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CHAPTER 3
RISK-ASSESSMENT MODEL FOR
POULTRY INSPECTION: ANALYTICAL APPROACH
As indicated in Chapter 2, it is generally accepted that the design
and selection of inspection strategies for controlling human health
risks associated with broiler chickens should be based on risk
assessment. The present committee concluded that a complete
quantitative risk assessment is not possible at this time because of a
lack of data and limited resources. However, a qualitative assessment
based on the concepts of risk assessment and the judgments of experts
can be done. An analytical approach developed by the committee to
conduct such an assessment is described in this chapter
OVERVIEW OF THE ANALYTICAL APPROACH
The analytical approach recommended for the conduct and application
of risk assessment requires first a Conceptual framework and second, a
risk model, For its conceptual framework, the committee adopted the
well-accepted view of the role and nature of risk assessment developed
in 1983 by the National Research Council's Committee on the
Institutional Means for Assessment of Risks to Public Health. That
committee proposed that risk assessment proceed in four steps (NRC,
1983~:
Hazard identification: Determinations based on qualitative and
quantitative evidence 9 of whether a particular agent (e.g., a
chemical or microorganism) is or is not causally linked to
particular health effects.
Dose-response assessment: Determination of the relationship
between the magnitude of exposure and the probability that a
given health effect will occur.
Exposure assessment: Determination of the extent of human
exposure before or after application of regulatory controls.
Risk characterization: Description of the nature and often the
magnitude of human risk, including attendant uncertainty.
Important in this conceptual framework is the relationship between
risk management and these four steps of risk assessment. The 1983 risk
assessment committee reported that:
30
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31
Regulatory actions are based on two distinct elements, risk
assessment . and risk management. Risk assessment is
· .
the use of the factual base to define the health effects of
exposure of individuals or populations to hazardous
materials and situations. Risk management is the process
of weighing policy alternatives and selecting the most
appropriate regulatory action, integrating the results of
risk assessment with engineering data and with social,
economic, and political concerns to reach a decis ion (NRC,
1983, p. 39.
This concept leads to two important conclusions. First, the primary
purpose of risk assessment is to support decisions regarding regulatory
actions. Although there are nonregulatory uses of risk assessment
corresponding to the full range of nonregulatory options for risk
management, the regulatory orientation of the above quotation is
appropriate to the responsibility of FSIS. The second conclusion is
derived from the first and from the desire that risk assessments not
prejudice or mislead decision makers. That is, to the greatest extent
possible, risk assessments should be devoid of value judgments.
Judgments are needed in risk assessment, but they should be judgments
of science unbiased by the scientist's preferences for specific
risk-management policies.
Partitioning risk assessment into four standardized steps helps to
ensure that there is a comprehensive accounting of the factors that
determine risk and minimizes the policy and value judgments that might
otherwise be inserted into the analysis. The key to risk
characterization, the final step in the risk- assessment process, is the
development and application of a risk model that guides the analyst in
integrating and drawing conclusions from the first three steps:
identification of the hazard, dose-response assessments, and exposure
assessment.
In a formal, quantitative risk assessment, the risk model consists
of equations and mathematical algorithms and is often implemented as a
computer code. These equations and algorithms may be developed to
varying degrees of rigor, depending on the problem and the needs of the
user. For qualitative risk assessment, the risk model is not
formalized to permit rigorous numerical calculations. A qualitative
model does, however, identify possible sources of risk and how they
might be linked to health effects, and thus can be a valuable tool. By
us ing such a model, investigators can conduct a formal review of the
data demonstrating that a hazard exists, and organize information on
dose-response relationships and exposures. Qualitative models are
useful because they provide a logical framework for asking specific
questions and deriving conclusions systematically. Qualitative risk
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32
assessment is essential before quantitative risk assessment can be
undertaken.
A model to determine the risks of a process as complicated as
poultry production and consumption must disaggregate the complex
processes leading to the generation of those risks. The model must
take into consideration points in the process at which hazard or risk
agents are introduced into poultry or poultry products and modification
of the quantities or characteristics of these agents by subsequent
steps in the process. It can then be used to identify and determine
the logical interrelationships of important critical factors that
control the level of risk--that is, activities and events that
introduce, alter, or determine the size of human health risks.
