Outbreak Linked to Spinach Forces Reassessment of
Food Safety Practices
Producers and Government
agencies seek science-based practices to reduce
risk at the minimum cost
Linda Calvin
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While
the risk of contracting a foodborne
illness from eating spinach is low,
spinach and leafy greens have been associated
with numerous outbreaks due to contamination
with E. coli O157:H7. |
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Many
growers have adopted voluntary Food
and Drug Administration guidelines (Good
Agricultural Practices) to reduce the
risk of microbial contamination.
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The
foodborne illness outbreak linked to
spinach forced the California spinach
and the broader leafy green industry
to consider new approaches to food safety.
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This
article is drawn from . . . |
Background
Information and Statistics: Fresh-market Spinach
|
You
may also be interested in . . . |
The
Economics of Food Safety: The Case of Green
Onions and Hepatitis A Outbreaks,
by Linda Calvin, Belem Avendaño, and
Rita Schwentesius, VGS-305-01, USDA, Economic
Research Service, December 2004.
Traceability
in the U.S. Food Supply: Economic Theory and
Industry Studies, by Elise Golan,
Barry Krissoff, Fred Kuchler, Linda Calvin,
Kenneth Nelson, and Gregory Price, AER-830,
USDA, Economic Research Service, March 2004.
“Produce,
Food Safety, and International Trade: Response
to U.S. Foodborne Illness Outbreaks Associated
with Imported Produce,” by Linda
Calvin, in International Trade and Food
Safety: Economic Theory and Case Studies,
edited by Jean Buzby, AER-828, USDA, Economic
Research Service, November 2003.
The ERS Briefing Rooms on:
Traceability
in the U.S. Food Supply
Vegetables
and Melons
Industry
Food Safety Actions |
On September 14, 2006, the U.S.
Food and Drug Administration (FDA) announced that
consumers should not eat bagged spinach because
of an outbreak of illness due to contamination with
the potentially deadly bacterium Escherichia
coli O157:H7. Stores and restaurants immediately
cleared bagged spinach from their shelves and menus.
Spinach harvesting and marketing ceased. There were
no U.S. fresh spinach sales for 5 days, before FDA
announced spinach from some areas was safe to consume.
Spinach from the main production area of California
was off the market for an additional 10 days.
By the time the outbreak was over,
204 people had become ill across 26 States and Canada,
104 had been hospitalized, 31 had developed the
serious complication of hemolytic-uremic syndrome
(HUS), and 3 had died (see box, “Escherichia
coli O157:H7”).
The Risk of Illness From
Spinach Is Low
While spinach and other leafy
greens have been associated with numerous foodborne
illness outbreaks, the risk of becoming ill from
spinach is low. In 2005, U.S. consumers ate 680
million pounds of fresh spinach, and the load of
contaminated spinach associated with the outbreak
totaled only 1,002 pounds. But leafy greens are
the most likely produce category to be associated
with an outbreak. Since 1996, leafy greens have
accounted for 34 percent of all outbreaks due to
microbial contamination traced back to a specific
fruit or vegetable, 10 percent of illnesses, and
33 percent of the deaths. Twenty of the 24 leafy
green outbreaks in the United States since 1996
have been associated with E. coli O157:H7
contamination. But none of the previous outbreaks
had the number of illnesses and deaths, publicity,
market impact, or industry response of the 2006
outbreak associated with spinach. Only two outbreaks
were associated with spinach, but they accounted
for all five deaths associated with leafy greens
over this period.
Many factors could influence the
number of outbreaks traced to produce, but two are
particularly relevant to spinach. First, consumption
of produce has increased, as has the share consumed
fresh. U.S. consumers are eating more spinach, up
90 percent since 1992, and eating more fresh—the
most risky form for microbial contamination. In
2005, the average consumer ate 2.4 pounds of fresh
spinach, up 180 percent since 1992. An estimated
75-90 percent of fresh-market spinach is processed
into fresh-cut salads or bagged spinach. Overall,
consumption of processed spinach has trended downward
since 1996. The heat used in processing kills E.
coli O157:H7.
The second factor affecting the
number of outbreaks is the increasing concentration
within the produce industry. If something goes wrong
at an operation handling a large volume of product,
the number of ill consumers may be quite large and
the outbreak may be more likely to be detected.
For example, in the capital-intensive bagged-salad
industry, two processing firms account for about
90 percent of the retail market.
The history of outbreaks associated
with leafy greens has put pressure on the industry
to improve food safety practices. Because most fresh
produce is grown in a natural environment, it is
vulnerable to microbial contamination. No set of
practices would eliminate all risk because produce
is not routinely treated with a “kill”
process, like pasteurization for milk, which would
eliminate microbial contaminants.
