Summary of Oral Evidence presented to IEGMP by Mr R Gardner, Directorate of Safety, Environment and Fire Policy, Mr J Mackay, Defence Logistics Organisation, and Mr K Tench, Army CIS Services Group, Ministry of Defence (MOD), on Friday 21 January 2000

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Mr Gardner noted that the Directorate of Safety, Environment and Fire Policy is responsible to the Secretary of State for Defence. All MOD personnel, including servicemen, within the UK are subject to the Health and Safety Work Act 1974. Overseas, MOD ensures compliance with the Health and Safety at Work Act 1974 or local standards if these are more stringent. Mr Gardner explained that military operations give rise to a number of exposure scenarios and noted that it is MOD policy to follow the guidelines from the National Radiological Protection Board (NRPB). He went on to give examples.

The Royal Air Force (RAF) operates aircraft with radar, often in the nose, but occasionally elsewhere, and aerials mounted on exterior surfaces. Although these do not give rise to significant exposures of those within the aircraft they may have effects on sensitive avionics equipment or on ground crew. In general it is expected that avionics are sensitive to lower exposures than those known to elicit effects in people. The RAF also operates high-frequency aerial farms, radar sites and satellite communications installations. These have been surveyed and exclusion zones established to ensure compliance with NRPB guidelines. Access to the exclusion zone is controlled by means of fencing carrying appropriate signs. In general exposures are controlled by a combination of administrative controls and physical barriers. It was noted that the distinctions between occupational and public exposures contained in the guidance from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) are somewhat artificial in a military context. For example, sailors on board ship are at work 24 hours a day. As ICNIRP is clear that its guidance is based on deterministic effects it is difficult to justify further restriction to take account of the additional exposure. On board modern plastic ships exposure levels in some cabins can be close to the occupational investigation level. Similarly, soldiers in the field live in close proximity to their equipment.

A number of army operations can give rise to exposure to radiofrequency (RF) fields. These include use of body-mounted radios, vehicle and ship-mounted radios, battlefield radars and classroom situations. In addition, aerial riggers might have to work in situations with multiple aerials. Services radio in Germany has to comply with German legislation on static broadcasters which is essentially the same as the ICNIRP public exposure guidelines. Some examples were given in more detail. The army has a requirement for a high-frequency man-pack radio system of up to 25 watts (W). Field strength measurements on a 25 W prototype have shown that investigation levels are exceeded. Although there are a number of possible options to overcome this problem, the best appeared to be to assess exposure against the basic restrictions rather than the investigation level. The Army has already funded NRPB to make an assessment against the basic restrictions using the voxel phantom, NORMAN, for an in-service 12 W radio. This modelling has suggested that a 25 W radio would give rise to exposures at the basic restriction. Although high localised specific energy absorption rates (SARs) have been observed in the legs and part of the gastro-intestinal tract these are not relevant as the limiting factor is whole body SAR. The unit operates between 1.5 and 30 megahertz (MHz) and was assessed to all the NRPB basic restrictions at frequencies across the band. The design of the proposed future radio would take operator exposure into consideration.

Another problem had arisen through the operation of 40 W high frequency radios in Land Rovers. New Land Rovers have been purchased with fibeglass tops and a new location for the antenna mounting. As a result field strengths at the operator position have been above the investigation level. This has necessitated corrective action and procedures have been put in place to ensure that the safety aspects of all new equipment are assessed as part of the procurement process.

Royal Navy warships carry a number of sources of RF including radars, communications aerials and aircraft. This situation is further complicated by the presence of ordnance, fuel and personnel in an extremely confined space; the only fresh air available is typically on the upper deck close to the antennas and this can result in near-field exposures for personnel. Most problems are encountered in the high-frequency region, and it has been necessary to develop new techniques to survey these situations. Ships are now monitored using a variety of instruments whilst sweeping radios through their frequency ranges. This approach has revealed the presence of previously unidentified hot spots arising from re-radiation and resonances. There is an ongoing programme to determine RADHAZ footprints for all existing platforms including warships, Royal Fleet Auxiliaries (RFA), shore stations, minor war vessels and Royal Maritime Auxiliary Service vessels; most major warships have now been measured, but some work remains in relation to RFAs and minor vessels. Radars are set up so that they cannot irradiate the deck or superstructure of ships and the main problems arise from communications aerials attached to the superstructure. Compliance with investigation levels would necessitate excluding personnel from the upper deck. In order to avoid this, exclusion zones are based upon basic restrictions and for high-frequency exposures are determined from measurable analogues; whole body SAR of 0.4 W/kg equates to an ankle current of 160 milliampere (mA), whilst a localised SAR of 20 W/kg equates to a wrist current of 100 mA. In addition action is required to reduce burns hazards resulting from contact currents and voltages at frequencies between 1.5 and 30 MHz.

There is no reason for MOD to believe that exposure of personnel or the public results in any risk that is not acceptable. They do not carry out routine monitoring of personnel; servicemen are subject to routine medicals, although these do not relate to non-ionising radiation exposure. If over-exposure is suspected then the personnel involved would be examined by a medical practitioner specialising in radiation medicine; several such cases are reported each year. There is no evidence for chronic effects. Microwave hearing is an established phenomenon, but rare, and reports of other hearing effects near radar installations have been investigated. MOD is collaborating with other industries in the Birmingham/NRPB study of occupational exposure. An epidemiological study had been carried out at the Defence Evaluation and Research Agency, Malvern, but has failed to find a significant association between exposure and well-being.

First issued 9 May 2000