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National Research Council (US) Committee on Airliner Cabin Air Quality. The Airliner Cabin Environment: Air Quality and Safety. Washington (DC): National Academies Press (US); 1986.

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The Airliner Cabin Environment: Air Quality and Safety.

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6Health Effects Associated with Exposure to Airliner Cabin Air

The survey of airliner cabin contaminants in Chapter 5 suggests a diverse set of adverse health effects that could arise from exposure to the cabin environment—from acute effects, such as irritation, inflammation, and infection, to long-term effects, such as neoplasms, reproductive disorders, and decrement in pulmonary function. The following sections review the epidemiologic literature on adverse health effects that have stemmed from cabin air, as manifested in passengers and crews of commercial airliners. Where it is relevant, we also include studies on general aviation and military aircraft crews.

Our review of the literature overlaps with that of Kraus,33 who reviewed epidemiologic studies of health effects in commercial pilots and flight attendants. Although his review focused on occupational effects unrelated to cabin air quality, he did present original data on occupational illness that are relevant to our study. He used 1979 California statistics on occupational illness and injury to compare the reported numbers of illnesses and injuries in flight attendants with the numbers expected, which were based on combined overall percentage distributions for all occupations. Flight attendants' reported occupational illness is generally much less than expected, except for infection, disease of the inner ear, respiratory disease, and aerotitis media; for these, ratios of observed to expected frequencies range from 9.8:1 (infections) to 209.1:1 (aerotitis media). It seems that the latter conditions are occupationally induced, but we know of no further relevant analyses of occupational-illness statistics.

We found almost no studies of health effects in airliner passengers, other than a few isolated case reports of miscellaneous diseases. The one exception is a Danish retrospective study47 of 773 airline passengers admitted to a Danish emergency ward from Copenhagen Airport in Kastrup in 1975–1976. The estimated annual turnover at that airport during the period was 8–9 million passengers. The most common illnesses were injury and poisoning (219 passengers), ''symptoms, signs, and ill-defined conditions'' (120), diseases of the circulatory system (67), diseases of the respiratory system (62), and infections and parasitic diseases (57). Many illnesses classed as "symptoms, signs, and ill-defined conditions" might have been related to the cabin environment, including hyperventilation, syncope and collapse, and ear problems; but it is not possible to attribute any of these illnesses or injuries directly to cabin air quality.

Health Effects of Concern

Irritation and Inflammation

Passengers and cabin crew in an airliner can be exposed to a number of substances that can cause eye, nose, and respiratory irritation, which also appear to be commonly reported by passengers and crew when complaining about the air quality in airplanes. There has been relatively little evaluation of these symptoms among aircraft occupants.

A questionnaire survey of flight attendants in 1978 found a high prevalence of reported eye discomfort.21 22 The survey form was distributed through the monthly magazine of the Association of Flight Attendants, which at that time represented flight attendants on 18 major airlines. Of the 774 who responded, 95% reported some eye discomfort while on an aircraft. Dry eyes and redness were reported by approximately 90% of the respondents; fewer reported other eye symptoms, such as blinking, blurred vision, and tearing. Over 90% reported smoking as a cause of their discomfort. Air-conditioning, cabin lights, wing reflection, and napping were also reported as contributing to eye problems. In general, the complaints were not correlated with the use of contact lenses, but attendants wearing soft contact lenses did report more problems with blurred vision and tearing. Although a high prevalence of eye discomfort was reported, the value of the study's conclusions is limited by the possibility of selection bias in the respondents to the survey and by the lack of a comparison group.

Three studies have attempted to evaluate symptoms due to ozone exposure on aircraft. In 1978, Reed et al., at the California State Department of Health, conducted a questionnaire study of flight attendants in three airlines: Pan American World Airways, which usually flew long distances at high altitudes; Pacific Southwest Airlines, which flew only short distances at lower altitudes; and Trans World Airlines, which flew both types of routes.50