In developing a model to assess the Herman health risks associated
with poultry, the committee reviewed the principal risk agents
associated with poultry production and consumption. These are
summarized below and are described in more detail in Chapters 4 and 5.
POULTRY RI SK AGENTS
The agents responsible for nearly all the human health risks
arising during the production and consumption of broiler chickens fall
into two categories:
.
^- THE RI SK MODEL
Pathogenic microorganisms or their toxins. These agents, such
as various species of Salmonella and Campylobacter, can
transmit diseases to humans when present in or on infected or
contaminated poultry tissues.
Poultry-borne chemical residues. As described in Chapter 2,
residues may be found in poultry intentionally given or exposed
in other ways to chemicals before slaughter. After exposure,
these chemicals may be concentrated and retained in the tissues
for long periods.
In general9 risk is dependent on the existence of three factors:
A source from which risk agents are generated or released into
the environment. For poultry production and consumption, the
risk source encompasses all the activities related to poultry
production, slaughtering, and processing.
A route of human exposure to the risk agents, e.g.,
distribution and consumption of poultry products.
A mechanism by which the exposures can generate adverse health
effects, e.g., through microbial and chemical factors , which
determine the health consequences resulting from human
consumption or other contact with poultry products.
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33
A risk model may be developed by identifying and linking all
significant influences on these three factors.
Figure 3-1 shows the major components, or submodels, of the risk
mode1. Figures 3-2 through 3-6 present each submodel in greater
detail, illustrating relevent factors and logical relationships. These
submodels are briefly described in the following paragraphs. More
detailed descriptions and references may be found in a report prepared
by another National Research Council committee (NRC, 19851.
Figure 3-7 combines the submodels to provide an overall account of
the risk source, exposure, and health effects. The figures themselves
are no more than a visual aid, and may be substantially amplified and
revised as FSIS brings its full expertise to bear on risk assessment.
Production Submodel
The first maj or component of the risk model (Figure 3- 2) accounts
for all risk factors associated with the production of live poultry.
The wholesomeness and safety of poultry products depends on the health
of the live birds, their feed, and the environment in which they are
raised. Thus, management practices and production technologies are
critical risk factors. Important production activities include
breeding, hatching, feed milling, and poultry health care, each of
which may affect microbiological or chemical hazards that reach the
consumer .
Methods of live poultry production may affect the wholesomeness of
poultry products in several ways. During breeding and hatching,
infection may be transmitted through the ovaries, through contaminated
eggs in breeder flocks, or as a result of exposure to infectious agents
in the hatchery. Infections may also occur during grow-out (Smitherman
et al., 1984~.
Other factors of concern are related to production facility
management. For example, methods of feed storage can promote or
prevent mat d growth and the production of mycotoxins , e. g., aflatoxin.
Water contact ning infectious agents such as Salmonella also presents
hazards (NRC, 1985, p. 128~. The condition of the feed provided during
the first few days of a b~rd's life is particularly important, since it
effectively establishes gut flora and the chick's ability to fight off
future contaminations (Mead and Impey, 1985; Nurmi, 1985; Snoyenbos et
al., 19789. The sanitation of the poultry housing facilities and
methods of manure and sewage disposal can also have implications for
public health.
Studies of Salmonella ecology clearly establish the genetic stock,
feed and feed ingredients, and environmental sources as critical points
at which hazards from this microorganism may be controlled during
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Representative terms from entire chapter:
poultry products
34
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PRODUCTION
FIGURE 3-2 Production submodel.
poultry production (Barnum, 1977; Bryan et al., 1976; NRC, 1969~.
