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~2
Food Safety Tools
This chapter describes some of the major modern tools available to regula-
tory agencies for use in developing food safety criteria and standards. Some of
these techniques or concepts are widely known and extensively used, whereas
others are still in the developmental stage. The description of these tools and the
discussion of their current or potential uses and applications to enhance food
safety have been organized as a progression from the better known to the novel.
In addition, the committee strived to circumscribe the material on each tool to
that which is relevant to food safety, recognizing that some of the sections, such
as "Statistical Process Control" and "The Economics of Food Safety Criteria,"
are not only foreign to many food processors and food safety regulators, but are
technical and scientific fields that only recently have been brought into play in
the food safety arena. Thus, in view of the limitations in space and time facing the
committee, the reader is referred to specialized treatises that expand on these
areas when additional information is desired.
HAZARD ANALYSIS AND CRITICAL CONTROL POINTS
Introduction
The Hazard Analysis and Critical Control Point (HACCP) system is a meth-
odology that constitutes the foundation of the food safety assurance system in the
modern world. Although a detailed history and description of HACCP principles
and applications are beyond the scope of this report, the invaluable contribution
that this food safety tool is making to improve public health, its central role in
69
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
present-day food processing, and its inseparable relationship to the issues dis-
cussed in this report demand a short introduction and description of it.
HACCP history goes back to 1959, when the National Aeronautics and
Space Administration (NASA) commissioned the Pillsbury Company to manu-
facture food products for use by astronauts during space missions. The stringent
safety requirements imposed on these foods were a reflection of deep concerns in
NASA about the potential consequences of foodborne sickness among astronauts
in space, as well as of food particles interfering with flight systems (Stevenson
and Bernard, 1995~. Although HACCP made its debut at the 1971 National
Conference of Food Protection (Stevenson and Bernard, 1995), analogous systems
(not yet designated as HACCP) had been in existence and had been applied in
practice in some food-processing operations, notably in the canning of low-acid
foods and in milk pasteurization. These operations included: (1) identification
and assessment of the hazards: Clostridium botulinum spores in canned low-acid
foods and milk-borne pathogens such as Mycobacterium tuberculosis, Brucella
spp., and Coxiella burnetii; (2) identification of the critical control point for these
hazards: heating at specified temperatures and for similarly specified times in
either of these operations; and (3) a system to monitor the critical control point:
time and temperature recorders. Despite the fact that these food-processing
operations had built-in notions of HACCP, the efforts of the Pillsbury team in
articulating the fundamentals of present-day HACCP and testing its effective-
ness, followed by additional contributions from the U.S. Army's Natick Labora-
tories, are nothing short of landmarks in food safety history.
HACCP is well established in the food-processing regulations of the United
States. However, its introduction proceeded slowly, beginning in the 1970s and
accelerating only until the mid-199Os. The migration of HACCP from textbooks
into the U.S. Code of Federal Regulations came about, in part, as a result of a
National Academies report (NRC, 1985a) that recommended the adoption of
HACCP ". . . universally in food protection programs . . ." and of subsequent,
instrumental efforts by the International Commission on Microbiological Specifi-
cations for Foods (ICMSF, 1988) and the National Advisory Committee on
Microbiological Criteria for Foods (NACMCF, 1998~. Other reports of the
National Academies (IOM, 1990, 1991; TOM/NRC, 1998; NRC, 1985a, 1985b)
have further endorsed the introduction or expansion of HACCP into the process-
ing and inspection of meat, poultry, seafood, and, in general, throughout the food
industry.
Implementation of HACCP by the food industry has been a slow and at
times painful process that still is in progress. To facilitate implementation of
HACCP by the food industry and help standardize HACCP training, a coalition
of industries and trade organizations in the United States formed the International
Meat and Poultry HACCP Alliance in 1994. This group has since endeavored to
"train the trainers" by conducting training courses and certifying HACCP trainers
who can further train personnel at the processing-plant level. In addition, the
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FOOD SAFETY TOOLS
71
International HACCP Alliance has contributed to the development of generic
HACCP plans for use by regulatory agencies in facilitating the preparation of
specific HACCP plans by food processors. There is also a Seafood HACCP
Alliance and a Juice HACCP Alliance. The committee recognizes the multiple
technical, financial, and educational efforts made by the food industry to imple-
ment HACCP, including the development and adoption of various interventions
to enhance the microbiological safety of the food supply often in anticipation of
regulations and commends such efforts.
National food safety regulatory agencies and international institutions have
published procedures for the development and implementation of HACCP plans.
Some of these are established national food regulations, such as those mandated
by the Food and Drug Administration (FDA) (21 C.F.R. part 114) and the U.S.
