Closing the loop: Emerging contaminants in agricultural environments (CLEA)

Water scarcity and the depletion of global phosphorus and potassium reserves within 100 years pose two of the largest threats to meeting the future food demands of a growing population. In response to this challenge, many countries have adopted a circular approach to agriculture which involves the use of sanitation to meet agricultural nutrient and irrigation demands. The reuse of resources such as treated wastewater and sludges is now a common practice in many countries, especially in arid and semi-arid areas where agricultural production is reliant on limited freshwater supplies. However, emerging contaminants can pass through wastewater treatment plants and contaminate the wastewater and sludges providing a pathway for these chemicals to inadvertently enter the environment. Furthermore, in rural areas and in countries with limited wastewater infrastructure, wastewater is commonly used as a source of irrigation following little- to no treatment prior to reuse. This is of particular concern as untreated wastewater typically contains higher loads of emerging contaminants such as pharmaceuticals and personal care products. Our previous work has demonstrated that pharmaceuticals can persist in soils with the potential to be taken up and accumulate in plants, which presents a risk to ecosystem and human health. Pharmaceuticals are biologically active chemicals and their presence in agricultural systems could result in undesired toxic effects for plant, soil and human health. Our scientific understanding of human health risks following the consumption of contaminated produce is particularly scarce and largely based on acceptable daily intake calculations which neglect to account for potential effects on a biological level, including the development of antimicrobial resistance. The proposed programme of research for the second phase of the Fellowship aims to fill these knowledge gaps by uniting scientific expertise to reveal fundamental biological insights with respect to ecosystem and human health impacts following wastewater reuse, with a particular focus on exposure scenarios with minimal wastewater infrastructure. The specific objectives will: Quantify ECs in partially treated wastewater used for irrigation, soil, and crops 2. Elucidate the composition and function of microbial communities in water, soil, and crops 3. Assess the presence and diversity of antibiotic resistance genes (ARGs) and their carriers 4. Characterise and model a baseline human health exposure scenario, and evaluate potential impacts on the gut microbiome following the consumption of contaminated crops Delivery of the objectives will be achieved using a combination of modelling, lab experiments and a spatio-temporal field monitoring campaign. Specifically, an established wastewater irrigation system in Mexico will be used as a basis to elucidate the contribution of partially treated wastewater to contaminant loads in agricultural systems. Mexico is a major consumer of human use chemicals such as pharmaceuticals, and faces severe contaminant-linked challenges due to inadequate wastewater treatment. There is an urgent need to establish the global risks of emerging contaminants such as pharmaceuticals in agricultural systems where wastewater is likely to be used without prior treatment. Outputs of this research will provide effective evidence for use by non-academic end users (e.g. environmental regulators, water industry, agricultural sector), guiding wastewater reuse policies to ensure the potential risks from contaminants are mitigated for whilst maximising sustainable reuse.