But voluntary FDA guidelines to
minimize the risk of microbial contamination
provide growers with a framework to use when developing
their food safety plans. Many growers have sophisticated
food safety programs. The conventional wisdom—there
are no statistics—is that most large commercial
growers of leafy greens have adopted voluntary FDA
guidelines to reduce risk and use third-party audits
to confirm that their practices are consistent with
the guidelines. But outbreaks have continued. In
an outbreak, some growers may not have used the
guidelines or may not have used them consistently
and correctly, or the guidelines may not have addressed
the specific mechanism of contamination for that
particular outbreak. FDA investigations, industry
efforts, and scientific research have not definitively
explained how leafy greens became contaminated or
how to avoid future contamination.
When planning their food safety
programs, growers must consider the expected benefits
and costs of an array of new, and perhaps costly,
practices that they could adopt that may reduce
their risk of contamination. In the past, growers
generally did not receive a price premium for produce
grown with safer practices, so there was no immediate
monetary benefit to offset the costs. There are
important benefits, however, to adoption of improved
food safety practices. Reducing outbreaks associated
with a particular firm protects sales, reputation,
and assets. Also, many retailers and foodservice
buyers require that their suppliers use the voluntary
FDA guidelines, so growers must adopt certain production
practices to maintain wide market access—a
very important incentive.
The Outbreak
On September 11, 2006, the Centers
for Disease Prevention and Control (CDC) received
notice of an outbreak of foodborne illness in Wisconsin.
Two days later, Wisconsin public health officials
preliminarily linked the outbreak to bagged spinach
based on epidemiological studies. Confronted with
an escalating number of cases—50 illnesses
in 8 States, including one death—the CDC feared
that the outbreak was still developing and that
contaminated spinach could still be in stores, restaurants,
or consumers’ refrigerators, posing a threat
to public health. On September 14, the FDA announced
that consumers should not eat bagged spinach; on
the next day, it expanded its warning to all fresh
spinach. FDA had never before made such a sweeping
announcement about a U.S. fruit or vegetable. Usually,
by the time an outbreak associated with fresh produce
is detected and the contaminated item is identified,
the outbreak is over and the product in question
has long since been consumed or discarded.
Most consumers remembered one
brand of bagged spinach produced by Natural Selection
Foods. Some sick consumers still had bagged spinach,
with firm name and lot number, in their homes, providing
FDA with a headstart in its investigation. If this
outbreak had been related to fresh bunched spinach,
the traceback could have taken much longer. On September
15, Natural Selection Foods recalled all of its
production. This firm packed spinach products for
30 companies, including bagged baby spinach for
Dole, which was eventually identified as the only
contaminated product.
Records of Natural Selection Foods
showed that four farms supplied spinach to the contaminated
batch of bagged baby spinach. Eventually, FDA narrowed
its focus to one farm and concluded that the problem
probably originated there from field-level contamination.
There were also factors that may have led to the
possible spread of contamination at the processing
plant. Unfortunately, FDA could not determine exactly
how the spinach became contaminated; even with rapid
detection of the outbreak and a quick traceback,
FDA arrived at the fields and processing facility
1 month after the contaminated spinach had been
harvested and packed into bags.
The contamination was traced to
a load of spinach from one 2.8-acre field packed
at one processing facility on August 15. This field
was part of a 50.9-acre parcel of land leased by
a firm for leafy green production; the owner of
the ranch used the rest of the property for grazing
cattle. The leafy greens were grown with organic
methods, but since the fields were only in the second
year of the 3-year transition to organic, the spinach
was sold as conventional. Organic, as well as conventional,
operations must address the threat of microbial
contamination. According to the California Food
Emergency Response Team, the grower did not contract
for a third-party audit for compliance with FDA’s
voluntary food safety guidelines before the 2006
growing season began. Potential environmental risk
factors at or near the field included the presence
of wild pigs and irrigation wells near surface waterways
exposed to feces from cattle and wildlife. The outbreak
strain of E. coli O157:H7 was identified
in samples of river water, cattle feces, and wild
pig feces on the ranch; the closest contaminated
sample was just under 1 mile from the spinach field.
But the precise means by which the bacteria spread
to the spinach remains unknown.
The FDA announcement initially
closed down the spinach market. But on September
29, FDA announced that “spinach on the shelves
is as safe as it was before this event.” Sales
began to pick up, but recovery varied by type of
spinach—bunched vs. bagged. USDA data on shipments
of bunched spinach show that the market rebounded
relatively quickly; in December, shipment volume
was higher than in December of the previous year.
Much of the adverse publicity focused on bagged
spinach, not bunched spinach. But bunched spinach
only accounts for an estimated 10-25 percent of
the fresh spinach supply. Retail sales value data
for bagged spinach and salads show a very different
story (USDA does not collect comprehensive shipment
and price data on bagged spinach and salads). Retail
sales of bagged spinach and bagged salads with spinach
have recovered more slowly than bunched spinach.