Department of Agriculture (USDA) (FSIS, 1996), while others, such as the Codex
Alimentarius guidelines on HACCP (CAC, 1997), play a central role in inter-
national food trade despite the fact that their adoption by Codex Alimentarius
member countries is voluntary.
There are numerous HACCP training manuals, including a few that are
international in nature (WHO, 1999), as well as a wealth of information on
HACCP from various sources. An example of these sources is a joint USDA/
FDA website that offers a variety of training materials (USDA/FDA, 2002~.
Continued training in HACCP principles to attain proper implementation by
industry personnel and consistent interpretation and monitoring of compliance by
inspectors from the regulatory agencies is necessary.
The Principles of HACCP
Unlike the traditional model for food safety assurance that has been used for
decades, HACCP does not rely on end-product testing to ensure the safety of food
batches, but on continuous control and monitoring of Critical Control Points
(CCPs) along the production and processing continuum. It is, therefore, a preven-
tive food safety assurance system in that it focuses on ensuring control of known
potential hazards before the product reaches the end of the line, as opposed to the
traditional corrective system that focuses on examining the final product and
determining whether any hazard of concern is present.
CCPs, in general, are defined in HACCP language as "those points where
loss of control would result in an unsafe food product," and more specifically as
"those points where the identified hazardous) may be prevented from entering the
food, eliminated from it, or reduced to acceptable levels" (Stevenson and Bernard,
1995~. It is noteworthy, however, that an intrinsic weakness of HACCP is that it
does not provide information on what these acceptable levels are or a guide on
how to set them. Linkage between public health goals and HACCP, through a
developing concept of Food Safety Objectives (described later in this chapter),
may enable regulators in the future to define numerical levels of tolerance for
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
foodborne hazards in foods at the point of consumption that could be translated
into "acceptable levels" at CCPs in food-processing plants.
The methodology for developing a HACCP plan calls for the systematic
application of seven principles:
1. Hazard analysis
2. Identification of CCPs
3. Establishment of critical control limits for each CCP
4. Establishment of monitoring procedures for each CCP
5. Establishment of corrective actions
6. Establishment of record-keeping procedures
7. Establishment of verification procedures
The process begins with the formation of a team that includes plant manage-
ment and personnel, as well as individuals who have expertise in foodborne
hazards and the particular product and process being used. The team prepares a
flow diagram of the production process and physically examines each of its steps
in the actual premises where production takes place. Points along the flow dia-
gram where the hazard may be prevented, eliminated, or reduced to acceptable
levels, and for which a control exists that can be established and monitored, are
designated as CCPs. Critical limits are then set for the parameters that can be
measured to determine that the control at each CCP is being effectively applied.
Monitoring procedures are then established, and corrective actions are predeter-
mined to be taken if a loss of control is indicated by a deviation from the critical
limits. The HACCP plan, along with records demonstrating that the controls at
each CCP have performed successfully and have been continuously monitored
during processing, are organized for ease of access by the processor and by
inspectors from the regulatory agency charged with ascertaining compliance with
the regulations. Finally, internal and external verification procedures are defined
to periodically assess the performance of the system and to revise the HACCP
plan whenever changes are introduced in the production process that could com-
promise the effectiveness of the system. Internal verification procedures may
involve such activities as instrument calibration, periodic product testing, and
records review, while external verification may involve expert audits and exter-
nal product testing.
Full compliance with Good Manufacturing Practices (GMPs) and the pre-
existence of Standard Operating Procedures for plant sanitation are assumed to be
in place when introducing HACCP into a food-processing plant. Therefore,
HACCP is not a stand-alone methodology, but part of a larger set of manufactur-
ing practices that include these preconditions. In addition, the HACCP plan is
specific for each processing plant, processing line, and product manufactured in
each line. As a result of discussions held during information-gathering meetings,
the committee has been made aware that inappropriate identification of CCPs and
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FOOD SAFETY TOOLS
73
inappropriate HACCP plans have caused problems in complying with HACCP
regulations. Similarly, the committee recognizes that inconsistency in the inter-
pretation and enforcement of HACCP rules between and within regulatory agencies
has hampered a smooth transition to the new food-processing inspection model
and monitoring of compliance with HACCP rules.
HACCP has revolutionized food safety assurance by bringing about a radical
change in the roles of regulators and regulated industries regarding food safety
responsibilities, as described in Chapter 1. The committee believes that despite
some continued disagreements between these sectors and some widely publi-
cized failures of the system notwithstanding the balance of progress in food
safety after implementation of HACCP in various sectors of the food industry is
decidedly favorable and commendable. The committee, therefore, endorses the
recommendations made by previous reports of the National Academies (IOM,
1990, 1991; TOM/NRC, 1998; NRC 1985a, 1985b) and strongly recommends
that the regulatory agencies continue to introduce and audit the implementation
of HACCP in all sectors of the food industry as appropriate.
