Motor Vehicles
As noted in chapter 1, the motor vehicles on our streets and highways are
the most common vehicles of injurious energy. There is substantial varia-
tion in the incidence and severity of the injuries associated with the
vehicles--variation that is predictable from the vehicles' physical character-
istics.
The probability of a crash is associated with characteristics that make
the vehicle more or less easy to handle.(11) For example, the instability in
moderate-speed turns of so-called utility vehicles has been demonstrated in
tests of remote-controlled vehicles and in analysis of crash and fatality
rates. The high center of gravity (central point of the vehicle's mass) from
the ground relative to the narrow distance between the wheels results in
susceptibility to rollover. The 1980 Jeep CJ-5 was found the most extreme
utility vehicle in this regard: it rolled over in a 90-degree turn at 22 miles per
hour and at 32 miles per hour in a rapid lane change such as one might make
to avoid hitting something in the road.(12) Fatal rollover crashes of Jeep CJ-Ss
in 1978 to 1979 were 11 per 10,000 registered vehicles, higher than the 8.2
rider deaths per 10,000 registered motorcycles,(13) and almost four times the
2.8 fatal crashes per year of all types of vehicles per 10,000 registered in
1979.(14) The high death rate of motorcyclists is related both to the problems
of handling a relatively unstable two-wheeled vehicle and to the limited pro-
tection the vehicle affords its riders in energy exchanges with the environ-
ment in crashes.
The incidence and severity of injury in (or by vehicles that hit pedes-
the environment that the vehicles and people impact. If the occupants are
restrained, they decelerate nearer the rate of the vehicle and seldom will be
injured if peak deceleration is below 35 g's. Unrestrained occupants strike
interior surfaces at about the speed of the vehicle before the crash
(Newton's first law). The load on the human tissues then depends on the
deceleration rate and the surface contacted. Any hard protrusions that are
struck, such as knobs and edges, reduce the surface area of the body that ex-
periences the forces and thus increase the load.
Surgeons in emergency rooms sometimes invent names for such vehicular
surfaces. For example, the "karate-chop dashboard" refers to those
dashboards with narrow edges pointed toward the occupants; in front crashes
their necks tend to strike the dashboard, resulting in such swelling of the
tissue that the trachea is closed and the person dies of lack of oxygen.(15) A
flat-surfaced, energy-absorbing dashboard with knobs either recessed or
missing would cause little or no injury when impacted at a force that can kill
when concentrated on the front of the neck.
Two fundamental characteristics of motor vehicles with respect to inci-
dence and severity of injury in crashes are size and weight; and these are
often confused with one another. Although there is some variation among
vehicles in the use of space and weight, in general greater size is more pro-
tective of occupants than weight. Weight is more aggressive to occupants of
other vehicles in multivehicle collisions than it is protective to occupants of
the heavier vehicle.(16) In slow-motion film of frontal crashes of light and
heavy cars, one can see the lighter car reverse direction during the crash,
which indicates that the occupants are experiencing much higher declera-
tions.(17) In fatal collisions of cars and heavier trucks, death is three times as
frequent in the car if the car is large ( > 115-inch wheelbase), and six times
as frequent if the car is smaller.(18)
Even if all vehicles were the same size, the death rate would be greater if
all vehicles were small than it would be if all vehicles were large because of
the greater space available for deceleration in larger vehicles. In single-
vehicle crashes, cars with wheelbases (distance from front to rear axles) less
than 101 inches have an average 60 percent higher death rate per vehicles
registered than cars with wheelbases of 120 inches or more.(19) Smaller cars
simply have less room for energy to be absorbed and occupants to deceler-
ate in a crash.
Equation 2.3 can be applied to calculate the stopping distance necessary
to decelerate from a given speed to O at a uniform deceleration of 30 g's.
From 60 miles per hour (88 feet per second) to a total stop, for example, O
= 882 + 2(32) (- 30)d and, thus, d = 4 feet. Many vehicles do not provide
sufficient energy absorption or deceleration space for survivable decelera-
ions to belted front seat occupants in frontal barrier crashes at 35 miles per
hour.(20) . Most people cannot experience more then 45 gs and those
with debilitating conditions (that make them more susceptible to injury can
be injured at less than 30 g's at a uniform maximum deceleration.(21) Of
course, uniform decelera-tion is not absolutely achievable.
