Complex Interactions Between Weather, and Microbial and Physicochemical Water Quality Impact the Likelihood of Detecting Foodborne Pathogens in Agricultural Water.

Agricultural water is an important source of foodborne pathogens on produce farms. Managing water-associated risks does not lend itself to one-size-fits-all approaches due to the heterogeneous nature of freshwater environments. To improve our ability to develop location-specific risk management practices, a study was conducted in two produce-growing regions to (i) characterize the relationship between Escherichia coli levels and pathogen presence in agricultural water, and (ii) identify environmental factors associated with pathogen detection. Three AZ and six NY waterways were sampled longitudinally using 10-L grab samples (GS) and 24-h Moore swabs (MS). Regression showed that the likelihood of Salmonella detection (Odds Ratio [OR] = 2.18), and eaeA-stx codetection (OR = 6.49) was significantly greater for MS compared to GS, while the likelihood of detecting L. monocytogenes was not. Regression also showed that eaeA-stx codetection in AZ (OR = 50.2) and NY (OR = 18.4), and Salmonella detection in AZ (OR = 4.4) were significantly associated with E. coli levels, while Salmonella detection in NY was not. Random forest analysis indicated that interactions between environmental factors (e.g., rainfall, temperature, turbidity) (i) were associated with likelihood of pathogen detection and (ii) mediated the relationship between E. coli levels and likelihood of pathogen detection. Our findings suggest that (i) environmental heterogeneity, including interactions between factors, affects microbial water quality, and (ii) E. coli levels alone may not be a suitable indicator of food safety risks. Instead, targeted methods that utilize environmental and microbial data (e.g., models that use turbidity and E. coli levels to predict when there is a high or low risk of surface water being contaminated by pathogens) are needed to assess and mitigate the food safety risks associated with preharvest water use. By identifying environmental factors associated with an increased likelihood of detecting pathogens in agricultural water, this study provides information that (i) can be used to assess when pathogen contamination of agricultural water is likely to occur, and (ii) facilitate development of targeted interventions for individual water sources, providing an alternative to existing one-size-fits-all approaches.

Review of water quality criteria for water reuse and risk-based implications for irrigated produce under the FDA Food Safety Modernization Act, produce safety rule.

Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria - including surface water, groundwater recreational water, and water reuse - in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.

U.S. farmers' opinions on the use of nontraditional water sources for agricultural activities.

Water is a key resource for agricultural production in the United States. Due to projected changes in water availability across the country, long-term sustainability of agricultural production may rely on finding alternatives to traditional water sources. The aim of this study was to assess farmers' opinions on the use of nontraditional water sources (e.g., agricultural runoff, treated wastewater, recycled water, produced water, untreated surface water, and brackish surface and groundwater) for agricultural activities. A survey was distributed to farmers (n = 746) in the Mid-Atlantic and Southwest regions of the United States (U.S.) about water availability and nontraditional irrigation water perceptions. Chi-square, Fisher's exact tests, f-tests, and multinomial and ordinal logistic regression analyses were conducted. Of farmers surveyed, 80% (431/543) considered the use of nontraditional water sources to be at least moderately important and 61% (444/727) would use nontraditional water if given the option. Each of the following factors individually increased the likelihood that a farmer considered nontraditional water very important for agriculture: Farmers who lived in the Southwest region compared to the Mid-Atlantic, farmers who were concerned about water availability compared with those who were not, farmers with a graduate or professional degree compared to those with less education, farmers with access to nontraditional water, and farmers with some knowledge of nontraditional water compared to those with no reported knowledge. Concern about water availability and knowledge of nontraditional water sources were significantly associated with willingness to use these water sources (p < 0.001 for both). Water quality, food safety and health risks were the main concerns regarding nontraditional water use across both regions. Willingness to use nontraditional water increased significantly if the water quality was proven to be as good or better than farmers' current water sources (63% vs. 84%; p < 0.001). Projects focused on nontraditional water use in agriculture should be regionally tailored as our data found significant differences between farmers in two distinct U.S. regions.