RISK ASSESSMENT
Various techniques have been examined for their potential to provide a sci-
entific basis for improving public health and to address emerging foodborne
diseases. Risk assessment has surfaced as one key method to embark upon these
challenges. The use of quantitative and qualitative risk assessments for biological
issues has emerged from the use of quantitative risk assessments for chemical and
environmental toxicology (Dourson et al., 2001; IFT, 2002; Neubert, 1999;
Paustenbach, 2000~. In simple terms, quantitative risk assessment uses math-
ematical equations, numerical data, and expert opinion to create a computer
simulation of reality. These computer models allow interested individuals to
explore various risk-management options. Quantitative risk assessment is useful
because it allows risk managers to see the entire situation related to a hazard
without being an expert on each one of the component factors. Risk managers can
rapidly examine various technical solutions to a problem using computer-based
models, while using their expert judgment on the social, political, and economic
factors that also influence how policies are perceived.
Risk assessment is usually presented as part of the overall risk analysis
paradigm, where risk analysis consists of risk assessment, risk communication,
and risk management (Figure 3.1) (dose, 2000~. Quantitative risk assessment is a
scientific process that addresses the magnitude of the risk and identifies factors
that control it. Risk communication is a social and psychological process that
promotes dialogue among different affected individuals regarding the risk.
Finally, risk management is a process that combines science, politics, economics,
and proper timing to arrive at a decision regarding what to do about the risk.
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74
\
FIGURE 3.1 Components of a risk analysis.
SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
-
-
Risk / \ Risk
Management
-
~ Assessment
Risk
Communication
-
Differences and Similarities Between Chemical and
Microbial Risk Assessment
Chemical risk assessment is a relatively mature field compared with that of
microbial risk assessment. This is due in part to the requirement for drugs and
chemicals to be approved or registered by either FDA or the U.S. Environmental
Protection Agency (EPA) prior to human exposure. Rigid guidelines have been
established and quantitative approaches to assessing adverse effects in humans
have been developed. Despite the differences in maturity, the overall paradigm of
chemical risk assessment has remarkable similarities to the emerging practice of
microbial risk assessment. A comparison of key differences and similarities may
benefit both fields.
In both fields, risk assessment is a component of the larger field of risk
analysis that also encompasses risk management and risk communication. A
variety of diagrams have been used to explain the interaction of these compo-
nents, including that shown in Figure 3.1. Chemical (and microbial) risk assess-
ments are typically divided into four parts: hazard identification, dose-response
assessment (or hazard characterization), exposure assessment, and risk character-
ization (Lammerding and Paoli, 1997; Neubert, 1999; Paustenbach, 2000~.
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FOOD SAFETY TOOLS
Hazard Identification
75
Hazard identification involves assessing whether the agent (chemical or
microbial) produces adverse effects in biological systems. Historically, this was
assessed for chemicals through the use of animal bioassay screens, but now it is
largely accomplished using in vitro systems and, recently, by techniques targeted
to advances in genomic sciences. Microbial risk assessments are typically initi-
ated in response to a public health concern, and hazard characterization in micro-
bial risk assessment typically uses epidemiological or outbreak data (Escherichia
cold 0157:H7 Risk Assessment Team, 2001; Salmonella Enteritidis Risk Assess-
ment Team, 1998~.
The hazard characterization step in microbial risk assessment includes iden-
tifying the organism that caused the public health concern and summarizing the
details regarding the exposure pathway and the microbial ecology of the particular
hazard (see Chapter 2~.
Dose-Response Assessment
Once an agent is identified as potentially injurious, the next phase is to define
the dose-response relationship. The techniques for chemical dose-response
assessments are well defined, while the same cannot be said for their microbial
counterparts.
Studies conducted in laboratory animals form the basis of the field of toxi-
cology and are readily used in chemical risk assessment. There is an extensive
experimental database of well-designed laboratory animal studies, all conducted
under agreed upon Good Laboratory Practice (GLP) guidelines (40 C.F.R.
§160.1~. GLP guidelines ensure that all tests conducted for regulatory action on a
drug or for chemical registration are conducted according to acceptable practices
and generate an auditable paper trail. The validity of this approach to chemical
risk assessment has a proven track record: FDA uses essentially these same
techniques in preclinical studies of human drugs. The determination of dose for a
human drug is based on knowledge of the dose-response relationship for both
beneficial and adverse effects. The extensive pro- and postmarketing drug approval
process validates the accuracy of these approaches.
Tolerances for man-made chemicals introduced into the food supply are
based on extrapolation of no-effect data from laboratory animal studies. Experi-
ences with FDA drug approval would indirectly support the validity of this
approach, as stated above. Microbial risk assessment is qualitatively quite different,
for microbial hazards are not man-made and usually are introduced into the food
supply only naturally or accidentally. Because of the host-pathogen specificity
differences, animal studies are of only limited use in microbial risk assessment.
