Quantitative microbial risk assessment of occupational and public risks associated with bioaerosols generated during the application of dairy cattle wastewater as biofertilizer

• Published in: The Science of the total environment 2020-11, Vol.745, p.140711-140711, Article 140711
• Main Authors: de Matos Nascimento, Andressa, de Paula, Vanessa Romário, Dias, Edgard Henrique Oliveira, da Costa Carneiro, Jailton, Otenio, Marcelo Henrique
• Format: Article
• Language: English
• Subjects: Aerosolization of pathogens; Atmospheric dispersion; Fertigation; Risk assessment
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.140711

The reuse or recycling of wastewater provides environmental and economic benefits, representing a sustainable and circular alternative for the management of liquid waste. However, the application of effluents to agricultural crops via spraying creates a potentially dangerous situation for individuals exposed to airborne pathogens. This study used Quantitative Microbial Risk Assessment (QMRA) tools to quantitatively assess the microbial risks of occupational and public exposures to bioaerosols in fertigation scenarios by spraying untreated and treated dairy cattle wastewater. Analyses of Escherichia coli (EC) and spores of Clostridium perfringens (CpSP) in raw and treated effluents as well as pathogen / indicator ratios from the literature were used to estimate the concentrations of Escherichia coli O157:H7 (EC O157:H7) and Cryptospodirium spp. (Crypto) in the air, and the results were applied to an atmospheric microbiological dispersion model. From the concentrations of pathogens in the air, infectious risks for downwind receptors were calculated. The risks of infection by EC O157:H7 to workers at 10 m and 50 m away from the emission source ranged between 3.81 × 10 1 and 2.68 × 10 3 pppy (per person per year), whereas to residents at 100 m and 500 m ranged from 4.59 × 10 1 to 1.51 × 10 4 pppy. Peak values (95th percentile) of occupational and public risks associated with the exposure to Crypto were 3.41 × 10 3 and 6.84 × 10 4 pppy at 10 m and 50 m from the source, respectively, and were lower than 1.48 × 10 6 pppy regarding exposures to CpSP. Anaerobic digestion reduced risks by approximately one order of magnitude. The distance from the source was inversely proportional to the risk of exposure. It is recommended that wastewater is treated prior to its reuse and the adoption of application methods with low aerosolization potential. In addition, the need for workers to use personal protective equipment (PPE) is highlighted. [Display omitted] •Risks linked to bioaerosols from dairy cattle wastewater applied as biofertilizer.•QMRA models considered E. coli O157:H7, C. perfringens and Cryptospodirium spp.•Anaerobic digestion reduced occupational and public risks by one order of magnitude.•Use of personal protective equipment (PPE) is needed to reduce occupational risks.•Public risks were inversely proportional to distance of houses from the source.