János Fent, Blanka Emődy-Kiss, Viktor Szentgyörgyi, Sándorné Lukács, András Gachályi, Susan Lakatos
Hungarian Defence Forces, dr.Radó György Military Medical Centre
Scientific Institute, Budapest, Hungary
On October 4, 2010 the dyke of a reservoir of an aluminum plant broke and villages Devecser and Kolontár (Hungary) were flooded by red sludge. Because of the high alkalinity of the sludge its immediate effect was evident. Many persons (civilians as well as rescuers) and animals became seriously burnt. However, the long-term physiological effects related to any contact with or just to the presence of the sludge still needs to be revealed.
The samples were taken from the greasy sludge which mulched the soil and from the upper 2-3 cm thick layer of dried sludge. The size distribution of particles was measured by light microscopy (for larger particles) and by dynamic light scattering (for smaller insoluble particles). To test biological effect semi-stable suspension was prepared according to the methods described by Bihari et al. (Part Fibre Toxicol. 5, 14.). In vitro platelet and granulocyte activation was measured in whole human blood of healthy donors, and cell viability and activation assays were performed on Jurkat cells at final concentration of 0.1 mg/ml sludge. Additionally the heavy metal element content of sludge was determined by atomic absorption spectroscopy.
The microscopically observable particles are more or less amorphous having an average diameter of 0.87 +/- 0.65 µm. Dynamic light scattering measurements revealed that smaller particles are also present in the dried sludge. The 0.22 µm filtered fraction of the sludge suspension could be characterized by an equivalent hydrodynamic diameter of 158±46 nm with a polydispersity index of 0.23±0.07. The suspension of dried red sludge did not result in either in vitro platelet or in granulocyte activation at concentration level up to 0.1mg/ml. We could not detect any changes in Jurkat cell viability and activation status in the presence of sludge in the culture medium (at a concentration of 0.1 mg/ml). Atomic absorption spectroscopy revealed Al, Fe, Na, Mn, K, Cr, Ni, Zn, Pb, As, Cu, Cd as main metal elements in the sludge.
A large amount of insoluble fine and ultrafine particulate matter was generated during the desiccation of the red sludge. It is reasonable to suppose that this matter can slather even distant area and jeopardize inhabitants. It is very promising that no direct cell toxicity was observable. Fortunately, the size of these particles is in the range where the deposition in airways is minimal (Witschger O, et al: HST 2005, 199 : 21-35.). Thus, only a small amount of the inhaled particles get into the blood stream where direct activation of platelets and granulocytes practically can be excluded. In conclusion, the most dangerous effect of these kinds of particles, such as deposition (accumulation) in various organs can be neglected according to our studies up to the date.