Sewage sludge does not induce genotoxicity and carcinogenesis

Abstract

Through a series of experiments, the genotoxic/mutagenic and carcinogenic potential of sewage sludge was assessed. Male Wistar rats were randomly assigned to four groups: Group 1 - negative control; Group 2 - liver carcinogenesis initiated by diethylnitrosamine (DEN; 200 mg/kg i.p.); Group 3 and G4-liver carcinogenesis initiated by DEN and fed 10,000 ppm or 50,000 ppm of sewage sludge. The animals were submitted to a 70% partial hepatectomy at the 3rd week. Livers were processed for routine histological analysis and immunohistochemistry, in order to detect glutathione S-transferase positive altered hepatocyte foci (GST-P+ AHF). Peripheral blood samples for the comet assay were obtained from the periorbital plexus immediately prior to sacrificing. Polychromatic erythrocytes (PCEs) were analyzed in femoral bone-marrow smears, and the frequencies of those micronucleated (MNPCEs) registered. There was no sewage-sludge-induced increase in frequency of either DNA damage in peripheral blood leucocytes, or MNPCEs in the femoral bone marrow. Also, there was no increase in the levels of DNA damage, in the frequency of MNPCEs, and in the development of GST-P AHF when compared with the respective control group.

Real scale environmental monitoring of zoonotic protozoa and helminth eggs in biosolid samples in Brazil

“…In Brazil, sewage networks and WWTP construction have expanded in recent years according to Brazilian Institute of Geography, to overcome a historical deficiency in this sector but, despite this growing, among the most important environmental problems are the generation and disposal of sewage sludge, main residue of the treatment (Heller 2007;Silva et al 2012).…”

“…Also, the application in agricultural soils can be geochemically sustainable method to eliminate the disposal problem in urban areas (Silva et al 2012). In 2006 and again in 2011, CONAMA (National Environmental Council) issued a legal norm (430/2011) that set limits on the presence of helminth eggs, Salmonella, fecal coliform and viruses in biosolid used for agricultural purposes.…”

“…With the population increase and urbanization, biosolid production also has increased and the application of this residue to soil for fertilization purpose represents the best option for disposal as this is rich in nutrients (Guadagnini et al 2013;Hachich et al 2013;Lima et al 2012;Lu et al 2012;Silva et al 2012). However, inherent in its use in agriculture are concerns about its effects on public health due to uncertainties surrounding the presence of enteric parasites, which can be sources of contamination in both food and surface water and groundwater; the low infective dose of certain pathogens, especially Cryptosporidium and Giardia; the possible growth of pathogenic bacteria, such as coliforms, which are used as indicators of safety but do not predict the presence of other pathogens (Abreu-Acosta and Vera 2011); and the potential for diseases caused by unknown agents (Santamaria andToranzos 2003, Sidhu andToze 2009).…”