It should also be noted that the theory that small cars are less hazardous
because of their crash-avoidance capabilities is not supported by data on
their overall crash frequencies. On average, subcompacts have slightly
higher crash-insurance claim frequencies than larger cars.(22)
The maximum braking capability and the maximum speed capability of
second. If no object (for example, another vehicle or fixed object) is en-
countered, a car braked at that capacity from 100 miles per hour requires
about 717 feet to stop while the same car braked at that capacity from 50
miles per hour requires only about 170 feet to stop. Notice that doubling the
speed of the vehicle quadruples the necessary stopping distance. Also, these
distances do not include reaction time of the driver before braking,
slick roads, or poor tire gripping capacity, any one or all of which would in-
crease the total stopping distance. While vehicles are not driven at their
maximum speeds all the time, they often fail to stop before striking people,
other vehicles, or objects at these and at much lower than capacity speeds.
The nature of injuries to a pedestrian struck by a motor vehicle is deter-
mined by vehicle speed at the time of impact, the shape and elasticity of the
material striking the pedestrian--usually the material on the front of the
vehicle, which is often sharp, pointed, and relatively inelastic sheet metal--
and the strain on the pedestrian's tissues.
Simulated pedestrian impacts have been tested with adult cadavers ar-
ranged so that their weight is on the right leg, as would be the case for an
adult pedestrian stepping from a sidewalk. At impact speeds of eleven to
twenty-eight miles per hour and bumpers twenty-five or more inches from
the road surface, the shearing force not only broke bones in the leg but also
in hip and knee joints, and vital organs in the abdomen were lacerated.
Bumper heights less than twenty-one inches from the road produced only
fractures.(23)
Data on injuries to pedestrians truck by bumpers of varying height
reveal the same result: higher bumpers are associated with more severe in-
juries.(24) In the same study, when the ratio of hood height to pedestrian
height was 0.46 to 0.5, the percentage of hip fractures was twice as high as
those at other ratio intervals. It should also be noted that bumpers at
heights that would strike adults in the legs or hips strike children more often
in the head or chest.
Firearms
The most common means of suicide and homicide in the United States are
firearms. These deaths, combined with the unintentional deaths from this
source, comprise the second most frequent cause of death associated with
mechanical energy.
Bullets are accelerated by the expanding gases that result from the ex-
plosion of gunpowder in guns. Their muzzle velocities commonly range
from 1,200 to 2,700 feet per second (818 to 1,841 miles per hour). At close
velocities generate so much energy that bones are sometimes broken by the
bullet as it passes through nearby soft tissue. The cells impacted by the
bullet are pushed aside at rates and amounts that greatly damage structure
not directly impacted.(25)
A slogan, popular in some circles, claims "guns don't kill people--
people kill people.': That slogan is not supported by the evidence. The
Federal Bureau of Investigation reports that although 23 percent of assaults
are committed with firearms, 63 percent of deaths from assaults occur from
firearm injuries.(26) Greater mechanical energy is generated by guns as com-
pared to cutting instruments, fists, and so on. Since nonfatal injuries from
assault are less likely to be reported to the police, particularly those that do
not involve the public disturbance generated by gunshots, the discrepancy
between those percentages could be substantially larger.
The Geneva Convention requires, for military use, fully jacketed bullets
that retain their approximate dimensions while moving through human
tissue. On the other hand, bullets commonly used for purposes such as hunt-
ing and target shooting are designed to expand or fragment; and they form
wounds in tissue of much greater volume than do those used by the military.
The size of the wounded area caused by such bullets, whether the victim is
an animal or human, averages more than twenty-seven times that created by
military bullets.(27) It is, Of course, the nonmilitary bullets that injure in most
nonwar firearm incidents.
The potential for death or disability from bullet wounds depends on the
nature of the tissue directly or indirectly impacted, the extent to which the
damage is reversible, and the prevention or control of infection in the wound.
Shotguns that spray pellets rather than a single bullet are less often involved
in human shootings than handguns and rifles, but they usually produce a
larger wound area. At a range of ten yards, 95 percent of the pellets from a
shotgun will enter the skin in a circle approximately nine inches in diameter.
