Electrical injury from subway third rails: serious injury associated with intermediate voltage contact

Bmis

Q I997 Elsevier

Vol.

33, No.

6,

pp. 575-518, 1997

Science Ltd for tSK1. All rights reserved Printed in Great Britain 0305-4179~47 $17.00 i rI.oi)

Plt: 50305-4179(97)00033-8

Electrical injury from subway third injury associated with intermediate contact* Joseph Rabban’, Jonathan

Adler’,

Carlo Rosen’, Jeffrey Blair’ and Robert Sheridan’

‘Department of Emergency Medicine, Massachusetts Institute, Boston, Massachusetts, USA

General Hospital, Boston, USA and ‘Shriners Burns

Background. Xlrilivay artd subway-associated electricaltrauma is rare arid typicaily irzvolaes high voltage (>20000) arc injurim. Wrf all rail sysfclns utiiix such high voltage. Wereport 16 cases qf electricai trauma dut, to 600 V direct contact with subway ‘fhird rails. Methuds. A case series of injured patienfs presenting to Shriners Bumi Institute, Bostan or Massachmetts General ffospifal befwcm 1970 and 199.5 was retrusycctively analyzed. Results. A tota/ (f 16 cases was identif%ud. Amorzg SCZWFI subway workers, the mechanism of rail contact was uninfentional by a ton!, a hand OY by jL?kJq; no deafhs occurred. Among nine null-!Jciuyafiurrai vi&u, injuries invalved suicide attempts, unintentional falls, or risk-taking behavior. This group suffered xreatcr bum srrvrity, operative procedures, and complications; three deaths uccurred.

Electrical injury, railways, occupational injury, intermediate vcjltage injury.

Keywurds:

burns,

Vol.

73, No.

6, 515-518,

1997

Introduction Serious

injuries

rails: serious voltage

often

occur around rail-transport are mechanical and involve a person or vehicle being struck by a train, with a higher amputation rate and fatality in the facilities. M05t of these injuries

*I’resented in part at the 1997 American Burn Association Annual Meeting, New York, NY. There was no financial or material wppori for this ‘4udy. No conflicts of interest relating to products or nr~anirations 2xisl.

former category’“. Behavioral and psychiatric factors are major determinants of injury: suicidal tendency has been shown to be present in the majority of subway injury victims; almost two-thirds have severe psychiatric illness; alcohol intoxication is present in up to 90 percent of victims’,“. Electrical trauma can also occur if contact is made with the electric cables which energize the rail car. High voltage (25000 V, alternating current) arc injury due to overhead railway cables used in eastern European railways has been described7. In addition to such overhead cables (catenary cables), energy can also be supplied via a ‘third rail’ which carries current through a rail parallel to the subway tracks. In the Boston subway system, the third rail voltage is 600 V direct current, considerably lower than high voltage systems. While the consequences of household electrocutions (lZO-22OV) and of true high tension electrocutions ( > 1000 V) are well documented, less is known about intermediate range (220-1000 V) electrical exposures. To our knowledge, only one case report of direct third rail injury at intermediate voltage exists’. We *report 16 cases of 600 V direct electrical injuries from subway third rails.

Setting Massachusetts Bay Transportation Authority operates 68.2 miles of third rail powered subway tracks through the Boston area, plus 58.4 miles of overhead cable powered tracks. The average daily ridership is over 600000 with 130 stops, operating 20 h per day. Third rail current runs continuously except for emergencies or routine maintenance. The voltage is 600 V, direct current, supplied by electrical sub-stations. Warning signs clearly identify areas where surface third rails are located and recorded warning messagesare played in station?.

§16

Eurns: Vol.

23,

No.

6,1997

surgical burn management. There were no deaths in this subway-worker group. Among the nine non-occupational events, suicidal intent was present in three victims (cases 9, 13, and 15); whether these suicidal victims intended contact with the third rail specifically or with an oncoming subway car was not documented in the charts; two of these victims had a prior history of suicidal actions. Three of the nine non-occupational victims unintentionalIy fell onto the subway tracks from an elevated platform and contacted the third rail; of these three, a 20-year-old man was alcohol intoxicated and tripped off the platform edge (case 8); a 46-year-old blind woman unknowingly stepped of the platform edge (case 11); and a 15-year-old boy who was trespassing in a subway tunnel tripped and landed on the third rail (case 10). None of these three had skeletal fractures. Deliberate contact with the live rail was made by a X-year-old boy who was dared under peer pressure to touch it (case 16). A 35-yearold man was &pulling a child off the tracks and unintentionally contacted the third rail in the process (case 14). Finally, the mechanism of injury in a 4lj-year-old man found unconscious on the tracks was unknown (case 12). Five of the nine non-occupational cases had initial loss of consciousness on scene; two suffered cardiac a:rrest at the scene. All but one of the nine non-occupational victims had third-degree burns of abdomen, upper extremities, back, head, or hands. Three patients required one surgical procedure each, three required two procedures each. An injury involving second-degree bilateral palm burns (case 14) required no operations. The peak CPK ranged from 85 to 21320 U/I (median 1537 U/l) among the non-occupational victims; myoglobinuria presented in two patients, though none developed renal failure. Compartment syndrome did not develop in any

MdlOdS

Sixteen cases, of electrical injury involving a subway third rail between 1970 and 1995 were identified and reviewed from the medical records at Massachusetts General Hospital and the burn registry at Shriners Burn Institute. Cases were identified from a database of electrically injured patients using ZCD-9 code 994.8 and associated E codes 925.0 to 925.9. Information extracted from patient records included age, sex, occupation, mechanism of injury, alcoho1 intoxication, severity of burns, urine myoglobin, serum creatinine operative phosphokinase (CPK) , procedures for wound management, length of hospital stay and complications.

