1.2. Steps of health risk
assessment
Many authors have localized the health risk assessment in four
steps which are mentioned below (Haas et al., 1999); (WHO, 1999);(Metcalf &
Eddy, 2007):
Hazard identification, defined as the process of determining
whether exposure to an agent can cause an increase in the incidence of a health
condition, is the most easily recognized in the actions of regulatory agencies
(Metcalf & Eddy, 2007). Also the identification of microbiology agent
capable of causing adverse health effects and which may be present in a food or
group of foods(WHO, 1999).
Dose-responsemay be defined as the determination of the
relationship between the magnitude of exposure (dose) to a chemical,
biological or physical agent and the severity and/or frequency of associated
adverse health effects (response)(WHO, 1999).The dose-response assessment is
the process of characterizing the relationship between the dose of an agent
administered or received and the incidence of an adverse health effect in
exposed populationsand then estimating the incidence of the effect as a
function of human exposure to the agent(Metcalf & Eddy, 2007).
Exposure assessment is the process of measuring or estimating
the intensity, frequency, and duration of human exposures to an agent currently
present in the environment. For microbial risk assessment, exposure assessment
describes the magnitude and/or probability of actual or anticipated human
exposure to pathogenic microorganisms or microbiological toxins(Haas et al.,
1999); (Metcalf & Eddy, 2007);(Fidjeland, 2010).
Risk characterization is the process of estimating the
incidence of a health effect under various conditions of the human exposure
described in exposure assessment. In addition, risk characterization may
require compiling all the data necessary for a given model and running
simulations (Haas et al., 1999); (WHO, 1999) and (Metcalf & Eddy, 2007).
1.3. Microbial risk
assessment
Haas et al., (1999) were defined microbial risk assessment
(MRA) as the process that is used to evaluate the likelihood of adverse human
health effects that can occur following exposure to pathogenic microorganisms
or to a medium in which pathogens occur.Other authors as WHO, (1999),Metcalf
& Eddy, (2007) andFidjeland, (2010)explained the microbial or
microbiological risk assessment process includes evaluation and consideration
of quantitative information; however, qualitative information is also employed
as appropriate. In other words, the microbial risk assessment should explicitly
consider the dynamics of microbiological growth, survival, and death in
foods and the complexity of the interaction between human and agent
following consumption as well as the potential for further spread (WHO, 1999).
Quantitative Microbial Risk Assessment (QMRA) is a tool used
to predict the consequences of potential or actual exposure to infectious
microorganisms(Haas et al., 1999). The methodology is based on the chemical
risk assessment concept for which the National Academy of Sciences published
recommended definitions and main principles (Höglund, 2001).QMRA thus
starts by a problem formulation where all the transmission routes and pathogens
of interest are identified. It then assesses the dose of a certain pathogen to
which an individual may be exposed and uses this dose in a dose-response model
to calculate the probability of infection. Risks are finally characterized by
taking into consideration the frequency of the exposure events for the range
ofpathogens studied, to estimate a total risk (Haas et al.,
1999);(Höglund, 2001).
| 