Despite precautions, however, exposures of poultry to pathogenic
microorganisms such as Salmonella are difficult to avoid. Total
confinement of primary breeding flocks has been studied as one means
for reducing the transmission of Salmonella through eggs. fumigation
techniques have been tried as well. There are methods to reduce the
Salmonella contamination of processed feeds; however, feed
contamination remains a widespread and serious problem (USDA, 1978>
Vaccines administered to prevent economically important diseases
may have public health consequences. In addition, most producers rely
on a variety of prophylactic medications, especially antimicrobial
agents and coccidiostats, to prevent or reduce the prevalence of
infectious agents and parasites (North, 19841. The type of antibiotics
as well as the quantity and time of their application on farms are
critical factors, because the residues from these substances can remain
in the tissues and present a health hazard to some people. Residues
from drugs and medicated feeds are often found in carcasses when they
are administered too soon before slaughter (USDA, 1984a). Drug
36
residues can also result from the accidental mixing of medicated and
nonmedicated feeds at the feed mill, during transport to the farm, or
at the farm itself. Antibiotic-resistant strains of pathogens may
emerge as a result of treating birds or using antibiotics in feed.
Chemical res idues can also result if the poultry are exposed to
pesticides and other agricultural or industrial chemicals (Booth, 1982;
Doull et al. 3 1980)e Pesticides may be applied to animals to control
insects or internal parasites, but most exposures of poultry result
from the application of pesticides to buildings, crops used for feed,
or feed storage areas. Industrial chemicals used in electrical and
mechanical equipment, e.g., polychlorinated biphenyls (PCBs) used in
some electric power transformers, can also leave residues. If not
detected in time, an accident, such as inadvertent contamination with
PCB or hexachlorobenzene, could introduce into the food chain high
levels of toxic substances that are not normally present (Booth, 1982;
Doull et al., 1980)0
Thus' poultry production practices have the potential for affecting
human health risks by determining whether and the extent to which
various hazardous agents enter the poultry supply. They are often
responsible for the diseases and contaminants that may be detected
during inspection. At present, however, the Food Safety Inspection
Service (FSIS) has no responsibility for monitoring the production
phase .
S laughter Submodel
The next major component of the risk model (Figure 3-3) includes
the risk factors related to slaughter and the inspection activities
conducted during this process. The critical points in slaughtering
operations include sanitary conditions during transport and during the
slaughtering process itself, as well as antemortem and postmortem
inspections and examinations for microbial and chemical contaminants.
Live poultry is usually sent by truck to the slaughtering plant in
specially built coops, baskets, or batteries. As noted in Chapter 2,
antemortem inspection is discretionary and is designed to ensure
compliance with regulations, with no apparent mechanism to selectively
emphasize those regulations that relate to issues important to the
public's health Nonetheless, most producers include this step in
their own quality control programs, in part to provide early data on
probable flock condemnation rates.
Poultry raising practices are such that a lot den ivered for
s laughter tends to have a common genetic and environmental background .
In addition, disease incidence in a giver lot is likely to be either
quite low or fairly high, resulting in distinct lot-to-lot distribution
of condemnation rates . However, inspectors conducting antemortem
inspection usually have no knowledge of the flock's history to aid them
in identifying human health hazards.
37
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38
During antemortem inspection, the FSIS inspector has an opportunity
to observe birds between the time of arrival and when they are hung on
the slaughtering line. Although birds may be rejected as a result of
antemortem inspection, the criteria for condemnation are not always
sensitive to the hazard posed to human health. For example, a bird
developing heat stroke in transit is placed in the same public health
category as one in terminal stages of septicemia salmonellosisO
Birds that pass antemortem inspection are placed on a 1ine leading
them to the various steps in the slaughtering process and to postmortem
inspection. The first step in the slaughtering process is often, but
not always, to stun the birds with an el ectrical shock Subsequently,
the birds pass through steps that may affect human health risk:
scalding, the removal of feathers, and the withdrawal of viscera. As
in the production phase, the management practices and processing
technologies used in these procedures can have a considerable impact on
microbial loads.
Most microbial contamination of the poultry's skin surfaces occurs
during defeathering (ICMSF, 1980~. In one automated study of plant
sanitation, Salmonella was isolated more often from pickers (machines
provided with many rubber prongs called fingers, which remove all the
feathers) than from any of the other equipment sampled, both before and
after the start of processing (Campbell et al., 19841. A possible
reason for this could be the complex construction of the pickers and
the inherent difficulty of adequately cleaning all the picker fingers.
