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Epidemiologic Notes and Reports Epidemic Psychogenic Illness in an Industrial Setting -- Pennsylvania

On April 21, 1982, three of approximately 220 employees at an electronic components manufacturing plant in Pennsylvania experienced nausea and headache and complained of disorientation. Suspecting a defect in the air-conditioning system, which had been turned on several days before, the company examined the system for refrigerant leaks but found none. On April 26, diesel fumes accidentally entered the production area of the plant from an automobile engine being tested in the anechoic chamber, an enclosed test area. The fumes apparently aroused concern among employees who, unaware of the source of the diesel odors, were concerned they might be exposed to toxic chemicals. During May, six episodes of illness occurred, causing the plant to be closed twice. Numerous workers became ill and were sent home; employees from the plant made 30 visits to the emergency room of a local hospital between April 21 and May 24.

On May 27 and 28, the National Institute for Occupational Safety and Health (NIOSH) initially evaluated the plant, surveyed medical records at the hospital emergency room, and interviewed the employees. Investigators also contacted representatives from the Occupational Safety and Health Administration (OSHA), a medical team from a local medical center, and representatives of a private environmental consulting firm, all of whom had investigated the illness before the NIOSH investigation. Extensive environmental investigations by OSHA and private consultants had not detected any deficiencies in ventilation or toxic concentrations of chemicals in the plant. Carbon monoxide, toluene, trichloroethylene, and ethyl acetate levels measured by these groups were well within the relevant current occupational standards and criteria. Sampling for lead, formaldehyde, sewer gas, and air-conditioning refrigerant revealed no detectable amounts.

In a meeting with all the plant's employees on May 28, a medical officer from NIOSH explained that the Institute's preliminary analysis of investigations done by the other groups indicated no toxic concentrations of chemicals and a marked decrease in the number and severity of cases since the company implemented various environmental controls. Employees were encouraged to inform supervisors of all illnesses and were told that NIOSH would inform employees of all subsequent test results.

Since a psychogenic component of the outbreak seemed possible, a medical officer returned on June 21 to administer a questionnaire to 213 (97%) employees; it covered such subjects as: general medical condition, physical work environment, non-physical work conditions (e.g., overtime and job security), and socioeconomic variables (e.g., education and income) (1). A case was defined as anyone who complained of recent illness and who either sought medical attention or was sent home after being seen by a paramedic.

Analysis showed that 98 (46%) employees given questionnaires reported symptoms, including lightheadedness, headache, sleepiness, and numbness and/or tingling of the face or extremities. Forty-one (42%) of these, all in production areas, met the case definition; workers without symptoms were classified as well; employees with symptoms but who neither went home nor sought medical attention were considered intermediate. Attack rates by departments within production areas followed no apparent pattern. Among production workers, 28% of females and 8% of males were classified as ill, and 39% of females and 8% of males as intermediate, while 33% of females and 84% of males were classified as well. More ill than well employees complained of bothersome odors (p 0.001), discounted the role of psychological factors in the outbreak (p 0.001), and believed the illness was likely to recur (p 0.05). Medical records from the emergency room provided no objective evidence of chemical toxicity. Blood gas analyses for seven of 11 ill workers showed respiratory alkalosis consistent with hyperventilation.

The poorly defined nature of the employees' illness, the absence of exposures to environmental contaminants in concentrations exceeding current occupational standards and criteria, and the presence of symptoms similar to those of hyperventilation suggest that this incident was an outbreak of psychogenic illness. The release of diesel fumes into the plant from an automobile engine may have contributed to a heightened awareness of various odors in the plant. The air-conditioning system was restarted on June 14; no unusual employee illness at the plant has since been reported to NIOSH (2). Reported by Hazard Evaluations and Technical Assistance Br, Div of Surveillance, Hazard Evaluations, and Field Studies, NIOSH, CDC.

Editorial Note

Editorial Note: Outbreaks of psychogenic illness have been described in industrial settings (3,4) and among schoolchildren (5-7). Although the phenomenon has typically been reported in plants with a largely female, relatively uneducated work force, sex and educational level are not necessarily risk factors. The fact that women without higher education are likely to find employment in stressful, low-paying, uninteresting jobs may explain in part why outbreaks of psychogenic illness are usually associated with unskilled or semi-skilled female workers (1,3,4).

Judging from the few literature reports of industrial psychogenic illness and from NIOSH's experience, many such outbreaks may go unreported (4). Some may be overlooked because symptoms are uncritically attributed to chemical exposures in the workplace.

In the present incident, NIOSH recommended to plant management that workers be educated in the proper use of chemicals and about their odors and health effects, that employees be allowed to tour the anechoic chamber to allay fears of exposure to radiation or chemicals from this area, and that meetings be held with employees to help dispel misconceptions about the term "psychogenic illness."

In future outbreaks of similar illness, NIOSH recommends that symptomatic persons be removed to a quiet room away from other employees. Unless trained medical personnel or lifesaving equipment are required, transportation for medical evaluation does not require an ambulance. If an ambulance must be called, use of sirens and flashers should be avoided near the plant.

Investigations of such outbreaks of possible psychogenic illness may involve personnel from medical centers, health departments, and regulatory agencies. Investigators should reflect on the possible connotations of the word "psychogenic" and emphasize the reality of signs and symptoms among those affected. If an investigation can help establish good communications between employees and management, the length of the outbreak may decrease and its spread to unaffected employees may be prevented.


  1. Colligan MJ, Smith MJ. A methodological approach for evaluating outbreaks of mass psychogenic illness in industry. J Occ Med 1978;20:401-2.

  2. National Institute for Occupational Safety and Health. Health hazard evaluation report no. HETA 82-273-1239. Cincinnati, Ohio: National Institute for Occupational Safety and Health, 1982.

  3. Smith MJ, Colligan MJ, Hurrell JJ. Three incidents of industrial mass psychogenic illness: a preliminary report. J Occ Med 1978;20:399-400.

  4. Elesh E, Moseley C, Pryor P, Singal M. Mass psychogenic illness in industry--NIOSH's role. Presented at the American Industrial Hygiene Conference Symposium on "The Diagnosis and Amelioration of Mass Psychogenic Illness," Chicago, Illinois, May 20-June 1, 1979.

  5. Knight JA, Friedman TI, Sulianti J. Epidemic hysteria: a field study. Am J Public Health 1965;55:858-65.

  6. Mohr PD, Bond MJ. A chronic epidemic of hysterical blackouts in a comprehensive school. Br Med J 1982;284:961-2.

  7. Small GW, Nicholi AM, Jr. Mass hysteria among schoolchildren. Early loss as a predisposing factor. Arch Gen Psychiatry 1982;39:721-4.

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