An occupational injury is bodily damage resulting from working. The most common organs involved are the spine, hands, the head, lungs, eyes, skeleton, and skin. Occupational injuries can result from exposure to occupational hazards (physical, chemical, biological, or psychosocial), such as temperature, noise, insect or animal bites, blood-borne pathogens, aerosols, hazardous chemicals, radiation, and occupational burnout.

While many prevention methods are set in place, injuries may still occur due to poor ergonomics, manual handling of heavy loads, misuse or failure of equipment, exposure to general hazards, and inadequate safety training.

Injury is damage to the body caused by external force. This may be caused by accidents, falls, hits, weapons, and other causes. Major trauma is injury that has the potential to cause prolonged disability or death.

In 2013, 4.8 million people died from injuries, up from 4.3 million in 1990. More than 30% of these deaths were transport-related injuries. In 2013, 367,000 children under the age of five died from injuries, down from 766,000 in 1990. Injuries are the cause of 9% of all deaths, and are the sixth-leading cause of death in the world.

The World Health Organization (WHO) developed the International Classification of External Causes of Injury (ICECI). Under this system, injuries are classified by

- mechanism of injury;

- objects/substances producing injury;

- place of occurrence;

- activity when injured;

- the role of human intent;

and additional modules. These codes allow the identification of distributions of injuries in specific populations and case identification for more detailed research on causes and preventive efforts.

The United States Bureau of Labor Statistics developed the Occupational Injury and Illness Classification System (OIICS). Under this system injuries are classified by

- nature,

- part of body affected,

- source and secondary source, and

- event or exposure.

The OIICS was first published in 1992 and has been updated several times since.

The Orchard Sports Injury Classification System (OSICS) is used to classify injuries to enable research into specific sports injuries.

A needlestick injury, percutaneous injury, or percutaneous exposure incident is the penetration of skin by a needle or other sharp object, which was in contact with blood, tissue, or other body fluid before the exposure. Occupational needlestick injuries primarily affect healthcare workers, who make up 80% of needlestick injuries in the United States. Various other occupations are also at increased risk of needlestick injury, including law enforcement, laborers, tattoo artists, food preparers, and agricultural workers. Though the acute physiological effects of a needlestick injury are generally negligible, these devices can transmit blood-borne diseases, placing those exposed at increased risk of contracting infectious diseases, such as hepatitis B (HBV), hepatitis C (HCV), and the human immunodeficiency virus (HIV). Among healthcare workers and laboratory personnel worldwide, more than 25 blood-borne viruses have been reported to be caused by needlestick injuries.

It is estimated that half of all occupational needlestick injuries are not reported. Additionally, an unknown number of occupational needlestick injuries are reported by the affected employee, yet due to organizational failure, institutional record of the injury does not exist. Increasing recognition of the unique occupational hazard posed by needlestick injuries, as well as the development of efficacious interventions to minimize the largely preventable occupational risk, encouraged legislative regulation in the US, causing a decline in needlestick injuries among healthcare workers.

Symptoms are dependent on the type of TBI (diffuse or focal) and the part of the brain that is affected. Unconsciousness tends to last longer for people with injuries on the left side of the brain than for those with injuries on the right. Symptoms are also dependent on the injury's severity. With mild TBI, the patient may remain conscious or may lose consciousness for a few seconds or minutes. Other symptoms of mild TBI include headache, vomiting, nausea, lack of motor coordination, dizziness, difficulty balancing, lightheadedness, blurred vision or tired eyes, ringing in the ears, bad taste in the mouth, fatigue or lethargy, and changes in sleep patterns. Cognitive and emotional symptoms include behavioral or mood changes, confusion, and trouble with memory, concentration, attention, or thinking. Mild TBI symptoms may also be present in moderate and severe injuries.

A person with a moderate or severe TBI may have a headache that does not go away, repeated vomiting or nausea, convulsions, an inability to awaken, dilation of one or both pupils, slurred speech, aphasia (word-finding difficulties), dysarthria (muscle weakness that causes disordered speech), weakness or numbness in the limbs, loss of coordination, confusion, restlessness, or agitation. Common long-term symptoms of moderate to severe TBI are changes in appropriate social behavior, deficits in social judgment, and cognitive changes, especially problems with sustained attention, processing speed, and executive functioning. Alexithymia, a deficiency in identifying, understanding, processing, and describing emotions occurs in 60.9% of individuals with TBI. Cognitive and social deficits have long-term consequences for the daily lives of people with moderate to severe TBI, but can be improved with appropriate rehabilitation.