During the period January 24-February 24, 2007,
5 months after the outbreak, the value of retail
sales of bagged spinach was still down 27 percent
from the same period a year ago, although that was
much improved from the low fall 2006 sales. Sales
of bagged salads with spinach show similar trends.
Sales of bagged salads without spinach were down
5 percent; part of the decline may be due to the
spinach outbreak, but there were also two smaller
outbreaks in late 2006 that were linked to lettuce
that probably shook consumer confidence.
In
2007, bagged spinach and salad retail sales
values still lag
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Percent
change in sales value
from a year ago for:
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January
24-
February 24, 2007 |
August
24, 2006-
February 24, 2007 |
|
Percent |
Bagged spinach |
-27 |
|
Bagged salad with spinach |
-24 |
|
Bagged salad without spinach |
-5 |
-8 |
Source: Perishables
Group, Facts, Figures & the Future. |
Voluntary “Good Agricultural Practices”
Provide Guidance
In 1998, FDA published a voluntary
guidance document “Guide to Minimize Microbial
Food Safety Hazards for Fresh Fruits and Vegetables,”
commonly known as Good Agricultural Practices, or
GAPs. This was a general, commonsense guide because,
at that time, there was very little specific research
to provide more concrete advice. FDA promotes voluntary
adoption of GAPs to minimize microbial contamination
at the field level instead of relying exclusively
on relatively ineffective testing to detect produce
that might be contaminated. GAPs are now an important
management tool used by growers in the United States
and in foreign countries, especially where growers
produce for the U.S. market.
In response to the continuing
problems in particular sectors of the fresh produce
industry, FDA has issued a series of warning letters
and initiatives. In January 2004, FDA and CDC met
with produce industry leaders to discuss numerous
foodborne illness outbreaks associated with produce.
At that meeting, industry representatives agreed
to take the lead
on developing commodity-specific GAPs that would
provide additional guidelines tailored to individual
commodities that had been implicated in recent foodborne
illness outbreaks. In April 2006, the produce industry
put out its “Commodity Specific Food Safety
Guidelines for the Lettuce and Leafy Greens Supply
Chain.” The FDA developed the Lettuce Safety
Initiative, and in August 2006, just at the time
people were getting sick from spinach, the FDA,
the California Department of Health Services, the
California Department of Food and Agriculture, industry,
and academics were meeting in California to discuss
upcoming visits to lettuce operations to try to
understand the contamination problem.
An Industry Under Pressure…
The California leafy green industry—growers,
shippers, and bagged spinach and salad processors—is
under strong pressure to avoid further outbreaks.
The industry faces a barrage of demands for immediate
improvements in food safety practices. FDA insisted
that the spinach and leafy green industry take the
lead in developing better food safety practices
while holding out the prospect of mandatory regulation—something
growers have traditionally tried to avoid. A group
of retail and foodservice buyers demanded improvements
in food safety. California State legislators called
for tougher mandatory standards, and Congress scheduled
hearings on food safety.
…Undertakes Initiatives
To Regulate Itself…
With the fall 2006 outbreak, all
spinach growers suffered from decreased consumer
demand for their product, even though only one grower’s
spinach was contaminated. The California leafy green
industry is trying to use the existing framework
of State marketing agreements and marketing orders
to regulate itself by encouraging all growers to
adopt a baseline level of food safety practices.
The two main challenges are identifying what practices
will reduce the risk of future outbreaks at the
minimum cost and getting all growers to adopt the
practices. New practices may reduce risk, but they
will undoubtedly raise costs and could bring structural
change to the leafy green industry, as some growers
find themselves with relatively higher costs than
others.
The Western Growers Association,
which represents fresh fruit and vegetable growers
in California and Arizona, led the California leafy
green industry’s drive for self-regulation
in California. In 2005, California accounted for
75 percent of total U.S. fresh-market production,
and Arizona’s winter production accounted
for another 16 percent. The California Leafy Green
Products Handler Marketing Agreement was approved
in March 2007, under the supervision of the California
Department of Food and Agriculture. By April 1,
2007, the beginning of the first year of the agreement,
71 handlers representing more than 99 percent of
all California leafy green production signed the
agreement. Handlers of leafy greens—firms
that move the product from growers to retail and
foodservice channels—who signed the agreement
are obligated to handle California product only
from growers who can show that they follow the Best
Practices and use a traceback system recognized
by the marketing agreement. Growers selling directly
to consumers at roadside stands and in farmers’
markets, generally small operations, are not covered
by the marketing agreement because they are not
considered handlers. Participation is voluntary,
but once handlers sign up for the agreement, they
must comply. Participation is an annual decision,
so there is no guarantee that participation will
remain at the current high level.
