Risk assessment is the determination of quantitative or qualitative estimate of risk related to a well-defined situation and a recognized threat (also called hazard). Quantitative risk assessment requires calculations of two components of risk (R): the magnitude of the potential loss (L), and the probability (p) that the loss will occur. An acceptable risk is a risk that is understood and tolerated usually because the cost or difficulty of implementing an effective countermeasure for the associated vulnerability exceeds the expectation of loss. "Health risk assessment" includes variations, such as risk as the type and severity of response, with or without a probabilistic context.
In all types of engineering of complex systems sophisticated risk assessments are often made within safety engineering and reliability engineering when it concerns threats to life, environment or machine functioning. The nuclear, aerospace, oil, rail and military industries have a long history of dealing with risk assessment. Also, medical, hospital, social service and food industries control risks and perform risk assessments on a continual basis. Methods for assessment of risk may differ between industries and whether it pertains to general financial decisions or environmental, ecological, or public health risk assessment.
Risk assessment consists of an objective evaluation of risk in which assumptions and uncertainties are clearly considered and presented. Part of the difficulty in risk management is that both the quantities by which risk assessment is concerned – potential loss and probability of occurrence – can be very difficult to measure. The chance of error in measuring these two concepts is high. Risk with a large potential loss and a low probability of occurrence, is often treated differently from one with a low potential loss and a high likelihood of occurrence. In theory, both are of near equal priority, but in practice it can be very difficult to manage when faced with the scarcity of resources, especially time, in which to conduct the risk management process. To see this expressed mathematically, one can define total risk as the sum over individual risks, , which can be computed as the product of potential losses, , and their probabilities, :
Even though for some risks , we might have , if the probability is small compared to , its estimation might be based only on a smaller number of prior events, and hence, more uncertain. On the other hand, since , must be larger than , so decisions based on this uncertainty would be more consequential, and hence, warrant a different approach.
Financial decisions, such as insurance, express loss in terms of dollar amounts. When risk assessment is used for public health or environmental decisions, loss can be quantified in a common metric such as a country's currency or some numerical measure of a location's quality of life. For public health and environmental decisions, loss is simply a verbal description of the outcome, such as increased cancer incidence or incidence of birth defects. In that case, the "risk" is expressed as
If the risk estimate takes into account information on the number of individuals exposed, it is termed a "population risk" and is in units of expected increased cases per a time period. If the risk estimate does not take into account the number of individuals exposed, it is termed an "individual risk" and is in units of incidence rate per a time period. Population risks are of more use for cost/benefit analysis; individual risks are of more use for evaluating whether risks to individuals are "acceptable".
Five-step process in risk assessment and management
|Risk assessment and management process|
|Establish the context||understand the operating context and environment|
|Identify the risks / hazards||identify the internal and external risks / hazards that poses threat|
|Analyze the risks||systemic analysis of various contributing and leading factors (e.g. extend of the exposure, multiple exposures)|
|Evaluate and prioritize the risks||characterize and prioritize the list of risks for further action|
|Tackle the risks||Identify the range of options to tackle the risk & implement the best choice using available resources|
In general health
There are many resources that provide health risk information.
The National Library of Medicine provides risk assessment and regulation information tools for a varied audience. These include:
- TOXNET (databases on hazardous chemicals, environmental health, and toxic releases),
- the Household Products Database (potential health effects of chemicals in over 10,000 common household products),
- TOXMAP (maps of the U.S. Environmental Protection Agency Superfund and Toxics Release Inventory data).
The United States Environmental Protection Agency provides basic information about environmental risk assessments for the public for a wide variety of possible environmental exposures.
The Environmental Protection Agency began actively using risk assessment methods to protect drinking water in the United States after passage of the Safe Drinking Water Act of 1974. The law required the National Academy of Sciences to conduct a study on drinking water issues, and in its report the NAS described some methodologies for doing risk assessments for chemicals that were suspected carcinogens, recommendations that top EPA officials have described as perhaps the study’s most important part.
Considering the increase in junk food and toxicity FDA required in 1973 that cancer-causing compounds must not be present in meat at concentrations that would cause a cancer risk greater than 1 in a million over a lifetime. The US Environmental Protection Agency provides extensive information about ecological and environmental risk assessments for the public via its risk assessment portal. The Stockholm Convention on persistent organic pollutants (POPs) supports a qualitative risk framework for public health protection from chemicals that display environmental and biological persistence, bioaccumulation, toxicity (PBT) and long range transport; most global chemicals that meet this criteria have been previously assessed quantitatively by national and international health agencies.
How risk is appraised
In the estimation of risks, three or more steps are involved that require the inputs of different disciplines:
- Hazard Identification, aims to determine the qualitative nature of the potential adverse consequences of the contaminant (chemical, radiation, noise, etc.) and the strength of the evidence it can have that effect. This is done, for chemical hazards, by drawing from the results of the sciences of toxicology and epidemiology. For other kinds of hazard, engineering or other disciplines are involved.