Additionally, no microbial equivalent of the FDA human-drug approval process
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
exists to validate any proposed dose-response relationships, although if properly
collected, outbreak data may help in this regard.
Experimental designs in chemical risk assessment are specific for different
toxicological endpoints (e.g., acute, subacute, chronic, reproductive, carcino-
genic). The mathematical form of the dose-response relationship is assessed
based on the biological mechanism of action of the chemical being studied. The
end result is a definition of a dose that does not produce adverse effects in
laboratory animals: the no-observed-adverse-effect level (NOAEL). There are
many variations on how this is determined and on how data from multiple studies
are combined (Neubert, 1999~. However, for the purpose of this discussion, the
key point is that in chemical risk assessment, the end product (derived from
standard toxicological testing protocols) is a defined dose considered safe by the
scientific community.
Microbial dose-response relationships have been derived from human feed-
ing trials (many done on volunteer prisoners in the early part of the twentieth
century), animal studies, and, increasingly, data from foodborne disease out-
breaks, as noted. As with chemical risk assessment, various endpoints can be
used, ranging from mild diarrhea to death; also, data from multiple studies can be
combined (Holcomb et al., 1999~. A variety of mathematical forms for microbial
dose-response has been proposed. Microbial dose-response equations do not
have as clear a link to a biological mechanism as in chemical risk assessment, due
in part to the complexity of the underlying biology.
The committee believes that defining microbial dose-response relationships
for foodborne pathogens is important if more accurate risk assessment results are
desired. Allocation of resources to fund basic research studies defining these
relationships would help to remedy this deficiency.
The host side of the dose-response relationship may also be different for
microbial and chemical risk assessments. Some researchers have suggested that
in the case of microbial risk assessment, a population's response to an infectious
pathogen is more variable than it is to acutely toxic chemicals and rivals the
complexity seen with carcinogens. This variability is due to altering immune
status as a function of genetics, environment, age, concurrent diseases, and a host
of other factors (ICMSF, 1998~. However, the response of an individual to a
chemical exposure is also variable based on many of the same factors and indi-
vidual differences in the inherent receptor sensitivity, pharmacokinetics (includ-
ing metabolism), and simultaneous exposure to a myriad of drugs and chemicals.
In both scenarios, the large degree of interindividual variability makes the risk
assessment process prone to large degrees of uncertainty.
In the drug arena, the development of population pharmacokinetic tech-
niques has partially reduced this uncertainty by identifying subpopulations that
vary significantly from the norm. Perhaps the most important difference is that
microbial dose-response assessment for infectious pathogens does not produce
any concept analogous to the NOAEL, since a single microbial cell may (under
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FOOD SAFETY TOOLS
77
the right circumstances) produce illness. It may, however, be possible to use a
risk assessment term analogous to the NOAEL for organisms like Staphylococ-
cus aureus or Bacillus cereus that cause illness through formation of a toxin in
the food, or for Listeria monocytogenes in healthy adults. Because microbial
dose-response assessment does not typically produce a NOAEL, the key point in
microbial risk assessment is that for many pathogens there is no safe dose. Even
if a microbial NOAEL could be determined, it might not be adopted. USDA's
Food Safety and Inspection Service (FSIS) has taken the position with respect to
Escherichia cold 0157:H7 that it is an adulterant, and hence, it is not allowed in
raw ground beef in any number (see Chapter 4~. While the agency could change
its position in this regard, it might be difficult to explain such a change to the
public, and so it might hesitate to do so. If a firm scientific basis for determining
no-effect levels for some pathogens existed, along with appropriate detection and
enumeration methods to ensure that microbial NOAELs are not exceeded, it
would still be necessary to convince the public that their safety would be suffi-
ciently assured by the implementation of the microbial NOAELs.
Exposure Assessment
The next step in either microbial or chemical risk assessment is to estimate
human exposure to the agent. For chemicals such as pesticides, environmental
compounds, and food additives, potential modes of exposure must be assessed.
These include assessing whether the primary routes are inhalation, dermal, or, in
the case of food chemicals or microorganisms, oral. Aggregate exposure must be
determined where multiple routes may contribute to human exposure. This often
occurs in the case of pesticides, where exposure may occur by inhalation after
spraying in a home or place of work, orally in food, or dermally by physical
contact with a sprayed surface. For chemicals, a major task of exposure assess-
ment is to determine the fraction of the dose that is actually absorbed into the
body, that is, the bioavailability. Additionally, it is important to determine if this
absorbed dose is metabolized, either to an inactive moiety or to an active and
potentially toxic metabolite.
