Merck Manual

Please confirm that you are a health care professional

honeypot link

Overview of Occupational and Environmental Medicine


Michael I. Greenberg

, MD, Drexel University College of Medicine;

David Vearrier

, MD, MPH, University of Mississippi Medical Center

Reviewed/Revised May 2022 | Modified Sep 2022
View Patient Education
Topic Resources

Occupational and environmental medicine (OEM) focuses on prevention, diagnosis, and treatment of occupation- and environment-related injuries and illnesses. The goal of OEM is to enhance workers' productivity by promoting workers' overall health and safety in the workplace, at home, and in the community.

OEM physicians aim to

  • Promote and protect the physical and mental health of workers, their family members, and communities through preventive strategies and education (eg, health and wellness programs)

  • Provide preemployment screenings to assess the ability of job applicants to meet core job requirements with reasonable accommodations

  • Determine whether an injury or illness is work-related (which may affect the setting of health care delivery and payment)

  • Diagnose and treat occupational and environmental injury and illness in an acute care setting

  • Facilitate the safe and productive re-entry of workers into the workplace (eg, by optimizing return-to-work timing) after an injury or illness

  • Assess the extent of the disability in workers and their ability to complete core job functions with reasonable accommodations after a long-term injury or illness

  • Assess the safety of the workplace with respect to environmental exposures and ergonomics, define work-related restrictions to protect workers' health, and make recommendations to protect workers

  • Promote workplace efficiency

Thus, OEM benefits both workers and employers.

The most common injuries and illnesses treated by OEM physicians in acute care settings are

Sometimes an injury (eg, a repetitive motion injury) is caused by a combination of work-related and non–work-related activities.

Sometimes environmental illnesses manifest with nonspecific symptoms. For example, carbon monoxide exposure may mimic viral illness, causing headache, nausea, and vomiting.

OEM physicians also treat patients exposed to environmental contaminants not related to work (eg, lead poisoning in children).

Patient Evaluation

In the acute care setting, OEM physicians consider whether an injury or illness is due to an occupational or environmental exposure. Obtaining a history, including where an injury occurred and what the patient was doing at the time of injury or illness, usually helps determine the extent to which the cause is work-related.

Considering potential environmental exposures in the differential diagnosis can help avoid a delay in diagnosis. The cause of some conditions, such as occupational asthma and contact dermatitis, may not initially be recognized as an occupational or environmental exposure, resulting in delay in controlling exposure to the inciting agent.

Two potential clues that an illness is due to an occupational or environmental exposure are

  • An unexplained sentinel event in a low-risk patient

  • A cluster of patients with similar symptoms or the same diagnosis

Although unexplained sentinel events occur without occupational or environmental exposures, such an event in a low-risk patient should suggest that an unidentified exposure may have contributed. For example, peripheral and retinal arteriosclerosis and angina occurring in young workers without a history of cardiac disease led to the discovery that occupational carbon disulfide exposure caused those findings, which are unusual in that age group.

A cluster of patients with similar symptoms or the same diagnosis should also raise suspicion for an occupational or environmental exposure. For example, a cluster of patients coming from the same building with complaints of headache, nausea, and vomiting indicates possible carbon monoxide exposure. A cluster of hepatic angiosarcoma (a rare cancer) among workers at a single plant led to the discovery that vinyl chloride is a human carcinogen. Clusters of bladder cancer have been linked to environmental arsenic contamination. Taking exposure histories from affected and unaffected workers and/or community members may help identify the occupational or environmental exposure responsible for a cluster.

OEM physicians may spend more time than other physicians investigating the cause of the injury or illness to establish the extent to which an illness or injury is work-related so that they can recommend to the employer ways to prevent future injury or illness. As part of this investigation, OEM physicians may do workplace safety evaluations, evaluate worker ergonomics, and obtain worker exposure histories. OEM physicians may collaborate with industrial hygienists during such investigations. In non–work-related environmental illnesses, such as lead poisoning Lead Poisoning Lead poisoning often causes minimal symptoms at first but can cause acute encephalopathy or irreversible organ damage, commonly resulting in cognitive deficits in children. Diagnosis is by whole... read more in children, OEM physicians typically do not visit the home environment but instead contact the local public health agency that is responsible for such activities.

