominal concentration of 10µg/L. However, these bioconcentration factors have to be considered as maximal values (BCFMAX). Indeed, despite its proven stability, tamoxifen can be potentially partially degraded during experiments. We now need to refine these results by using a direct analytic method (i.e. LC-MS/MS).

Tamoxifen ecotoxicity and resulting risks for aquatic ecosystems.

Tamoxifen, a drug used to treat cancer, is regularly found in hydrosystems at concentrations of several hundred ng L(-1). To characterize its ecotoxicity, we implemented a battery of bioassays on organisms belonging to 3 different trophic levels: Pseudokirchneriella subcapitata, Chlorella vulgaris and Chlamydomonas reinhardtii, for primary producers, Daphnia magna (immobilization, grazing and reproduction) for primary consumers, and Danio rerio for secondary consumers (embryotoxicity test). In view of the results obtained and the ecotoxicity values of tamoxifen available in the literature, we established a PNEC (Predictive No Effect Concentration) equal to 81 ng L(-1) for continental water. This PNEC allowed us to calculate Risk Quotients (RQ) for 4 continental hydrosystems in 4 different countries in which measures of tamoxifen had already been performed on surface waters. In two of the situations studied, RQs were higher than 1, reaching a maximum of 2.6. These results show the need to deepen the characterization of ecotoxicological risks linked to the discharge of tamoxifen in surface waters. In addition, we propose applying this approach to other drug residues detected in the environment.

Experimental assessment of the bioconcentration of (15)N-tamoxifen in Pseudokirchneriella subcapitata.

Nowadays, pharmaceutical compounds (PC) are ubiquitous in aquatic ecosystems. In addition to direct ecotoxicity, the bioconcentration of PC in organisms is a phenomenon which could have an impact on the whole ecosystem. In order to study this phenomenon, we exposed unicellular algae (Pseudokirchneriella subcapitata) to (15)N-tamoxifen, an anticancer drug labelled with a stable nitrogen isotope used as a tracer. By measuring (15)N enrichment over time, we were able to measure the increase of tamoxifen content in algae. This enrichment was measured by an elemental analyser coupled with an isotopic ratio mass spectrometer (EA-IRMS). Algal cells were exposed for 7d to 3 concentrations of tamoxifen: 1, 10 and 100µgL(-1). Our result shows a high bioconcentration in algae from the first minutes of contact. The highest bioconcentration factor measured is around 26500. We also observe that bioconcentration is not linked to the exposure concentration. This study is the first to use stable isotopes in order to monitor PCs in aquatic organisms such as algae. The use of stable isotopes in ecotoxicology offers interesting perspectives in the field of contaminant transfer in organisms and along the trophic web.

Co-encapsulation of Daphnia magna and microalgae in silica matrices, a stepping stone toward a portable microcosm.

We report on the first silica encapsulation of a metazoan (Daphnia magna), with a high initial viability (96% of the population remained active 48 h after encapsulation). Moreover, the co-encapsulation of this crustacean and microalgae (Pseudokirchneriella subcapitata) was achieved, creating inside a silica monolith, the smallest microcosm developed to present. This artificial ecosystem in a greatly diminished scale isolated inside a silica nanoporous matrix could have applications in environmental monitoring, allowing ecotoxicity studies to be carried out in portable devices for on-line and in situ pollution level assessment.

Characterisation of the ecotoxicity of hospital effluents: a review.

The multiple activities that take place in hospitals (surgery, drug treatments, radiology, cleaning of premises and linen, chemical and biological analysis laboratories, etc.), are a major source of pollutant emissions into the environment (disinfectants, detergents, drug residues, etc.). Most of these pollutants can be found in hospital effluents (HWW), then in urban sewer networks and WWTP (weakly adapted for their treatment) and finally in aquatic environments. In view to evaluating the impact of these pollutants on aquatic ecosystems, it is necessary to characterise their ecotoxicity. Several reviews have focused on the quantitative and qualitative characterisation of pollutants present in HWW. However, none have focused specifically on the characterisation of their experimental ecotoxicity. We have evaluated this according to two complementary approaches: (i) a "substance" approach based on the identification of the experimental data in the literature for different substances found in hospital effluents, and on the calculation of their PNEC (Predicted Non Effect Concentration), (ii) a "matrix" approach for which we have synthesised ecotoxicity data obtained from the hospital effluents directly. This work first highlights the diversity of the substances present within hospital effluents, and the very high ecotoxicity of some of them (minimum PNEC observed close to 0,01 pg/L). We also observed that the consumption of drugs in hospitals was a predominant factor chosen by authors to prioritise the compounds to be sought. Other criteria such as biodegradability, excretion rate and the bioaccumulability of pollutants are considered, though more rarely. Studies of the ecotoxicity of the particulate phase of effluents must also be taken into account. It is also necessary to monitor the effluents of each of the specialised departments of the hospital studied. These steps is necessary to define realistic environmental management policies for hospitals (replacement of toxic products by less pollutant ones, etc.).