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3.2 Mechanism (Cause) of Injury

For injury-related deaths, the mechanism (cause) of injury was determined according to the International Classification of Disease, 10th Revision⁷ (ICD-10) external cause of injury coded as the underlying cause (see Section 5.1 for more information about the source and coding of fatal injury data). The reportable mechanism categories are based on standard groupings of ICD-10 external cause codes in the external-cause-of-injury mortality matrix (http://www.cdc.gov/nchs/injury/injury_tools.htm).

The reportable mechanism categories for injury-related deaths are shown below (Table 4). Each level of indentation corresponds to a data selection detail level (see Section 2.3). Definitions of these mechanism categories are provided further below in this section.

For injuries resulting in hospitalization subsequent to emergency department (ED) treatment or injuries resulting in an ED visit followed by release (without hospitalization or other transfer), the mechanism of injury was defined as the precipitating cause (i.e., the cause that started the chain of events that led to the injury). The mechanism of injury was assigned by trained coders referring to narrative information from patient medical records (see Section 5.2 for more information about the underlying data).

The reportable mechanism categories for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in an ED visit followed by release (without hospitalization or other transfer) are shown below (Table 5). Each level of indentation corresponds to a data selection detail level (see Section 2.3). Definitions of these mechanism categories are provided further below in this section.

There is substantial, but not complete, overlap between the set of mechanism (cause) categories reportable for injury-related deaths and the set of categories reportable for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment only. Categories that are reportable for all injury outcomes often, but not always, share a similar definition. Transportation-related categories are defined (further below) separately for injury-related deaths and for injuries resulting in hospitalization or ED treatment only. Categories that are not transportation-related are defined immediately below, for all injury outcomes collectively when applicable:

BB/Pellet: This category is separately reportable only for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment followed by release. It refers to penetrating-force injuries resulting from a metal BB, pellet, or other projectile shot from a compressed air or CO2-powered BB or pellet gun. This category excludes air gun projectile injuries from plastic pellets; such injuries are reported under the category struck by/against.

Bite/Sting: This category is separately reportable only for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment followed by release. It refers to injuries due to human bites or animal bites, poisonous or nonpoisonous snake and lizard bites, poisonous or nonpoisonous insect and spider bites, bee and wasp stings, scorpion stings, and stings from coral or jellyfish; and due to penetration of the skin by poisonous or nonpoisonous plant parts. This category covers the separately reportable categories of dog bite and other bite/sting. Injury-related deaths due to such causes are reported under the category natural/environmental.

Cut/Pierce: This category refers to injuries resulting from an incision, slash, perforation, or puncture by a pointed or sharp instrument, weapon, or object. This category excludes injuries due to being struck by or striking against a blunt object; such injuries fall into the category struck by/against. It also excludes injuries due to animal bites; such injuries fall into the category natural/environmental (when fatal) and the categories dog bite and other bite/sting (when resulting in hospitalization subsequent to ED treatment or resulting in ED treatment only).

Dog Bite: This category is separately reportable only for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment followed by release. It refers to injuries caused by dog bites. This category excludes injuries from other animal bites; such injuries fall into the category other bite/sting. Injury-related deaths due to dog bites are reported under the category natural/environmental.

Drowning/Submersion: This category refers to suffocation (asphyxia) resulting from submersion in water or another liquid. It excludes drowning/submersion injuries associated with water transport accidents; such injuries fall into the transportation-related categories transport, other (when fatal) and other transport (when resulting in hospitalization subsequent to ED treatment or resulting in ED treatment only).

Fall: This category refers to injuries resulting from striking a surface at the same or lower level following abrupt descent due to the force of gravity.

Firearm: The category refers to penetrating-force injuries resulting from bullets or other projectiles shot from powder-charged guns. This category includes gunshot wounds from powder-charged handguns, shotguns, and rifles.

Fire/Burn: This category refers to injuries due to exposure to smoke, fire, or flames; and due to contact with hot objects (e.g., appliances or machinery) or substances (e.g., liquids or vapors). It includes injuries to the upper airway, lower airway, or lungs due to smoke inhalation. For injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment only, this category additionally includes chemical burns. For injury-related deaths, this category covers the separately reportable categories fire/flame and hot object/substance.

Fire/Flame: This category is separately reportable only for injury-related deaths. It refers to deaths due to exposure to smoke, fire, or flames. This category covers the separately reportable category residential fire/flame.

Foreign Body: This category is separately reportable only for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment followed by release. It refers to injuries resulting from the entrance of a foreign body into or through the eye or other natural body opening but which does not block an airway or cause suffocation (asphyxia). Examples include a pebble or dirt in the eye, a BB in the ear, and a small child’s toy in the esophagus. Injury-related deaths due to such causes are reported under the category other specified and classifiable.

Hot Object/Substance: This category is separately reportable only for injury-related deaths. It refers to deaths due to contact with hot objects (e.g., appliances or machinery) or substances (e.g., liquids or vapors).

