Ecotoxicity of nanomaterials in relation to the freshwater microalga Raphidocelis subcapitata

Silver is the most frequently represented nanomaterial in available products, ranging across a variety of commercial and medical goods. Their main justification for inclusion in these products relates to their unique properties compared to both their bulk (larger particulate) and ionic equivalents. It is established that silver is highly toxic to a range of aquatic organisms, and despite its existence in low concentrations in the environment, concerns have been raised over products containing silver nanomaterials as a potential emerging pollutant. Within the EU the environmental risk assessment of chemicals is regulated by the Registration, Evaluation and Authorization of Chemicals (REACH) regulation, and toxicity testing deployed according to a series of tiered production/import thresholds. At the lowest regulatory production/import threshold of one tonne, the Organisation for Economic Co-operation and Development (OECD) 201: Freshwater Alga and Cyanobacteria, Growth Inhibition Test can be deployed to evaluate the toxicity to the aquatic environment via assessment of the impact of chemicals on algal species, over a 72 hour test duration. Due to the unique physico-chemico properties of nanomaterials, there is considerable uncertainty over the suitability of such test protocols for these materials. Thus, there may be a requirement for alternative test systems. In addition, the proliferation of the nanotechnology industry has created a diverse range of materials whose safety needs to be assessed. There is therefore an immediate need for rapid environmental risk assessment in order to keep pace with commercial activities. This thesis addresses such considerations in four stages. First, the OECD 201 test was applied to evaluate the toxicity of a representative silver nanoparticle (20-150 μg/l Ag as NM300K, at 24-72 hours) and AgNO3 (0.2-30 μg/l Ag, at 24-72 hours), following dispersion in two different growth media, and the influence of different medium conditions such as humic acid (through the use of environmentally relevant concentrations of Suwannee River humic acid, [5 and 50 mg/l) and pH (6 and 8) on silver nanoparticle toxicity was investigated. In addition, a miniaturised version of the OECD 201 test was developed and compared to the standard test method, as a means to increase the rate and efficiency at which laboratories can generate toxicity data. Finally an alternative, short term sublethal photosynthetic endpoint was investigated in order to identify an alternative measure of toxicity to algae and inform the toxic mechanism of action of silver to algae, and correlations with the standard growth inhibition endpoint presented. It was found that the OECD 201 test was suitable to evaluate toxicity in NM300K and enabled identification of a 72 hour growth inhibition effective concentration (EC50) of 54-130 μg/l Ag. Of interest was that silver nanoparticle toxicity decreased with exposure duration and were affected by test medium composition. AgNO3 toxicity was higher than NM300K (72 hour EC50 = 5-7 μg/l Ag)., but subject to the same time and media effects Humic acid decreased the toxicity of both forms of silver in a concentration dependent manner, and pH 8 test medium increased toxicity relative to pH 6. The proposed miniaturised test was found to be as sensitive as the standard method (for NM300K) across a similar range of test conditions. Finally, the short-term photosynthetic sublethal endpoint indicated that silver may act in a similar way to known phototoxic substances, and by measuring this endpoint a high correlation was found with later 72 hour growth inhibition. Obtained data therefore demonstrate that the OECD 201 test can be used with R. subcapitata as a tool to assess nanoparticle toxicity, and that there are opportunities to increase the efficiency of testing via miniaturisation of the test system and the use of additional toxicity endpoints

How Cuba burned with the ghosts of British slavery: race, abolition and the Escalera

It is the purpose of this paper to show how the taking of British West Indians into slavery in Cuba and the repression of a supposed uprising were closely connected. The Escalera, while not directly caused by the presence of these black British subjects, was nevertheless partly the result of interrelated events that began with the importation of the latter into Cuba by white British planters escaping the abolition of slavery and the slave-trade in the British colonies. With Cuba still firmly a slave society, they were maintained in bondage, along with other black British West Indians who were kidnapped from their home islands by unscrupulous traders, and sold to Cuban planters hungry for labourers. Despite the presence in Havana of a Mixed Commission for the Suppression of the Slave Trade, charged with ensuring that such breaches of the anti-slave-trade treaties did not go unchallenged, many British representatives in Cuba were themselves implicated in the continuance of slavery, until the appointment in 1840 of the militant abolitionist David Turnbull as British Consul and Superintendent of Liberated Africans. Turnbull forcefully investigated and sought freedom for all those black British subjects who were being held in slavery in the island. While the Spanish accusations made against him of conspiring for revolution were probably false, his actions (combined with the presence in the island of other abolition-minded British migrants, as well as that of the enslaved black British subjects themselves) had a destabilizing effect upon the Cuban slave system, acting as a catalyst for the unsuccessful uprising of 1843/44, and the subsequent brutal repression

The survival advantage of pancreas after kidney transplant

Patient survival after pancreas after kidney transplant (PAK) has been reported to be inferior to patient survival after simultaneous pancreas–kidney transplant (SPK). The authors examine national data to further explore allograft (kidney and pancreas) and patient survival after PAK. Kaplan–Meier and Cox proportional hazard models were used to analyze Organ Procurement and Transplantation Network data from 1995 to 2010. The analysis compared PAK and SPK candidates and recipients. Kaplan–Meier analysis results showed that PAK after either a living or a deceased donor kidney transplant is associated with increased kidney graft survival compared with recipients with type 1 diabetes who received only a kidney. The best kidney allograft survival was for patients who received a living donor kidney followed by PAK. Receiving a living donor kidney was associated with increased pancreas allograft survival compared with receiving a deceased donor kidney. PAK transplant recipients who receive both organs have a survival advantage compared with uremic candidates who receive neither (SPK waitlist). Compared with uremic diabetic waitlist patients, SPK and PAK recipients showed similar overall patient survival. Successful PAK offers a survival advantage compared with receiving neither a kidney nor a pancreas transplant. These data also suggest that receiving a pancreas (after kidney) transplant may have a protective effect on the kidney allograft

Deepwater Horizon Oil Spill: Highlighted Actions and Issues

This report highlights actions taken and issues raised after the April 20, 2010 explosion on the Deepwater Horizon offshore drilling rig and the resulting oil spill in the Gulf of Mexico

Deepwater Horizon Oil Spill: Highlighted Actions and Issues

This report highlights actions taken and issues raised as a result of the April 20, 2010, explosion on the Deepwater Horizon offshore drilling rig, and the resulting oil spill in the Gulf of Mexico. Readers can access more extensive discussions in various CRS reports, identified at the end of this report

Deepwater Horizon Oil Spill: Highlighted Actions and Issues

This report highlights actions taken and issues raised as a result of the April 20, 2010, explosion on the Deepwater Horizon offshore drilling rig, and the resulting oil spill in the Gulf of Mexico