Sanitation by-products (i.e.
greywater, human urine and toilet compost) reuse for agriculture
presents an opportunity to enhance food security while overcoming water
scarcity and fertilizers issues in developing countries. However, the risks to
health from farmers and consumers’ exposure to pathogenic micro-organisms
persistent in sanitation by-products has hindered their popularity in these
regions. This study was conducted to apply a quantitative microbial risk
assessment to estimate the annual risk probability of Salmonella infection associated with these sanitation by-products
reuse for lettuce production and explore options for health risk reduction.
Risk was performed a Monte Carlo simulation
for farmers and consumers. The exposure routes were contaminated soil
ingestion, urine/greywater/compost ingestion and lettuce consumption without
washing. Results showed that the annual infection risks of Salmonella through ingestion contaminated soil associated with
urine and compost were typical scenario: 9.04 × per-person-per-year (pppy) and 2.97 × pppy, respectively, are higher than the WHO
benchmark (≤1.0 × pppy). Conversely, those contaminated from greywater were 6.83 × pppy are meet
the WHO benchmark. On the other hand, annual risks through lettuce
consumption fertilized with urine (1.20 × pppy) were less than
the risks from compost (6.20 × pppy) and greywater (7.76 × pppy). Moreover, the annual risks of infection from greywater ingestion (1.77 × pppy) exhibits a much higher risk than that urine ingestion (6.20 × pppy)
approximately two orders of magnitude, and which are higher than the WHO
tolerable limit of risk. The risk assessment outcomes of using sanitation by-products to lettuce production should be
promoted with proper awareness of the risk by farmers and consumers.