Occupational Medicine
A Basic Guide

05: Safety In the Workplace

Impaired Workers
Jerald Cook, MD, MS, FACOEM

The Americans with Disabilities Act (ADA) broadly defines “physical or mental impairment” as any physiological disorder, disfigurement, or anatomical loss affecting one or more body systems. The definition also includes any mental or psychological disorder, such as intellectual disability, organic brain syndrome, emotional or mental illness, and specific learning disabilities.1 Impairment at work increases “presenteeism,” which is defined as workers being on the job but, because of illness or other medical conditions, not fully functioning.


Impairment in this section refers primarily to neurocognitive reduction in performance—generally a temporary condition resulting from medication or substance use or from an internal or external stressor. In safety-sensitive positions, this situation can be dangerous, but in all positions, it can reduce productivity.


Often, neurocognitive impairment is thought to be the result of drug or alcohol use (used legally or illegally). The increase in the use of controlled substances, novel psychoactive substances (so-called “designer drugs” that may be legal and unregulated), and cannabis has indeed contributed to the complexity of impairment in the workplace. But workers may be impaired for various reasons, including many that are temporary or short-term and unrelated to substance use. Factors that may distract a person from focusing on his or her tasks can be related to family or relationship problems, mental or physical fatigue, extreme environmental conditions, or other situations. Examples of potentially impairing conditions with neurocognitive effects include:


  • physical conditions such as chronic pain; fatigue from inadequate sleep, working long hours, shiftwork, or multiple jobs; intoxication from substances such as alcohol or drugs; use of sedating medications; or a medical problem that may not be diagnosed
  • depression, anxiety, hypomania, addiction, compulsive disorders, attention deficit, or posttraumatic stress disorder
  • severe stress from a personal tragedy, such as a death in the family, home robbery, or home fire; a relationship or financial crisis; care of a child, elder, or someone with special needs; and even preparation for an activity such as an exam or a wedding
  • work-based trauma such as conflict with an employer or coworkers, sexual harassment or bullying, and extreme environmental conditions such as cold, heat, wind, or noise


Some of these issues may be chronic and others only intermittently problematic. If stressors become overwhelming or otherwise affect the worker to the point of impairment, it is important that they be addressed. If the worker has a safety-sensitive position, continuing to work as usual when impaired can present an unreasonable risk. But, even if the worker does not hold such a position, impairment can negatively affect worker health and productivity. Impairment is therefore an important issue for employers, who have safety responsibilities as well as a vested interest in having workers functioning at their highest potential. Individual workers, coworkers, supervisors, safety officers, human resource officers, and occupational health providers each play a role in identifying impairment, and in taking action.


Identifying Impairment


Impairment in the workplace is identified by behavior—whether witnessed directly by a supervisor or by another employee. The closer someone is to a worker, the more opportunity there is to notice subtle changes, although coworkers may be hesitant to suggest that a colleague is impaired. Sometimes there are immediate signs; other times there is a concerning pattern of behavior. Whether it is falling asleep while working, slurred speech, increasing absenteeism, mood changes, or persistent errors, impaired workers often have more than one visible sign.


Some signs of impairment are listed below. The behavior may be more significant if it represents a noticeable change from previous behavior.


  • Odor of alcohol or drugs, glassy or red eyes, unsteady gait, slurred speech, or poor coordination
  • Personality changes, erratic behavior, or mood swings; increased interpersonal conflicts or overreaction to criticism
  • Changes in personal hygiene, such as not bathing or washing clothing
  • Family disharmony, evident through a change in how the worker speaks of family members
  • Inappropriate verbal or emotional response
  • Isolation from colleagues
  • Lack of focus or concentration and forgetfulness
  • Lying and/or providing implausible excuses for behavior
  • Working in an unsafe manner or involvement in an accident or incident
  • Consistent lateness, absenteeism, or reduced productivity or quality of work
  • Falling asleep while working
  • Frequently leaving the workspace
  • Significant and persistent errors or sloppy, illegible work
  • Non-compliance with policies
  • Doing enough work to just “get by”