Machinery: This category refers to injuries resulting from the operation of machinery such as drill presses, fork lifts, large power-saws, jack hammers, and commercial meat slicers. This category excludes injuries involving machines not in operation, falls from escalators or moving sidewalks, and injuries from powered lawn mowers, powered hand tools, or home appliances.

Natural/Environmental: This category refers to injuries resulting from exposure to adverse natural and environmental conditions (such as severe heat, severe cold, lightning, storms, and other natural events) as well as lack of food or water. For injury-related deaths, this category additionally covers dog or other animal bites, poisonous or nonpoisonous snake and lizard bites, poisonous or nonpoisonous insect and spider bites, bee and wasp stings, scorpion stings, and stings from coral or jellyfish; and contact with poisonous or nonpoisonous plant thorns, spines, or sharp leaves.

Other Bite/Sting: This category is separately reportable only for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment followed by release. It refers to injuries due to human or animal bites (excluding dog bites), poisonous or nonpoisonous snake and lizard bites, poisonous or nonpoisonous insect and spider bites, bee and wasp stings, scorpion stings, and stings from coral or jellyfish; and due to penetration of the skin by poisonous or nonpoisonous plant parts. Injury-related deaths due to most of these causes are reported under the category natural/environmental; injury-related deaths due to human bites are reported under the category struck by/against.

Overexertion: This category refers to acute overexertion causing damage to muscles, tendons, ligaments, cartilage, joints, or peripheral nerves. It includes injuries due to lifting, pushing, or pulling; and due to excessive force (e.g., the stretching or pulling of an arm or leg by another person or inanimate object). It also includes strains and sprains not due to falling.

Poisoning: This category refers to harmful effects due to the ingestion, inhalation, injection, or absorption through the skin of a drug, toxin (biologic or other), or other chemical agent. This category includes drug overdoses. It does not include harmful effects from normal uses of therapeutic drugs (i.e., unexpected adverse effects from drugs correctly administered) or bacterial illnesses such as food poisoning. For injury-related deaths, this category additionally covers chemical burns.

Residential Fire/Flame: This category is separately reportable only for injury-related deaths. It refers to deaths due to exposure to smoke, fire, or flames occurring in a noninstitutional place of residence.

Struck By/Against: This category refers to injuries due to being struck by (hit) or crushed by a human, animal, or inanimate object other than a vehicle or machinery; and due to striking (hitting) against a human, animal, or inanimate object other than a vehicle or machinery.

Suffocation: This category refers to inhalation, aspiration, or ingestion of food or other objects resulting in blockage of the airway and/or causing suffocation, and mechanical suffocation due to hanging, strangulation, lack of air in a closed place, a plastic bag or collapsing earth. This category excludes injuries resulting from foreign bodies that do not block the airway; such injuries fall into the categories other specified and classifiable (when fatal) and foreign body (when resulting in hospitalization subsequent to ED treatment or resulting in ED treatment only). This category also excludes injuries due to smoke inhalation; such injuries fall into the category fire/burn.

Other Specified: This category is separately reportable only for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment followed by release. It refers to injuries due to specific causes that do not fit into one of the specific cause categories. Examples include injuries due to explosions, fireworks, electric current, exposure to radiation, and animal scratches.

Other Specified and Classifiable: This category is separately reportable only for injury-related deaths. It refers to injuries due to specific causes that are separately classified but that do not fit into one of the specific cause categories. Examples include injuries due to explosions, fireworks, electric current, exposure to radiation, entrance of a foreign body into or through the eye or other natural body opening which does not block an airway or cause suffocation (asphyxia), and being caught or crushed in or between objects.

Other Specified/NEC: This category is separately reportable only for injury-related deaths. It refers to injuries due to specific causes that are not separately classified (not elsewhere classifiable).

Unknown/Unspecified: This category refers to injuries for which the underlying or precipitating cause is not adequately documented (i.e., on the death certificate or in the ED report).

The following transportation-related categories are reportable for injury-related deaths:

Motor Vehicle Traffic: This broad category refers to motor vehicle deaths that are traffic-related (occurring on public roadways). It incorporates the separately reportable categories motor vehicle traffic, motorcyclist; motor vehicle traffic, occupant; motor vehicle traffic, pedal cyclist; motor vehicle traffic, pedestrian; motor vehicle traffic, other person; and motor vehicle traffic, unspecified person.

Motor Vehicle Traffic, Motorcyclist: This category refers to deaths among drivers or passengers of motorcycles resulting from collisions, loss of control, or other events involving other vehicles, objects, pedal cyclists, or pedestrians and which are traffic-related (occurring on public roadways). It includes deaths among drivers or passengers of classic-style motorcycles, sidecars, mopeds, motorized bicycles, and motor scooters.

Motor Vehicle Traffic, Occupant: This category refers to deaths among drivers or passengers of motor vehicles involved in collisions, rollovers, or other events involving other vehicles, objects, pedal cyclists, or pedestrians and which are traffic-related (occurring on public roadways). It includes deaths among occupants of cars, pickup trucks, SUVs, vans, heavy transport vehicles, buses, ATVs, and snowmobiles.

