Human Safety Risk Assessment

in its scientific meaning, has two components, namely hazard and exposure. To swim in an ocean is hazardous, but people living inland are never exposed to swimming in the ocean. This means that their personal risk of being harmed by the ocean is very small. 

Chronic toxicity does not parallel the acute toxicity. Chlorpyriphos and paraquat for instance, have medium acute toxicity, but a high 

TABLE 11.12 Examples of Toxicological Tests Required for the Registrstlon of a 

2 Acute dermal toxicity Rat Accidental exposure or skin 

3 Skin and eye irritation. Rat, rabbit Damage of eye or skin after 

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Becking, G.C. and B.H. Chen. 1998. International programme on chemical safety (IPCS) environmental health criteria on human health risk assessment. Biol. Trace Elem. Res. 66 439-452. 

In the human health risk assessments in this case study, the margin of exposure (MOE) is defined as the amount of a substance required to produce adverse health effects in animal experiments, divided by the amount that a human receives. The larger the MOE, then the lower the risk from exposure. The MOEs for atrazine and simazine are very large for both cancer and noncancer effects and suggest an ample margin of safety (Tables 8.1 and 8.2). 

See also Benchmark Dose Chemical-Specific Adjustment Factor (CSAF) Environmental Protection Agency, US International Programme on Chemical Safety Risk Assessment, Human Health Uncertainty Analysis. 

Human health risk assessment of the type introduced above is not the only risk assessment modality operative in various areas. A second approach is that of the Precautionary Principle (see, for example, Percival 2006). The Precautionary Principle figures in health risk assessment to some extent but here it is presented for discussion within the final topic of this work, lead regulation. While this approach has been defined in various ways and often appears to be misunderstood, it basically describes a proactive, a priori, and more conservative methodology in terms of the consumer sector. This approach attempts to prevent or minimize risk of any public health and safety hazards before commercial introduction of a product occurs. Substances enter or do not enter the commercial domain based on evaluations generated beforehand. 

There are many risk assessment concepts in existence. Some look at secnrity risk assessments—how adversaries, with intent and ability, can create risk. Others look at risks in a very quantitative fashion, such as human health and toxic chemical exposure. The UK rail sector uses a quantitative approach to defining a tolerable level of risk to the public from a rail accident mixed with a qualitative safety risk assessment based on hazard analyses. Some people are looking at risk from a business perspective and will focus on financial risk (credit and liquidity risk in financial institutions). And even others will look at the entire risk to an enterprise or a business and evaluate enterprise risk—risk across the entire business enterprise. This approach will be very comprehensive and not just consider financial or technical (engineering)... 

By the increased use of what can be described as Case for Safety risk assessments and, in the process, ensuring specific consideration of human error potential. 

Incorporating human error in case for safety risk assessment For many years there has been a requirement in the nuclear industry for plants to develop a Safety Case and have it approved by regulators in order to obtain a licence to operate. The Safety Case is, essentially, a very comprehensive quantified risk assessment based on the aggregated probability of an event (for example, the escape of radiation) against a defined benchmark probability. Once the licence has been granted, the Safety Case has to be formally reviewed at defined intervals. 

Process Hazards Analysis. Analysis of processes for unrecogni2ed or inadequately controUed ha2ards (see Hazard analysis and risk assessment) is required by OSHA (36). The principal methods of analysis, in an approximate ascending order of intensity, are what-if checklist failure modes and effects ha2ard and operabiHty (HAZOP) and fault-tree analysis. Other complementary methods include human error prediction and cost/benefit analysis. The HAZOP method is the most popular as of 1995 because it can be used to identify ha2ards, pinpoint their causes and consequences, and disclose the need for protective systems. Fault-tree analysis is the method to be used if a quantitative evaluation of operational safety is needed to justify the implementation of process improvements. 

Performance-influencing factors analysis is an important part of the human reliability aspects of risk assessment. It can be applied in two areas. The first of these is the qualitative prediction of possible errors that could have a major impact on plant or personnel safety. The second is the evaluation of the operational conditions under which tasks are performed. These conditions will have a major impact in determining the probability that a particular error will be committed, and hence need to be systematically assessed as part of the quantification process. This application of PIFs will be described in Chapters 4 and 5. 

The objective of consequence analysis is to evaluate the safety (or quality) consequences to the system of any human errors that may occur. Consequence Analysis obviously impacts on the overall risk assessment within which the human reliability analysis is embedded. In order to address this issue, it is necessary to consider the nature of the consequences of human error in more detail. 

Banks, W., Wells, J. E. (1992). A Probabilistic Risk Assessment Using Human Reliability Analysis Methods. In Proceedings of the International Conference on Hazard Identification and Risk Analysis, Human Factors, and Human Reliability in Process Safety. New York American Institute of Chemical Engineers, CCPS. 

International Programme on Chemical Safety (1994) Assessing human health risks of chemicals derivation of guidance values for health-based exposure limits. Geneva, World Health Organization (Environmental Health Criteria 170) (also available at http //www.who.int/pcs/). 

Many clinical studies have been performed on human subjects to assess the effect of soy isoflavones on chronic disease risk factors with no ill-effects (see Section 10.4). The safety profile of isoflavones is, however, difficult to establish because of the limited sample sizes and short periods of investigation of such studies. At present the upper tested limits are ... 

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