An arena where risk assessment is routinely applied to chemicals is in the
drug approval process. Pharmaceutical drugs are somewhat different in this
respect than other chemicals because hazard characterizations and dose-response
assessments are conducted in the preclinical phases of drug development in order
to estimate a tolerable dose for humans. Hazard identifications for pharmaceuti-
cals are essentially validated in the first phase of human testing. The appropriate
dose is finally determined after the second and third phases of human testing,
which seek to determine effectiveness and obtain additional safety information.
When the drug's sponsor applies to FDA for approval of its application to market
the drug, a determination is made on whether it is safe and effective and may be
released to the marketplace. The approval process necessitates balancing the
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
potential benefits of the drug to the patient population against the risks that it
might pose. Through the initial testing or postmarket surveillance, information
may arise that suggests that certain specific patient populations are more at risk
than others for adverse effects or treatment failures; such information may be
reflected in labeling information that guides proper drug use. If information is
developed later that changes the risk/benefit ratio significantly, FDA may require
that the drug be withdrawn from the market.
Exposure assessment in quantitative microbial risk assessment (QMRA)
involves modeling movement of the pathogen through the production system.
Both temporal (in time) and spatial (in space) exposure data are relevant to this
step. Exposure assessment results in an estimate of the likelihood of pathogen
ingestion by the consumer.
Exposure assessment for microorganisms is quite different from that for
drugs or other chemicals, primarily because (at least with bacterial pathogens)
some microorganisms can increase or decrease in number in the food under
suitable conditions. Aggregate exposure to multiple chemicals is often consid-
ered, especially with carcinogens. Although each chemical exposure to an indi-
vidual in a given time period might not produce illness, such exposures may
produce subclinical organ damage, induce metabolic changes, or result in accu-
mulation that could modify subsequent responses. In contrast, if repetitive expo-
sure to low levels of infectious microbes occurs, host immunity may decrease risk
(ICMSF, 1998), but counterexamples also exist (Maijala et al., 2001~. Unlike a
chemical that has a constant potency (unless degraded), a microbe is dynamic and
adaptable. Virulence factors acquired from other organisms could change the
inherent infectivity and pathogenicity of a foodborne microorganism (ICMSF,
1998~.
In food-processing operations that combine raw materials from multiple
sources, microbial or chemical contamination in some of these raw materials
would have differing effects on contamination in the resulting product. While a
chemical contaminant would be diluted during mixing, similar dilution of bacte-
rial contaminants would mean that the bacteria are spread throughout the mix
(e.g., by breakup of microbial colonies that initially may be highly localized into
what is referred to as "point source" or "hot spots" in the incoming raw material).
For example, consider the mixing of meat trimmings in a grinding operation
where a point source of either a chemical or a bacterial pathogen occurs. Dilution
of the chemical from a point source to a larger mass of product would be expected
to reduce the hazard by decreasing the concentration of the chemical a consumer
would ingest. In the case of bacteria, mixing meat trimmings from multiple
sources (animals, producers, packing plants, states, countries) would increase the
volume of contaminated ground product and, because of bacterial growth, the
potential number of consumers that might be affected.
The spread of bacterial contaminants would also seriously confound attempts
to trace back the source of contamination to a specific supplier of raw material.
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FOOD SAFETY TOOLS
79
This effect is well known in the dairy industry, where milk that contains antibiotic
residues from an individual cow will be diluted in the tank truck after mixing with
milk containing no antibiotic residues. Thus, because of similar dilution effects,
ground-meat products would be expected to raise no major concerns regarding
chemical residues; but, unlike the situation in whole-muscle meat, chemical hot
spots would likely be spread in ground meat. Therefore, the microbiological risk
in ground meat may be expected to be greater than any chemical risk. The same
logic could be extended to processing food from multiple sources or to consump-
tion of a contaminated item in a multi-ingredient meal (e.g., vegetables, meat, and
sauces).
There are also some differences in the analytical detection of microbes versus
chemicals that may impact data used in exposure assessment calculations. Concerns
about sampling strategies are fairly similar for both chemicals and microbes,
although the latter may be more prone to localization from hotspots of point-
source microbial contamination.
In the chemical residue arena, the development of multiple drug-class residue
screening assays that would detect and quantify multiple contaminants in a single
assay has been the focus of recent research efforts. Once considered cost prohibi-
tive, these techniques are based on gas chromatography/mass spectrometry and
are now feasible. Similar developments have begun to occur in the microbiological
arena (see Chapter 1~.