Of questionnaires mailed to 3,280 flight attendants, 1,330 completed questionnaires were received. The authors estimated that 61% of flight attendants on active status returned questionnaires, which included questions on symptoms related to ozone exposure, on other risk factors, on characteristics of the flights, and on the time course of symptoms. Ozone exposures were believed to be much higher in the high-altitude long-distance flights. The prevalence of some symptoms possibly related to ozone exposure (chest pain, difficulty in breathing, and persistent cough) was significantly higher among the attendants on the high-altitude flights than among those in the other two airlines. No significant differences were found in the prevalence of other symptoms, such as extreme fatigue and back pain, which would not be expected to be caused by exposure to ozone. Flying on particular high-altitude aircraft (e.g., B-747 and B-747-SP, not equipped with a catalytic unit to abate ozone in the cabin air) was associated with symptoms of ozone toxicity. In general, this study found a higher prevalence of symptoms of ozone toxicity among flight attendants with higher exposures to ozone. Although limited by the response rate and the lack of direct ozone measurements, this study did indicate possible problems due to exposures during high-altitude long-distance flights.

Another questionnaire study of symptoms due to ozone exposure among flight attendants was conducted in 1977 by Tashkin et al., at the University of California, Los Angeles.52 A questionnaire directed at flights on the B-747-SP was sent to 450 flight attendants in the Los Angeles area, of whom 248 responded; a questionnaire directed at flights on the B-747 was sent to the same 248 attendants and produced only 38 responses; and a similar questionnaire directed at both aircraft was sent to 850 attendants in the New York area, of whom only 65 responded. The questionnaire results were evaluated by three independent observers, who knew which aircraft the respondents had worked on and who graded symptoms on the basis of their possible relationship to ozone exposure. In addition, 21 flight attendants who had experienced severe respiratory symptoms while on B-747-SP aircraft received a more detailed medical evaluation, including pulmonary function testing, about 2 wk after the problem flight. The attendants who flew on the B-747-SP aircraft reported a higher prevalence of ozone-related symptoms (throat irritation, cough, difficulty in breathing, etc.) while on the aircraft than afterward and a higher prevalence than the attendants who flew on the standard B-747 in both the New York and Los Angeles portions of the study. The results of all the pulmonary function testing on the 21 selected participants were normal, as expected on the basis of time since exposure. Although it suggested that symptoms were due to ozone exposure, this study was limited by the lack of direct measurements of ozone exposure and by the very poor rate of response to the questionnaires, particularly in the comparison group.

A third study was performed by the Occupational Health Clinic of San Francisco General Hospital in 1984 at the request of the Independent Union of Flight Attendants.30 The study was designed to see whether the prevalence of ozone-related symptoms reported by Reed et al.50 persisted on long-haul, high-altitude flights and whether respiratory symptoms on these flights were associated with objective decreases in pulmonary function. The study consisted of two phases. In Phase I, all Pan American World Airways flight attendants based in San Francisco, London, or California were mailed a self-administered questionnaire concerning symptoms, medical diagnoses, smoking, and occupational history. Results of the questionnaire were compared with the data of Reed et al. A small selected group of flight attendants who noted ozone-related symptoms on the questionnaire were asked to participate in Phase II. For Phase II, each participant was instructed in the use of a Mini-Wright peak flow meter to measure peak expiratory flow rate (PEFR) and measured PEFR every 2 h while awake (total duration was not reported). Preflight (more than 12 h since last flight) and postflight (any time within 12 h of landing) PEFR measurements were then compared with unpaired t tests.

For Phase I, approximately 1,000 flight attendants were sent the survey; 280 returned completed questionnaires. A followup survey indicated that many nonrespondents failed to respond because their identity would not be protected. Demographically, the responding sample was similar to that of the Reed et al. sample, but older. Prevalence rates of chest pain or tightness (65%), shortness of breath (65%), and cough (57%) were similar to or slightly higher than those reported by Reed et al. Symptoms were more prevalent on B-747-SP flights and were more prevalent among those who had ever smoked than among nonsmokers.

Of the 20 flight attendants asked to participate in Phase II, only eight yielded analyzable data. Mean preflight PEFRs were always higher than postflight PEFRs, by 7-35 L/min (average, 21 L/min). The statistical analysis of the data is incorrect, so it is difficult to judge the statistical significance of these results. Two flight attendants had preflight-postflight differences in PEFR of over 20% in 24 h associated with long flights.