Modified Coring Tool Designs Reduce Iceberg Lettuce Cross-Contamination.

Contaminated coring tools may transfer bacteria to iceberg lettuce. The efficiency of coring tool design modifications in reducing bacterial transfer to lettuce heads was evaluated under simulated field operations. The standard coring tool consists of a stainless steel cylindrical tube welded to a tab that is inserted into a plastic handle. Design modifications included removal of the welded portion, incorporation of a shorter front straight bottom edge, or an angled bottom edge toward the front. In the first study, coring tools of four different designs were inoculated by dipping in a tryptic soy broth (TSB) suspension that contained 8.85 Log CFU/mL of Escherichia coli K-12 and then were used to core 100 lettuce heads, consecutively. Use of the standard tool resulted in 91% ± 9% positive lettuce heads. Removing the welded surface from the standard tool resulted in the highest reduction of E. coli transfer (44% ± 11.9% positive lettuce heads, P < 0.05), whereas incorporation of a short front straight edge with no welding resulted in 65.6% ± 5.6% of the cored lettuce heads being positive for E. coli. Removal of the welded surface resulted in a 40% decrease in E. coli contamination among the last 20 cored lettuce heads (81 to 100), which indicates that coring tool design modifications resulted in reduced cross-contamination. In the second study, the transfer of Salmonella to coring tools after their immersion in rinsing solutions was evaluated using imaging. The tools were dip inoculated for 2 min in water, water with lettuce extract, or TSB containing 7 Log CFU/mL bioluminescent Salmonella Newport; they were then imaged to observe spatial distribution of bacteria. There was greater retention and spatial distribution of Salmonella on the surface of tools immersed in water containing lettuce extract than in TSB and water. The results of the second study indicate that rinsing solutions that contain lettuce particulate and organic load could facilitate cross-contamination of Salmonella Newport to tool surfaces.

Understanding grower perceptions and attitudes on the use of nontraditional water sources, including reclaimed or recycled water, in the semi-arid Southwest United States.

The use of nontraditional water sources, including reclaimed or recycled water, has become a desirable option to meet increasing demands in water stressed regions. In the Southwest United States, utilization of alternative water sources is becoming increasingly common, including use for landscape irrigation, environmental enhancement, cooling and power generation, potable reuse, and as a source water for agricultural irrigation. While much research has gone into identifying public perception towards water reuse schemes, little attention has been given to understanding grower attitudes, perceptions, and knowledge on the use of nontraditional water, including reclaimed water, in agriculture and how that may influence grower acceptance and production practices. This unique study utilized a needs assessment survey of growers (n = 521) within the Southwest region of the United States to gain an understanding of industry attitudes and needs regarding nontraditional water in agriculture. Results indicate that the majority of survey respondents were concerned with water availability (67.49%) yet less than half (48.30%) thought using a nontraditional water source in agriculture was 'very important'. Interestingly, respondents rated irrigation of 'food crops' third (42.20%) among agricultural activities for which they would be willing to use nontraditional water sources, behind irrigation of forage crops (61.60%) and dust control (61.60%). The importance of the use of nontraditional water sources in agriculture was influenced mostly by farm size (p = 0.007) and primary water source (p = 0.016), and the level of education was significant in respondent's level of concern over water availability (p = 0.021). Information on the quality of nontraditional water sources, showing that it is as good or better than respondents current sources, was found to shift rejection and uncertainty towards acceptance by 16.04%. The results of this study provide insight into perceived risks, willingness to use, drivers and constraints to grower adoption, and preferred methods of education regarding water reuse in agriculture. These findings can be used by water managers and planners to aid in the adoption of nontraditional waters, including reclaimed or recycled water, in agriculture thus extending water resources, securing food supplies, and protecting public health.