The temperature of scald water (52°C; 126°F) and the thorough
washing of poultry carcasses are critical in poultry slaughtering
operations because of the potential for transfer and cross-
contamination of Salmonell a and other microorganisms during
defeathering (Green et al., 1982~.
Perhaps the most important step of sanitary dressing is the proper
removal of the gastrointestinal (GI) tract. Since Salmonella and other
enteric bacteria originate in the digestive tract and fecal material of
the slaughtered bird' it is extremely important to prevent
contamination of the carcass by spilled GI tract contents or smeared
fecal matter (ICMSF, 1980~. The likelihood of contamination increases
in birds with localized or generalized diseases, infections, or
contamination.
After postmortem inspection, as noted in Chapter 2, the birds are
passed as food or condemned in 1 of the 11 categories listed in
Table 2-2. In fiscal year 1983, for all classes of poultry, less than
1% of the poultry examined were condemned during postmortem inspection
(USDA, 1984c). In general, inspectors base their condemnation
decisions on five criteria: condition of tissue (diseased or
abnormal), type of disease (localized or generalized; acute or
chronic), impairment of important body functions (e.g., uremia,
icterus, toxemia), injurious to health of consumer (e.g. 9 tissues
containing toxic chemical res idues or ~ nfectious agents), and
39
appearance (offensive or repugnant) (USDA, 1984b). Carcasses are
usually condemned because of the presence of a visible anatomic lesion
or specific condition (e.g., air sacculitis) rather than by cause
(e.g., a specific infectious agent). The inspection system is not
designed to detect human pathogens unless they produce an observable
lesion. Neither pathogenic microorganisms that typically reside in the
gastrointestinal tracts and on external surfaces of poultry nor
chemical residues are generally detectable by routine organoleptic
inspection procedures (i.e., sight, smell, or touch). Condemned
carcasses and parts are promptly destroyed to prevent their entrance
into the human food chain (Libby and Humphreys, 1975~.
Info oration collected by the U.S. Department of Agriculture in
previous years indicates "passed-b~rd error rates" (percentage of
passed birds with gross and visible lesions) of approximately 1% to
1 . 5 % and that there are large inspector-to- inspector and day- to - day
variations but small plant- to-plant variations. These estimates were
obtained from 1969 to 1973, when condemnation rates were approximately
5%, and are not likely to be applicable now, when condemnation rates
are roughly 1% (Booz-Allen & Hamilton, Inc ., 1977) . They indicate
nevertheless, that error rates may equal a substantial fraction of
condemnation rates. Carcasses contaminated with chemical residues and
bacteria are generally not identifiable during inspection because these
conditions are rarely visible. Therefore, these factors are not
included in the error rate.
Other aspects of the inspection process with public health
significance are inspection of plant sanitation (Kauffman and
Schaffner, 1974), monitoring of residues, and reinspection of carcasses
see Chapter 2~.
The residue monitoring program emphasizes the control of
chlorinated hydrocarbon pesticides; however, evidence of a variety of
other chemicals is also sought. During fiscal year 1983, 424 samples
of young chickens were analyzed for 15 different chlorinated
hydrocarbon residues. There were 73 positives, but only one that
exceeded established tolerances (for chlordane) (USDA, 1986~. Some
poultry producers operate their own residue programs, working with FSIS
to detect violative residues and remove contaminated products from food
channels.
Chilling and freezing of poultry carcasses (broilers; fryers ~ at
temperatures of 40~F (4°C) or less within 4 hours after slaughter
are critical factors in inhibiting microbial growth (CFR, 19839.
Carcass reinspection involves the sampling of carcasses that have
passed routine postmortem inspection, dressing, and wash-and-chilling
operations (see Chapter 2~. Final carcass washing is a risk factor
influencing biological contamination levels. Germicides such as
chlorine may be helpful, although the efficacy of chlorination under
some conditions is not certain (NRC, 1985~. The design of final
washers used on poultry evisceration lines (e.g., water pressure,
nozzle type, location, and procedures) can also influence microbial
counts.
