Strategies for containment of biological risk in reclaiming a large urban area used as a waste pit by a serum and vaccine factory

Abstract number: 1733_1065

Amendola A., Bianchi S., Canuti M., Koncan R., Zanetti A., Tridente G., Cornaglia G.

Objectives: The 12,000 m² waste pit of the former Istituto Sieroterapico Milanese, in the urban centre of Milan, Italy, has recently been reclaimed after nearly a decade of complete abandonment. Since the early 1900s, different bio-pharmacological products – vaccines, prophylactic sera, blood flasks, waste of various animal origins – had been buried at a depth not exceeding 1.5 m. Some material, such as animal waste, had decomposed in direct contact with the soil for a variable number of years, and therefore dispersed pathogens are likely to have interacted with the soil's own microbicidal properties. Other materials, such as human or veterinary vaccines, were recovered as sealed vials, and there was presumably a risk that their contents (either liquid or lyophilised) might have been totally or partially preserved. The aim of the whole exercise was to carry out a thorough reclamation whilst minimising the potential biological risks.

Methods: A preliminary electro-magnetometric investigation was performed on the whole area, identifying those sub-areas with uneven soil homogeneity attributable to the alleged presence of heterologous materials. A pilot intervention zone, the so-called `first experimental module', was used to set up and test all the procedures. All the operations were conducted under a special tensostructure (base, 30×30 m), with air exchangers and extractors endowed with both `absolute' (i.e., high-specification fluid filters used to remove small solid particles) and activated carbon filters. Removal of the soil was done using excavators over the whole area.

Results and Conclusions: Given the obvious impossibility of treating the whole area either by autoclaving or incineration, vibratory sifting of the possibly contaminated soil was necessary, permitting gross separation of the foreign materials. The sifted soil was subsequently put back in the original areas and submitted to 120-days' quarantine. The bio-pharmacological products isolated were stored in special containers and incinerated, after careful sampling for future studies of their residual biological activities related to both bacteria (Brucella abortus, Salmonella spp., Streptococcus spp., Bacillus anthracis) and viruses (Newcastle Disease Virus, Rhabdovirus, Canine Distemper Virus, Pestivirus, Poliovirus). Despite the lack of similar experience worldwide, the whole procedure was carried out under optimal conditions and with adequate levels of both environmental and human safety.