Resuh Electrical injury cases consisted of seven occupational victims (all male subway workers) and nine nonoccupational victims (E/9 male) (‘Pclble I). None of the victims were struck by subway cars. Among subway workers, the injury mechanism was either unintentional contact of hand or metal tools with the third rail (cases 2,4, and 6); assumption that the third rail was inactive while working on the rail (case 3); or an unintentional fall onto the third rail (cases I and 7). The injury mechanism was not documented in one occupational event (case 5). Four of the seven workers suffered initial loss of consciousness but none experienced cardiac arrest. Sums among workers consisted of first-, second-, or third-degree injury and primarily involved the hands or face; there were no cases of compartment syndrome. No cases developed myoglobinuria or renal failure; the peak serum CPK ranged from 45 to 1188 U/l (median 133 U/I). Two cases required Table I.

Burn Case

As=

Sex

Occupational 1 22 2 40 3 40 4 41 5 23 5 33 7 53

victims

Non-occupational 8 20 9 27

10

15

11 12 13 14 15 16

46 46 17 35 25 16

l M M M 1

Mechanism raii’ contact

of

fell off moving train touched rail by hand assumed rail ‘dead’ tool touched rail hammer touched rail fell off bridge on rail

victims fell off platform suicide attemat trespassing, tripped M b!ind, fell off platform F M suicide attempt M pulling child off tracks w Id suicide attempt M ‘dared’ to touch rail M M

LOC = loss of consciousness,

CPK = creatinine

LOC

Cardiac arrest

Y Y Y N N N Y 417 Y N Y Y Y

N N 519 phosphokinase,

~~ Degree

N E N 1 N 017 Y N N Y N N N N N 2t9

Urine m yoglobiti

Site

Peak CPK

1188 133

2 2 1 1 1 3 3

face hand face, wrist hand face face, hand, arm

3 3 3 3 3 3 2 3 3

abdomen, neck hands arm, facehand shoulders head thigh, back hands hands hand

N Ii leg

N N 917 Y N N Y

N

45 77 325

21320 1095 8669 1537 14100 85 5220

z/5 Surgery

= surgical

Surgery

procedures

for wound

management.

Death

N 0 0 0 2 1 3

Ii N N N N 017

0 2 2 1 1 2 0 1 0 9

Y N N Y Y N N N N 319

Rabban et al..: Electrical injury from subway third rails patient, Death occurred in three of these nine patients, including the two suffering cardiac arrest on scene (cast ,‘3and 11).

Discussion Electrica trauma in subway injuries is rare. Neither a London Underground study of 100 injuries” nor a Swedish railway study of 2Y4 deaths”’ identified any elcctdcal injuries. Infrequent references to electrical injury do appear in the literature, but are rarely discussed in detail. A 2hyr review of Toronto Subway System deaths identified one electrocution death among 119 fatal accidents?. Schmidtke investigated 6090 suicides on German railways and indicated J small number of cases within a group of lh who made ‘contact with electrified cables’; no further discussion follows”. Chosh reported five cases of electrocutions in a 1 yr study of 230 Indian Railways occupational accidents, but the contexts of the electrocutions were not described”. Similarly, a mentjon of ‘12 casesof ‘accidental high voltage injury in railway areas’ in Hamburg goes without further discussion’ ‘. The only full description is Koller’s series of cvrrhead railway cable arc-injuries in Czechoslovakia’. The overhead cables carried 25Ol)OV of alternating current to the railway cars. Eleven victims suffered arc-induced thermal burns. These were primarily teenage boys who came in proximity tn the cables while playing on top of rail cars. The mean body surface area grafted was 21 percent. The injury mechanisms and outcomes of these 16 cases differ in many ways from Keller’s high voltage beries. First, the Boston subway system is powered by a hOfl V direct current third rail, which runs along the ground parallel to the tracks for a total of 68 miles. The system utilizes intermediate voltage power for several reasons. In long distance electric railway systems, such as in Europe, high voltage is needed due to the power loss over the long distance between electrical substations; in the Boston system, the distance between electrical substations is short, thus allowing a lower voltage. An advantage of an intermediate voltage system is that cable size and insulating equipment size can be kept to a minimum. Additionally, arcing between the current and a ‘ground’ occurs at greater distances as the voltage increases. The Boston system involves 21 miles of tunnel; the physical clearance between the tunnel and third rail defines the arc-free distance and therefore limits the maximum voltage allowed to prevent against arcing’:“. Thus, the injuries reported here are intermediate voltage, direct current whereas Keller reports high voltage thermal arcing. Unlike Koller’s series, there were no witnessed arcs, no flash burns, and no clothing ignitions. The epidemiology of injury also differs, in part because the Boston third rail runs along the ground; although 58.4 miles of overhead ‘catenary’ cables run through the system in addition to the 68.2 miles of third .rail, all our cases involve contact with the