At a range of forty yards, the circle's diameter is about thirty-six inches.(28) The
muzzle energy is inversely related to the number of pellets per shell. At a muz-
zle velocity of about 1,300 feet per second, the muzzle energy can vary by a
factor of forty depending on the number and weight of the pellets.(29)
Plastic ammunition, which is sometimes used for target practice with
handguns and rifles and for riot control in European countries, is unlikely
to produce a serious wound except in the eye. Tests using cadavers resulted
in failure to penetrate the skin when such ammunition was fired at a range
of twenty feet.(30)
Elevation
It is perhaps pushing the concept of vehicle to refer to elevation as the
vehicle of the mechanical energy that kills people in falls. In some cases the host
is no more elevated than his or her own height at the time of a fatal fall.
And, in the fall, it is the potential energy of the host converted into kinetic
energy that results in injury if it is not sufficiently absorbed by any material
impacted at the end of the fall. Nevertheless, given that velocity due to the
acceleration of the body will be greater the higher the point from which a
body falls, perhaps the concept is appropriately applied.
The Consumer Product Safety Commission uses a sample of emergency
room visits in hospitals around the United States to estimate the number of
injuries associated with particular kinds of products. In 1978, there were
about 572,000 treated injuries that involved stairs, steps, ramps, or land-
ings (31)--about one such injury for every 400 persons in the country.
Fatal injuries in falls are highly concentrated among the elderly, in part
because impairments in perceptual and motor skills, as well as medical con-
ditions, increase their likelihood of falling; furthermore, their frailty in-
creases their vulnerability to energy exchanges that would not seriously in-
jure younger persons. Children, on the other hand, sometimes fall to their
deaths from windows, fire escapes, or outside landings. Epidemiologists in
New York City found that these deaths were concentrated in areas with
high-rise buildings. Of 132 deaths from falls to children under five years of
age during 1965 through 1969, 85 percent came after falls from windows
and an additional 4 percent came after falls from fire escapes.(32)
Asphyxiation
Any matter that blocks intake of oxygen into the lungs for more than a few
minutes will result in permanent brain damage. Lack of oxygen for a few
minutes beyond the point of brain damage results in death. Water in the
lungs is the most common form of asphyxiation: drowning accounts for
about 6,500 deaths annually.
Because of the fragmented way in which national data are collected, a
systematic attribution of drowning and other forms of asphyxiation to
specific vehicles is not possible. While water is the obvious vehicle in drown-
ing, no national data have been collected on the circumstances bearing on
the incidence. The Coast Guard reports fatalities (33) related to boating--
about 1,400 in 1979--but not all boating deaths are drownings.
In a study of 117 drownings in Maryland, 52 percent were in rivers or
creeks; 17 percent in lakes, ponds, reservoirs, and the like; 14 percent in the
Chesapeake Bay, including its harbors; and ii percent in swimming pools.
Waters of such disparate sizes and degrees of human exposure as the ocean,
bath water, and collections in ditches and holes were each involved in less
than 3 percent of the drownings. (34) The extent and type of exposure to the
various bodies of water is unknown aand poses an interesting problem for
epidemiological study. The large involvement of rivers and creeks, where
water is more likely to be moving swiftly, suggests that the kinetic energy of
the water is an important contributor to drownings.
Watercraft were involved in 29 percent of the drownings studied in
Maryland. More than two-thirds of the watercraft were small rowboats or
outboard motorboats and 15 percent were canoes. Nationally, boating-
related deaths reported to the Coast Guard were mainly associated with out-
board motorboats (56 percent) or those propelled by oars or paddles (21
percent), where the means of propulsion was known. Since boats without
motors do not have to be registered in most states, the numbers in use are
not known precisely.
The incidence of deaths associated with sailboats is low, less than 3 per-
cent of boating deaths in Maryland, where sailing is popular, and 2 percent
nationally. One suspects that the kinetic energy of the boats propelled by
motors and/or of the fast-moving waters when they are used in rivers and
creeks (where few would attempt sailing) is a prime factor in drownings and
other deaths from boating. The Coast Guard does not use mutually ex-
clusive categories in its classification of "causes," so it is not possible to say
that the 17 percent of boating deaths in rapid or rough water are all of this
kind, or that those attributed to operator error, falls, and so on were not
related to the speed of the water or of the involved boats.
Not counted in the Maryland data were an additional sixteen deaths
from drowning in hurricane-generated floodwaters. Floods may drown or
injure by the mechanical energy of swift-moving objects in the water. In
cases in which dams or piles of waste with water behind them give way sud-
denly, injury may also occur from explosions, fires, and downed electric
lines caused by the wall of water moving "everything in its path."(35) Flood-
waters may also impede rescue efforts or damage medical facilities so that
treatment of injuries is delayed.
