After an introduction and welcome by Francis Brodie and Hazel Newey, the first speaker, Simon Lloyd of The National Radiological Protection Board, spoke on the 'Hazards Associated With Radio-Illuminated Items'. He began with an illustration of the measurable radio activity levels of an historic watch and posed the question of what are the hazards, both long and short term, of association with this watch and other radio-illuminated objects? He explained succinctly the different types of radioactive emission; alpha rays which travel only a few centimetres, beta rays which travel further but can be stopped with perspex or glass, and gamma rays which are very penetrating and can only be reduced using lead. Historically, and until the 1960s, radium 226 was the material used in illuminating paints, today we use promethium 147 and tritium. Promethium and tritium emit the relatively non-harmful beta rays, whereas radium 226 emits all three types. Radium 226 is a product of the decay of Uranium 238, and decays in turn, emitting radon gas and forming other radioactive materials until stability is reached with non-radioactive lead. Dosages of radioactivity are measured in milli or micro Sieverts, the average chest x-ray gives a dose of 0.02mSv, and a fatal dose is about 3,000mSv. The measurable dose of Radium 226 in a watch is about 0.1mSv per hour (ie. 5 chest x-rays) at very close proximity, but this figure only applies to a very localised area. A watch is rarely handled and closely scrutinised for any dangerous length of time. In order to reach the dose limit you would have to ingest the paint scraped off several watches, the loose material being more of a hazard. He outlined the main conditions of The Radioactive Substances Act 1993, exclusions to which include those working solely with clocks and watches, and working with small amounts of promethium and tritium. However items such as compasses and altimeters are NOT excluded. A second regulation, the Ionising Radiations Regulations 1985, provides for designation of areas and responsible persons where large collections are involved.
This was followed by a case study in which Mike Lambert of The National Museums and Galleries of Wales (NMGW) described the hazards of working with geological collections. He started with an overview of the geological stores and conditions presently maintained within them. Of the enormous number of known minerals only a small proportion are radioactive, eg. radium, thorium, uranium, and rare earth species, but all three types of radiation emission are found. Following the passing of the 1985 Ionising Radiation Regulations NMGW staff became concerned that the geological collections presented a radiation hazard. They purchased a dose rate meter to measure radiation in microSieverts per hour, and a contamination monitor to detects very low levels of alpha and beta radiation. A gamma ray survey of the store was carried out, and a plot made of the results. Alarmingly, a hot spot of 90microSv per hour (0.09mSv) was measured in one of the bays and was traced to where the uranium collection was closely packed and stored. In the centre of one of these drawers it measured 200microSv per hour. Under the Ionising Radiation Regulations the store was designated a controlled area and the 750 radioactive minerals identified were separated and spread out in less restricted storage space. Both gamma detectable and contamination monitor detected minerals were re-stored in this way. Due to the friable condition of some minerals, a subsequent survey of the store was made to check against contamination by the move. The only unexpected radiation detected was on the disposable filter of the air conditioning. After unsuccessful replacement of the filter, it was realised that this was radon radiation resulting from the decay of uranium and thorium minerals. Radon is soluble in water and in body fluids. This discovery initiated a radon survey which revealed unsafe levels of radon within the store, and contamination of the rest of the building. The decision was taken to remove all radioactive materials to a separate store with extract system, isolation shutters and fan failure alarms.