For the marketing agreement, leafy
greens are defined as iceberg, romaine, green leaf,
red leaf, butter, and baby leaf lettuce; escarole;
endive; spring mix; spinach; cabbage; kale; arugula;
and chard. Imported leafy greens sold by participating
handlers are not required to be produced with the
Best Practices, but handlers may voluntarily use
the guidelines for their imports (fresh-market spinach
imports in 2005 accounted for about 4 percent of
U.S. consumption). A charge of approximately 2 cents
per 50 pounds of product supports an inspection
program to ensure compliance.
The California leafy green industry,
with the help of scientists, developed the new Best
Practices guidance document for California producers.
This builds on the previous commodity-specific GAPs,
which were intended to provide guidance for all
growers of leafy greens. A marketing agreement is
flexible, and Best Practices can evolve over time.
The FDA reviewed the document, but it does not endorse
private food safety plans. Some growers’ practices
already exceeded the Best Practices guidelines,
while others had to upgrade their practices to comply.
Retail and foodservice buyers concerned about food
safety may accept the Best Practices as sufficient,
but others may impose additional food safety requirements.
Unlike FDA’s initial guidance
document and the commodity-specific GAPs, the new
Best Practices defines specific criteria and target
values for controls and monitoring. For example,
the original GAPs document warned farmers that “water
quality should be adequate for its intended use.”
At the time, FDA was justifiably reluctant to specify
what adequate water quality was because it did not
have enough data to support specific thresholds.
The new Best Practices are much more specific, but
the science is still relatively weak. For example,
the standards for well water require testing before
production begins and monthly testing during the
production season. The document recommends specific
tests for measuring levels of generic E. coli
(nonpathogenic E. coli) in the water and
an action plan to be applied if counts reach certain
numerical thresholds. The increased water testing
is expected to be one of the more costly provisions
of the Best Practices, and farmers would like to
understand what the impact will be on risk levels.
In the absence of more relevant science, the water
standard is based on the Environmental Protection
Agency’s recreational water use standards.
Also, while generic E. coli is a general
indicator of fecal contamination or insanitary conditions,
it is not a specific indicator for E. coli
O157:H7.
Now that the California industry
has implemented a marketing agreement, it is also
considering a State marketing order. For a marketing
order, growers would vote on whether they want to
make Best Practices mandatory. A marketing order
would apply to the whole industry, not just those
who voted for it. To protect its competitive position
and to minimize the risk of outbreaks elsewhere
that would further shake consumer confidence in
leafy greens, the California industry is considering
whether to pursue a Federal marketing agreement
or order that would cover the entire U.S. leafy
green industry. In addition, the industry would
like to find a mechanism to impose the same food
safety standards on imports. Arizona producers are
now considering a marketing agreement in their State.
…but Some Advocate
Mandatory Standards
For the first time, some in the
produce industry are calling for the Federal Government
to step in and regulate food safety. In January
2007, the United Fresh Produce Association adopted
a set of principles declaring that for food safety
standards to be credible to consumers, they must
be mandatory, Government approved, based on commodity-specific
needs, applied consistently across producers of
the same commodity, and subject to Federal oversight.
This would resolve the problem that growers face
of determining what level of precautions is enough.
Support for this position probably varies among
producer groups.
Whoever sets the standards—industry
or government—will have the same challenge:
to develop science-based practices that reduce risk
at the minimum cost. Ongoing scientific research
will contribute to this evolving process. In April
2007, Fresh Express, a large bagged salad company,
distributed $2 million of funding to support scientific
research on E. coli O157:H7 in leafy greens.
Scientists from universities, FDA, CDC, and the
California Department of Health Services participated
in the selection of the projects. The Center for
Produce Safety was established in April at the University
of California in Davis. This center is supported
by pledges of over $5 million from the Produce Marketing
Association, Taylor Farms, Western Growers Association,
the California Farm Bureau Federation, the California
Department of Food and Agriculture, and the University
of California.
Escherichia coli O157:H7
Escherichia coli
O157:H7 is a harmful bacterium that lives
in the intestines of healthy animals, including
cattle, deer, and wild pigs, and is excreted
in their feces. Most E. coli, some
of which live in the human intestine, are
harmless to humans and known as generic E.
coli. But E. coli O157:H7 causes
diarrhea, often bloody. People become sick
1-7 days after exposure, but usually within
2-3 days. Most healthy adults recover completely
within a week, but E. coli O157:H7
can cause hemolytic-uremic syndrome (HUS),
which can lead to kidney failure and even
death. HUS is most likely to occur in young
children and the elderly. The Centers for
Disease Control and Prevention estimate that
there are 73,000 infections and 61 deaths
per year. The most common sources of outbreaks
of E. coli O157:H7 in the United
States include food (beef, leafy greens, sprouts,
and unpasteurized juice) and water contaminated
with feces, and animal contact. Fresh produce
is now the leading cause of E. coli
O157:H7 foodborne illness outbreaks in the
United States. |
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