Recent studies of asphyxiation in children, excluding cases of drowning,
smoke inhalation, and aspiration of vomitus, indicate the involvement of a
variety of objects that lodge in the throat or trachea, strangle through
pressure on the throat, or cover the mouth and nose. Flexible, round objects
such as hotdogs, pacifiers, balloons, and candy were particularly evident;
but hard objects such as small wooden balls, rattles, and nuts and bolts were
also found. Strangulation occurs most often when children's throats are
either trapped between crib slats or beds and mattresses or hanged on ropes
and cords, including cords holding pacifiers around their necks. Somewhat
less common are entanglements between pieces of furniture, including parts
of high chairs, in clothing, and in closing windows.(36,37) Old refrigerators
that cannot be opened from the inside by children also kill.
Children's asphyxiations result from a combination of exposure to ob-
jects and their developmental stages that determine their use of or move-
ment in relation to these objects. Infants (less than one year old) are more
often smothered or strangled by objects around the face and neck, while
older children are more often asphyxiated by ingested objects.
Heat Energy
Too much heat exposure for too long or too little heat exposure for too long
will damage human tissue. Most such damage to residents of the United
States is from too much heat, the inhalation of the by-products of combus-
tion, or the depletion of oxygen. The physics and chemistiy of combustion
are complex and vary according to 1) the concentration and type of heat
source; 2) the chemistry, shape, and size of a combustible; 3) oxygen con-
centration; 4) the vaporization of gases; and 5) the presence or absence of
catalysts.(38) Combustion of some materials under certain conditions is so
rapid that the accompanying shock waves or pressures can injure directly or
indirectly through the generation of mechanical forces. These injuries are
usually attributed to "explosion" rather than to "fire."
As students of the energy crisis are well aware, many materials are not
easily converted into heat energy. Nevertheless, the everyday environments
of home, transportation vehicles, work places, and schools contain mate-
rials that are easily ignited when exposed to ignition sources. While most
heat-related deaths occur from incineration or asphyxiation from smoke
and other by-products of burning materials, severe but usually nonfatal
burns also occur from contact with water and space-heating devices that are
heated beyond human tolerance.
Any time there is a heat differential among solids, liquids, or gases in
proximity to one another, including those that make up the human
organism, there will be heat transferred from the medium at higher tem-
perature to the medium at lower temperature. Heat is transferred by a mix-
ture of conduction, radiation, and convection. Substances that conduct
heat rapidly are often used for that purpose, while substances that conduct
heat slowly are used for insulation where heat transfer is undesirable. Ra-
diant heat is energy in the form of electromagnetic waves of various lengths
from sources as distant as the sun. Heat in this form can be concentrated or
diffused by various means, such as prisms or reflectors. Finally, convection
is the transfer of heat by the flow of a gas or liquid.
Burns usually occur first to the skin or in the mouth as these surfaces are
exposed to sufficient heat. The heat is conducted to deeper tissue depending
on the temperature and length of exposure. Irreversible epidermal injury oc-
curs at temperatures of sixty-five degrees Celsius in one second, but as low
as at forty-five degrees Celsius for an exposure of 10,000 seconds. Necrosis
of tissue below the epidermis begins at temperatures a few degrees higher in
the same periods of time.(39)
Recovery from burns is a function of the area of the body surface, the
depth of penetration, and the degree of infection that commonly occurs in
necrotic tissue. A satisfactory index that predicts the probable outcome as a
function of a combination of these factors has not been developed. In addi-
tion, clinical classifications of burns vary somewhat from one burn center
to another. The probability of loss of life or permanent disability increases
exponentially as a function of the surface area burned. The vital nature of
the organs affected by deep burns determines their loss or reduced function.
