Facts, Analysis and Comment.

Depleted Uranium

This is the third in a series of information notes which have been prepared to help generalist civil servants handle issues involving science and risk. It looks at the way in which the British Government was, for once, much more effective than its opponents in handling media and public interest in a health scare concerning soldiers' exposure to depleted uranium (DU). The case study provides a nice test of the advice contained in the first two notes, on risk and radiation and radioactivity.

The scare was all about soldiers' exposure, in the Balkans, to depleted uranium. And once media interest began (in Italy), there was never much doubt that it would become a classic, for it fed on all the following "fright factors" listed in my note on risk:-

Best practice, summarised in that note would suggest that the MoD

Before considering whether the MoD did any or all of these things, let us first look at:-

Scientific Advice about DU

My note on radiation and radioactivity recommends that officials should "make sure that your scientific advisers (and those advising lobby groups) tell you what equivalent dose (measured in millisieverts (mSv)) might be received by those exposed to the radiation. We on average receive a dose of 2.6mSv each year so a further dose of less than 3mSv is not worrying."

The basic scientific facts are as follows. First, uranium is a naturally occurring element. It cannot therefore be highly radioactive, or else it would have decayed out of existence a long time ago. However, one form (uranium 235) is somewhat more radioative than its other form (U-238) and can be used to make atomic bombs. (There are 7 grams of U-235 and 993 gramms of U-238 in every 1000 grams of naturally occuring uranium.) Natural uranium is therefore processed to retrieve the uranium 235, leaving the even less radioactive uranium 238 behind, in the form of "depleted uranium". And because it is a very hard metal, and even denser than lead, DU is used in a number of ways, including to tip ammunition and armour-plate tanks.

Ah! But what about millisieverts? Crucially, the answer depends upon whether the DU is outside you:- i.e. in whole shells, in armour plating etc., or inside you, as inhaled dust after a shell has exploded.

The reason for the difference is that the sort of radiation produced by DU (alpha radiation) cannot travel very far, and cannot penetrate other metals. So, as DU is typically covered in other metals, even the small amount of radiation which it gives off cannot do much harm. Indeed, DU is so safe (even if not covered in another metal) that a Government Minister was once interviewed by journalists with a lump of DU sitting prominently on his desk, so as to drive home the innocuous nature of the product. And a scientist has calculated that even the driver of a tank armoured with DU will only receive 0.0018 mSV per hour (compare our natural annual dose of 2.6 mSv). You certainly should not therefore aim to spend your life in a tank, but the radiation risk is pretty minimal.

But what if the DU turns to dust after the impact of the shell, and what if you then inhale it? The key point now is that the stuff is inside you, without any shielding, and is emitting radiation inside your lungs. The risk is then much higher - and much less well understood. Almost all predictions about the effect of radiation on the body are based on a model (the ICRP model) which was developed by using the observed cancer rates in the survivors of atomic bombs exploded over Japan during the Second World War. These were high dose, high dose-rate exposures to external radiation. These risks are extrapolated, in the ICRP model, to lower doses, lower dose-rates and internal radiation. Those concerned about the effect of DU on soldiers and others believe that these extrapolations are, and therefore the model itself is, fatally flawed.

There are other possible dangers. An article in the 6 September 2008 edition of the New Scientist drew attention to test-tube and animal research which suggested that DU might increase the risk of cancer, and to a number of theories which might account for genetic damage - although there is no epidemiological evidence that this has happened in populations exposed to DU.

Handling the Risk in Whitehall

As noted above, openness, clarity and concern are likely to be the best tactics. And the MoD seem to have responded in text book fashion, beginning with an official statement in the House of Commons which, to the lay reader, seemed to summarise the risk, and the Department's response, quite well:-

The department also decided to publish considerable information on its web site, including admissions of errors in earlier internal documents.

Finally, the department appears to have cooperated with, and possible encouraged, prestigious Royal Society reports in May 2001 and March 2002 with broadly reassuring conclusions. Interestingly, however, the first of the two reports was followed by a public meeting organised by the Royal Society which exposed the key weaknesses in the report, which were that:

Those concerned about the effects of DU therefore continued to press their case, which deserves careful consideration. However, as this note is about the handling of media and public interest in the issue, it is worth noting that the MoD seem conclusively to have won the first few rounds in the battle for public opinion. Crucially, the Department followed best practice in demonstrating open-ness, clarity and concern. And those on the other side of the argument made all the mistakes. Some of them appeared fanatical or obsessive. An earlier version of this note led to my receiving a number of emails, including the following:

And some of them seem to go out of their way to reduce the effectiveness of what they say. One of the (otherwise very effective) anti-MoD speakers at the Royal Society chose to address the audience wearing a bow tie and beret, presumably carefully chosen so as to mark him out from the otherwise rather grey establishment ranks which confronted him, but equally certain to ensure that his views were heavily discounted by that audience before he even opened his mouth.

In the long term, however, the jury remains out. The MoD won the first encounter and, although interesting research continues - see the New Scientist article mentioned above, no firm evidence has yet emerged emerge which damages its credibility.