These results suggest that efforts to reduce onboard ozone concentrations have not had an effect on the prevalence of ozone symptoms and that flights might be accompanied by decreases in PEFR. Phase I had several limitations, including a lower response rate and an older population than the Reed et al. study, a self-administered questionnaire, and a lack of ozone measurements. Phase II was hampered by very small numbers, self-selection, use of flow meters with questionable accuracy, self-administered data collection, an ambiguous protocol for data collection (which allowed different persons to contribute different numbers of observations), a lack of ozone measurements in flight, and inappropriate data analysis. If these limitations are kept in mind, this study's conclusions can be regarded as only suggestive until confirmed by appropriately designed studies.

In each instance of potential irritation and inflammation, passengers and crews with pre-existing disease or disorders of the organs affected suffer increased effects. People with upper respiratory infections suffer more from pressure changes and possibly from low humidity. People wearing soft contact lenses have more eye symptoms that result from low humidity. Patients with chronic pulmonary disease might have more symptoms from inhaling ozone. The medical literature discusses these increased susceptibilities, but does not document them.

Asymptomatic sinus disease has been the subject of a number of studies. One study23 of 211 Air Force pilots aged 25–35 showed radiographic evidence of maxillary sinus abnormality in 25%, but no control group was studied. A followup study compared these Air Force pilots with two groups of Air Force employees who had no flying experience. One comparison group consisted of 100 new airmen trainees who were below age 25; the second consisted of 100 men aged 25–35 who were patients in an Air Force hospital for diagnostic procedures not related to ear, nose, or throat symptoms and had no flying experience. The prevalence of maxillary sinus abnormality among the two control groups was 26% and 29%, respectively. Another study27 compared 1,284 asymptomatic flyers with a control group of 200 nonflyers. The reported prevalence of abnormalities of the paranasal sinuses was 22% in the control group and 15.6% in the flyers. Selection of the controls and comparability of the two groups were not reported.

Other conditions associated with mucous membrane inflammation have been found in airliner cabin occupants. Aerotitis media and other middle ear conditions have been reported as significant health problems for flight attendants.33 55 These conditions might be due to cabin pressure changes, but mucous membrane inflammation could contribute to them.


Only one study has clearly documented the occurrence of an outbreak of infectious disease related to airplane use.43 An outbreak of influenza occurred in 1978 in Alaska. Because of an engine malfunction, an airliner with 54 persons aboard was delayed on the ground for 3 h, during which the aircraft ventilation system was reportedly turned off. Within 3 d of the incident, 72% of the passengers became ill with influenza. One passenger (the index case) was ill while the aircraft was delayed. Serologic evidence of influenza infection was found in 20 of 22 passengers tested, and the virus was isolated from eight of 31 passengers whose serum was cultured. Documentation of this outbreak was assisted by the circumstance that all the passengers traveled to one small town and by the alertness of the local physician. Similar outbreaks could result from crowded flights with an infectious person and not be documented or noticed, because passengers would disperse after landing.

Persons with coincidental acute and chronic infections suffer more from superimposed infections acquired on the aircraft. In addition, increasing numbers of people with diminished resistance to infection might be traveling as passengers—specifically, patients undergoing chemotherapy or x-ray therapy for malignancies and those infected with the HTLV-III virus (acquired immune deficiency syndrome). There is no evidence that that virus can be transmitted through the air.

Respiratory Impairment

Various constituents of the aircraft environment could lead to respiratory impairment in passengers or crew. The manifestations of respiratory impairment are diverse and include pulmonary diseases, acute respiratory illness, sinus disease, sarcoidosis, and spontaneous pneumothorax.

Several studies have investigated pulmonary function in flight attendants or pilots. One report found that higher percentages of members of self-selected groups of Miami-and New York-based Pan American World Airways flight attendants, but not San Francisco-based flight attendants, had spirometric abnormalities than of an age-and sex-matched Michigan group.44 The finding is difficult to interpret, because of the self-selection process, questions of comparability of measurements in the flight attendants and the Michigan group, and failure to take smoking history into account. Another study reported, as expected, an absence of pulmonary function abnormalities in a select group of 21 flight attendants who were tested 2 wk after experiencing respiratory symptoms during B-747-SP flights.52

A study of 257 active United Airlines pilots revealed that 12% had evidence of minimal to moderate ventilatory impairment.15 Disease prevalence increased with age and smoking history, but no comparisons were made with a nonpilot population, so it is difficult to assess the importance of the finding. Similar findings have been reported for general aviation airmen.37