- Dose-Response Analysis, is determining the relationship between dose and the type of adverse response and/or probability or the incidence of effect (dose-response assessment). The complexity of this step in many contexts derives mainly from the need to extrapolate results from experimental animals (e.g. mouse, rat) to humans, and/or from high to lower doses, including from high acute occupational levels to low chronic environmental levels. In addition, the differences between individuals due to genetics or other factors mean that the hazard may be higher for particular groups, called susceptible populations. An alternative to dose-response estimation is to determine a concentration unlikely to yield observable effects, that is, a no effect concentration. In developing such a dose, to account for the largely unknown effects of animal to human extrapolations, increased variability in humans, or missing data, a prudent approach is often adopted by including safety or uncertainty factors in the estimate of the "safe" dose, typically a factor of 10 for each unknown step.
- Exposure Quantification, aims to determine the amount of a contaminant (dose) that individuals and populations will receive, either as a contact level (e.g., concentration in ambient air) or as intake (e.g., daily dose ingested from drinking water). This is done by examining the results of the discipline of exposure assessment. As different location, lifestyles and other factors likely influence the amount of contaminant that is received, a range or distribution of possible values is generated in this step. Particular care is taken to determine the exposure of the susceptible population(s).
Finally, the results of the three steps above are then combined to produce an estimate of risk. Because of the different susceptibilities and exposures, this risk will vary within a population. An uncertainty analysis is nearly always included in a health risk assessment.
When risks apply mainly to small sub-populations, there is uncertainty at which point intervention is necessary. For example, there may be a risk that is very low for everyone, other than 0.1% of the population. It is necessary to determine whether this 0.1% is represented by:
- all infants younger than X days or
- recreational users of a particular product.
If the risk is higher for a particular sub-population because of abnormal exposure rather than susceptibility, strategies to further reduce the exposure of that subgroup are considered. If an identifiable sub-population is more susceptible due to inherent genetic or other factors, public policy choices must be made. The choices are:
- to set policies for protecting the general population that are protective of such groups, e.g. for children when data exists, the Clean Air Act for populations such as asthmatics or
- not to set policies, because the group is too small, or the costs too high.
Acceptable risk criteria
The idea of not increasing lifetime risk by more than one in a million has become commonplace in public health discourse and policy. It is a heuristic measure. It provides a numerical basis for establishing a negligible increase in risk.
Environmental decision making allows some discretion for deeming individual risks potentially "acceptable" if less than one in ten thousand chance of increased lifetime risk. Low risk criteria such as these provide some protection for a case where individuals may be exposed to multiple chemicals e.g. pollutants, food additives or other chemicals.
In practice, a true zero-risk is possible only with the suppression of the risk-causing activity.
Stringent requirements of 1 in a million may not be technologically feasible or may be so prohibitively expensive as to render the risk-causing activity unsustainable, resulting in the optimal degree of intervention being a balance between risks vs. benefit. For example, emissions from hospital incinerators result in a certain number of deaths per year. However, this risk must be balanced against the alternatives. There are public health risks, as well as economic costs, associated with all options. The risk associated with no incineration is potential spread of infectious diseases, or even no hospitals. Further investigation identifies options such as separating noninfectious from infectious wastes, or air pollution controls on a medical incinerator.
Intelligent thought about a reasonably full set of options is essential. Thus, it is not unusual for there to be an iterative process between analysis, consideration of options, and follow up analysis.
For audits performed by an outside audit firm, risk assessment is a crucial stage before accepting an audit engagement. According to ISA315 Understanding the Entity and its Environment and Assessing the Risks of Material Misstatement, "the auditor should perform risk assessment procedures to obtain an understanding of the entity and its environment, including its internal control."<evidence relating to the auditor’s risk assessment of a material misstatement in the client’s financial statements. Then, the auditor obtains initial evidence regarding the classes of transactions at the client and the operating effectiveness of the client’s internal controls.In auditing, audit risk is defined as the risk that the auditor will issue a clean unmodified opinion regarding the financial statements, when in fact the financial statements are materially misstated, and therefore do not qualify for a clean unmodified opinion. As a formula, audit risk is the product of two other risks: Risk of Material Misstatement and Detection risk. This formula can be further broken down as follows: inherent risk X control risk X detection risk.
In public health
In the context of public health, risk assessment is the process of characterizing the nature and likelihood of a harmful effect to individuals or populations from certain human activities. Health risk assessment can be mostly qualitative or can include statistical estimates of probabilities for specific populations. In most countries the use of specific chemicals or the operations of specific facilities (e.g. power plants, manufacturing plants) is not allowed unless it can be shown that they do not increase the risk of death or illness above a specific threshold. For example, the American Food and Drug Administration (FDA) regulates food safety through risk assessment.
