3.2. Risk assessment

Risk assessment is the rational application of safety principles to available options for handling hazardous materials. The following characteristics are considered when evaluating a potential pathogen:

• the agent’s biological and physical nature;
• the sources likely to harbor the agent;
• the h;
• the procedures that may disseminate the agent;
• the best method to effectively inactivate the agent.

The biological nature of pathogens determined their distribution into risk groups.

Risk groups of pathogens

Microorganisms that are human pathogens can be categorized into risk groups (RG) based onthe transmissibility, invasiveness, virulence (i.e., ability to cause disease), and the lethality of thespecific pathogen. Risk groupings of infectious agents (RG1 through RG4) approximatelycorrespond to biosafety levels (BSL1 through BSL4), which describe containment practices,safety equipment, and facility design features recommended for safe handling of thesemicroorganisms.

Beginning with RG1 agents, which are nonpathogenic for healthy human adults, the schemeascends in order of increasing hazard to RG4.

RISK GROUP 1 agents are not associated with disease in healthy adult humans. Examples: E.coli K-12, Saccharomyces cerevisiae.

RISK GROUP 2 agents are associated with human disease that is rarely serious and for whichpreventive or therapeutic interventions are often available. Examples: enteropathogenic E. colistrains, Salmonella, L. monocytogenes, Cryptosporidium, and Staphylococcus aureus.

RISK GROUP 3 agents are associated with serious or lethal human disease for whichpreventive or therapeutic interventions may be available (high individual risk but lowcommunity risk). Examples: human immunodeficiency virus, Brucella abortus, Mycobacteriumtuberculosis.

RISK GROUP 4 agents are likely to cause serious or lethal human disease for whichpreventive or therapeutic interventions are not usually available (high individual risk and highcommunity risk). Examples: Ebola virus, Cercopithecine herpesvirus 1 (Herpes B or Monkey Bvirus).

Consideration of the risk group assignment, however, merely is a starting point for thecomprehensive risk assessment. Further attention must be given to the circumstances, such asthe planned procedures and the available safety equipment. Then, the recommendedprecautions may be increased or decreased relative to those based solely on the risk groupassignment and adjusted to reflect the specific situation in which the pathogen will be used.Microorganisms in RG1 require use of standard basic biological laboratory facilities andmicrobiological practices, whereas those in RG4 require maximum containment facilities andpractices. Some of the agents likely to be handled experimentally at UW-Madison are RG2 orRG3 pathogens; designated as moderate and high hazard, respectively. These agents typicallyrequire more sophisticated engineering controls (e.g., facilities and equipment) than are availablein standard laboratories, as well as special handling and decontamination procedures. Consideration also is extended to microorganisms that cause diseases in animals and/or plants,which are not categorized into risk groups as are human pathogens. The desired containmentfor animal and plant pathogens is based on the severity of the disease and its ability todisseminate and become established in the local environment.

The progression from invasion to infection to disease following contact with an infectiousagent depends upon the dose, route of transmission, invasive characteristics of the agent,virulence and resistance of the exposed host. Not all contacts result in infection and even fewerdevelop into clinical disease. Even when disease occurs, its severity can vary considerably.Attenuated strains should be handled with the same precautions as the virulent strain unless thereduced pathogenicity is well documented and is irreversible. Viral vectors, even if renderedreplication defective, still may pose a threat of recombination with wild-type strains and/orunintentional delivery of their foreign genes. It is prudent to assume virulence.

Which human pathogens are harbored by plant products?

Four priority pathogens have been identified by the regulatory agencies as the initial focus of foodborne illness source attribution work: Salmonella, E. coli O157:H7, Listeria monocytogenes, and Campylobacter. Furthermore, surveys of plant products have shown the potential for high-risk plant productsto be also contaminated with L. monocytogenes, Aeromonas spp., E. coli,B. cereus, C. botulinum, andSalmonella, when they are consumed raw.Contamination of fresh cut fruit and vegetables,as discussed in the previous section, can occur during growth, harvest orprocessing and storage of harvest and packing in a modified atmosphere.

The presented risk assessment will review the hazards associated with food businessesregulated under the food safety schemes of Food Regulation andincludes plant products, such as fresh cut fruits and vegetables, unpasteurized juice, andvegetables in oil. Risk assessmentforms part of an overall process, called risk analysis. Risk analysis isused by governments and industry to assess, manage, and communicate the riskassociated with particular food or food groups and in turn aims to reduce the risk of foodborne illness.

The Codex Alimentarius Commission (CAC) divides riskanalysis into three components:

• Risk assessment – a process by which the potential risk posed by food safetyhazard(s) is determined;

•Risk management – the process of determining alternatives to control thehazards identified in the risk assessment; and

• Risk communication – the exchange of information on risk and riskmanagement amongst interested parties.

CAC (1999) has identified four components of risk assessment:

• Hazard identification – the process of identifying potential hazards associatedwith the food.

• Exposure assessment – an estimation of the potential human exposure to thehazard,which includes the use of data such as the occurrence in a particular foodand/or potential consumption rates of the food. Exposure assessment can be defined as the set of circumstances that influence the extent of exposure.

• Hazard characterisation – the evaluation of the potential illness associatedwith the hazard.

• Risk characterisation – the process of determining the probability ofoccurrence and severity of the adverse health effects based on theinformation collected in the hazard identification, exposure assessment andhazard characterisation. Risk characterization can be viewed as a “quantitative measurement” of the probability of adverse effects under defined conditions of exposure. Some authors, when evaluating the effect of plant pathogens, also add the step of dose-response evaluation, which involvesdetermination of the relationship between the magnitude of exposure and probability of the adverse effect.