A similarity between chemicals and microbial pathogens is that all chemicals
and pathogens do not have, qualitatively or quantitatively, the same propensity
for causing human illness. Chemicals may exert a number of different types of
toxicological reactions, including allergenicity, immunotoxicity, mutagenicity,
carcinogenicity, and "classic" chemical toxicity (renal, hepatic, etc.) seen with
many pesticides and drugs. A single chemical may exhibit the full spectrum of
effects depending on the dose and length of exposure. Quantitative structure-
activity relationships have also been developed that help in the prediction of these
chemical effects. For microbes, a similar diverse spectrum of potential adverse
effects can be observed depending on the species, serotype, strain, or host differ-
ences. For example, ingestion of foods contaminated with some strains of E. cold
may produce a transient gastrointestinal disturbance, while exposure to strains
such as 0157:H7 may be fatal for some individuals. Finally, detection of a
chemical allows one to estimate whether the sample exceeds tolerance. Tech-
niques such as polymerase chain reaction (PCR), which amplifies deoxyribo-
nucleic acid (DNA), can detect and in some cases can also quantify patho-
gens (Hein et al., 2001a, 2001b; Li and Drake, 2001~. However, rapid tests that
determine microbial viability and infectivity are just becoming available (see
Chapter 1~.
The issue of multiple points of contamination within a food-processing estab-
lishment is also different for some chemical classes versus microorganisms
because of the ability of some of the latter (e.g., bacteria, molds) to multiply and
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
\ Marginal
social benefit Marginal
social cost /
I. #~d i.. - id i.. - id i.. - ad i.. - ~
I
Higher level of safety
~ 00°/0
FIGURE 3.4 Toward a public health goal: relating an appropriate level of protection
(ALOP) to marginal social benefit and cost.
benefits coincide (Figure 3.4~. (As stated above, it is unlikely that definitive
values can be provided of costs and benefits, and therefore such curves convey
the most likely values around which confidence intervals must be built.) The
inability of consumers to fully identify a product level of safety compared with
the greater knowledge that processors have of the ability of a process to deliver
safety (termed "imperfect and asymmetric" information problems in the litera-
ture) suggests that the market will fall short in providing the socially optimal
level of protection for the particular product or pathogen under review.
Economic efficiency requires that the ALOP to aim for be at the point where
marginal social costs equal marginal social benefits (Figure 3.4~. Away from this
equilibrium, either society desires a safer product and would benefit more than
the additional costs of the stricter regime (points to the left of ALOP), or society
is expending too many resources compared with the additional safety gains real-
ized (to the right of ALOP). The ALOP can be related to the particular public
health goal of the regulator because the model is stated in dollar terms but is
partially based on population measures (benefit estimates). It is important to note
that marginal social costs and marginal social benefits may change given the
form of a regulation, the particular population and food product under assess-
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FOOD SAFETY TOOLS
123
meet, and, over time, with a change in available technology or changing con-
sumer demands or consumption patterns. Therefore, the ALOP and the most
efficient food safety criteria are likely to be dynamic, given changing consumer
tastes and preferences, risk tolerances, industry capabilities, and government
oversight functions.
An example of how such marginal social costs can be calculated, highlight-
ing costs to companies from the adoption of particular food safety strategies, is
shown in Figure 3.5. Four possible strategies or combinations of efforts having
various levels of effectiveness and cost are shown. Various interventions (single-
or multiple-hurdle strategies) can be assessed based on their cost of implementa-
tion (possibly reported for various sizes or types of plants) and the most likely
effectiveness (e.g., ability of the process to reduce the presence of a particular
pathogen by x logic) and, therefore, on their ability to attain a performance
standard (S) with a certain probability. Similarly, if S were a food safety objec-
tive, then the technique could be used to assess sets of interventions adopted by
various companies throughout the supply chain. The horizontal line in Figure 3.5
indicates points associated with the concept that multiple strategies may meet the
necessary effectiveness (S) but with different varying costs.
Effectiveness
__—
_c
B
_- C
ma_
~-
c1
Cost
FIGURE 3.5 Relationship between the effectiveness (i.e., pathogen reduction) and cost
of hypothetical food safety strategies available to food-processing companies.
SOURCE: Jensen et al. (1998), Markarian et al. (2001~.
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
Strategies such as point D (Figure 3.5) are dominated by each of the other
options (A, B. and C) in the figure; these other options have either lower cost
(like point A) or higher effectiveness (points B and C), or both. The curved line
passing through points A, B. and C links all of the most favorable strategies and
therefore provides an optimal path of technical food safety effectiveness. The
area to the right of the curved line also suggests that there are marginal costs for
various levels of food safety (for example, consider moving from point B to C).
The standard S in Figure 3.5 will result in a cost of at least Cat based on where the
optimal curved line and horizontal line intersect. Technical effectiveness (the
frontier) is dynamic; innovations shift the curve up, allowing enhanced effectiveness
for the same cost. Process criteria essentially dictate the particular strategy that
must be followed by the industry (for example, strategy at point D). However,
this may not result in the lowest cost (compare A with D). Furthermore, process
criteria likely prevent the selection of more effective interventions (like B or C).