In project management
In project management, risk assessment is an integral part of the risk management plan, studying the probability, the impact, and the effect of every known risk on the project, as well as the corrective action to take should that risk occur. Of special consideration in this area are the relevant codes of practice that are enforced in the specific jurisdiction. Understanding the regime of regulations that risk management must abide by is integral to formulating safe and compliant risk assessment practices.
In information security
IT risk assessment can be performed by a qualitative or quantitative approach, following different methodologies. One important difference in risk assessments in information security is modifying the threat model to account for the fact that any adversarial system connected to the Internet has access to threaten any other connected system. Risk assessments may therefore need to be modified to account for the threats from all adversaries, instead of just those with reasonable access as is done in other fields.
Another notable difference is the strategic nature of IT risk assessments. Unlike tactical vulnerability assessments and penetration testing which aim to identify and close specific gaps in security, IT risk assessments are functional at the executive level to examine the broader picture of IT risk management.
Megaprojects (sometimes also called "major programs") are extremely large-scale investment projects, typically costing more than US$1 billion per project. Megaprojects include bridges, tunnels, highways, railways, airports, seaports, power plants, dams, wastewater projects, coastal flood protection, oil and natural gas extraction projects, public buildings, information technology systems, aerospace projects, and defence systems. Megaprojects have been shown to be particularly risky in terms of finance, safety, and social and environmental impacts.
Quantitative risk assessment
Quantitative risk assessments include a calculation of the single loss expectancy (SLE) of an asset. The single loss expectancy can be defined as the loss of value to asset based on a single security incident. The team then calculates the Annualized Rate of Occurrence (ARO) of the threat to the asset. The ARO is an estimate based on the data of how often a threat would be successful in exploiting a vulnerability. From this information, the Annualized Loss Expectancy (ALE) can be calculated. The annualized loss expectancy is a calculation of the single loss expectancy multiplied by the annual rate of occurrence, or how much an organization could estimate to lose from an asset based on the risks, threats, and vulnerabilities. It then becomes possible from a financial perspective to justify expenditures to implement countermeasures to protect the asset.
In software evolution
Studies have shown that early parts of the system development cycle such as requirements and design specifications are especially prone to error. This effect is particularly notorious in projects involving multiple stakeholders with different points of view. Evolutionary software processes offer an iterative approach to requirement engineering to alleviate the problems of uncertainty, ambiguity and inconsistency inherent in software developments.
Criticisms of quantitative risk assessment
Barry Commoner, Brian Wynne and other critics have expressed concerns that risk assessment tends to be overly quantitative and reductive. For example, they argue that risk assessments ignore qualitative differences among risks. Some charge that assessments may drop out important non-quantifiable or inaccessible information, such as variations among the classes of people exposed to hazards, or social amplification. Furthermore, Commoner and O'Brien claim that quantitative approaches divert attention from precautionary or preventative measures. Others, like Nassim Nicholas Taleb consider risk managers little more than "blind users" of statistical tools and methods.
In shipping industry
In July 2010, shipping companies agreed to use standardized procedures in order to assess risk in key shipboard operations. These procedures were implemented as part of the amended ISM Code.
In environment: Environmental Risk Assessment
Environmental Risk Assessment (ERA) aim at assessing the effects of stressors, often chemicals, on the local environment. A risk is an integrated assessment of likelihood and severity of an undesired event. In ERA, the undesired event often depends on the chemical of interest and on the risk assessment scenario. This undesired event is usually a detrimental effect on organisms, populations or ecosystems. Current ERAs usually compare an exposure to a no-effect level, such as the Predicted Environmental Concentration/Predicted No-Effect Concentration (PEC/PNEC) ratio in Europe. Although this type of ratio is useful and often used in regulation purposes, it is only an indication of an exceeded threshold. New approaches start to be developped in ERA in order to quantifiy this risk and to communicate effectively on it with both the managers and the general public.
- Acceptable loss
- Benefit risk
- Control self-assessment
- Cost risk
- Digital Continuity
- Edwards v. National Coal Board
- Extreme risk
- Flood risk assessment
- Form 696
- HACCP: hazard analysis and critical control points, risk assessment in food
- Hazard (risk)
- Hazard Identification
- Health Impact Assessment
- Information assurance
- List of auditing topics
- ISO 28000
- ISO 31000
- Megaprojects and Risk
- Network Theory in Risk Assessment
- Optimism bias
- PIMEX a video exposure monitoring method
- Probabilistic risk assessment
- Probit model
- Project risk management
- Reference class forecasting
- Reliability Engineering
- Safety Engineering
- Risk aversion
- Risk based auditing
- Risk management
- Risk management tools
- Risk matrix
- Risk (statistics)
- Security risk
- Strategic misrepresentation
- RFC 4949
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- Risk Assessment Worksheet and Management Plan A comprehensive guide to risk assessment in project management, includes template - By John Filicetti