Characterization Of Human Exposure To Sewage Sludge In The Chain: Treatment, Agricultural Use And Consumption Of Vegetables

The aim of this study was to characterize human exposure to microbiological contamination (bacteria and viruses) via ingestion, considering the following scenarios: treatment of sludge (scenario 1); use of sludge as fertilizer (scenario 2) and consumption of vegetables fertilized with sludge (scenario 3). Exposure was characterized by the levels of Escherichia coli, cultivable enteric viruses (CEV) and somatic coliphages (SC) in the samples: sewage sludge under treatment (SST); handwashing water (HW) in treatment and planting; mix soil + sludge (MSL) and the vegetables lettuce and carrots. In scenario 1, SST samples presented < 10% humidity and class A pattern around 50-60 days; SC concentrations ranged from 9.1 x 10(2) to 1.9 x 10(5) PFU.g(-1) TS, and CEV ranged from 2.42 to 7.15 PFU.g(-1) TS. In scenario 2, CS were detected in 72% of HW samples, and concentrations ranged from 10 to 330 PFU.m C. E. coli concentrations <= 10(2) NMP.100 mL(-1) were detected in HW-treatment samples (63.7%). Viruses were not detected in 100% of HW-treatments samples, and 17.4% of HW-plantings had CEV concentrations between 3 and 4092 PFU.mL(-)(1) . All the vegetable samples were negative for SC and CEV. Considering the characteristics of the scenarios evaluated, sewage workers, rural workers and consumers of vegetables were exposed to low concentrations of E. coli and CEV. Somatic coliphages were resistant to heat treatment and planting, which supports their potential as indicators of CEV.