The strategies that meet (and in this case exceed) standard S are both B and
C. The particular intervention that would be selected by industry is less clear
when facing a performance standard (which is considered more flexible, since
many options to meet the standard may be available) as opposed to process
criteria. This situation illustrates the difficulty in forecasting costs in response to
a performance standard. Certain companies may decide to exceed the standard by
a long measure, while others may choose to meet the standard and no more.
Resulting from these different decisions, an array of potential costs can be estab-
lished creating a large range (with a well-defined lower bound Car, Figure 3.5) of
estimates for the related economic impact assessment of performance standards.
This wide range of impact-assessment estimates would also be related to a broad
range for the marginal social cost estimate (recall the marginal social cost curve
in Figure 3.4), with the lower bound relating to the minimal cost (C~ in Fig-
ure 3.5) of achieving standard S. This illustrates the difficulty of performing
economic impact assessments.
Because of the complicated situation presented above, the committee con-
cluded that uncertainty still exists with respect to the economics of food safety
regulations. The following are examples of questions that need to be answered:
Has the correct balance of incentives to innovate, benefits, and costs been
achieved? From an economic standpoint, are performance standards or process
criteria better for food safety? Which economic sector benefits most from perfor-
mance standards? What about performance criteria? In economic terms, what are
the consumer, government, and industry responses to performance standards and
performance criteria? Traditional economics suggest that performance standards
should lead to a no-higher set of industry (company) costs, yet performance
standards may cause the government sector to incur additional costs. Therefore,
the specifics of a particular performance standard should be assessed to deter-
mine this balance. Further research in these areas is required to better answer the
questions above and similar ones not yet raised.
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FOOD SAFETY TOOLS
125
THE IMPACT OF CHANGING TECHNOLOGY:
NEW DIAGNOSTIC TOOLS
Any regulatory system is heavily dependent on the technology available to
detect deviations from regulatory performance standards. For that matter, the
performance standards themselves may be influenced by available diagnostics,
with the requirement for nondetectable levels as established by regulations having
less meaning when it is possible to detect problems (such as the presence of
specific pathogens) with a 10-, 100-, or 1,000-fold increase in sensitivity.
Current regulatory standards for foodborne pathogens, in almost all instances,
assume use of traditional culture techniques to determine the presence and number
of pathogens or indicator organisms in a product. However, culture techniques
tend to be slow, with two or three days often required for initial isolation of a
microorganism, followed in many instances by several days of additional testing
to confirm that the microorganism isolated is indeed pathogenic or that it carries
the necessary virulence genes to represent a hazard to humans. There has been
increasing movement toward the use of immunological assays in diagnostics
which, when combined with traditional culture techniques, can provide results in
less time and with greater accuracy. However, it is genetic techniques that have
the greatest potential for revolutionizing these more traditional approaches. There
is now increasing experience with PCR, and PCR and probe-based methods are
being used with increasing frequency. Examples in work with seafood include
the use of DNA probes for V. vulnificus (Wright et al., 1996) and pathogenic
(tdh-, trh-, or tlh-containing) strains of V. parahaemolyticus (DePaola et al.,
2000), and use of PCR assays for the tdh gene in assessing possible virulence of
clinical and environmental V. parahaemolyticus strains (Young et al., 2002~.
Further rapid advances in molecular diagnostics may be anticipated, includ-
ing the development of some microarray assays for pathogenic microorganisms.
Microarrays, as currently formulated, are multiple assay arrays on glass slides on
which hundreds or thousands of probes are spotted, permitting a test sample to be
screened against all probes simultaneously. Currently, the most common applica-
tion of microarrays is to measure the presence and quantity of up to 20,000
messenger ribonucleic acid (mRNA) transcripts from mammalian cells (Schena
et al., 1996~. However, genomic microarrays to distinguish among species of
bacteria using the 16S ribosomal RNA gene have also been reported (Bavykin,
2001), with each probe on the microarray selected to identify a species of bacteria.
In addition, microarrays have been used to identify genes lost between different
strains of E. cold (Ochman and Jones, 2000), Helicobacter (Salama et al., 2000)
and Staphylococcus (Fitzgerald et al., 2001~. With microarrays it is theoretically
possible to immediately and quantitatively identify many, if not all, potential
pathogens in a sample; to identify strains carrying specific virulence genes or
strain subsets that have been linked with increased transmission potential (i.e.,
superclones); and to identify other genes of interest, including resistance genes.
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
While such microarray systems are not currently available commercially, they
represent a very promising technology for food safety applications.
The rapid advances being seen in this field of diagnostic technology under-
score the need for flexibility in any regulatory approach or development of per-
formance standards. This includes a need for flexibility at several levels.
