-
A
technology (such as pesticide to control insect pests)
that seems harmless may have long-term environmental
effects.
- The
actions of human beings have become a primary influence
on the health of the earth.
Industry
spoke out strongly against Carson's book, claiming that the
book was based on feeling and not hard scientific evidence.
This perceived lack of scientific evidence prompted the President
of the United States to convene a scientific committee to
investigate the long-term environmental effects of the application
of DDT. The initial study demonstrated no threat to human
health. A later study, of course, found that not only was
DDT bio-accumulative, but that is was also causing a decline
in the raptor population because it affected reproductive
ability, mainly by making the egg shells too thin to survive
incubation.
The
environmental health and public health movements converged
in the 1970s. Most people were concerned about their risk
of cancer from exposure to certain man-made pollutants. The
combination of this popular movement and politics resulted
in the testing of chemicals, usually via animal testing,
to determine if the chemical was carcinogenic. Because it
was difficult, and in some cases impossible in the short term,
to determine the effect of exposure on humans of many chemicals,
the birth of the concept of risk assessment resulted.
The
approach to assessing human health risk from chemical exposure
differs substantially from the approach for assessing microbiological
risks.
| Feature
|
Chemical
Risk Assessment |
Microbiological
Risk Assessment |
| Pollutant
Concentration |
Assumed
to be lowered over time through dilution. |
Pathogen
concentration may increase or decrease or change in virulence. |
| Hazard
Identification |
Compiling
a list of pollutants and potential sources which contribute
to increased loading of the environment. Requires experimental
trials to determine and prove causal association. |
Compiling
a list of bacteria associated with the source of food
or the method of production or processing. |
| Exposure
Characterization |
|
Single-cell
pathogen may be undetectable at slaughter but can reproduce
to pose a later problem.
Pathogens may be introduced at any point.
Risk
may change at any point in food processing and distribution.
|
| Impact
of Exposure |
Cumulative
for long-term exposure. |
May
be acute or chronic. |
| Estimation
of Risk |
Risk
based on pollutant concentration, body weight, and other
factors. |
Difficult
to estimate risk of human infections because of multiple
factors involved in individual susceptibility. |
Risk
assessment is the science of identifying and evaluating potential
hazards and potential exposures. The two basic factors associated
with risk assessment are
-
The
likelihood of an event, and
-
The
consequences if it occurs.
Risk
assessment provides an analytical framework to support decisions
related to food safety. Food safety risk assessment involves
the development of either quantitative or qualitative models. A
model is basically a mathematical framework of components
that are used to assess the risk for any given commodity
or process.
The
first step in the risk assessment framework is to identify
the potential microbiological hazard. The goal of microbiological
hazard identification is to identify the organism and
determine its potential effect on people. There are many
tools for assisting in identifying foodborne pathogens.
Some are
the "Bad Bug
Book" of the FDA, the
CDC's Mortality and Morbidity Reports and
guidelines
for clinicians,
as well as the
government's Food Safety Information Center,
USDA/FDA
Foodborne Illness Education Information Center,
and
the
Department of Commerce's Seafood Inspection Service.
In the private sector, the
Center for Science
in the Public Interest,
the National
Food Processors Association,
and the
International
Food Information Council are
three of many hundreds worldwide.
 |
Microbiological hazard identification is accomplished
by observing and defining the types of adverse health
effects associated with exposure to foodborne agents.
These health effects are evaluated through measures such
as morbidity ratios, disease severity as determined by
the ratio of hospitalized cases to the total number of
cases in an outbreak, mortality ratio, and attack rates.
Hazard identification also involves specific routes of
transmission. Hazard identification may also involve statistical
analyses and literature reviews for existing information/studies
regarding the pathogen of concern.
Risk
characterization, the next step in risk analysis, is one
of the most important steps. Risk characterization takes
information from microbiological hazard identification
and uses qualitative or quantitative tools to assess and
predict the exposure for people. Risk characterization
serves to bridge risk assessment and
risk communication,
allowing for the discussion of confidence and uncertainties
in analysis. The foundations of risk characterization
are embodied in:
-
Exposure
assessment - determining the routes of exposure and
the likelihood of being exposed
-
Dose-response
assessment - determining the variation in impact following
exposures to differing levels of foodborne pathogens.
Exposure
assessments may be either qualitative or quantitative. Qualitative
exposure assessments are generally used when there is insufficient
quantitative information about the bacteria. Many qualitative
exposure assessment models focus on identifying the point
of entry of the pathogen. At a minimum, they should identify
and rank the microbes' entry potential and identify and
rank the potential of the microbes to spread. An example
of a qualitative
exposure assessment tool has
been developed by the Ontario Ministry of Agriculture.
Quantitative
exposure assessments often involve more elaborate mathematical
or predictive models. These models are used to:
-
Predict
the effect of changes in food processing or food storage
on microbial growth, and
-
Model
food handling procedures to obtain optimal reduction
in microbial growth.
Two
quantitative exposure assessment models that are readily
accessible are those of the
USDA's
Agricultural Research Service,
and the AMIF.
Dose-response
risk assessment also may be either qualitative or quantitative.
Qualitative dose-response risk assessments, in many cases,
are limited by available data. Some times, because of
the paucity of data, they are based on anecdotal information.
In this case, it is difficult to determine the minimum
exposure necessary to cause a negative effect - the so-called
Lowest Observed Effect Level (LOEL).
Quantitative
dose-response risk assessments attempt to determine the
number of vegetative cells - or spores - that will result
in morbidity. Animal studies are often employed, with
the results being extrapolated to humans. As any toxicologist
knows, this method is not nearly as reliable as actually
observing infection and resulting morbidity in humans.
The acute nature of foodborne illness, as well as its
extensive underreporting by clinicians, who many times
fail to identify either the agent of the disease, militate
against quantitative dose-response risk assessments.
|
