Types of risk assessment

There are two major types of risk assessment, which are not mutually exclusive. The first produces an objective probability estimate based upon known risk information applied to the circumstances being considered - this is a quantitative risk assessment. The second type is subjective, based upon personal judgement backed by generalised data on risk - the qualitative assessment. Except in cases of especially high risk, public concern, or where the severity consequences of an accident are felt to be large and widespread, qualitative risk assessments are adequate for their purpose and much simpler to make. The legal requirements refer to this type of assessment unless the circumstances require more rigorous methods to be used. 

To describe the safe system of work which such a risk assessment shows to be necessary, a method statement may be required for example for demolition work, the erection of steel structures and asbestos removal. Method statements will be discussed later in this chapter, but it is worth observing at this point that risk assessments are used to generate method statements which are themselves a stated sequence of events designed to minimise risks by giving advance warning, knowledge and information to the recipients. 

Significant findings are to be recorded where five or more people are employed by an employer. According to the MHSWR Approved Code of Practice, the record should contain a statement of the significant hazards identified, the control measures in place, the extent to which they control the risk(s) and the population exposed to the risk(s). Cross-reference can be made to manuals and other documents. Any risks which remain uncontrolled should be highlighted some companies collate them in residual risk registers for easy reference. 

As the regulations require review of assessments in specified circumstances, and as it will be necessary to review for changed circumstances over time, it would be prudent to include in the documentation a note of the date the assessment was made and the date for the next regular review. Similarly, it would be wise to include a note to employees reminding them of their duties under MHSWR to inform the employer of any circumstances which might indicate a shortcoming in an assessment. 

In 1994 the HSE published guidance entitled Five Steps to Risk Assessment , a leaflet setting out the most basic steps in the process and providing a specimen format for recording the findings of assessments. The leaflet has since been updated and reissued. The simplistic approach presented has much to commend it. Comments contained in the text give useful pointers to the approach to risk 

---

There is a continuing interest in the development of biomarker assays for use in environmental risk assessment. As discussed elsewhere (Section 16.6), there are both scientific and ethical reasons for seeking to introduce in vitro assays into protocols for the regulatory testing of chemicals. Animal welfare organizations would like to see the replacement of toxicity tests by more animal-friendly alternatives for all types of risk assessment—whether for environmental risks or for human health. 

Note that some of the risk information is actuarial (based on statistical data, typically collected and organized by insurance companies), and some of it has been derived from the type of risk assessment discussed in this book (chloroform in chlorinated drinking water, afla-toxin in peanut products). While the uncertainties associated with the figures in Table 11.2 are much greater for some risks than for others (not a trivial problem in presentation of risk data), such a presentation, it would seem, is helpful to people who are trying to acquire some understanding of extremely low probability events, of the order of one-in-one million. 

PCBs (polychlorinated biphenyls) A family of chemicals composed of biphenyl molecules that have been chlorinated to varying degrees, performance assessment A type of risk assessment in which the potential long-term impacts of hazardous waste disposal on human health and the environment are evaluated for the purpose of determining whether disposal of specific wastes at specific sites should be acceptable, persistence The length of time that a contaminant persists in the environment. 

Extrapolation methods are used for various types of risk assessment. Methods may be used in the process of deriving environmental quality objectives, in the registration of new substances, and in the process of site-specific risk assessment. Suter (1993) called these approaches prospective (the former 2) and retrospective (the latter) risk assessments. The specific process in which extrapolation methods are used has implications for the concepts to be applied and the data to be used as input in extrapolation. Strictly described approaches are in place for the derivation of environmental quality criteria (EQCs) and the registration of pesticides and newly developed substances. The prescribed approaches for deriving EQCs can differ between jurisdictions. The approaches for retrospective investigations have more degrees of freedom. A characteristic of the latter approach is that the methods can make use of measured local exposure levels and can estimate local risk with known precision (or known uncertainty ). The latter is uncommon for EQCs. 

Functowicz, S.O. and Ravetz, J.R. (1992) Three types of risk assessment and the emergence of post-normal science. In Krimsky, S., and Golding, D. (eds.) Social Theories of Risk. Praeger, Westport and London, pp 251-273. 

Human health risk assessments (HHRAs). also sometimes called multiple-path health risk assessments or, simply, health risk assessments, are a type of risk assessment that addresses the long-term exposure of the public to the approved, long-term stack releases as they affect air, water, food, and so... 

The terms health risk assessment, human health risk assessment, and multiple-path health risk assessment all apply to the same type of risk assessment. 

It is unlikely in such cases that the use of complex and highly species-specific models applied to the tested species will provide a better estimate of overall risk to nontarget species in general. In other cases, the questions addressed in risk assessments may be highly site and/or species specific. For example, in retrospective risk assessments, the aim is often to identify causes of observed impacts on defined populations occupying an actual habitat. For these types of risk assessment it is feasible and often necessary to employ models that incorporate much more of the relevant ecological and biological details because these can be clearly defined and their incorporation can reduce the uncertainty in the risk assessment. 

Among a few specific methods of handling pollution problems, quantitative techniques for assessing environmental risks due to contamination of environmental media by unwanted chemicals are becoming increasingly popular. Many ptqters and presentations such as [10] mention application of this type of risk assessment studies being carried out in the USA, Canada and Western European countries. 

Depending on the nature of the policy change or budget cut, there may be suitable checklists which can be utilized to evaluate this type of change. Otherwise a brainstorming or What-If technique may be appropriate for this type of risk assessment. Refer to Appendix A for information about risk assessment tools. 

For non-historical events the spots in Fig. 1 are based on various types of risk assessment. See e.g., Blikra et al. (2006) for arguments related the two Aknes events in Fig. 1. 

Type of risk assessment technique is also discussed in Clause 2 of Chapter 11. Now, after gaining some knowledge about technique selection standards, it is better to focus attention on the various standards applicable for different PHAs. 

LOPA, like most risk assessment tools, is suitable for this type of risk assessment, using the following approach ... 

Funtowicz, S.O., and J.R. Ravetz. 1985. Three Types of Risk Assessment A Methodological Analysis. Pp. 831-848 in Environmental Impact Assessment, Technology Assessment, and Risk Analysis, edited by V.T. Covello, J.L. Mumpower, P.J. Stallen, and V.R. Uppuluri. New York Springer-Verlag. 

Examples of the types of risk assessment studies that have been conducted include the measurements of the survival of EKl and EK2 hosts under differing environmental conditions, the probability of transfer of DNA clones to exogenous organisms, and the probability that a DNA clone will express its function following escape. 

---