40
Packing and Further Processing Submodel
Packing and further processing of broilers and fryers are also
critical factors (Figure 3-4~. Then carcasses are cut, pathogens on
the surfaces of the carcasses, including species of Salmonella,
Campylobacter, Clostridium, and Staphylococcus, can contaminate
workers' hands, cutting boards, knives, tabletops, saws, and other
pieces of equipment, and can then be transferred directly or via
cleaning cloths to other equipment. The effectiveness and extent of
efforts to minimize cross -contamination at this stage and to improve
the sanitation of processing equipment constitute risk factors. The
temperature in rooms for deponing, slicing, and storage and the
durations of storage are also critical points that determine whether
contaminating organisms multiply.
For frozen products the critical points up to the time of freezing
are the same as those for chilled products In addition, proper
packaging, rapid freezing, and the time and temperature at which
products are frozen and subsequently thawed also influence the counts
of microorganisms (Peterson and Gunnerson, 1974~. For vacu~m-packed
poultry products, it is important to maintain anaerobic conditions in a
carbon dioxide and nitrogen atmosphere so that growth of the aerobic
flora that commonly spoil unpackaged raw poultry can be inhibited.
For dried poultry, the moisture content should be lowered enough to
provide shelf stability It is therefore essential that the drying
rapidly decrease the Aw of these products to levels at which
pathogens do not multiply. During the drying process, therefore, the
rapidity of the procedure and temperature control are critical points.
For cooked, uncured products, the quality of the raw ingredients is a
critical control point as are the duration of cooking (which should be
sufficient to kill yeasts, molds, parasites, and viruses), the
temperature of cooking (130- 167°F, or 54- 75°C), the rate of cooling
(pathogens can multiply in cooked products held too long at certain
temperatures), the handling of the products after cooking (e.g., an
entry point for Salmonella)(Bryan, 1980), equipment sanitation, and
subsequent cold storage (when micrococci, streptococci, and other
psychrophilic bacteria may multiply). For uncured canned products,
acidity is important. Products with a pH of 4.6 or less are considered
high-acid products and need only heating to ensure shelf stability
Low-acid uncured canned foods (pH greater than 4.6) must be given
time-temperature exposures that kill up to 1012 Clostridium botulinum
spores. For cured canned poultry, critical factors are proper curing
(including adequate salt and nitrite concentrations), quality of
LAW (water activity) is the ratio of the water pressure of a food
to that of pure water at the same temperature. It is the measure of
water in food available for use by microorganisms that have specific
cardinal requirements for Aw.
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46
the risk. For example, the number and severity of potential
health effects may be influenced by the level of microbial
contamination of feed, the degree of contamination of the
carcass during evisceration, the extent of cross-contamination
during cutting, and other factors.
3. Compare the degree to which alternative strategies can affect
the critical factors.
4. Use the conceptual risk model to determine how impacts on
critical factors relate to incremental changes in the
likelihood that health effects will occur in consumers and the
magnitude of those effects.
Data are currently insufficient to permit the last step to be based
on formal quantitative models. Nevertheless, this task can be
performed qualitatively by using the risk model to guide the
professional judgments necessary to reach a qualitative conclusion
about the impacts on human health. As appropriate quantitative data
are collected, the various steps outlined above may be used to produce
quantitative measures of risk. Regardless of whether risk estimates
are quantitative or qualitative, such assessments are essential to the
identification and selection of FSIS strategies for protecting public
health. Described below is a generalized logic for incorporating risk
assessment into the planning process.
USING RISK ASSESSMENTS TO PROTECT HEALTH
A substantial assurance that health risks do not reach unacceptable
levels is surely a critical function of the FSIS program. Potential
adverse health consequences vary in frequency and severity, and
evidence concerning them ranges from nearly nothing to conclusive. An
optimal health-protection program (including inspection) can exploit
these variations both to increase effectiveness of inspection
procedures and to reduce costs of their implementation. Put simply, it
is important to determine what types of risk and evidence pertaining to
that risk justifies what set of actions.