Workplace Safety Evaluation

In certain settings, an OEM physician may request or be asked to evaluate workplace safety. Workplace safety hazards (see table ) can be categorized as

  • Air contaminants

  • Chemical hazards

  • Biologic hazards

  • Physical hazards

  • Ergonomic hazards

The physician assesses the workplace for one or more of these types of hazards and recommends ways to reduce potential risks for workers to the employer. When making recommendations, an OEM physician considers the hierarchy of hazard controls.

Elimination, the most effective form of hazard control, involves removing a hazard from the workplace entirely, without replacing it.

Substitution, the second most effective form of hazard control, involves replacing a hazard in the workplace with a less dangerous substitute. Examples of substitution include use of a newer machine with additional safety features or use of a different solvent with a better safety profile.

When elimination and substitution are not viable options, engineering controls, administrative controls, and personal protective equipment (PPE) are considered. Engineering controls involve minimizing worker exposure to a hazard by physically isolating workers from a process or machine. Administrative controls change the way workers interact with the hazard, either by improving training and procedures or limiting the total time a worker is exposed to the hazard. PPE is the least effective method of hazard control and may be ineffective if PPE does not fit or seal on the worker, workers do not use their PPE, or they need to quickly remove PPE during an emergency while they are still exposed to the hazard.

Discussions with workers, the employer, engineers and other scientists, and an industrial hygienist may be useful in determining which workplace modifications are feasible and would optimize worker safety. (See also The National Institute for Occupational Safety and Health (NIOSH): Hierarchy of Controls.)


Disability Assessment

Some workplace injuries and illnesses resolve completely in a relatively short time. Others have a longer-lasting and sometimes permanent effect on workers' ability to do some (or even all) tasks of their job. The presence and degree of disability may necessitate a change in workers' duties or even prevent them from working. OEM physicians are frequently asked to assess disability either as the treating physician or as an independent medical expert. In the US, systems that require disability assessment include state worker’s compensation programs, the Social Security Disability System, Civil Service Retirement System, and Railroad Retirement Board. Each agency has regulations that establish whether a worker is disabled and whether the disabled worker should receive disability benefits.

During these assessments, OEM physicians do the following:

  • Assess whether one or more organ systems is impaired

  • Determine the severity and permanency of the impairment

  • Communicate those findings to the relevant agency

Impairment is defined as loss of function in a body part (eg, shortness of breath with FEV1/FVC < 70% predicted in a patient with COPD [chronic obstructive pulmonary disease]). Two comprehensive systems for evaluating and documenting impairment are provided by the Social Security Administration (see Consultative Examinations: A Guide for Health Professionals [referred to as the green book] and Disability Evaluation Under Social Security [referred to as the blue book]); the American Medical Association [AMA]) also has provided one (see AMA Guides® to the Evaluation of Permanent Impairment).

Disability is defined as the inability to do activities (including activities necessary for employment) due to an impairment (eg, being unable to walk more than 10 feet [3 meters] due to COPD). The OEM physician is also often asked to assess and report the degree of disability. A variety of disability rating systems are available to improve objectivity in the disability assessment (eg, Oswestry Disability Index). In some cases, the physician may order a functional capacity evaluation, which is a formal assessment of maximal physical work ability administered by a physical or occupational therapist.


OEM physicians may order

  • Medical diagnostic testing

  • Exposure testing (of patients and/or the environment)

Medical diagnostic testing is often needed to assess the effects of injuries and exposures (eg, x-rays of bones and joints, chest x-rays and oximetry for acute inhalation). Post-injury medical testing (eg, tests of pulmonary function Overview of Tests of Pulmonary Function Pulmonary function tests provide measures of airflow, lung volumes, gas exchange, response to bronchodilators, and respiratory muscle function. Basic pulmonary function tests available in the... read more ) may be done to determine whether organ damage has occurred secondary to a workplace exposure or incident.

Exposure testing (eg, of patients and/or the environment) may be needed to determine the extent of occupational exposure to a substance on a regular basis (medical surveillance) and/or after a workplace incident (eg, unintended release of a substance). Depending on the substance involved, samples may need to be sent to a reference laboratory. In some cases, OEM physicians request that an industrial hygienist complete workplace testing, such as air sampling or surface sample testing.