Dille20 compared the prevalence of asthma, emphysema, bronchiectasis, bronchitis, and other unclassified pulmonary diseases in a population of 288,000 active civil airmen with the prevalence of these diseases reported in the U.S. National Health Survey and found a much higher prevalence in the general population. That was expected, because of the self-selection of active airmen. The long-term followup of the U.S. Navy's "1,000-aviator cohort" revealed that decrements in pulmonary function were associated with cigarette-smoking, coronary arterial disease, and weight gain.38 No correlation was reported between a career in military aviation and the development of pulmonary disease; but a career in military aviation was a dichotomous variable, which was coded (present) if a person had 15 yr or more of flying history and not coded (absent) otherwise, and is at best a weak measure of exposure.

Several incidental reports have noted spontaneous pneumothorax in pilots, but presented no comparisons with nonpilot populations, so it is impossible to judge whether the risk is increased by a flying career or by onboard environmental conditions.19 24 25

One British investigation11 has studied the prevalence of pulmonary lesions resembling sarcoid granulomata in 2,000 autopsy reports after 700 aviation accidents. Military crews had a higher rate than civil airmen, who had a higher rate than passengers or glider pilots. Review of the incidence of clinical sarcoidosis in the Royal Air Force in 1962–1977 showed a much greater overall incidence than the 3 per 100,000 in the general U.K. population; the aircrew incidence averaged 14.4 cases per 100,000, and the ground crew, 10.8 cases per 100,000. Because of inconsistencies in the autopsy reports and clinical incidence rates and the lack of corroborating evidence, no conclusions were drawn by the author. This pathologic but often asymptomatic lesion needs to be searched for in other well-controlled studies.

Jasinski31 showed acute respiratory illness to be a common problem in flight attendants, but it cannot be determined from the report whether the incidence was higher than that found in other populations. An Italian study48 of morbidity in flying personnel appeared to suggest higher rates of acute respiratory illness than in nonflying airline employees, but the details of the study were not reported. The work by Kraus33 cited earlier suggested higher rates of respiratory disease in flight attendants.

Isolated autopsy findings of hypoxia, intoxication, hyperventilation, and carbon monoxide intoxication in military pilots have been reported. 26 36 49 The relevance of these reports to the commercial airliner cabin environment is uncertain. One report42 showed that contamination of the ventilation system (in military aircraft) with lubricating oil could lead to intoxication.

As noted earlier, patients with underlying pulmonary disease are more susceptible to changes in cabin air that affect pulmonary function. Thus, any increase in the partial pressure of carbon dioxide (pCO2) in the air will adversely affect patients with chronic obstructive pulmonary disease (COPD) who are already functioning with an increased blood pCO2 and increased alveolar pCO2. A further increase might make it even more difficult to maintain a normal blood pH. Similarly, the decrease in oxygen partial pressure (pO2) that occurs at 8,000 ft is safe for normal people, but possibly hazardous for patients with COPD. One study of patients with COPD who were placed at reduced pO2 as they would be at 8,000 ft showed that patients without overt pulmonary failure can expect no trouble and that those with symptomatic COPD can be tested in advance by their physicians to determine whether they will need supplementary oxygen if they must fly.51

Cardiovascular Effects

The effects of cabin air quality on cardiovascular function in normal persons and patients with underlying disease are of interest. There is no evidence of any effects in people with normal hearts and blood vessels, other than occasional anecdotes of venous thrombosis and pulmonary embolism, which are much more likely to be associated with inactivity than with air quality. A high percentage of adults have some underlying coronary arterial disease, which theoretically could be made worse by the products of cigarette-smoking.3 79 Although angina pectoris might result from myocardial ischemia, there is no evidence that myocardial infarction would be caused by inadequacies in cabin air quality.

The many papers on coronary arterial disease and resulting sudden death of pilots are not reviewed here, because they are concerned with screening and related health examinations, rather than with possible deleterious effects of cabin air.

Some persons with symptomatic cardiovascular disease are under medical care, so decisions about the possibly increased hazards of reduced pO2 and exposure to cigarette smoke, carbon monoxide, and ozone could be made by their physicians.


