SUMMARY. Some of the most important documented European terrorist attempts in the last 20 years are analysed. In all the disasters considered, the blast occurred in closed spaces (pubs, stations, etc.). After a short review of the potential wounding processes related to the conventional blast thermic load, skin bums and respiratory injuries are considered, with regard to distribution, severity, and the various injury associations. In conclusion a comparative study is made between the theoretical clinical pictures and the most common injuries seen in this kind of disaster.

The use of bombs as offensive weapons by terrorist groups and professional criminals has become increasingly more frequent. During the last 20 years Europe has been the scene of various bomb attacks. Between 1970 and 1975 in Northern Ireland alone 15,665 persons were injured by bombs and 1,390 were killed. In Italy the bomb explosion at Bologna Central Railway Station in August 1980 caused 291 casualties, with an immediate mortality rate of 25.1%.

This paper has two aims:

1. to analyse from the physiopathological point of view the possible blast lesions in closed spaces, with particular reference to skin and/or airway burns;
2. to verify the presence, the seriousness and the typology of these traumas by means of a statistical enquiry into some of the most serious and best documented terrorist attacks.

After examining the literature of the last 20 years, we decided to concentrate on the casualties in the following bomb outrages: in two pubs in the centre of Birmingham (1974), two pubs in Guildford (1974), the Arms Room at the Tower of London (1974), and Bologna Central Station (1980).
The explosive charge of the bombs varied between I and 90 kg and most of them were in the form of booby-traps.
All the explosions took place in a confined space and at times when there were certain to be crowds.
We have excluded from our analysis the very significant experiences of Northern Ireland because the aetiolo.gy was dual (bombs and bullets) and the scene of the explosions variable.
We have not taken into consideration the pathologies of patients treated in casualty departments and then discharged, minor lesions or lesions that were inadequately documented and thus prevented a homogeneous comparison.

When a bomb explodes in a closed environment a number of lesions may occur as a result of different mechanisms. The lesions may be:

1. primary, due to the effects of pressure changes in the environment;
2. secondary, due to pieces of the bomb-casing, secondary projectiles or the collapse of walls;
3. tertiary, due to the effect of acceleration on the body or parts of it;
4. flash lesions and lesions caused by hot gases;
5. inhalation of toxic gases produced by the detonation and/or by combustion

Setting aside points 1, 2 and 3, we will analyse the possible cutanous and/or respiratory damage caused by burns after conventional bomb explosions in a closed space.

Cutaneous lesions are generally partial -thickness (first-degree and superficial second-degree) flash burns, affecting the most exposed parts of the body (face, hands and legs). They are caused by the thermic energy caused by the detonation. The seriousness of the burn depends both on the increase in skin temperature and on the duration of exposure. The total quantity of heat absorbed by the skin is equal to the algebraic sum of the single fractions transmitted by radiation, conduction and convection.
In explosions bums are above all caused by the emission of thermic radiation and by contact with hot air that is rich in various kinds of dust and powder.
The exposure to heat can be quantified as "heat flow", i.e. the number of calories passing through 1 CM2 of skin surface in 1 sec (cal/CM2/SCC.). The time factor is significant only if dispersion mechanisms are activated and therefore, in the event of almost instantaneous exposure (as in our case), or at any rate not exceeding 10 sec, the time factor can be ignored (cal/CM2).
With regard to conventional explosions it would be very interesting to be able to relate the seriousness of a flash burn to the temperature increase in the environment and to exposure time. The only relevant data in the literature are those of Ashe and Roberts. Unfortunately their conclusions are unreliable as regards explosions in confined spaces where, because of the "spalling effect- of the wall structures, the air is contaminated by a greater or lesser amount of dust, with a consequent increase in its thermic conductivity.
In more general terms it is possible to identify a number of factors which serve as predictors of the seriousness of bums caused by an exploding device. These are:

1. the type and quantity of the explosive material;
2. the place of the explosion;
3. secondary ignition.

If we exclude aggressive thermic devices (napalm or phosphorus bombs), which obviously cause a dramatic increase in burn pathology, these three factors are interrelated. In particular, secondary ignition depends on the quantity of explosive used, the site of the explosion (confined space), and the presence in the area of particular substances (gas, fuel, various propellents, etc.). These circumstances modify the typology of the disaster, with a considerable increase in the number of fire burns.

The blast wave, amplified by the tunnel effect, together with the inhalation of hot air can in theory cause thermal damage prevalently located in the upper airways. An examination of the literature reveals that 3-15% of patients admitted to burns centres present inhalation lesions. In explosions, although the data are rather more uncertain or at any rate difficult to interpret, it is legitimate to hypothesize respiratory lesions due to the following reasons:

1. the topography of flash bums;
2. the production of smoke, fumes, and dust in confined spaces;
3. blast lung.

