Australia Model Code of Practice Managing the Risks of Biological Hazards at Work 5.1: Assess likelihood from the nature of the hazard (communicable or not, multiple transmission routes, ease of infection), of the source (constant, routine, seasonal or occasional presence) and of the exposure (who, how long, how often, and whether activities or environment raise it), the consequences (vulnerable people, severity or fatality, immediate or gradual, short or long term, reversible or not, psychological effects) and the effectiveness of existing controls against industry standards, vaccines and treatments; do more as severity rises, assess multiple hazards together, and assess off-site work such as field trips

What does 5.1 require?

In assessing risk the PCBU considers the likelihood of exposure, looking at the nature of the hazard (communicable like measles and gastroenteritis viruses or non-communicable like tetanus and Legionella; spread through multiple sources as norovirus is; how easily it infects, by brief proximity or only through an open wound), the nature of the source (constant such as water near farmland, routine such as cleaning animal enclosures, seasonal such as harvest or pollen, occasional such as mosquito surges after rain) and the nature of the exposure (who has contact, for how long and how often, from a postal worker's brief delivery to a nurse's hours of home care several times a week, and whether the activities or environment increase exposure through close contact, animals, outdoor insects or poor indoor air); the possible consequences, including whether people at higher risk of severe harm may be exposed, whether exposure could cause severe injury or illness or death (toxins from venomous animals), whether harm is immediate or gradual, short or long term, reversible or irreversible, and whether there are psychological consequences such as trauma after bites or stress while awaiting test results; and the effectiveness of existing controls, including what is already in place, current industry and Australian Standards, and the availability, use and effectiveness of preventatives such as vaccines and of medical treatments. Risk rises with likelihood and consequence (grain dust outside harvest versus prolonged high exposure leading to hypersensitivity pneumonitis, asthma, bronchitis, byssinosis and cancer), and more must be done for severe risks, as with Hendra virus compared with tinea among horse workers. Multiple hazards are assessed together to see combined impacts and shared controls such as ventilation and air cleaning, and work outside the formal workplace such as field trips and site surveys must be assessed as part of the process, with authoritative sources consulted on potential impacts.