The Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO) recently published a report examining the food safety risks of chemical contamination of water used in agri-food systems.

The report underlines that, as water systems face unprecedented pressure from climate change and increased demand driven by population growth, the reliance on alternative water sources for agricultural use is rising—sometimes leading to the use of water of lower or unknown quality. These water sources can contain a range of contaminants that pose a food safety risk, including chemicals; however, these waterborne chemical contaminants have yet to be comprehensively considered as a food safety risk.

To address knowledge gaps, FAO/WHO conducted a risk prioritization exercise to identify and qualitatively assess key chemical hazards in water of relevance for food safety, including 1) collection of data on reported chemical hazards in water sources, 2) qualitatively assessing reported chemicals for uptake into foods, and 3) collecting data on reported exposures to chemicals from waterborne sources.

Chemical contaminants can enter water sources through various routes, including natural geological and biological processes, persistent organic pollutants (POPs), agricultural and industrial activity, wastewater and stormwater, and water infrastructure or treatment sources.

The exercise identified several chemicals and chemical groups as “high-priority” based on reported dietary exposures resulting from agrifood water sources exceeding health-based guidance values (HBGVs):

• Anatoxin-a and analogues (assessed as anatoxin-a)
• Arsenic
• Cadmium
• Cylindrospermopsins (assessed as cylindrospermopsin)
• Fluoride
• Lead
• Microcystins and nodularins (assessed as microcystin-LR)
• Perfluorooctanoic acid (PFOA), a type of per- and polyfluoroalkyl substance (PFAS)
• Perfluorooctane sulfonic acid (PFOS), a PFAS
• Radium
• Saxitoxins (assessed as saxitoxin)
• Thallium.

A further 11 chemicals/groups were identified as “medium-priority” for dietary exposures from waterborne sources approaching HBGVs: Carbamazepine, chlorate, cobalt, lithium, mercury, nickel, polychlorinated dibenzo-p-dioxins/furans (PCDD/F) and dioxin-like polychlorinated biphenyls (DL-PCBs), perchlorate, (Di(2-ethylhexyl) phthalate (DEHP), selenium, and uranium.

Finally, 29 chemicals with a likelihood of entering the food chain from agri-food water sources were rated as “low-priority” for food safety, including, but not limited to: aluminum, N,N-diethyl-meta-toluamide (DEET), nitrate, organochlorine pesticides, organophosphorus flame retardants, polycyclic aromatic hydrocarbons (PAHs), the PFAS type perfluorohexanoic acid (PFHxA), diisononyl phthalate (DINP), tetracyclines, triazine herbicides, and disinfection byproducts from sanitizers.

The report emphasizes that many chemical contaminants in agrifood water sources lack food safety risk management guidelines—a gap that needs urgent attention.

Additionally, emerging issues and developing technologies are affecting water use and recycling, raising food safety concerns and driving the need for ongoing risk assessment. Such issues include:

• Climate change
• Advances in chemistry
• Alternative water sources
• New food production systems
• Chemical mixtures
• Antimicrobial resistance (AMR).

To identify and manage waterborne chemical contaminants as food safety risks requires improving and standardizing the assessment of dietary exposure from waterborne contaminants. The report calls for a “One Health” approach to risk management, considering the interdependencies of contaminant occurrence in water with water scarcity, food security, animal, crop, environmental, and human health.