Exposure Factors for Wastewater‐Irrigated Asian Vegetables and a Probabilistic Rotavirus Disease Burden Model for Their Consumption

Abstract

Many farmers in water-scarce regions of developing countries use wastewater to irrigate vegetables and other agricultural crops, a practice that may expand with climate change. There is a number of health risks associated with wastewater irrigation for human food crops, particularly with surface irrigation techniques common in the developing world. The World Health Organization recommends using quantitative microbial risk assessment (QMRA) to determine if the irrigation scheme meets health standards. However, only a few vegetables have been studied for wastewater risk and little information is known about the disease burden of wastewater-irrigated vegetable consumption in China. To bridge this knowledge gap, an experiment was conducted to determine volume of water left on Asian vegetables and lettuce after irrigation. One hundred samples each of Chinese chard (Brassica rapa var. chinensis), Chinese broccoli (Brassica oleracea var. alboglabra), Chinese flowering cabbage (Brassica rapa var. parachinensis), and lettuce (Lactuca sativa) were harvested after overhead sprinkler irrigation. Chinese broccoli and flowering cabbage were found to capture the most water and lettuce the least. QMRAs were then constructed to estimate rotavirus disease burden from consumption of wastewater-irrigated Asian vegetables in Beijing. Results indicate that estimated risks from these reuse scenarios exceed WHO guideline thresholds for acceptable disease burden for wastewater use, signifying that reduction of pathogen concentration or stricter risk management is necessary for safe reuse. Considering the widespread practice of wastewater irrigation for food production, particularly in developing countries, incorporation of water retention factors in QMRAs can reduce uncertainty regarding health risks for consumers worldwide.

Microbial contamination along the main open wastewater and storm water channel of Hanoi, Vietnam, and potential health risks for urban farmers

“…However, other studies reported that the use of wastewater from Nhue River was significantly associated with helminth and intestinal protozoa infections as well as self-reported diarrhoea (Pham-Duc et al, 2013. In order to better understand the risk of the specific causative agents, a context-specific QMRA is required (Mok and Hamilton, 2014). For example, as shown by Pham-Duc (2012), the estimated risk of diarrhoeal diseases due to the exposure to wastewater reused for rural agriculture across communities in Hanam was 100-fold greater than the acceptable risks (Pham-Duc, 2012).…”

Treated Greywater Reuse for Hydroponic Lettuce Production in a Green Wall System: Quantitative Health Risk Assessment

“…For example, a rotavirus infection estimation from consuming crops that have been irrigated with effluents from stabilization ponds was 10 −3 and 10 −4 [45], and the median annual probability of infection from the consumption of vegetables that have been irrigated with wastewater using an overhead sprinkler also ranged from 10 −3 to 10 −4 per year [46]. The daily probability of illness from eating raw unwashed vegetables irrigated with untreated wastewater the Bogotá river receives from the city and towns ranged between 0.62 and 0.85 [47].…”

Wastewater Reuse in Agriculture: A Review about Its Limitations and Benefits

“…Hamilton and Mok [156] conducted an experiment to determine the volume of water collected in Asian vegetables and lettuce after irrigation by sprinkling with wastewater. The proposed objective contributed to the decrease in the knowledge gap, associated with the estimation of rotavirus microbiological risk in high consumption products in China.…”