Elapsed Time Between Wastewater Irrigation, Harvesting, Marketing, Preparation, and Consumption of Vegetables and Fruits and Associated Public Health Risks in Selected Cities, Tanzania

Abstract

The reuse of wastewater treatment plant effluents for irrigation of vegetables and fruits is increasingly practiced in urban and peri-urban agriculture in Tanzania due to water scarcity and growing food demand. Concerns remain regarding microbial contamination and public health risks associated with the short time interval between irrigation, harvesting, marketing, preparation, and consumption of fresh produce. The study assessed the elapsed time between wastewater irrigation, harvesting, marketing, preparation, and consumption of vegetables and fruits and the associated public health implications among farmers and consumers in Mwanza, Dodoma, and Dar es Salaam cities. A community cross-sectional study was conducted among 400 participants comprising farmers and consumers between September 2025 and March 2026. Data were collected using structured questionnaires. Frequencies, percentages, means, medians, modes, standard deviations, relative risk, and p-values were computed. Statistical significance was set at p < 0.05. Among 400 participants, 147 (36.75%) were farmers using wastewater effluents for irrigation. Wastewater irrigation was significantly associated with exposure risk (RR = 2.14, p = 0.003). Irrigation occurred mainly two to three times per week, with an average frequency of 1.73 times per day (SD = 0.46). Most irrigation activities occurred between 6:00 am and 9:00 am, while harvesting occurred between 8:00 am and 11:30 am. Irrigation to harvesting was reported by 26.25%, compared with 12.25% after harvesting. The mean time required to sell produce was 2.55 hours (SD = 0.80). Farmers required an average of 15 minutes (SD = 4.35) to transport produce from farms to homes, while consumers required 9.17 minutes (SD = 7.97) from markets to homes. Most vegetables were consumed cooked (93.0%), whereas fruits were consumed raw (100%). Vegetable preparation averaged 18.77 minutes (SD = 3.88), fruit preparation 13.70 minutes (SD = 3.86), and vegetable cooking 12.92 minutes (SD = 4.15). Slightly cooked vegetables were preferred by 73.75% of participants. The short interval between wastewater irrigation, harvesting, marketing, and consumption creates conditions favourable to pathogen transmission, which may increase the risk of foodborne disease.