Foodborne illness from contaminated agricultural water is a significant problem. Although Congress has directed the U.S. Food and Drug Administration (FDA) to specifically address this problem, the agency has struggled to find sufficient scientific basis to justify specific agricultural water quality standards. Administrative law decisions issued by the U.S. Supreme Court this summer are likely to make matters worse. We need innovative regulatory approaches that reduce harm in the short term while providing the scientific evidence needed for long-term solutions.

Recurrent outbreaks of foodborne illness have alerted federal authorities to the presence of harmful microbial pathogens in irrigation water used to grow fresh fruits and vegetables. The problem has become so severe that contaminated fruits and vegetables are now the leading cause of foodborne illness in the United States. By one estimate, contaminated leafy greens alone cause 2.3 million acute illnesses annually, representing an annual economic loss of $5.2 billion.

Because using potable water to irrigate crops would be prohibitively expensive, farmers are forced to source water from rivers, canals and wells – all of which are vulnerable to potential contamination from wildlife and livestock. Investigations into several high-profile disease outbreaks in leafy vegetables have identified the leakage of manure from nearby livestock farms into irrigation canals as one of the sources of contamination.

The problem is not new. As early as 1997, industry guidelines identified microbial contamination of farm water from livestock as a significant threat to human health. After decades of lobbying by consumer groups demanding a federal regulatory response, the Food Safety Modernization Act signed by President Barack Obama in 2011 required the FDA to set “science-based minimum standards” for farm water quality within two and a half years. But the agency has struggled to meet that requirement.

From the beginning, FDA searched in vain for a scientific basis to justify minimum quantitative standards. After the statutory deadline passed, the agency was successfully sued by consumer protection groups and finally published a “Product Safety Rule” in November 2015. The rule included plans to phase in quantitative agricultural water quality limits and testing requirements between 2019 and 2021, depending on the size of the operation. In 2019, the agency delayed initial enforcement of the rule until 2022. Then, in 2021, the agency proposed replacing its quantitative water quality limits and testing requirements with qualitative assessments of agricultural water quality before harvest. Last month, FDA published a revised final rule on agricultural water.

The new rule does not prescribe minimum water quality standards. Instead, farmers must conduct annual assessments to identify any conditions that are “reasonably likely to create known or reasonably foreseeable hazards.” They must also “determine whether measures are necessary to reduce the potential for contamination” and ensure that farm water is “safe and of adequate quality for its intended use.”

The rules draw farmers’ attention to factors that can affect the microbial quality of agricultural water – such as the location and type of water source, the method of application, the characteristics of the crops and climatic conditions. If farmers find that their agricultural water “is not safe or does not have sufficient hygienic quality for the intended use”, they must “make the necessary changes and take appropriate measures to determine whether the changes have been effective”.

Throughout the process, the FDA has been caught in a bind. On the one hand, federal law requires the agency to set science-based minimum standards for agricultural water. When it initially failed to do so, the agency was forced to comply by court order. On the other hand, experts agree that there is no scientific evidence to support specific quantitative limits for agricultural water quality. Scientists have yet to develop reliable methods to measure the microbial quality of agricultural water or to estimate rates of pathogen transmission from water to crops and the resulting pathogen exposure of consumers. In addition, scientists lack dose-response data that would allow regulators to calculate safe exposure limits for pathogens.

Although there is solid and growing scientific evidence that microbial contamination of agricultural water poses a threat to human health, this scientific evidence is insufficient to reliably quantify the impact of different water quality levels on the occurrence of foodborne illnesses. Faced with an insoluble dilemma, the agency has opted for a rule that simply highlights potential sources of contamination and calls on producers to exercise due diligence.

What else can be done?

Going forward, regulators should prioritize verifiable mitigation measures that provide new policy-relevant information that could ultimately lead to more precise agricultural water quality standards. For example, recent advances in public health surveillance and outbreak investigations have enabled regulators to detect outbreaks more quickly. By alerting consumers and removing contaminated products from store shelves earlier in the course of an outbreak, these advances have reduced the number of casualties per outbreak. At the same time, better surveillance and investigation are generating data that may one day allow regulators to link specific food safety precautions on farms to quantifiable public health benefits.

In addition, regulators should also look beyond the farm for solutions. Food processors, for example, can perform post-harvest sanitation to kill pathogens. Although the current practice of washing with chlorinated water has proven inadequate to disinfect contaminated produce, technological innovations using radiation, ozone, ultraviolet and blue light, and cold plasma could eventually provide a post-harvest killing step in the production process that allows for cost-effective neutralization of pathogens.

Regulators should also consider strategies aimed at preventing contamination of agricultural waters by livestock operations in the first place. Recent field trials have shown that vaccinating herds dramatically reduces the number of cattle shedding pathogens. Escherichia coli and the bacterial concentration in the stool of those who do. Other studies have shown that supplementing the diet with probiotics or various foods – such as orange peel, cottonseed and seaweed – also reduces pathogen shedding.

Implementing these measures will not be easy. Public health surveillance and outbreak investigations are expensive, and there is no indication that Congress is currently willing to allocate large amounts of money to food safety funding. Innovative technologies must be adopted by industry and consumers, which takes time. Measures for cattle production may be the most difficult. The cattle and dairy industries are not enthusiastic about additional regulations. They have successfully lobbied against legislation that would allow the FDA to test for pathogens during farm inspections, and industry lawyers have successfully brought legal challenges to attempts to tighten existing regulations on manure discharges into waterways.

Finally, the conservative two-thirds majority of the US Supreme Court has issued a number of opinions on administrative law – including the recently decided cases of Loper Bright Enterprises v. Raimondo And Ohio v. EPA— that give agency officials less discretion in making policy and empower federal courts to question the adequacy of the scientific analyses of agency experts. These decisions threaten to hamper FDA officials’ efforts to fulfill their statutory mandate to implement quantitative, science-based standards for agricultural water quality.

Unfortunately, agricultural wastewater contamination is expected to continue to pose a major challenge for regulators for the foreseeable future and will remain a persistent cause of foodborne illness.

Timothy D. Lytton is Regents’ Professor and Professor of Law at Georgia State University College of Law.