Currently, there is a perception on the part of regulatory agencies that iden-
tification of a pathogen for regulatory purposes is not "real" unless a micro-
organism is isolated. Regulations need to be changed to recognize that molecular
and other rapid methods can produce results of comparable or greater accuracy
than those obtained with traditional culture techniques; there must be provisions
in regulatory actions for the use of data obtained with such methods.
Any regulatory approaches, including the establishment of performance stan-
dards, must have built into them sufficient flexibility to take advantage of the
improvements in diagnostics that will almost certainly occur.
THE LIMITS OF SCIENCE
Some portion of the public surely is skeptical about most scientific pro-
nouncements because of the seemingly conflicting advice, over time, from studies
conducted in areas such as nutrition and health. However, the committee recog-
nizes that many people believe that science and technology, given time and
money, can fix everything. While this expectation may not hold for vexing
problems deemed to be natural in origin (e.g., in respect to diseases such as
cancer and acquired immune deficiency syndrome), man-made problems seem
amenable to man-made solutions. Pathogens in store-bought foods are likely
perceived by many as a man-made problem (e.g., E. cold in juices). When the
committee held an open meeting to hear testimony from families that had suffered
tragic losses from foodborne illness, the speakers (on the record as well as in
private pleas in hallways after the session) urged committee members to "do
something" to prevent others from suffering as they had. Eminent scientists, it
was their heartfelt belief, could solve the problem.
Scientists and engineers have developed skills and made discoveries that do
enable the solutions to numerous problems of human origin. One example is the
carnage done over the years because of vehicle accidents. Technological and
legal changes that have made cars and their passengers safer have reduced the
vehicular death and disability toll. While increased enforcement could further
reduce the problem, this toll could be dramatically reduced through technology
by designing all vehicles much like military tanks, but such a drastic step would
dramatically increase the costs of vehicular travel and, through greater fuel needs,
their environmental impact. Even where science and technology have solutions,
their costs may be greater than society is willing to pay to achieve the projected
benefits. In these cases, society must determine the trade-off between costs and
benefits by tackling the question: What is the optimum level of safety we should
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FOOD SAFETY TOOLS
127
seek to achieve? To pick an extreme example, it soon will be possible to test food
for all pathogens and toxins of concern; all food could, in theory, be sampled
prior to consumption. Such a system would of course be entirely impractical,
both financially and logistically, although it would make the food almost
thoroughly safe for the consumer.
For our society, ensuring food safety is certainly an important goal that has
not yet been adequately achieved. Policymakers who wish to improve the food
safety system need to ensure adequate government financial resources for the
creation and enforcement of safety rules. Food safety requirements imposed upon
the food industry have financial consequences that may result in higher food
prices. For example, significant changes could be made in animal husbandry and
slaughter practices that would reduce the level of pathogens in food sold to the
public. Science might be able to discover better, less expensive means to deal
with pathogens in the food supply. Vaccines might be created that prevent food
animals from being colonized by pathogens that, while harmless to the animals,
are a danger to people. Simple, safe methods to kill pathogens on produce might
be developed. Some scientific advances that their proponents claim will lead to a
net benefit in food safety such as food irradiation and changes involving genetic
modification are opposed by some members of the public because of concerns
that one set of risks is being exchanged for another, to the frustration of many in
the scientific community (Henderson, 2002~.
Although there are limits to what science can achieve in consumer protec-
tion, a more significant limit in the food safety system may well be the willing-
ness of the public to accept the costs of implementing the measures that are
available. Given the high costs to our society of morbidity and mortality that are
related to foodborne illness, it would be sensible to require investment in food
safety that yields a positive return. That is, to the extent that expenditures to
improve food safety overall exceed the costs of the harm, these expenditures
should definitely be made (and prices allowed to rise to cover the extra costs).
Making such changes might interfere with consumer expectations about the low-
cost availability of food. Some of the least-expensive interventions (such as hand
washing by food handlers and improving retail worker and consumer compliance
with safe food handling and cooking guidelines) are the most difficult to attain
because they necessitate changing behaviors of vast numbers of people. How-
ever, while everyone must purchase food and eat (and thus everyone has an
interest in keeping down the cost of food), the harm from serious foodborne
illness falls on a small fraction of the population. Are the many willing to devote
resources to prevent serious harm to the few? Those who have lost loved ones
(many of whom have been young children) to foodborne illness answer this
question loudly in the affirmative; others are far less certain. While science and
technology will continue to search for and discover answers to problems involv-
ing foodborne illness, inexpensive answers are often unavailable or impractical.
Where to draw the line between requirements that should be implemented and
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SCIENTIFIC CRITERIA TO ENSURE SAFE FOOD
that are reasonably cost-effective, and those that would be beneficial but would
have too great an impact on food pnces, is a question for politics rather than for
science.
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Representative terms from entire chapter:
performance standard