Governmental agencies may become involved after certain workplace incidents. The National Institute for Occupational Safety and Health (NIOSH) does a Health Hazard Evaluation when requested by a worker, a union official, or an employer. The Occupational Safety and Health Administration (OSHA) may inspect the workplace after complaints by a worker, after referral from another governmental agency, or on a targeted basis after reports of injuries or illnesses (see OSHA Fact Sheet: Inspections).

OEM physicians working with governmental agencies may order diagnostic testing to determine the extent of environmental exposure to a substance in a community or population. Such testing may be prompted by environmental release of a substance or documented environmental contamination by a substance.

Treatment and Return to Work

OEM physicians treat workers for acute and chronic illnesses and injuries that occurred at the workplace, using the same methods and standards of care that apply to patients outside of occupational medicine. Consultation with a specialist, subspecialist, or physical or occupational therapist may be necessary. Some employers have a network of specialists to whom the OEM physician can refer patients.

An important goal of the OEM physician is returning a worker to the workplace. Research indicates that early return to work can reduce long-term work absenteeism and long-term disability. When workers with an acute injury or illness cannot return to their typical work routine, they may be assigned transitional duty (sometimes called light or modified duty). For example, the OEM physician may recommend limitations on pushing, pulling, lifting, sitting, and standing based on the current clinical condition of the worker.

Preemployment Screening

OEM physicians provide preemployment screening and government-required screening of job applicants, including for the US Department of Transportation (DOT), the military, and private employers. In preemployment and government-required screening, OEM physicians evaluate whether a potential worker will be able to safely fulfill the duties of the applicable position. Considerations include preexisting chronic illnesses or conditions, use of drugs that may cause impairment, substance abuse, and physical examination findings. Frequently, preemployment drug testing is done.

Many companies follow DOT protocols for their drug testing policy, which includes a preemployment urine drug test (see DOT: Office of Drug and Alcohol Policy and Compliance). Other companies choose to use alternative samples such as oral fluid or hair.

Worker Screening and Surveillance

OEM physicians provide medical screening and surveillance of workers in workplaces with potential exposures to hazardous substances. In the US, the Occupational Safety and Health Administration (OSHA) issues medical screening and surveillance standards for general industry and for states and individual companies; a number of substances are included (see OSHA: Medical Screening and Surveillance).

Medical screening is done to detect disease or dysfunction before a person would normally seek medical care. For example, people who may be at high risk of certain conditions are screened (eg, periodic cholesterol testing or A1C testing).

Medical surveillance involves periodic evaluations of one or more workers over time to look for workplace hazards that require targeted prevention measures (eg, periodic blood lead levels in workers who might be exposed to lead). Surveillance usually relies on screening results from a group of workers being evaluated to look for abnormal health trends.

Depending on the substance involved, either screening, surveillance, or both may be indicated.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

  • American College of Occupational and Environmental Medicine: Provides guidelines for determining whether injuries and illness are work-related and for managing and preventing work-related health problems and disability (eg, low back disorders, work-related asthma). Other resources include information about promoting health and productivity.

  • Association of Occupational and Environmental Clinics: Provides a list of open-access, peer-reviewed journals and organizes conferences to promote sharing of research related to diversified fields of medicines, science, and technology.

  • Occupational Health and Safety Administration: Sets and enforces standards to ensure safe and healthful working conditions for workers. Provides information about workers' rights, hazard recognition, COVID-19, fall prevention, suicide prevention, personal protective equipment, and documentation requirements.

  • Pediatric Environmental Health Specialty Units: Provides information about how environmental factors (eg, hurricanes, floods, lead, wildfires, marijuana, vaping) affect the health of children and adults of reproductive age. Also provides contact information to experts in various areas of the US.

  • National Institute for Occupational Safety and Health (NIOSH): Provides guidance and authoritative recommendations for improving safety and health in the workplace, including such topics as nail gun safety and the health implications and applications of nanotechnology.

  • Centers for Disease Control and Prevention (CDC): Workplace Health Promotion: Provides workplace strategies for specific conditions (eg, work-related musculoskeletal disorders, depression, stress, cancer), a national survey of workplace health programs (eg, risk assessment for employees) and practices, and resources and tools employers can use to train employees.

View Patient Education
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!