Critical analysis of the Brazilian legislation for agricultural use of sewage sludge to the assessment of quantitative microbiological risk

Abstract

This paper discusses, under the perspective of Quantitative Microbial Risk analysis (QMRA), the standards established in the Brazilian legislation for the agricultural use of biosolids. Two exposure scenarios were investigated for application of classes A and B biosolids: (i) consumer’s risk, arising from the consumption of leaf and root crops eaten raw; (ii) worker’s risk, arising from the involuntary ingestion of particles of biosolids and biosolids amended soil. The results suggest that higher risks were associated with occupational risk (worker’s risk) rather than consumer’s risk, and regarding the considered pathogens, with the transmission of virus, followed by helminths, protozoa, and bacteria. It is speculated that the current version of the Brazilian legislation may be too strict for Class A biosolids, regarding both the microbial standards and applications’ restrictions; moreover, just ‘banning’ the use of Class B biosolids may be too a stringent measure. It is also suggested that Class A helminth standard sounds too strict, but, on the other hand, Class B standard seems to be too lax. This work demonstrates the great potential of using QMRA for the assessment of risks related to agricultural use of biosolids. However, it is emphasized that better data on the occurrence and removal of pathogens in sewage sludge / biosolids, as well as about soil and crop contamination, are needed, so that more sound exposure scenarios, reflecting the Brazilian context, can be elaborated.