been suggested—since this is the act of ‘straining at stool’ which is allegedly deleterious.
The plinth of the conventional WC is typically around 380–400 mm in height. For squatting this would have to be halved. One consequence of reducing the height is that the buttocks take a much greater proportion of body weight. So the contouring of the lavatory seat itself becomes much more critical for comfort. But as you would not have to sit there for so long it probably would not matter so much.
For a discussion of the ergonomics of the more conventional sorts of lavatory, see McClelland and Ward (1976, 1982).
Ware (c. 1580) was a little smaller than this, measuring 10 ft 81/2 in. wide by 11 ft 1 in. long (3265×3380 mm). It came from the Crown Inn, in the village of Ware in Hertfordshire (on the old road from London to Cambridge) where it was something of a tourist attraction. It is now in the Victoria & Albert Museum. Parsons (1972) recounts the story of a party of six couples who travelled up from London to use it for
‘a frolick’.
People who suffer from back trouble are often advised to sleep in ‘a hard bed’.
Experience indicates that, not uncommonly, this advice turns out to be incorrect—
and in some cases an excessively hard bed can make things worse rather than better.
Norfolk (1993) reports a questionnaire survey of the advice that osteopaths give their patients concerning these matters. Of the osteopaths in his sample, 93% said they offered their patients advice about choosing a bed; although, interestingly enough, 83% also said that they would welcome more technical information on the ergonomics of bed design. Many were very critical of what Norfolk refers to as the
‘current vogue’ for excessively hard mattresses, with 98% of the sample saying that (presumably in their experiences and those of their patients) beds can be too firm for comfort. This has been confirmed in a user trial reported by Nicholson et al.
(1985).
Part of the problem seems to be based upon a confounding of two different physical properties of the bed which we could call ‘conformability’ and ‘sag’.
Conformability is the ability of the bed to adapt to the contours of the body and to support it in a diversity of positions with a minimal build-up of pressure hot-spots.
Conformability is principally a property of the mattress itself. There are a variety of ways of achieving this technically, in terms of the design of the bed springs, etc.
Figure 7.5 A historical review of bed widths.
Unless the mattress is very soft indeed, however, the tendency of a bed to sag into a hammock shape will be more a property of the construction (or state of wear) of the supporting surface upon which the mattress is placed. For both sleeping comfort and postural support, it would seem desirable that the combination of mattress and bedstead (or supporting surface) should provide conformability without sag.
115
Health and safety at work
About 400 people are killed each year in the UK, in accidents that take place at work.
(The exact figure fluctuates a little from year to year.) A further 16000 are seriously injured; and at least ten times this number sustain injuries that although they are of a less severe nature, are none the less serious enough to keep them off work for three days or more (and thus find their way into the official statistics). Added to this we have an unknown (but doubtless very great) number who sustain minor injuries requiring first aid treatment only, and an unknown (but again large) number who develop diseases or ill health, of one sort or another, as a result of their work.
(Figures from HSE Annual Reports.)
If we take fatalities as an index, however—and there seems to be good reason to do so, since they are likely to have been recorded more carefully than mishaps with less severe consequences—then the available evidence seems to indicate that work is getting steadily safer. The UK annual fatality rate currently stands at around 1.3–1.7 deaths per 100000 employees. In 1981 it was 2.1 per 100000; in 1971 it was 3.6 per 100000; in 1961 it was 5.6 per 100000; and in the first decade of this century it was 17.5 per 100000 (Figure 8.1). The downward trend is thought to be due in part to better regulation of working practices, and in part to changes in the nature of work such that fewer people are engaged in its more hazardous varieties.
Table 8.1 shows fatal and non-fatal accidents broken down by their principal direct cause, as recorded in the official statistics. The figures for non-fatal accidents are for 1992 (the most recent statistical year available at the time of writing.) The figures for fatalities are based on the previous seven years, which have been lumped together, in order to average out the annual fluctuations which arise in the data because of the relatively small numbers involved. The fatality figures do not include the 167 lives that were lost on 6 July 1988 in the Piper Alpha oil rig disaster.
The table is set out by rank order for the non-fatal accidents. The data have a number of striking features. In the case of the non-fatal accidents, the top seven statistical categories account for about 90% of all the accidents. For the fatalities, the grouping is slightly less marked, with the top seven categories accounting for just 80% of the total. More importantly, the rank orderings for the fatal and non-
fatal accidents are quite different. The largest difference is for lifting and handling accidents, which take first place in the case of the non-fatal accidents, but are in last place in the case of the fatalities. You would find similar differences if you were to compare non-fatal accidents having different degrees of severity. The differences can in many cases be predicted on a common sense basis, in that they reflect the relative propensity for causing serious injury of different types of mishap. Thus the relative positions of ‘fall on the level’ and ‘fall from a height’ are different for the fatal and non-fatal accident in Table 8.1. Overall you are much more likely to fall on the level
Figure 8.1 Fatal accidents at work, 1900–1991.
Table 8.1 Accidents at work, classified by principal cause.
Source: All figures based on HSE Annual Reports. Non-fatal accidents are for the year 1992. Fatal accidents are for the period 1986–1992 (excluding those resulting from the Piper Alpha disaster).
than to fall from a height; but if you fall from a height the injuries are more likely to be severe ones.
The relative frequencies with which accidents having consequences of varying degrees of severity occur, are often summarized in the form of an accident triangle.
Figure 8.2 is an example, based on the UK figures summarized at the beginning of this chapter together with additional data from various sources. We note, however, that the shape of the triangle will be very different for different types of accident.
Thus for ‘fall from a height’, where we have about 130 lost-time injuries per fatality, the triangle is sharply peaked; whereas for ‘lifting and handling’ accidents (about 50000 injuries per fatality) the ‘triangle’ is almost flat.
The accident triangle is a reflection of the two factors (or sets of factors) that determine the risks inherent in an activity or working practice: the probability of a particular event (i.e. accident) occurring, and the probability of particular consequences (i.e. injury) resulting from such an event (should it occur).
The distinction can be an important one, insomuch as the steps required to control these two components of risk may in some cases be different. Thus the distinction is sometimes drawn between primary safety, the prevention of accidents per se and secondary safety, the protection of the person in the accident situation. (For example designing safer roads and more ‘crashworthy’ vehicles respectively; or making loads easier to handle, as against providing safety boots in case you drop them on your feet.) An equivalent distinction may be drawn for preventive medicine in general, where it is customary to speak of primary prevention (of the precursors of disease), secondary prevention (of the disease itself) and tertiary prevention (of its long-term consequences).
A closely related distinction is the one that is nowadays drawn between risk and hazard, a hazard being the potential to cause harm and a risk being the likelihood that this harm will be realized. (The UK Health and Safety Executive now uses these terms in this way.) The distinction is clearly an important one. The terminology is
Figure 8.2 The accident triangle.
confusing, however, since in everyday language the words ‘risk’ and ‘hazard’ are used interchangeably (see, e.g., the definitions of these words given in the Oxford English Dictionary).