Human factors generally

We discussed the use of system training as a control in Sect. 15.3. Whilst human factors generally represent controls at the least effective end of the spectrum many systems rely on the behaviour of users to mitigate risk to some extent. Training is one way by which users can be encouraged to adopt consistent behaviours and develop a culture of best practice. If one intends to justify in the safety case that risk... 

It should be emphasized that the PIFs considered in this chapter, although generally considered important by human reliability specialists, are not meant to be exhaustive in their coverage. Other selections, such as those considered by the methods such as TRIPOD and HP AM (Chapter 2), are possible. It is recommended that the advice of an experienced human reliability or human factors specialist is sought when deciding which PIFs should be covered in a specific situation. 

In subsequent sections the emphasis will be on the human factors aspects of these systems. In general, the design principles which will be set out will apply to both types of system. However, distinctions will be made where appropriate. 

Several companies have expressed the cDNA coding for human factor VIII C in a variety of eukaryotic production systems (human VIII C contains 25 potential glycosylation sites). CHO cells and BHK cell lines have been most commonly used, in addition to other cell lines, such as various mouse carcinoma cell lines. The recombinant factor VIII product generally contains only VIII C (i.e. is devoid of vWF). However, both clinical and preclinical studies have shown that administration of this product to patients suffering from haemophilia A is equally as effective as administering blood-derived factor VIII complex. The recombinant VIII C product appears to bind plasma... 

Human factors need to be properly considered in the design and appfication of any detection system. Studies have shown that explosive detection systems generally perform less effectively in realistic field trials than in laboratory tests and that one of the biggest causes of this shortfall is failure to properly consider the operator/ system interface. 

The assessment factors generally apphed in the estabhshment of a tolerable intake from the NOAEL, or LOAEL, for the critical effect(s) are apphed in order to compensate for rmcertainties inherent to extrapolation of experimental animals data to a given human situation, and for rmcertainties in the toxicological database, i.e., in cases where the substance-specific knowledge required for risk assessment is not available. As a consequence of the variabihty in the extent and nature of different databases for chemical substances, the range of assessment factors apphed in the establishment of a tolerable intake has been wide (1-10,000), although a value of 100 has been used most often. An overview of different approaches in using assessment factors, historically and currently, is provided in Section 5.2. 

The 1997 consultation addressed the topic of safety factors, which is vitally important for die protection of public health. Setting MRLs is in fact based on a series of assumptions. One assumption is that humans are at least as sensitive as the most sensitive laboratory animal to a potentially toxic residue. Another assumption is diat all the residues covered by the MRLs are as toxic as the parent substance. A third assumption is that residues free from the human gastrointestinal tract are all totally bioavailable. A fourth assumption is the safety factor used to infer an ADI from a NOEL, including the additional safety factor, generally with a value of 2, to establish a provisional ADI until further information is available to convert this into a definite ADI. Other assumptions are the overestimation of consumer exposure to drug residues and the reduction of MRL values to take account of normal conditions under which the veterinary drugs are administered. 

The safety factor Itself may vary, depending upon the nature of the test data available and on other Judgmental factors. When long-term animal studies are available, the 100-fold safety factor generally Is applied. The food additive procedural regulations (21-CFR 170.22) refer to a safety factor of 100 to 1 in applying animal test data to humans. Exceptions to the 100-fold safety factor may be allowed for certain substances and under certain circumstances of use for example, in the case of micronutrients or macronutrients, or when information on dose-response effects in humans Is available. 

Global deviations should sometimes be considered in a HAZOP review. Global deviations are generally considered the effects that would simultaneously effect the entire process or facility. These are, but not limited to, equipment layout, seismic activity, flooding, sandstorm, extreme weather conditions, loss of power, human factors, etc. 

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