When the pressure within the skull (intracranial pressure, abbreviated ICP) rises too high, it can be deadly. Signs of increased ICP include decreasing level of consciousness, paralysis or weakness on one side of the body, and a blown pupil, one that fails to constrict in response to light or is slow to do so. Cushing's triad, a slow heart rate with high blood pressure and respiratory depression is a classic manifestation of significantly raised ICP. Anisocoria, unequal pupil size, is another sign of serious TBI. Abnormal posturing, a characteristic positioning of the limbs caused by severe diffuse injury or high ICP, is an ominous sign.

Small children with moderate to severe TBI may have some of these symptoms but have difficulty communicating them. Other signs seen in young children include persistent crying, inability to be consoled, listlessness, refusal to nurse or eat, and irritability.

Presentation varies according to the injury. Some patients with head trauma stabilize and other patients deteriorate. A patient may present with or without neurological deficit. Patients with concussion may have a history of seconds to minutes unconsciousness, then normal arousal. Disturbance of vision and equilibrium may also occur. Common symptoms of head injury include coma, confusion, drowsiness, personality change, seizures, nausea and vomiting, headache and a lucid interval, during which a patient appears conscious only to deteriorate later.

Symptoms of skull fracture can include:

- leaking cerebrospinal fluid (a clear fluid drainage from nose, mouth or ear) may be and is strongly indicative of basilar skull fracture and the tearing of sheaths surrounding the brain, which can lead to secondary brain infection.

- visible deformity or depression in the head or face; for example a sunken eye can indicate a maxillar fracture

- an eye that cannot move or is deviated to one side can indicate that a broken facial bone is pinching a nerve that innervates eye muscles

- wounds or bruises on the scalp or face.

- Basilar skull fractures, those that occur at the base of the skull, are associated with Battle's sign, a subcutaneous bleed over the mastoid, hemotympanum, and cerebrospinal fluid rhinorrhea and otorrhea.

Because brain injuries can be life-threatening, even people with apparently slight injuries, with no noticeable signs or complaints, require close observation; They have a chance for severe symptoms later on. The caretakers of those patients with mild trauma who are released from the hospital are frequently advised to rouse the patient several times during the next 12 to 24 hours to assess for worsening symptoms.

The Glasgow Coma Scale (GCS) is a tool for measuring degree of unconsciousness and is thus a useful tool for determining severity of injury. The Pediatric Glasgow Coma Scale is used in young children. The widely used PECARN Pediatric Head Injury/Trauma Algorithm helps physicians weigh risk-benefit of imaging in a clinical setting given multiple factors about the patient—including mechanism/location of injury, age of patient, and GCS score.

Occupational heat stress is the net load to which a worker is exposed from the combined contributions of metabolic heat, environmental factors, and clothing worn which results in an increase in heat storage in the body. Heat stress can result in heat-related illnesses, such as heat stroke, hyperthermia, heat exhaustion, heat cramps or heat rashes. Although heat exhaustion is less severe, hyperthermia is a medical emergency and requires emergency treatment, which if not provided can even lead to death.

Heat stress causes illness but also may account for an increase in workplace accidents, and a decrease in worker productivity. Worker injuries attributable to heat include those caused by: sweaty palms, fogged-up safety glasses, and dizziness. Burns may also occur as a result of accidental contact with hot surfaces or steam. In United States, occupational heat stress in becoming more significant as the average temperatures increase but remains overlooked. There are few studies and regulations regarding heat exposure of workers.

Diffuse axonal injury, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact. Axons are stretched and damaged when parts of the brain of differing density slide over one another. Prognoses vary widely depending on the extent of damage.

Systems also exist to classify TBI by its pathological features. Lesions can be extra-axial, (occurring within the skull but outside of the brain) or intra-axial (occurring within the brain tissue). Damage from TBI can be focal or diffuse, confined to specific areas or distributed in a more general manner, respectively. However, it is common for both types of injury to exist in a given case.

Diffuse injury manifests with little apparent damage in neuroimaging studies, but lesions can be seen with microscopy techniques post-mortem, and in the early 2000s, researchers discovered that diffusion tensor imaging (DTI), a way of processing MRI images that shows white matter tracts, was an effective tool for displaying the extent of diffuse axonal injury. Types of injuries considered diffuse include edema (swelling) and diffuse axonal injury, which is widespread damage to axons including white matter tracts and projections to the cortex. Types of injuries considered diffuse include concussion and diffuse axonal injury, widespread damage to axons in areas including white matter and the cerebral hemispheres.