Several constituents of cabin air might increase the risk of neoplasia, including passive smoking and exposure to radiation. However, published reports contain little documentation of cancer incidence in flying personnel.

Kraus33 reviewed Milham's study41 of occupational mortality in Washington State, which gave proportional mortality ratios for many occupational categories, including pilots, navigators, and flight attendants. Statistically significant increases were seen in rectal cancer in pilots and navigators, but significant reductions in lung cancer. These observations have not been confirmed in other data bases.

In 1981, the Centers for Disease Control carried out a health hazard evaluation for the Independent Union of Flight Attendants (IUFA).45 IUFA mailed a questionnaire to approximately 6,000 of its members. Responses were received from 9%; the reason for the low response rate is that a response was requested only if the member had cancer. Crude incidence and prevalence rates were compared with statistics from the Birmingham Regional and Connecticut Tumor Registries. Only skin cancer showed an excess risk among flight attendants: 3–10 times the expected rates. The possible environmental causes relevant to skin cancer are exposures to sunlight, ionizing radiation, arsenicals, and hydrocarbons. Although the results were suggestive, the study had clear limitations, including the possible failure of those who might have had cancer to respond, unconfirmed self-reported diagnoses, and lack of a control group.

Three case reports of nasopharyngeal cancer in bush pilots suggested that the cancers could be related to pressure changes,5 6 54 but presented no substantiating evidence.

Reproductive Disorders

A few studies on reproductive disorders or pregnancy outcome in flight attendants have been reported. Menstrual disorders are thought to be related primarily to stress and interruption of circadian rhythm, but there is some speculation that they can be attributed to solar radiation,16 which might also predispose to unfavorable pregnancy outcome.

Cameron14 presented data on menstrual function in 98 Swiss flight attendants. Long-term followup data on reproductive outcome were available on only 50 women. There was a general suggestion that no increase in menstrual disorders was associated with flying, but that the miscarriage rate among married ex-hostesses was high. Iglesias et al.29 reported the results of interviews of 200 flight attendants who sought medical assistance for various clinical problems; 39% reported unfavorable changes in menstrual cycles 6–24 mo after beginning aeronautical service. Both these studies had problems of recall and self-reporting, lack of controls, self-selection, and small numbers of participants (particularly the long-term followup in the Cameron study), so no reliable conclusions can be drawn.

A Czechoslovakian study28 found a significantly higher percentage of pathologic pregnancies and deliveries in flight attendants after 2–7 yr of flying than in the general population. High rates of spontaneous abortion and premature delivery were also reported. Details of this study were not available to the Committee, but it does not appear to have used appropriate controls.

One study34 compared pregnancy outcome in U.S. Air Force women with age-and time-matched civilian patients. Although the Air Force women had generally higher rates of perinatal death, low-birthweight babies, small-for-gestational-age babies, and prematurity, the differences were not statistically significant; there were several significant differences in risk factors, including nulliparity, race, and marital status. In addition, the duties of the Air Force women in this study varied, so they were not good surrogates for flight attendants.


Mendez Martin40 surveyed various Spanish studies that showed that urinary calculosis was a common disease of flight personnel, possibly attributable in part to their low-humidity environment. English-language reports on this problem are sparse.32


The available information on the health of airliner crews and passengers stems largely from ad hoc epidemiologic studies or case reports of specific health outcomes, although occupational-health statistics have been used in at least one study. The conclusions that can be drawn from the available data are limited to a great extent by the self-selection of the subjects of studies, the lack of comparison groups, and a lack of exposure information. The major findings must be reviewed with this caveat in mind.

The one study that used occupational-health statistics33 found that flight attendants had higher rates of respiratory disease, aerotitis media, infections, and diseases of the inner ear than other California workers. Although these findings are important, the Committee feels that they should be verified by using additional occupational-health statistics from different sources and periods. The lack of specific exposure information makes it difficult to attribute the high rates to cabin air quality. However, increased rates of aerotitis media in flight personnel have been documented in other studies.55

A higher prevalence of ozone-related (self-reported) symptoms was found in flight attendants on long, high-altitude flights than on short, low-altitude flights.50 Despite some limitations in the study, it offered some evidence that ozone-related health problems exist among flight attendants. Results of another study30 suggested that the prevalence of ozone-related symptoms continues to be high. Neither study correlated reported symptoms with direct onboard ozone measurements. To our knowledge, there have been no similar studies on passengers.