Motor Vehicle Traffic, Pedal Cyclist: This category refers to deaths among pedal cycle riders resulting from collisions with motor vehicles and which are traffic-related (occurring on public roadways). It includes deaths among riders of standard bicycles, mountain bikes, tricycles, and unicycles.

Motor Vehicle Traffic, Pedestrian: This category refers to deaths among pedestrians due to motor vehicle collisions which are traffic-related (occurring on public roadways).

Motor Vehicle Traffic, Other Person: This category refers to deaths among riders of railways trains or railway vehicles, streetcars, animals, or animal-drawn vehicles involved in collisions with motor vehicles and which are traffic-related (occurring on public roadways).

Motor Vehicle Traffic, Unspecified Person: This category refers to deaths among persons involved in traffic-related collisions or other accidents between motor vehicles or between motor vehicles and other land conveyances (e.g., railway trains or railway vehicles), for which the decedents’ specific modes of transport are not known.

Pedal Cyclist & Pedestrian, Other: This category refers to deaths among pedal cyclists and pedestrians due to collisions or accidents that are traffic-related (occurring on public roadways) but do not involve motor vehicles (e.g., a collision between a pedal cyclist and a pedestrian) or that are not traffic-related (not occurring on public roadways) but may involve motor vehicles. It incorporates the separately reportable categories pedal cyclist, other and pedestrian, other.

Pedal Cyclist, Other: This category refers to deaths among pedal cyclists due to collisions or accidents that are traffic-related (occurring on public roadways) but do not involve motor vehicles (e.g., a collision between a pedal cyclist and a pedestrian) or that are not traffic-related (not occurring on public roadways) but may involve motor vehicles.

Pedestrian, Other: This category refers to deaths among pedestrians due to collisions or accidents that are traffic-related (occurring on public roadways) but do not involve motor vehicles (e.g., a collision between a pedal cyclist and a pedestrian) or that are not traffic-related (not occurring on public roadways) but may involve motor vehicles.

Transport, Other Land: This category primarily refers to land-transport motor vehicle deaths due to collisions or accidents that are not traffic-related (not occurring on public roadways). It further includes deaths among riders of animals or animal-drawn vehicles due to loss of control or collisions with pedestrians, pedal cyclists, stationary objects, and railway trains/vehicles; deaths among occupants of railway trains/vehicles or streetcars due to collisions with motor vehicles or rolling stock; and deaths due to intentional (i.e., suicide or homicide) crashing of motor vehicles.

Transport, Other: This category primarily refers to deaths due to injuries involving motorized or non-motorized modes of transportation not on land. Examples include drowning and other types of injuries associated with watercraft accidents, injuries due to aircraft accidents, and injuries due to ski lift or suspended cable car accidents.

The following transportation-related categories are reportable for injuries resulting in hospitalization subsequent to ED treatment or injuries resulting in ED treatment only:

Motor Vehicle Occupant: This category refers to injuries to drivers or passengers of motor vehicles involved in collisions, rollovers, or other events involving other vehicles, objects, pedal cyclists, or pedestrians and which are either traffic-related (occurring on public roadways) or non-traffic-related. It includes injuries to occupants of cars, pickup trucks, SUVs, vans, heavy transport vehicles, and buses. This category covers the separately reportable category motor vehicle traffic occupant.

Motor Vehicle Traffic Occupant: This category refers to injuries to drivers or passengers of motor vehicles involved in collisions, rollovers, or other events involving other vehicles, objects, pedal cyclists, or pedestrians and which are traffic-related (occurring on public roadways). It includes injuries to occupants of cars, pickup trucks, SUVs, vans, heavy transport vehicles, and buses.

Motorcyclist: This category refers to injuries to drivers or passengers of motorcycles resulting from collisions, loss of control, or other events involving other vehicles, objects, pedal cyclists, or pedestrians and which are either traffic-related (occurring on public roadways) or non-traffic-related. It includes injuries to drivers or passengers of classic-style motorcycles, sidecars, mopeds, motorized bicycles, and motor scooters.

Pedal Cyclist: This category refers to injuries to pedal cycle riders resulting from collisions, loss of control, or other events and which are either traffic-related (occurring on public roadways) or non-traffic-related. It includes injuries to riders of standard bicycles, mountain bikes, tricycles, and unicycles.

Pedestrian: This category refers to injuries to pedestrians due to motor vehicles and which are either traffic-related (occurring on public roadways) or non-traffic-related. This category includes injuries to persons struck by cars, pickup trucks, SUVs, vans, heavy transport vehicles, and buses.

Other Transport: This category refers to injuries to persons boarding, alighting, or riding in or on railway trains and vehicles, streetcars, power scooters, battery-powered carts, ATVs, snowmobiles, go-carts, animals and animal-drawn conveyances, ski lifts, suspended cable cars, water transport, air transport, and space transport. This category also includes pedestrian injuries where the injured person was struck by a motorcycle, bicycle, or railway train.

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