Focal injuries often produce symptoms related to the functions of the damaged area. Research shows that the most common areas to have focal lesions in non-penetrating traumatic brain injury are the orbitofrontal cortex (the lower surface of the frontal lobes) and the anterior temporal lobes, areas that are involved in social behavior, emotion regulation, olfaction, and decision-making, hence the common social/emotional and judgment deficits following moderate-severe TBI. Symptoms such as hemiparesis or aphasia can also occur when less commonly affected areas such as motor or language areas are, respectively, damaged.

One type of focal injury, cerebral laceration, occurs when the tissue is cut or torn. Such tearing is common in orbitofrontal cortex in particular, because of bony protrusions on the interior skull ridge above the eyes. In a similar injury, cerebral contusion (bruising of brain tissue), blood is mixed among tissue. In contrast, intracranial hemorrhage involves bleeding that is not mixed with tissue.

Hematomas, also focal lesions, are collections of blood in or around the brain that can result from hemorrhage. Intracerebral hemorrhage, with bleeding in the brain tissue itself, is an intra-axial lesion. Extra-axial lesions include epidural hematoma, subdural hematoma, subarachnoid hemorrhage, and intraventricular hemorrhage. Epidural hematoma involves bleeding into the area between the skull and the dura mater, the outermost of the three membranes surrounding the brain. In subdural hematoma, bleeding occurs between the dura and the arachnoid mater. Subarachnoid hemorrhage involves bleeding into the space between the arachnoid membrane and the pia mater. Intraventricular hemorrhage occurs when there is bleeding in the ventricles.

Fractures of facial bones, like other fractures, may be associated with pain, bruising, and swelling of the surrounding tissues (such symptoms can occur in the absence of fractures as well). Fractures of the nose, base of the skull, or maxilla may be associated with profuse nosebleeds. Nasal fractures may be associated with deformity of the nose, as well as swelling and bruising. Deformity in the face, for example a sunken cheekbone or teeth which do not align properly, suggests the presence of fractures. Asymmetry can suggest facial fractures or damage to nerves. People with mandibular fractures often have pain and difficulty opening their mouths and may have numbness in the lip and chin. With Le Fort fractures, the midface may move relative to the rest of the face or skull.

Needlestick injuries are a common event in the healthcare environment. When drawing blood, administering an intramuscular or intravenous drug, or performing any procedure involving sharps, accidents can occur and facilitate the transmission of blood-borne diseases. Injuries also commonly occur during needle recapping or via improper disposal of devices into an overfilled or poorly located sharps container. Lack of access to appropriate personal protective equipment, or alternatively, employee failure to use provided equipment, increases the risk of occupational needlestick injuries. Needlestick injuries may also occur when needles are exchanged between personnel, loaded into a needle driver, or when sutures are tied off while still connected to the needle. Needlestick injuries are more common during night shifts and for less experienced people; fatigue, high workload, shift work, high pressure, or high perception of risk can all increase the chances of a needlestick injury. During surgery, a surgical needle or other sharp instrument may inadvertently penetrate the glove and skin of operating room personnel; scalpel injuries tend to be larger than a needlestick. Generally, needlestick injuries cause only minor visible trauma or bleeding; however, even in the absence of bleeding the risk of viral infection remains.

Musculoskeletal disorders (MSDs) are injuries or pain in the human musculoskeletal system, including the joints, ligaments, muscles, nerves, tendons, and structures that support limbs, neck and back. MSDs can arise from a sudden exertion (e.g., lifting a heavy object), or they can arise from making the same motions repeatedly repetitive strain, or from repeated exposure to force, vibration, or awkward posture. Injuries and pain in the musculoskeletal system caused by acute traumatic events like a car accident or fall are not considered musculoskeletal disorders. MSDs can affect many different parts of the body including upper and lower back, neck, shoulders and extremities (arms, legs, feet, and hands). Examples of MSDs include carpal tunnel syndrome, epicondylitis, tendinitis, back pain, tension neck syndrome, and hand-arm vibration syndrome.

Excessive exposure to hand arm vibrations can result in various patterns of diseases casually known as HAVS or VWF. This can affect nerves, joints, muscles, blood vessels or connective tissues of the hand and forearm:

- Tingling 'whiteness' or numbness in the fingers (blood vessels and nerves affected): This may not be noticeable at the end of a working day, and in mild cases may affect only the tips of the fingers. As the condition becomes more severe, the whole finger down to the knuckles may become white. Feeling may also be lost.