In one series of 1,683 hospitalized burn cases, 241 (14 percent) died. Of
these, 27 percent died from tissue incineration, 16 percent from septicemia
(infection spread in the bloodstream), 14 percent from pulmonary damage,
14 percent from fluid imbalance, and the remainder mostly from cardiopul-
monary complications.(40)
The study of hospitalized cases probably results in underestimation of
the importance of asphyxia due to smoke and reduced oxygen in fires. A de-
tailed study of about half of the fire injuries in Ohio in 1976 revealed that
asphyxia was involved in 69 percent of fatal fire injuries compared to 40 per-
cent of nonfatal fire injuries.(41)
The Ohio research and a similar investigation of California fires in 1975
included data on ignition sources and the materials that burned in home
fires. In these fires, the most frequent ignition source was cigarettes (29 per-
cent), followed in order by cooking units (9 percent), space-heating systems
(8 percent), "incendiary/suspicious" causes (6 percent), and electrical
systems (4 percent). These sources were similarly ranked for nonfatal in-
juries, with cigarettes somewhat less involved (18 percent) and the others
somewhat more involved. In 31 percent of fatal fires and 14 percent of non-
fatal injury, the ignition source was undetermined.
In fires ignited by cigarettes, the material first ignited was predomi-
nantly bedding or mattresses (31 percent), upholstered chairs and sofas (29
percent), and newspapers (14 percent). Materials primarily ignited by cook-
ing units were fat and grease (57 percent) and food starches (14 percent).
Fires related to transportation were mainly in motor vehicles. Three-
quarters of deaths and 92 percent of injuries in transportation fires were in
motor vehicles. Automobiles accounted for 46 percent of the transporta-
tion-fire deaths and 56 percent of the injuries in the Ohio and California
data. In front-to-rear crash tests of six 1973 model cars at speeds of thirty-
six to forty miles per hour, fuel spillage from ruptured gas tanks occurred in
every case and a spontaneous fire was ignited in one. The fire filled the
passenger compartment of the struck car almost instantaneously.(42)
Chemical Energy
The interaction of a chemical compound with the chemistry of human cells
may result in harmful changes to the cells. The variety of such chemical
reactions and the toxicity of each are too complex to examine in detail in a
general survey of agents of injury. The reader interested in such detail
should consult a textbook on toxicology.(43)
The effects of chemicals are dependent on the characteristics of the cells
or organs involved. They also vary according to the chemicals' concentra-
tions and in relation to the age of the individual, genetic susceptibility, and
the presence or absence of other chemicals. The effect as a function of con-
centration is called the dose-response curve, which may be a straight line or
curvilinear. The LD50 is the median concentration at which 50 percent of
people die. The extent of variation in lethal doses is determined by the other
factors mentioned above.
If a chemical is used in human beings for therapeutic purposes, the ratio
of the LD, to the median dose necessary for therapy, called the ED50 yields
an index of potential harm relative to usefulness. Where fully developed dose-
response curves are known, variations of the therapeutic index give a more
precise comparison of risk to benefits. For instance, one would like to know
whether LD1, the lethal dose for 1 percent of the population, is well above
ED99--the effective therapeutic dose for 99 percent of the population. Similar
knowledge of nonfatal effects is available for some chemicals, but not for
many others.
Toxicologists divide the process of harm by a chemical into three phases:
exposure, toxokinetic, and toxodynamic. Most exposure to acutely poisonous
substances occurs through swallowing or breathing the chemical. The tox-
okinetic phase refers to the chemical's absorption through the membranes of
the alimentary canal or in the lung sacs and the distribution, metabolism, and
excretion in the vascular and waste disposal systems. The interaction of the
chemical with receptors in target tissues constitutes the toxodynamic phase.
The most frequent exposures to acutely toxic concentrations of chemi-
cals occur when drugs--most commonly analgesics, antipyretics, sedatives,
and hypnotics--are ingested in greater than therapeutic doses. Alcohol,
presumably used mostly for nontherapeutic reasons, is consumed in amounts
sufficient to account for about one in seven poisoning fatalities. Finally,
carbon monoxide generated by cars parked with the motor running is the
chemical most often inhaled in fatally toxic concentrations.
The form of a chemical--liquid, crystalline, and so on--may effect the
speed of absorption and distribution when ingested. In some cases, enhance-
ment of or antagonism to toxicity is also a function of form. The presence or
absence of other materials in the alimentary canal, blood stream, and organs
may interact chemically with the substances or lengthen the time of absorp-
tion and distribution. In the case of inhaled gases, the concentration in the air
is the primary determinant of absorption. The absorption of inhaled droplets
or dusts is moderated by the size of the particles.
