Table 4.5 Qualitative measures of likelihood Level Descriptor Example description A Rare May occur only in exceptional circumstances; may occur once in 100 years B Unlikely Could occur within 20 years or in unusual circumstances C Possible Might occur or should be expected to occur within a 5–10-year period D Likely Will probably occur within a 1–5-year period E Almost certain Is expected to occur, with a probability of multiple occurrences within a year Table 4.6 Qualitative measures of consequence or impact Level Descriptor Example description 1 Insignificant Insignificant impact or not detectable 2 Minor Health minor impact for small population — Environment potentially harmful to local ecosystem with local impacts — contained to site. 3 Moderate Health minor impact for large population. — Environment potentially harmful to regional ecosystem with local impacts — primarily contained to on-site. 4 Major Health major impact for small population — Environment potentially lethal to local ecosystem. Predominantly local, but — potential for off-site impacts. 5 Catastrophic Health major impact for large population. — Environment potentially lethal to regional ecosystem or threatened species. — Widespread on-site and off-site impacts. Table 4.7 Qualitative risk estimation Consequences 1 2 3 4 5 — — — — — Likelihood Insignificant Minor Moderate Major Catastrophic A Rare Low Low Moderate High High — B Unlikely Low Low Moderate High Very high — C Possible Low Moderate High Very high Very high — D Likely Low Moderate High Very high Very high — E Almost certain Low Moderate High Very high Very high — Microbial health risk A quantitative risk assessment can be applied to microbial hazards, based on the approach described in Chapter 3 and Appendix 2 of Phase 1 of the guidelines (NRMMC–EPHC–AHMC 2006). The approach uses the following reference pathogens: for protozoa and helminths Cryptosporidium • a rotavirus and adenovirus combination for enteric viruses •
Table 4.5 Qualitative measures of likelihood Level Descriptor Example description A Rare May occur only in exceptional circumstances; may occur once in 100 years B Unlikely Could occur within 20 years or in unusual circumstances C Possible Might occur or should be expected to occur within a 5–10-year period D Likely Will probably occur within a 1–5-year period E Almost certain Is expected to occur, with a probability of multiple occurrences within a year Table 4.6 Qualitative measures of consequence or impact Level Descriptor Example description 1 Insignificant Insignificant impact or not detectable 2 Minor Health — minor impact for small population Environment — potentially harmful to local ecosystem with local impacts contained to site. 3 Moderate Health — minor impact for large population. Environment — potentially harmful to regional ecosystem with local impacts primarily contained to on-site. 4 Major Health — major impact for small population Environment — potentially lethal to local ecosystem. Predominantly local, but potential for off-site impacts. 5 Catastrophic Health — major impact for large population. Environment — potentially lethal to regional ecosystem or threatened species. Widespread on-site and off-site impacts. Table 4.7 Qualitative risk estimation Consequences Likelihood 1 — Insignificant 2 — Minor 3 — Moderate 4 — Major 5 — Catastrophic A — Rare Low Low Moderate High High B — Unlikely Low Low Moderate High Very high C — Possible Low Moderate High Very high Very high D — Likely Low Moderate High Very high Very high E — Almost certain Low Moderate High Very high Very high Microbial health risk A quantitative risk assessment can be applied to microbial hazards, based on the approach described in Chapter 3 and Appendix 2 of Phase 1 of the guidelines (NRMMC–EPHC–AHMC 2006). The approach uses the following reference pathogens: • Cryptosporidium for protozoa and helminths • a rotavirus and adenovirus combination for enteric viruses
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