- Fingers change colour (blood vessels affected): With continued exposure the person may suffer periodic attacks in which the fingers change colour when exposed to the cold. Initially the fingers rapidly become pale and feeling is lost. This phase is followed by an intense red flush (sometimes preceded by a dusky bluish phase) signalling the return of blood circulation to the fingers and is usually accompanied by uncomfortable throbbing.

- Loss of manual dexterity (nerves and muscles affected): In more severe forms, attacks may occur frequently in cold weather, not only at work, but during leisure activities, such as gardening, car washing or even watching outdoor sports and may last up to an hour causing considerable pain and loss of manual dexterity and reduced grip strength.

In extreme cases, the sufferer may lose fingers. The effects are cumulative. When symptoms first appear, they may disappear after a short time. If exposure to vibration continues over months or years, the symptoms can worsen and become permanent.

MSDs can arise from the interaction of physical factors with ergonomic, psychological, social, and occupational factors.

Grade 1: if there is no initial lesion on the area, no amputation or lasting effects are expected

Grade 2: if there is a lesion on the distal body part, tissue and fingernails can be destroyed

Grade 3: if there is a lesion on the intermediate or near body part, autoamputation and loss of function can occur

Grade 4: if there is a lesion very near the body (such as the carpals of the hand), the limb can be lost. Sepsis and/or other systemic problems are expected.

A number of long term sequelae can occur after frostbite. These include transient or permanent changes in sensation, paresthesia, increased sweating, cancers, and bone destruction/arthritis in the area affected.

Facial trauma, also called maxillofacial trauma, is any physical trauma to the face. Facial trauma can involve soft tissue injuries such as burns, lacerations and bruises, or fractures of the facial bones such as nasal fractures and fractures of the jaw, as well as trauma such as eye injuries. Symptoms are specific to the type of injury; for example, fractures may involve pain, swelling, loss of function, or changes in the shape of facial structures.

Facial injuries have the potential to cause disfigurement and loss of function; for example, blindness or difficulty moving the jaw can result. Although it is seldom life-threatening, facial trauma can also be deadly, because it can cause severe bleeding or interference with the airway; thus a primary concern in treatment is ensuring that the airway is open and not threatened so that the patient can breathe. Depending on the type of facial injury, treatment may include bandaging and suturing of open wounds, administration of ice, antibiotics and pain killers, moving bones back into place, and surgery. When fractures are suspected, radiography is used for diagnosis. Treatment may also be necessary for other injuries such as traumatic brain injury, which commonly accompany severe facial trauma.

In developed countries, the leading cause of facial trauma used to be motor vehicle accidents, but this mechanism has been replaced by interpersonal violence; however auto accidents still predominate as the cause in developing countries and are still a major cause elsewhere. Thus prevention efforts include awareness campaigns to educate the public about safety measures such as seat belts and motorcycle helmets, and laws to prevent drunk and unsafe driving. Other causes of facial trauma include falls, industrial accidents, and sports injuries.

The main symptoms of heat stress are perspiration, increased heart rate, and dehydration. Other general symptoms include painful muscle cramps, extreme weakness, nausea, dizziness, headache, breathing fast and clammy, pale, cool, and/or moist skin or red, dry skin.

Vibration white finger (VWF), also known as hand-arm vibration syndrome (HAVS) or dead finger, is a secondary form of Raynaud's syndrome, an industrial injury triggered by continuous use of vibrating hand-held machinery. Use of the term "vibration white finger" has generally been superseded in professional usage by broader concept of HAVS, although it is still used by the general public. The symptoms of vibrating white finger are the vascular component of HAVS.

HAVS is a widespread recognized industrial disease affecting tens of thousands of workers. It is a disorder that affects the blood vessels, nerves, muscles, and joints, of the hand, wrist, and arm. Its best known effect is vibration-induced white finger (VWF), a term introduced by the Industrial Injury Advisory Council in 1970. Injury can occur at frequencies between 5 and 2000Hz but the greatest risk for fingers is between 50 and 300Hz. The total risk exposure for hand and arm is calculated by the use of ISO 5349-1, which stipulates maximum damage between 8-16Hz and a rapidly declining risk at higher frequencies. The ISO 5349-1 frequency risk assessment does not match the estimated risks for vibration-induced white finger well.

