Potentially harmful elements and polycyclic aromatic hydrocarbons in the soils of Acerra, southern Italy

In recent years, Campania region in southern Italy has been subject to the attention of media for the alleged wide-scale contamination of an area with an original agricultural vocation interested, nowadays, by the presence of high environmental impact industrial activities and uncontrolled waste dumping. Often dumped waste, specially tyres and other materials containing metals, are also illegally burned in the open countryside by criminal people to recover second raw material to resell. Due to this infamous practice, the territory, around the town of Acerra has been informally renamed as “Land of Fires”. Furthermore, Acerra together with the small towns of Marigliano and Nola represent the vertices of an ideal polygon defined by Senior and Mazza (2004) as the “Triangle of death”. According to these authors, the population living in the area, heavily exposed to toxic and carcinogenic substances, is, on the average, affected by a incidence rate of cancer and affine pathologies higher than the regional average. With the aim of defining the actual environmental conditions of the Acerrra area and its surroundings, a total of 121 topsoils samples were collected across the whole area to determine the concentrations of some potentially toxic elements (PTEs) (i.e. As, Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Se, Sn, Tl, V e Zn). In addition, further 33 soil samples were collected, at a lower sampling density, to determine concentrations of 16 among the most harmful compounds belonging to the family of polycyclic aromatic hydrocarbons (PAHs). Concentrations of PTEs and PAHs were compared with the guidelines established for residential lands by Italian Environmental Law (D.lgs. 152/2006) (IEL) and the first results showed that several elements (mainly Tl, Be, Sn and to a lesser extent V, Cu, Zn, Pb) and compounds (i.e. benzo(a)pyrene, benzo(ghi)perylene, indeno(123,cd)pyrene and benzo(b)fluoranthene) pose an hazard for exposed local population. Specifically, the north-eastern sector of the study area appears to be characterized by low hazard, while the area south of Acerra is associated with a significant environmental hazard since, on the average, more than 7 contaminants, among the ones considered, show values exceeding the guidelines values established by IEL. A relevant hazard is also recorded in correspondence with the urban centres of Acerra, Pomigliano, Brusciano and Marigliano, where an higher number of contaminants, including Cu, Pb, Zn, benzo(a)pyrene, benzo(ghi)perylene and indeno(123,cd)pyrene, exceed the relative guidelines. The so-called diagnostic ratios were used for the discrimination of the emission sources relating to PAHs. Results obtained show that, in almost the whole area, most of the compounds in soil derive from pyrogenic processes, that is formed when organic matter is exposed to high temperatures in anoxic conditions, rather than petrogenic processes. A Preliminary Quantitative Risk Assessment carried out using the total concentrations of PAHs, expressed as benzo(a)pyrene-equivalent concentrations, allowed to estimate the carcinogenic risk for the resident population deriving from the exposure to these compounds. Near urban centers (mainly Acerra), as regards children, the risk associated with an increase of cancer incidence resulted to be 2 in a million people, while for adults it resulted in 7 in a million: the admissible threshold for individual risk is normally set at 1 case in a million.