Moving away from radioactivity, Barry Marshall of The Science Museum spoke about the hazards associated with industrial materials. He concentrated on four materials: polychlorinated biphenols (PCBs), asbestos, mercury, and lead, describing the medical hazards and steps taken within the Science Museum to identify and remove them. PCBs are found in coolant oils. They are a non-conductor of electricity and were used extensively until being banned in the 1970s. Objects in which they are found include medical x-ray equipment, transformers, capaciters, and fluid filled vacuum pumps. PCBs were also sometimes mixed with trichlorobenzene, a hazard in itself. A screening kit is used to test for their presence and they are removed commercially, and the containers cleaned and returned. Asbestos is a fibrous mineral, commonly occuring in two forms, the white chrysotile, and the more dangerous blue crocidolite form. It has a high melting point (above 1,000�C), and is therefore attractive for industrial applications eg. rigid insulation (board and card), loose fill, and woven and cement mix applications. Science Museum staff keep a register of all items containing asbestos, and if it must be handled, spray wet the surface first to reduce the level of loose fibres. Non-collections can be consolidated with water based emulsion paint, but a PVA emulsion, Vinamul, is used for collections. Mercury is found in thermometers, barometers, amalgum, and mirrors. Spillages are cleared up using a mercury clean-up kit, and a fume cupboard used when working with it. Unsealed guages on a thermometers etc. can be sealed with an oil film. Lead is often found in hazardous alloys with antimony and arsenic. Objects made of such alloys include type metal, radiation shielding, pipes and cables, sash weights and toys. It forms hazardous salts of carbonates and oxides when in proximity to organic acids and moisture, these salts are friable, and respiratory equipment is needed when handling them. Dust and loose salts should be removed under IMS or water. He recommended that future collecting policies reject hazardous materials, or that the hazard is removed before acquisition. Known hazards must be highlighted by the use of tie on labels, and a gallery or stores hazard log should be compiled, specifying the position of each object and the hazard associated with it.
Jane Henderson then spoke about the compilation of risk assessments for museum work, reminding us that if we have a COSHH assessment or Manual Handling assessment, a risk assessment may not be needed. Hazard is defined as the potential to cause harm, risk is the likelihood of it happening. Hazard and risk in the workplace are usually a series of circumstances which can be identified by asking five simple questions, what, who, when, where, why, and how? In this way the danger, to whom it is a danger, where it is located, and in what circumstance it is dangerous, is identified. The last question 'what if?' can be answered by a simple mathematical risk rating system. Risk = Likelihood x Severity. Both factors are given three levels and values, and the resulting figures will tell you what is the most likely risk which must be eliminated. This is reduced by prevention, discontinuation, enclosure, substitution, isolation, and reduction of time of exposure. The LAST line of defence is personal protective equipment (PPE).
Joan Waters of The Science Museum then talked on ' A Curatorial Approach To Chemical Hazards, with special reference to experimental and industrial chemical collections. These collections are historically important, either for the chemicals themselves, or the vessels in which they are contained. The department continually reviews the need to keep these chemicals, but dispose of them only if there are compelling reasons. They also review regularly the storage system, balancing safety with a policy of open storage. The largest problems are caused by toxic dyes from the textile industry, many of which have illegible labels and cannot be disposed of under COSHH regulations unless the contents are known. These are presently being re-stored by placing in polycarbonate containers packed and padded with plastozote. The outside of the container is labelled accordingly. Another risk, and this one largely unknown, is whether these historic chemicals have become more dangerous with time. Historic chemicals were not necessarily 100% pure, and even those whose formulae are known may have dangerous degradation products.
The last speaker, Russel Turner spoke about the hazards associated with the treatment of lead. Oxides and carbonates have small particles and are easy to inhale, and there is a small hazard of skin absorption. Objects which may contain lead are lead paint, pipes, roofing, and sheeting. The alloys are also dangerous, and include lead stearates which are added to plastics as stabilisers. The major risks lie with the welding, cutting, casting of lead and it'a alloys. It should be noted that there is nothing you can do after ingestion and lead workers have to be regularly checked. The maximum level allowed is 80mg per 100ml of blood generally, and for a pregnant woman the figure is 40mg per 100ml. If working in difficult situations PPE is vital, as is use of an efficient extraction system, and it is important to have a stringent cleanliness regime when working with lead. The lead in air standard set over 8hrs is low, 0.15mg/m , blast cleaning to remove oxides is an efficient cleaning method, and removes dangerous salts prior to welding. His final warning was not to forget the other and more obvious hazard associated with lead, it's weight.
Although all speakers were addressing the hazards associated with museum work, the message was that if sensibly assessed, the dangers are controllable.
Helen Moody