517 ground third rail. A notable pattern is that almost haIf of our cases were occupational. While working alongside the tracks, unintentional contact with the third rail by hand or tool was responsible for three of the seven cases. One readily modifiable cause of occupational electrocution is the assumption that the third rail is ‘deenergixed’ when it is in fact still ‘live’. Clear mechanisms for identifying when the power is running can eliminate such injury. The overall US incidence of electrical injuries among subway/r;lilway workers is unclear. However, in 1993, among the 324 occupational deaths due to electric current, IlllIlt? were passenger transit workers”. While electrical fatalities constitute only 5 percent of all US occupational fatalities”‘, recognition of the potential morbidity associated with this MO V source can contribute not only to primary prevention but also to targeted medical care when injury does occur. Among the non-occupational injuries, three distinct patterns emerge: suicide>attempts, unintentional falls, and trespassing. C)f the three who attempted suicide, two had made prior attempts. Suicidal behavior is prevalent among most studies of :jubway and railway injury. Up to 8Y percent of all subway fatalities are associated with suicidal intent’, up to 58 percent of a11 injured victims have a documented psychiatric history and 39 percent have a history of previous suicide attempt”, The specific intent oi these three individuals to make contact with the third rail as opposed to contxt with a train car could not be determined. Some authors argue that specific suicide methods can be ‘suggested’ via dramatic media coverage of such events and can lead to suicide epidemics by way of imitation; several studies have attempted to demonstrate this ‘copy-cat’ phenomenon in various subway suicide t’pidemics’“-‘H, While the danger of the third rail is made clear in the multitude of warning signs, we are unable to conclude that these individuals intended to specifically commit suicide by electrocution. Furthermore, the 16 injuries we studied were isolated in time; there was no temporal pattern to the events. Unintentional falls from elevated passenger platforms in underground stations led to three third rail injuries. Tn such stations, tracks run approximately 4 ft below the passenger platforms; the third rail runs along the outer edge of the rail furthest from the platform. Thus, it is highly unlikely that a victim would land on top of the third rail en route to the ground. Although chart records dn not provide details, we speculate that the electrical contact occurred after the victims landed and most likely while moving about on the tracks. The fact that one victim was blind and one was intoxicated supports this notion. Whereas all but one of 11 injuries in Keller’s series were due to trespassing and risk-taking behavior, we report only two cases. In one instance, heavy fencing failed to deter a young boy from exploring a track yard prior to contacting a third rail. The second instance was the result of a peer pressure dare to

518

deliberately touch the live rail. Thus, the incidence of risk-taking related injury was lower. Clinically, several additional patterns emerge. Although the number of observations is small, differences appear in the outcome of subway workers versus non subway-workers who suffer such electrical injuries. Subway workers received smaller, less severe burns of hand or face; two required surgical intervention, and no fatalities occurred. Non-occupational victims had higher morbidity and mortality. All had large third-degree burns. Two cases suffered cardiac arrest on the scene and, along with one other victim, ultimately died. This outcome difference might be explained by the quality of the electrical contact. The rail contact that subway workers experienced was either through a. metal tool, or directly through the hand or face. In. both incidents involving tools, the workers were found away from the rails. The remaining subwayworker cases described being jolted away from the rail. However, the bodies of all but two of the non subway-worker victims were found still in contact with the third rail. Three fell from elevated platforms and thus may have been unable to move away, though none suffered skeletal fractures. These nine cases all had larger burn surface areas and bum severity than the subway workers, explaining the higher incidence of myoglobinuria and higher CPK values. In addition, in the non-occupational group, the incidence of suicidal intent, alcohol intoxication, and risk-taking activity further explain the greater morbidity and mortality in this group. In conclusion we have identified an intermediate voftage (600 VI) of direct current which can produce serious and lethal injury. Though electrical injuries are classically categorized as either high (> 1000 V) or Bow (< 1000 V) this series suggests that the low range be further subdivided. Some authors refer to a ‘household’ mnge of O-220 V. Although serious mjuries and fatalities have been reported in household range contacts, most household exposures result in little significant morbidity1g-z3. These 16 cases of 600 V third rail electrocutions involved significantly greater morbidity and mortality. The effects of this voltage do not appear similar at all to household voltages and should not be similarly classified with them as low range exposures. This series suggests value in classifyin g an intermediate voltage range from SO0to 1000 V, in order to distinguish the more serious clinical outcomes of such injury from that of household range injury.

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Paper accepted 4 March 1997. Covvesporzdence should be addressed fo: Joseph Rabban, 16 Harvard

Place, Brookline

MA 20146, USA.