One epidemiologic study43 documented that outbreaks of influenza can be associated with unusual operating conditions, but the incidence of such outbreaks is unknown, as is their dependence on operating conditions.

The literature on respiratory disease is sparse and fragmented and is of no value in assessing health effects associated with cabin air quality. Except for miscellaneous reports, there is no solid information on an association of neoplasia with cabin air quality.

The English-language reports on pregnancy outcome in flight attendants are flawed, and the Committee has not fully evaluated foreign-language reports that purport to show increased rates of unfavorable pregnancy outcome. The effect of cabin air quality in inducing unfavorable pregnancy outcome is also unknown.

Mendez Martin40 has reported that urinary calculosis is common in flight personnel, but the Committee is aware of no corroboration of this finding.

Monitoring and Surveillance of Crew and Passenger Health

Data on the health of passengers and crew have three potential sources: airlines, flight attendant unions, and FAA. The populations monitored can be conveniently divided into pilots, flight attendants, and passengers.


FAA requires medical certification of pilots every 6 mo and thus has considerable information on the health status of active civil airmen,12 as well as statistics on medical disqualifications.4 18 Because of this requirement and the expense of training pilots, many airlines routinely monitor the health status of their pilots.46

Several studies have looked at the health of pilots. Buley13 and Kulak et al.35 Investigated cases of in-flight airline incapacitation, primarily with an eye to correlating such incidents with accidents and to determining whether stricter medical certification could reduce in-flight incapacitation. No attempt was made to relate incapacitation to specific occupational hazards or to contrast incidence rates with those in a comparison group. There has been one long-term followup study of mortality and morbidity in military pilots.38 As one might expect, their health is better than that of the general population or of age-matched Framingham men, but there was no comparison with a suitably selected control group.

The extensive data available on the health of pilots are of little use in studying the health effects of cabin air. A primary limitation is that the special cockpit environment is not indicative of the general cabin environment. In addition, the orientation of health monitoring is to ensure that certified pilots are free of health problems that might jeopardize their ability to operate a plane safely; thus, its purpose is not to detect potential health effects of the working environment. For the system to meet the latter purpose, several important and fundamental changes would need to be made, including the addition of followup of retired airmen, elimination of self-selection problems (airmen who, for health reasons, elect not to renew their licenses do not appear in the current records), collection of additional data (on both health and exposure) pertinent to occupational hazards, and the implementation of a sophisticated statistical analysis and reporting system.

Flight Attendants and Passengers

No monitoring or surveillance activities appear to be directed solely at the health of flight attendants. A few airlines indicated that some pre-employment health data were available to them and that some additional medical records on selected flight attendants were kept. However, these records are considered proprietary and were not available to the Committee. More important, it appears that no airline monitors the health of all its flight attendants routinely. Airlines do maintain records of workers' compensation and disability claims, but only a portion of these data can be released. A few airlines appear to keep records of employees' service histories (flight times, routes, and types of service).

A few airlines indicated that they maintain records on incidents of passenger illness (some limited only to oxygen use and passenger complaints about air quality), but the adequacy of these records for monitoring purposes is unknown.

Other than accident and incident data (see the following section), FAA collects no data on the health of flight attendants or passengers.

The flight attendant unions have periodically sponsored mail-questionnaire surveys on health-related issues, but do not sponsor routine data collection directed at monitoring the health of flight attendants.

The Association of Flight Attendants receives reports submitted by flight attendants concerning poor cabin air quality. From January 1977 to April 1982, 297 reports were received, and descriptive statistics were tabulated for presentation to the Subcommittee on Aviation of the U.S. Senate Committee on Commerce, Science, and Transportation. The value of these reports in assessing health risks is questionable, in that they appear to be voluntary and therefore self-selected. In addition, no standard protocol for reporting is used, so the information gathered is fragmentary and selective. The number of incidents reported per year from 1977 through 1982 varied erratically (21, 70, 6, 46, 135, and 66). In view of the number of flights per year, the reported incident rates seem low, although there might be some underreporting; there is no basis on which to establish an expected rate for these reports.10

FAA Surveillance Activities

FAA has claimed regulatory jurisdiction over the cabin as a workplace. FAA asserts that its responsibility toward passengers is related to their safety and claims not to have regulatory authority over health. No federal agency monitors the health of flight attendants.