Signs and symptoms may include a limp or paralyzed arm, lack of muscle control in the arm, hand, or wrist, and lack of feeling or sensation in the arm or hand. Although several mechanisms account for brachial plexus injuries, the most common is nerve compression or stretch. Infants, in particular, may suffer brachial plexus injuries during delivery and these present with typical patterns of weakness, depending on which portion of the brachial plexus is involved. The most severe form of injury is nerve root avulsion, which usually accompanies high-velocity impacts that commonly occur during motor-vehicle collisions or bicycle accidents.

Some examples of symptoms experienced by patients with RSI are aching, pulsing pain, tingling and extremity weakness, initially presenting with intermittent discomfort and then, with a higher degree of frequency.

Based on the location of the nerve damage, brachial plexus injuries can affect part of or the entire arm. For example, musculocutaneous nerve damage weakens elbow flexors, median nerve damage causes proximal forearm pain, and paralysis of the ulnar nerve causes weak grip and finger numbness. In some cases, these injuries can cause total and irreversible paralysis. In less severe cases, these injuries limit use of these limbs and cause pain.

The cardinal signs of brachial plexus injury then, are weakness in the arm, diminished reflexes, and corresponding sensory deficits.

1. Erb's palsy. "The position of the limb, under such conditions, is characteristic: the arm hangs by the side and is rotated medially; the forearm is extended and pronated. The arm cannot be raised from the side; all power of flexion of the elbow is lost, as is also supination of the forearm".

2. In Klumpke's paralysis, a form of paralysis involving the muscles of the forearm and hand, a characteristic sign is the "clawed hand", due to loss of function of the ulnar nerve and the intrinsic muscles of the hand it supplies.

Frostbite is when exposure to low temperatures causes freezing of the skin or other tissues. The initial symptom is typically numbness. This may be followed by clumsiness with a white or bluish color to the skin. Swelling or blistering may occur following treatment. The hands, feet, and face are most commonly affected. Complications may include hypothermia or compartment syndrome.

People who are exposed to low temperatures for prolonged periods, such as winter sports enthusiasts, military personnel, and homeless individuals, are at greatest risk. Other risk factors include drinking alcohol, smoking, mental health problems, certain medications, and prior injuries due to cold. The underlying mechanism involves injury from ice crystals and blood clots in small blood vessels following thawing. Diagnosis is based on symptoms. Severity may be divided into superficial (1st and 2nd degree) or deep (3rd and 4th degree). A bone scan or MRI may help in determining the extent of injury.

Prevention is by avoiding low temperatures, proper clothing, maintaining hydration and nutrition, and staying active without becoming exhausted. Treatment is by rewarming. This should only be done when refreezing is not a concern. Rubbing or applying snow to the affected part is not recommended. The use of ibuprofen and tetanus toxoid is typically recommended. For severe injuries iloprost or thrombolytics may be used. Surgery is sometimes necessary. Amputation, however, should generally be delayed for a few months to allow determination of the extent of injury.

The number of cases of frostbite is unknown. Rates may be as high as 40% a year among those who mountaineer. The most common age group affected is those 30 to 50 years old. Evidence of frostbite occurring in people dates back 5,000 years. Frostbite has also played an important role in a number of military conflicts. The first formal description of the condition was in 1814 by Dominique Jean Larrey, a physician in Napoleon's army.

A repetitive strain injury (RSI) is an "injury to the musculoskeletal and nervous systems that may be caused by repetitive tasks, forceful exertions, vibrations, mechanical compression, or sustained or awkward positions".

An occupational disease is any chronic ailment that occurs as a result of work or occupational activity. It is an aspect of occupational safety and health. An occupational disease is typically identified when it is shown that it is more prevalent in a given body of workers than in the general population, or in other worker populations. The first such disease to be recognised, squamous-cell carcinoma of the scrotum, was identified in chimney sweep boys by Sir Percival Pott in 1775. Occupational hazards that are of a traumatic nature (such as falls by roofers) are not considered to be occupational diseases.

Under the law of workers' compensation in many jurisdictions, there is a presumption that specific disease are caused by the worker being in the work environment and the burden is on the employer or insurer to show that the disease came about from another cause. Diseases compensated by national workers compensation authorities are often termed occupational diseases. However, many countries do not offer compensations for certain diseases like musculoskeletal disorders caused by work (e.g. in Norway). Therefore, the term work-related diseases is utilized to describe diseases of occupational origin. This term however would then include both compensable and non-compensable diseases that have occupational origins.

A toxic tort claim is a specific type of personal injury lawsuit in which the plaintiff claims that exposure to a chemical or dangerous substance caused the plaintiff's injury or disease.