Drug Testing Programs


Workplace drug-testing programs, discussed previously in this chapter, are deterrents, but they are not intended to identify currently impaired workers or all workers using illicit substances. A worker’s positive drug test provides objective data showing that drugs have been used; subsequently, the occupational health provider may be asked to evaluate an individual for impairment. But drug testing reveals use, not impairment; the only test that correlates to impairment in a relatively consistent manner is blood alcohol content. Workplace drug testing policies should acknowledge this principle, so that workers and unions are aware, prior to testing, that human resources actions will be based on evidence of use alone. If the occupational health provider is asked to determine impairment following a positive drug test, a comprehensive evaluation, as opposed to the forensic test alone, is necessary.

Strategies for Managing Impairment


Employers should collaborate with employees, occupational health and safety staff, and union representatives (if applicable) to design an impairment policy that outlines the acceptable code of behavior and level of safety performance for the workplace. The ADA protects workers from discrimination for alcoholism or drug addiction, but it does not protect them from illicit drug use or alcohol intoxication while at work. The ADA also forbids employers from prohibiting prescription medications. However, the ADA does allow employers to require medical examinations that can include a review of prescribed medications when there is evidence of a job performance or safety problem—as long as the policy applies to all employees in the same job category. The workplace impairment policy should include evaluation protocols for potentially impaired workers (in the occupational health clinic versus the emergency department, for example) and how impaired workers will be sent home. A supervisor should consider whether the impaired worker requires a medical evaluation prior to leaving work, and how he or she is going to get home safely.


It is not uncommon for employers to send employees to an occupational health clinic for an impairment evaluation without providing sufficient information on which to base the evaluation. This practice is not helpful to the occupational health provider, especially if he or she is unable to reach the employer for additional information, and ultimately can diminish the usefulness of the health care provider’s report. The employer should provide an explanation of the behavior and incident that prompted the evaluation, including the results of drug testing, if performed at the time of suspected impairment. The evaluation should characterize the use of potentially impairing substances (including therapeutic use, abuse, addiction, or other misuse), acceptability of continued use of any prescription medications in the workplace, and any recommendations for follow-up for medical conditions that are of safety concern.


Only when these steps are taken can the provider inform the employer of whether the worker is safe to return to work and capable of carrying out the essential functions of his or her position.


Managing Workforce Performance


When potential problems with worker performance arise, it is best for supervisors to communicate with their employees in a direct and timely manner. Performance management conversations can be difficult, so it is best if they are planned ahead of time, even if they do not necessarily go as planned. If the supervisor thinks that medical issues may be a factor in a worker’s performance, conferencing with an occupational health provider to prepare for the conversation can be helpful. During the conversation with the worker, supervisors should focus on observed behavior with specific examples. A single event does not necessarily indicate impairment, but collective incidents can indicate a significant issue. Rather than take an accusatory approach, supervisors should inform the worker of safety concerns for the individual as well as for others, and even for equipment, if relevant. In most cases of drug or alcohol addiction, initial denial of the problem is common. Taking an approach that is not threatening or judgmental can help put employees at ease.


Ensuring Health and Productivity


Impairment is not just an issue for workers in safety-sensitive positions. Impaired employees can cause a lot of damage in an office settings as well—for example, producing erroneous reports that can have a tremendous effect on a company. Impaired workers driving to meetings are the company’s liability.


Presenteeism can cut individual productivity by one-third or more, which can be a tremendous invisible expense to the employer.


When considering the range of ways in which workers can be impaired, providers and employers should take a broad perspective, understanding the many possible causes of impairment besides just substance use. By paying close attention to stressors that affect all workers at times, and making proactive decisions in the workplace, employers can improve safety and reduce presenteeism. In the  short term, making this effort may appear to be an inconvenience or more work, but overall it improves the health of the workforce, increases productivity, and reduces mishaps.




1. U.S. Department of Labor. Regulations to Implement the Equal Employment Provisions of the Americans With Disabilities Act 29 CFR 1630.2. Accessed on 4/20/2018.