When movement of a chemical in an organism is primarily through sim-
ple diffusion across membranes, the concentration in the organism increases
as the concentration ingested or inhaled increases. If the chemical's move-
ment depends on carrier molecules, it will increase to a saturation point and
level off. Elimination of the substance may also be limited by the presence
of carriers or factors in the metabolic system that can process only so much
of the chemical in a given period of time. The relative acidity or alkalinity of
urine in combination with the ionization of a substance can result in absorp-
tion through the walls of the renal tubules and thus slower elimination.
Toxicologists often refer to the half-life of a substance, meaning the
period of time it takes for half of the substance to be eliminated. There is
enormous variation in the half-life of chemicals, from a few hours in the case
of alcohol to years in the case of fat-soluble pesticides such as DDT, aldrin,
and dieldrin. Persons who have damaged livers, kidneys, or deficiencies in
certain enzymes will retain chemicals longer than individuals in good health.
Damage is effected when the chemical produces a lesion; it may also
result if the substance interferes with a process necessary for normal func-
tion. There is substantial disagreement as to whether or not chemicals that
are known to be toxic above certain concentrations are totally benign at
lower concentrations. Carbon monoxide, for example, competes with oxy-
gen for positions on hemoglobin molecules and wins. At a sufficient concen-
tration of the chemical, an exposed person will die from lack of oxygen. The
acute effect is reversible if the carbon monoxide is removed before anoxia
causes damage. We do not know however, whether relatively low concen-
trations of carbon monoxide impair nervous system functioning, thus in-
creasing the risk in driving or other hazardous activities.
For purposes of regulatory standards, a certain concentration of a
chemical in the environment or in an individual--such as the level of
alcohol in the blood or breath of drivers--can be designated as legally per-
missible. Less than 0.10 percent alcohol by weight in blood or breath is
allowed for driving, even though lower concentrations increase the risk to
the driver and to others. Solvents, lead, and other toxic substances may
have similar effects.
Electrical Energy
Electrical energy is inherent in matter and is generated in large, concen-
trated quantities in economically developed areas. Use of shields and
automatic cutoff devices results in substantial control of electricity such
that its potential exposure in damaging amounts to human beings is less
than that of the forms of energy previously discussed. Nevertheless, where
controls are inadequate or unused by electrical workers or other users, elec-
trical injuries occur. Concentrated electrical energy in storms is also an oc-
casional source of human damage.
Atoms are made up of electrons (negatively charged), protons (positively
charged), and neutrons (neutrally charged). Gain or loss of electrons in or-
bit about the nucleus determines whether the atom is positively or negatively
charged. The flow of electrons is electric current. The atoms of different
materials, including human tissues, vary in their tendency to hold an elec-
trical charge.
The term amperes refers to electrical current flow in a unit of time and
varies as a function of the electromotive force (volts) divided by the
resistance to conductivity (ohms) that characterizes the materials and situa-
tion involved. The extent of damage to human tissues in contact with elec-
trical energy increases with amperage. Muscular paralysis occurs at about
0.02 amperes, ventricular fibrillation at 0.10 amperes, and ventricular
paralysis at 2.0 or more amperes. The resistivity of skin varies one hundred
fold as a result of its wetness--100,000 ohms when dry but 100 ohms when
soaked. The water serves as a low-resistance conductor if the water is in
contact with the ground.(44) Thus, a 120-volt electrical current will have low
amperage (0.001) in contact with dry skin, but will be high enough (0.12) to
cause ventricular fibrillation if the skin is soaking wet and in contact with
the ground.
In a study of sixty-four individuals hospitalized with electrical injuries,
76 percent were injured by contact with more than 100 volts. Two-thirds
contacted the electricity with one or both hands; it exited to the ground
through one or both legs or feet in 69 percent of the cases. Thirty-two am-
putations were performed on nineteen patients, involving loss of seventeen
fingers or toes, eight arms, three legs, two feet, and one hand. The remain-
ing case was a shoulder disarticulation. Cardiac complications were found
in twenty-three patients (36 percent), and sixteen (25 percent) suffered
neurological complications.(45)
A study of 220 deaths attributed to electricity during twenty-two years
in Dade County, Florida, included vehicles of the electricity. More than
two-thirds of the ninety-three high-voltage (> 1000) cases were workers who
touched a power line (27 percent) or were in contact with objects that con-
tacted a power line, such as a derrick or crane (41 percent). In twenty-six
nonwork cases of high-voltage electrocutions, touching a downed or defec-
tive line (31 percent) or an antenna in contact with a line (23 percent) were
most common.
