Source: United States Environmental Protection Agency (EPA)
A dose-response or concentration-response (probability) relationship describes how the frequency and severity of adverse health effects (the responses) are related to the amount and condition of exposure to an agent (the dose provided) (The National Institutes of Health, 2003).
A two-step process
Two types of risk assessments
RfD = NOAEL (or LOAEL or BMDL)/UFs
The reference dose (RfD), No-Observed-Adverse-Effect Level (NOAEL), lowest-observed-adverse-effect level (LOAEL), Benchmark Dose Lower-confidence Limit (BMDL), uncertainty factors (UFs).
The cancer risk is determined by use of the following equation: Cancer Risk = Exposure x Slope Factor
Total cancer risk is calculated by adding the individual cancer risks for each pollutant in each pathway of concern (i.e., inhalation, ingestion, and dermal absorption), then summing the risk for all pathways.
Three basic approaches for quantifying exposure
Each approach is based on different data and has different strengths and weaknesses.
The combination of approaches can greatly strengthen the credibility of an exposure risk assessment:
Environmental Risk Assessments (ERA)
This is similar to a health risk assessment, in line with frequency, severity and exposure risk assessment methodology. ERA examines the effects of an entity or agent on humans (health risk assessment) and ecosystems (ecological risk assessment). The steps and methods used in an ERA will differ, depending on the risks, receptors, and end-points investigated (Fairman, et al. 1999).
Environmental risk assessment of marine activities
Source: Coastal Wiki
Natural disaster risk assessment (World Meteorological Organization, 1999)
An additional vulnerability variable is added to the frequency, severity and exposure methodology. The law enforcement sector combating money laundering and terrorist financing also use this approach per thematic area.
An example is flood risk assessment, which requires an intensive amount of data and can also be used to evaluate the net benefits of a proposed flood-mitigation programme.
Expected losses = hazard x exposure x vulnerability
Disaster risk assessment (Thinda, 2009)
A serious disruption to the functioning of a community that causes widespread human, material, economic or environmental losses, which exceeds the ability of the affected community to cope with its own resources.
Disaster risk = H x V/C
H is Hazard, V is Vulnerability and C is Capacity to mitigate and respond to disaster events.
This method would add value to an OHS risk assessment by taking into account the vulnerability of workers, systems, processes and other organisational assets.
Terrorist attack risk assessment
The USA Department of Home Land Security uses an approach to allocate funds to state or local governments to enhance their ability to prepare for and respond to terrorist acts. This fund allocation requires an assessment of risk using a formula as follows:
R=T*V*C
Threat (T) to a target/area, vulnerability (V) of the target/area, consequence (C) of an attack on that target/area.
The assessment can be asset- or geography-based as illustrated in the charts below.
Asset-based risk analysis attributes
State geographic risk analysis attributes
Source: Masse, O’Neil & Rollins, 2007
Terrorist attacks and other technical risk assessments, such as environmental health risk assessments, require technical and medical knowledge to assess frequency, severity, exposure, and vulnerability, which gives an indication of sophisticated matrix-based methods by unpacking the risk value components into their contributing factors to analyse and evaluate risks.
Other types of risk assessment
Future Research Directions (Aven, 2016)
The concept of emerging risk has gained increasing attention in recent years. Flage and Aven (2015) performed an in-depth analysis on the emerging risk concept, and in particular its relation to black swan type of events through the known/unknown. Some emerging risks relate to an activity when the background knowledge is weak but contain indications or justified beliefs that a new type of event would occur in the future and potentially have severe consequences on something humans value. The weak background knowledge makes the specification of scenarios difficult (consequences and the event itself) (Flage & Aven, 2015).
Further development in risk assessment techniques is expected to address the challenges linked to the knowledge dimension and the time dynamics. There is a need to balance different risk management strategies in an adaptive manner, including cautionary strategies and attention to signals and warnings. There is also a need for research and development (R&D) to obtain adequate modelling and analysis methods to handle the different types of systems. Examples include critical infrastructures, such as electrical grids and transportation networks, which are complex systems and are often interdependent. There is potential for significant improvement in the way security is assessed by developing frameworks that integrate the standard security approaches and the ways of assessing and treating uncertainty. The paper by Aven (2013) provides an example of work in this direction.
Societal risk decision-making become a challenge, which is characterised by many, diverse stakeholders. Some of the challenges and research issues relate to the following aspects (Aven & Zio, 2014; SRA, 2015):