Face bums are a classic indirect criterion used for the diagnosis of suspected respiratory burns.
The aggression by the dust and fumes that are usually produced by explosions in closed spaces can cause airway lesions. The obstructive effects of the inhalation of dust are well known (the "spalling effect- of collapsing'walls). Experimental studies have shownthat the minimum quantity of dust required to suffocate a man is 100 gr/M3 (Desaga, 1950).
The analysis of smoke lesions closely related to the actual explosion is more complex. In the event of secondary ignition, due to the incomplete combustion caused by the consumption of oxygen, a number of toxic substances are liberated, such as carbon monoxide (C0), short-chain aldehydes (acrolein), ketones and organic acids. The harmfulness of these compounds is twofold, as they exert an irritant, obstructive and caustic action on the airways and at the same time have systemic action.
The commonest cause of immediate death in fire victims continues to be CO poisoning.
The pulmonary damage due to the primary effect of the shock wave is responsible for "blast lung", which is characterized by haemorrhage ' plcuroparenchymal lacerations, rupture of the interalveolar septa, interstitial emphysema and lesional pulmonary oedema. Although there is no aetiological connection between respiratory burns and blast lung, this syndrome should at least in theory have a predictive value of respiratory thermal lesion. In fact it represents a sure indication of exposure of the airways to an explosion; it is also an efficient contributory cause of the onset of ARDS in synergy with a form of thermal stress that otherwise is not significant.

Our analysis of the data in our possession indicates that the number of injured persons varies from the lowest figure of 37 (Tower of London) to the highest of 291 (Bologna Railway Station).
About a third of the more severely injured patients had to be admitted to hospital.
The percentage of bum patients varies from 55% to 26.1% of the total number of injured persons hospitalized.
Apart from a few exceptions the burns are mostly superficial (first- and second-degree) and the BSA is on average 20%.
The body areas most frequently affected are the face, hands and legs; the bum is often associated with other traumatisms and in particular with penetrating wounds of the soft parts. Airway burns and eye burn injuries were not reported.

The comparison between theoretico-experimental data and statistical findings demonstrates that the burns due to bomb explosions in confined spaces are normally the second most frequent pathology, after osteoarticular lesions, and in some cases are the most frequent cause of hospital admission (6 patients out of 10 admitted to Birmingham General Hospital).
The extent of the body surface involved ranges between 10 and 50%, with a mean value of 20%; depth does not exceed second degree, and distribution is quite characteristic with its prevalent involvement of the most exposed parts of the body (hands, face, and in women also the legs). With regard to flash burns the different distribution between the two sexes is due to the protective action of clothing.
Despite the constant involvement of the face, eye burns were extremely rare because of the immediate eyelid-closing reflex.
In contrast to our expectations, no burns of the airways were observed; the reason for this is the low risk of secondary ignition, which is possible only in the case of very high explosive charges or the use of thermic attacking agents such as napalm or white phosphorus.
However it is not possible to rule out thermal damage other than from toxic or mechanical causes as a possible cause of immediate or early mortality in patients with pulmonary distress.
In conclusion, flash burns alone do not represent a particular problem of immediate and/or definitive surgical treatment. However, there are some aggravating factors:

1. the particular localization of the burns;
2. the constant association with other traumas which are characterized by considerable losses of substances and require reconstructive treatment that is not always easy to give;
3. the massive arrival of casualties in health facilities that are not always able to cope with such emergencies.

RÉSUMÉ. Les Auteurs analysent quelques-uns des plus importants attentats terroristes documentés en Europe dans les derniers vingt ans. Dans tous les désastres pris en considération l'explosion s'est produite en lieux clos (bars, stations, etc.). Après un bref examen de l'évolution potentielle des lésions causées par la charge thermique conventionelle de l'explosion, les Auteurs considèrent en particulier les brûlures cutanées et les lésions respiratoires en rélation à leur incidence, distribution, sévérité, et aux différentes associations lésionelles. En conclusion les Auteurs proposent une étude comparative entre les tableaux cliniques théoriques et les lésions plus communes que l'on rencontre en ce type de désastre.

BIBLIOGRAPHY

1. Beeley J.M., Crow J., Gareth Jones J., Minty B. et al.: Mortality and lung histopathology after inhalation lung injury. Am. Rev. Respir. Dis., 133: 191, 1986.
2. Brismar B., Bergenwald L.: The terrorist bomb explosion in Bologna, Italy, 1980: an analysis of the effects and injuries sustained. J. Trauma, 22: 216, 1982.
3. Caro D,, Irving M.: The Old Bailey bomb explosion. Lancet, 1: 1433, 1973.
4. Cooper G.J., Maynard R.L., Cross N.L., Hill J.F.: Casualties from terrorist bombings. J. Trauma, 23: 955, 1983.
5. Cooper G.J., Pearce B.P., Stainer M.C. et al.: The biornechanical response of the thorax to nonpenetrating impact with particular reference to cardiac injuries. J. Trauma, 22: 994, 1982.
6. Coppel D.L.: Blast injuries of the lungs. Br. J. Surg., 63: 735, 1976.
7. Di Vincenti R.C., Pruitt B.A., Reckler J.M.: Inhalation injuries. J. Trauma, 11: 109, 1971.
8. Frykberg E.R., Hutton M.J., Balzer R.H.: Disaster in Beirut: an application of mass casualty principles. Mil. Med, 11: 563, 1987.
9. Hadden W.A., Rutherford W.H., Merrett J.D.: The injuries of terrorist bombing: a study of 1532 consecutive patients. Br. J. Surg., 65: 525, 1978.
10. Kennedy T.L., Johnston G.W.: Civilian bomb injuries. Br. Med. J., 1: 382, 1975.
11. Tucker K., Lettin A.: The Tower of London bomb explosion. Br. Med. J., 3: 287, 1975.
12. Waterworth T.A., Carr M.J.T.: Report on injuries sustained by patients treated at the Birmingham General Hospital following the recent bomb explosions. Br. Med. J. 2: 25, 1975.