Only 45 percent of the low-voltage cases were workers, and their deaths
were mainly due to energized tools, electrical equipment, and wiring. Ap-
pliances accounted for 40 percent of electrocutions of nonworkers. Only
sixteen (7 percent) of the total deaths were caused by lightning. The authors
noted that death from electrical energy is sometimes attributed to other
causes unless there is careful investigation of potential sources of electrical
conduction.(46)
Ionizing Radiation
Acute injury from ionizing radiation has been rare, with the exception of
the bombings of Hiroshima and Nagasaki during World War II. Whether
the prevailing fear and care that has thus far been taken to prevent exposure
to radiation at such huge rates and amounts could have been generated
without that horrible experience is unknown.
The nuclear reactions involved in weapons and nuclear power plants
depends on nuclear fission. Fission occurs when unstable uranium isotopes
are bombarded with neutrons to begin a chain reaction of particle exchange.
The amount of energy thereby released in heat, light, and charged particles
Or "rays" from small amounts of fissionable material is almost beyond
human comprehension. In weapon form, the resultant, uncontrolled reac-
tion is called an atomic explosion. When the heat from the reaction is used
to promote fusion of hydrogen isotopes, as it is in hydrogen bombs, the
energy released is multiplied.
Despite supposedly fail-safe procedures and mechanisms to prevent
unintentional nuclear detonation, in at least one case a nuclear weapon was
dropped to earth from an airplane and only one of the six mechanisms to
prevent a nuclear reaction remained intact. Numerous other weapons have
been jettisoned or were in planes that crashed.(47) In the generation of elec-
tricity from nuclear power, the probability of nuclear explosion is of less
concern; but workers in generating plants and people in close proximity to
the plants could be exposed to acutely injurious concentrations of radiation
under certain conditions.
A hydrogen bomb has not been used against human populations, but
knowledge of the Hiroshima-Nagasaki atomic bomb blasts and of the
energy released in tests has led to estimates of the potential effects on
populations concentrated in cities. The Hiroshima bomb generated the
energy equivalent of fifteen kilotons (15,000 tons) of TNT and killed about
100,000 people, not counting the long-term health effects due to radiation
exposure. A sixty-kiloton bomb killed approximately 100,000 people in
Nagasaki. The destructive capacity of these bombs was tiny compared to
the bombs and warheads now deployed in the strategic arsenals of the
United States, Soviet Union, United Kingdom, and France.
Hydrogen warheads that have the energy-equivalent power of up to
twenty-five megatons (one megaton is a million tons) of TNT that can be
delivered by missile between continents are currently deployed. The United
States and Soviet Union, by the mid-1970s, had more than 10,000 tactical
nuclear weapons deployed in Europe, each as large as the Nagasaki bomb.
Some smaller tonnage weapons are delivered by field artillery over distances
shorter than fifteen miles. Total deployment of nuclear weapons by the
nuclear powers is estimated to contain the destructive power of about sixty
tons of TNT for every person on the earth.
The actual consequences of a nuclear detonation used against human
populations would depend on the concentration of the populations relative
to the point of detonation and the structures and vehicles in which they were
located. Also, most of the deaths would occur from the mechanical force of
the blast (50 percent) and the heat energy generated (35 percent). About 5
percent would die from the injurious effects of ionizing radiation and an ad-
ditional 10 percent from its long-term effects. A one-megaton nuclear
warhead would destroy apartment houses, killing most of the people in
them over an area of some thirty-nine square miles. Most people in wooden
homes in an area of some ninety-eight square miles would die. (48)
An exchange of weapons up to twenty-five megatons, each targeted on
the major cities of any two countries, would destroy the civilization of those
countries and render them uninhabitable. Not only would tens of millions of
people die, but those who survived would be faced with virtually no medical
facilities or personnel to treat the immediate wounds and burns that would
number in the millions.(49) Disease would probably become rampant because
of the complete breakdown of sanitation, the absence of medical care, and
the suppression of bodily resistance by radiation exposure. The destruction
of communication and supply systems, as well as the fear of radiation by
potential suppliers of food and shelter, would very likely result in shortages
of food and shelter for survivors. Many experts believe that the prolifera-
tion of nuclear weapons of ever-widening variety with their diversified
delivery systems will result in their eventual use. Thus, this currently most
uncommon source of acute injury has the potential to be our most common
destroyer.
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