Limited information and uncertainties create difficulties in each
step of risk assessment. Hazard identification is often uncertain;
e.g., there may be only poor evidence on the clinical significance of
certain strains of Salmonella found in broiler chickens or on the
carcinogenicity of a chemical residue. Dose-response relationships are
hard to establish with precision and may vary from time to time, place
to place, and (especially) consumer to consumer. It is also difficult
to assess exposures with any degree of completeness or certainty, since
only a small percentage of broiler chickens can be tested for specific
chemical or microbial hazards. Because of these and countless similar
problems knowledge about the health risks attributable to broiler
chickens is somewhat fragmentary and uncertain.
47
The current FSIS inspection program is relatively inflexible and is
not well suited for providing information needed to resolve these
uncertainties. For example, every bird must pass organoleptic
inspection, and line speeds are fixed at specific rates. Sample sizes
for testing and surveillance of chemical residues are also fixed; no
opportunity is provided for adjusting the detection sensitivity to
changing perceptions regarding the magnitudes of the hazards or the
likelihood that residues will be found. Opportunities for resolving
uncertainties are missed; for example, birds condemned during
organoleptic inspection are not examined to learn what they can teach
regarding the assessment and abatement of health risks. The inspection
itself cannot ordinarily distinguish contaminated from uncontaminated
birds, whether the contamination is microbial or chemical.
Information might be collected to build a base of knowledge for
improving inspection effectiveness. For example, if the first,
approximately random 10% of a flock is unusually healthy, the remaining
90% is likely to be healthy too. An infection in one grow-out house
may well be present in an adjacent house. If a prohibited practice is
detected at one place or time in a slaughter operation, it is pass ible
that there may be other prohibited practices at other places and times
in that operation. Indeed, inspectors often believe quite strongly
that they can distinguish good flocks and good operators from bad ones.
This continuum in knowledge and the parallel continuum in risk are
not, on the whole, reflected in either the strategies of FSIS for
inspection or the more general control of health hazards. The methods
used cannot be tailored to changing situations and do not maximize the
potential for learning. Thus, an opportunity exists to improve both
the ruble c health and the cost-effectiveness of the FSIS inspection
procedures by adopting procedures capable of account' ng for substantial
gradations in both risk and knowledge about risks in general and about
circumstances contributing to risk. To protect health, inspection
should be deliberately and objectively targeted to maximize, for a
given expenditure of resources, the return in reduced morbidity and
mortality. This return will vary from one activity to another, from
one producer to another from one time to another, and in other ways.
Formal risk assessment is the key to capturing ~ organizing ~ and
interpreting the evidence that can be brought to bear on the optimum
use of inspection resources. It will identify problems in a clear and
organized way; produce the best possible estimate of the likelihood
that a risk exists, and if so, its size; and make clear the kinds and
degrees oF uncertainty attached to that estimate. This information can
then be translated into a detailed strategy to protect human health,
including the development of specific regulations and instructions to
inspection staff.
A comprehensive strategy for reducing the health risks attributable
to poultry should be based on a broad conceptual model of how those
risks arise and on assessments of the nature and magnitude of those
48
risks made at the highest level of precision attainable. Furthermore:
the risk reduction strategy should be cost effective and designed to
take advantage of the full range of tools available to FSIS. Any
health protection program is likely to involve several steps, but there
is no agreed-upon classification of these steps, such as there is for
the four steps in risk assessment. Some of these activities are listed
below. Their order should not be construed as an implication of their
priority
· Establish objectives and set priorities .
· Identify and analyze alternatives for achieving priority
obj ectives such as the following: e . g., 100% organoleptic
inspection or a requirement for a withdrawal period after use
of a drug.
Identify potential hazards and set tolerances or action levels
(targets and goals) for each, including considerations of
possible synergistic interactions.
Select and implement a control program.
Conduct monitoring and surveillance and interpret results.
Take appropriate steps to ensure compliance (by producers) and
enforcement (by FSIS).
Conduct research to improve the model' the risk assessments, or
the data on which they are based.
These kinds of activities should be developed as an integrated
package; they are substantially less independent than the steps in risk
assessment. Several categories of such activities are discussed below.
