Food Protection Trends - May/June 2022 - 187

safety (21). In 2015, the FDA finalized the Food Safety
Modernization Act (FSMA) Produce Safety Rule (PSR),
outlining science-based practices to reduce the prevalence
and transmission of pathogens to produce, including through
agricultural water (9).
The FSMA PSR highlights information on contamination
routes and best practices to minimize risks of contamination.
One of the routes focuses on agricultural water quality
and highlights the needs for testing water and establishing
a microbial water-quality profile (MWQP) (38). This
profile is developed using generic Escherichia coli as an
indicator organism for fecal contamination, with a testing
frequency dependent on the inherent risks associated with
the agricultural water source (38). There are three primary
water source types associated with produce operations:
public water supplies, groundwater, and surface water. Public
(municipal) water supplies assume the lowest risk of microbial
contamination, because the water is treated and its microbial
quality is regularly monitored by a utility entity; however,
this source may be cost prohibitive for large operations that
consume a great amount of water (45). Groundwater (e.g.,
well water) is considered a moderate risk with the potential for
microbial contamination events because of poor aquifer quality
and/or well structural integrity. Although more convenient
to access and use (12), surface water (e.g., ponds, rivers,
creeks, and rainwater catchment systems) are considered
the highest risk, because growers are generally unable to
completely isolate surface water sources from external sources
of microbial pollution (i.e., contaminated soil and wild animal
and/or livestock feces). Besides the water source, factors
such as proximal livestock density (15, 19), climate (22, 28),
and frequency of water treatments (e.g., chlorine shock and
filtration) (3, 40) can affect microbial water quality.
The PSR states that all agricultural water must be " safe
and of adequate sanitary quality for its intended use " (21
CFR 112.43) (38). Based on a rolling 4-year dataset of E. coli
test results, an agricultural water source used for preharvest
operations (i.e., irrigation and fertigation) must have a
geometric mean (GM) of less than 126 CFU of E. coli per
100 mL of water and a statistical threshold value (STV) of
410 CFU or less of generic E. coli per 100 mL of water. Both
mathematical values are important when building a MWQP,
because the GM provides information on the average amount
of generic E. coli in the water source and the STV captures
the variation in E. coli levels during the year-potentially as
a result of adverse events (i.e., rainfall). Water sources used
for postharvest purposes (i.e., rinsing produce or washing
hands) must contain no detectable E. coli per 100 mL of water
(38). Moreover, untreated surface water is not permitted for
postharvest use. Although the FDA extended the compliance
dates of the PSR agricultural water testing requirements to
facilitate grower adherence to the rule, studies indicate that
agricultural water remains one of the least understood topics
of the FSMA PSR in midwestern states (5, 25, 26, 29). To the
authors' knowledge, the microbial safety of agricultural waters
in these states has rarely been studied, with the exception of
Iowa (2). Bhullar et al. (2) reported few contamination events
for groundwater sources in Iowa; however, contamination of
agricultural surface waters with generic E. coli was prevalent in
Iowa, with some surface water samples exceeding the FDA's
maximum allowed GM thresholds.
Each year, Kansas and Missouri growers produce approximately
$26 million (17) and $81 million (6) of fruits and
vegetables, respectively, with recent notable increases in the
production of specialty crops. For example, berry production
increased dramatically in Kansas, with the number of
blueberry farms increasing by 269%, blueberry acres increasing
by 250%, blackberry farms increasing by 112%, and blackberry
acres increasing by 260% from 2007 to 2017 (23). Thenumber
of Kansas farms producing tree fruit also increased by 46%
from 2007 to 2017 (23). To support the outputs of this growing
industry, the purpose of this study is to understand the
microbial quality of agricultural waters used by growers in
Kansas and Missouri and identify opportunities for extension
education and outreach. The objectives of this study are thus
to (1) evaluate and (2) compare the prevalence of microbial
contamination in agricultural water sources on Kansas and
Missouri farms.
MATERIALS AND METHODS
Sample collection and submission
From 2018 to 2020, individual growers, extension educators,
or trained laboratory personnel collected water samples from agricultural
water sources on Kansas and Missouri produce-growing
operations (Figure 1), following shared instructions prepared
by the Kansas State University (KSU)/University of Missouri
Extension produce safety team (see supplemental documentation).
The water samples were collected in 100-mL sample
containers with added sodium thiosulfate (IDEXX Laboratories,
Westbrook, ME), to reduce the effect of residual chlorine
on E. coli stability during transit, and then mailed overnight or
submitted in person in a refrigerated cooler box with ice to a
microbial water-quality testing laboratory for analysis according
to their state of residence. Kansas growers submitted water
samples to the Food Safety Laboratory at KSU in either Olathe
or Manhattan, whereas Missouri growers submitted the samples
to the KSU lab in Olathe or the Missouri State Public Health
Laboratory (MSPHL). The samples were accompanied by a
submission form specific to the laboratory to provide information
on water sources (see supplemental documentation). Water
samples were received from various locations in eastern Kansas
and throughout Missouri, as shown in Figure 1. Because these
labs provide microbial water testing services free of charge to
produce growers through grant funding, multiple entries from
the same grower may have occurred throughout each year. In
addition, it was unknown whether the operations that submitted
samples for analysis treated their agricultural water before use in
production or postharvest activities.
May/June Food Protection Trends 187
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