Putting measurements into context

2012-05-11 14.09.03

A copy of William Blakes’s iconic monotype print of Isaac Newton is one of the works selected by Marianne Faithfull  for the DLA Piper Series: Innocence and Experience, exhibition  being shown at Tate Liverpool until 2 September.

It’s unusual for scientists to be portrayed in art, and at first glance Newton appears as a heroic figure. He’s sitting on a rock, apparently under the sea, concentrating intently on his work, leaning over a scroll, using a set of compasses, producing geometric drawings. But  he is ignoring his surroundings, turning his back upon the beauty of the natural world.

According to the Tate’s website:

Blake …….. was critical of reductive scientific thought. In this picture, the straight lines and sharp angles of Newton’s profile suggest that he cannot see beyond the rules of his compass. Behind him, the colourful, textured rock may be seen to represent the creative world, to which he is blind.

For Blake, Newton personified a materialist world view where everything can be investigated, measured and categorised in opposition to his own belief in the importance of imagination, emotion, and mysticism.

I think there’s some interesting points here that could be applied to occupational hygiene. An important part of our work is undertaking measurements to evaluate exposures to hazardous agents.  But there’s a danger here that we can become a little like Blake’s Newton. We can become obsessed with the “accuracy” of the measurements and in gathering numbers.

Now, while I think it is important that our measurements are “accurate”, just how accurate do they need to be? If we are comparing with a limit of, say, 100 ppm, do we really need to know whether the concentration is 99 or 101 ppm? Well, given the large range of variability in workplace exposures, in both of those cases I’d say there was a problem. And if we’ve only taken a few samples (which would normally be the case) I’d probably be looking to improve controls  even if the results from a small survey were more than about 25% of the limit.

And that’s the key point really. Occupational hygiene isn’t about measurement – it’s about control. I’d agree with one of the statements made by Lawrence Waterman, who gave the Warner lecture that opened the BOHS Conference in Cardiff earlier this year, paraphrasing Karl Marx

“Occupational hygienists have measured exposure; the point is to control it”

Measurements are important, but they’re a means to an end, not the end in themselves. And given that with most surveys  we will normally have only taken a small number of samples, in order to interpret the results we need to know what was going on when they were taken. We need to gather what is often called the “contextual information” – details on the process, what specific tasks the individual workers were carrying out, what controls were in place, environmental conditions and anything else that could have an influence on exposure.

When evaluating exposure we need to use “multiple sources of evidence”. Exposure measurements are usually a key element of this, but we also need to observe what’s going on, talk to people to get an understanding of the process and how it’s being carried out on the day, check control measures and gather other relevant information. By doing that we can build a more complete picture to help us understand how exposure is occurring and whether control needs to be improved. If we don’t, we can end up like Blake’s Newton, obsessing over measurements while ignoring what’s going on around us and failing to understand the world.

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