Establish Priorities
Any feasible program for risk management will require establishment
of priorities for reducing or eliminating factors that contribute to
risk. Such priorities and the frequency and intensity of monitoring
should be based on risk assessment, but for most kinds of FSIS
interventions it is only the relative risks of the various alternatives
that are of concern. For example, in choosing among postmortem
inspection strategies, it is the potential increase ox decrease from
current levels of health risks that is most important.
Thus, there would be much value in having a scheme for relative
ranking of all poultry-borne risks, including microbial hazards, even
if the absolute magnitudes of those risks remain uncertain. In Chapter
5, for example, it is shown how different carcinogenic hazards can be
ranked on a common qualitative scale. A broader system of ranking may
require a substantial research program as well as field testing.
A scheme for assessing relative risks need not include estimation
of the absolute risk of any of the substances to be ranked It is
necessary only that the scheme incorporate in a systematic way some
measures of both pathogenicity and exposure. Both of these components
are essential and must be determined to an adequate degree of
49
accuracy. For example, the data on Class 1, 2, and 3 chemicals (see
Chapter 5) vary widely in quality and content, and these differences
must be taken into account in a systematic way.
The primary purpose of a relative risk assessment is to ensure that
two major risk-management activities--monitoring of feed and water and
monitoring of poultry products (including whole birds)--are given a
level of emphasis reflecting the probability that the risk factor will
be found in food intended for human consumption, the level of risk that
may result if it escapes detection, and the extent to which the risk
can be reduced.
Identify Problems of Risk Management, and Set Acceptable Levels of Risk
After analyzing a broad range of hazards, Lowrance (1976) concluded
that ''a thing is safe if its risks are judged acceptable." This is
not a tautology; perfect safety is a chimera, but very small risks may
be deemed acceptable when the costs (in the broadest sense) of their
further reduction exceed the expected benefits. For example, FDA does
not in general concern itself with carcinogens that are believed to
produce cancer risks of less than one per million persons exposed at
the maximum allowable dose over a lifetime. Acceptability of risk
depends on many things, including the type of outcome (e.g., skin rash
vs. cancer), whether the risk is already common or familiar, and
whether the risk is known to exposed persons and assumed voluntarily
(Fischhoff et al., 1978~. Perceptions of risk to health are important
whether or not they are in line with the best quantitative estimates.
Both the definition of risk and the determination that certain
risks cannot be eliminated at an acceptable cost are generally very
difficult. Risk management, including the setting of acceptable levels
of risk, is a political rather than scientific task and hence outside
the committee's purview. The committee notes, however, that risk
management should ordinarily be based on the best available scientific
risk assessment and an objective analysis of the appropriate role of
risk assessment in risk management. Furthermore, risk-management goals
should be precisely stated in quantitative, evaluable terms. For
example, a maximum tolerance level below the lowest detectable level
(microbial or chemical) would be unenforceable.
Monitoring and Surveillance
There will be a continuing need for monitoring and surveillance to
ensure that FSIS program goals are met--goals that can be partitioned
into structure, process, and outcome. It will also be necessary to
fine-tune inspection activities and to update the system to keep pace
with changing risks and production practices.
Of particular importance for the monitoring program is the
selection of sampling rates. Statistical sampling strategies can be
devised to ensure, with a specified degree of confidence, that products
so
containing excessive levels of chemical residues are identified for
removal from the food supply. The desirable degree of confidence for
potentially high risk substances should be greater than for other
substances. In Chapter 5 of this report, the committee recommends
specific criteria for chemical residues posing different levels of
potential risk to public health. Chapter 6 describes a risk ranking
scheme, which can be used not only to develop monitoring strategies,
but also to aid other data gathering efforts.
Risk assessment plays several important roles in a program to
control or eliminate health hazards posed by broiler chickens. All are
based on applying, with varying degrees of rigor, the elements of a
conceptual model of risk and rely on the use of specific types of
data. An effective risk management scheme will require each of these
program elements, although not all need to be within the direct control
of FSIS (indeed, some are already established at FDA and EPA).
Nevertheless, it is important that FSIS ensure adequate coverage of the
full range of activities needed in risk management and that the agency
acquire substantial knowledge of the adequacy of each activity.
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