The Préfecture maritime for the Atlantic and for the UK side the MCA conducted risk assessments prior to an attempt to tow the abandoned vessel. These assessments were composed of the classic elements relating to a shipping accident: drift predictions for the wreck, the containers liable to fall into the sea and the slicks of bunker fuel in the event of a spill.
Upon departure from Antwerp, the bunkers of the MSC Napoli contained 3,512 tonnes of IFO 380 and 152 tonnes of marine diesel. However this particular case represented an exceptional situation. The MSC Napoli was transporting 2,318 containers, carrying 41,730 tonnes of goods, including around 1,700 tonnes of hazardous products: 167 kg of explosives, 177 tonnes of gases, 462 tonnes of flammable liquids, 107 tonnes of flammable solids, 61 tonnes of oxidants, 143 tonnes of toxic materials and over 200 tonnes of corrosive materials.
From mid-afternoon on 18 January, urgent analysis of the risks connected to products classified as hazardous in the ship's manifest had to be conducted. In practice, from a 106-page list containing up to 7 entries per page, the challenge was to identify two types of dangers which were subsequently discussed by a group of experts: the dangers for responders (explosive or flammable products and toxic gases) and the dangers for the marine environment (aquatic pollutants, toxic products for flora and fauna).
The problem with this type of situation is not the hazardous nature of an isolated product, available in the specialised literature but rather the problem, as demonstrated by the MSC Rosa M, of interference between products, such as a product which is flammable when in contact with water being close to a heat reactive substance. The problem is also managing to react quickly without neglecting any aspect, in particular in the case of packages as the danger caused by a product or contact between products is not only a question of composition, but also depends on packaging.
A product packaged in metal barrels may withstand several weeks in seawater, while the same product in sealed plastic bags which will float on the surface or in cardboard boxes which will disintegrate in the water should not be considered in the same way. A substance which is denser than water in packaging with good buoyancy should not be considered in the same way as the same product in bulk in a container which will sink quickly. Unfortunately, packaging lists often use vague terminology such as "box" or "package", which do not allow their water resistance to be determined.