Other than the medical data collected for pilot certification (discussed above), the health data on passengers or flight crews that are systematically collected by FAA are very limited. They are reported in the Accident/Incident Data System (AIDS), described as follows in the AIDS user's guide:53

The Accident/Incident Data System (AIDS) contains data records for general aviation accidents/incidents, air carrier incidents, and, beginning with 1982, air carrier accidents. The system consists of various data bases, computer hardware, computer programs and manual procedures which in combination produce a functional capability for the user. The system gives additional data elements, provides for English-like retrievals and reports, puts emphasis on ad hoc retrievals, provides easily utilized standard reports and provides user access through data terminals.

The basic design of the AIDS system is to provide the user with current and accurate information about general aviation accidents and incidents coupled with the facility to produce ''standard'' reports and "ad hoc" reports based on specific requirements. Several standard report formats can be requested by specifying: time-period of interest, national/regional criteria, and event selection criteria (type of accident, etc.). Specialized queries can be prepared and input by trained users. Additionally, the tools exist for conducting statistical analyses of the data contained in the data base.

The objectives of AIDS are laudable, and the Committee is optimistic that the system will prove to be a valuable research aid for aviation safety. We were impressed by the documentation of the computer system designed to gain access to the data base and by the data coding system.

However, AIDS is relatively new and has yet to realize its full potential. The Committee experienced two difficulties in using the system. First, we were unable to find an accessible, concise, and thorough description of the collection system and its data base contents. Without good information on the data collection process, the Committee found it difficult to judge the quality of the data (for health monitoring purposes) and the desirability of using them for health monitoring. For example, the description of the criteria used for defining an accident or an incident in the FARs39 is insufficient to enable one to be certain of the quality of health data that enter AIDS. In addition, the Committee found that, although access to the data base itself appears good, descriptive and summary statistics on such items as number of fires by cause and number of passenger deaths by cause were not readily accessible.

In summary, the Committee feels that AIDS has potential as a health monitoring or surveillance tool, but that considerably more effort by FAA will be required to make it effective. It is insufficient merely to collect data and provide access to them. It is important that at least basic statistical summaries of key information be produced routinely. The Committee also notes that the purpose of AIDS is to monitor accidents and incidents; therefore, in its current form it has no value for monitoring chronic health effects of air travel in passengers or crew.

Groups at Increased Risk

Aircraft at cruising altitudes maintain artificial cabin altitudes of 5,000–8,000 ft. Because of the associated decrease in pO2 compared with that at sea level, passengers with specific health problems might be at increased risk while flying. A number of committees in special and general medical associations publish guidelines for physicians to use in advising patients about air travel.1 17 Of most general coverage is a list, prepared by the American Medical Association's Commission on Emergency Medical Services, of conditions in which air travel is contraindicated.2 The list is presented here for information, although the Committee found little material on these conditions in passengers traveling on aircraft.

  • Cardiovascular—myocardial infarction within the preceding 4 wk, cerebrovascular accident within the preceding 2 wk, severe hypertension, decompensated cardiovascular disease, or any condition that restricts cardiac reserve. Patients with chronic cardiovascular problems, such as cyanotic congenital heart disease or coronary insufficiency, should have supplemental oxygen whenever flight altitude is greater than 22,500 ft.
  • Bronchopulmonary—pneumothorax, congenital pulmonary anomaly, or vital capacity less than 50%. Patients with chronic pulmonary problems—such as cystic fibrosis, emphysema, chronic asthma, or fibrotic pulmonary conditions—should have supplemental oxygen whenever flight altitude is greater than 22,500 ft.
  • Eye, ear, nose, and throat—recent eye surgery, acute sinusitis, or acute otitis media. Patients who must fly during the congestive stage of upper respiratory infection should use local shrinking agents or oral decongestants.
  • Gastrointestinal—abdominal surgery within the preceding 2 wk, acute diverticulitis or ulcerative colitis, acute esophageal varices, or acute gastroenteritis.
  • Neuropsychiatric—epilepsy (unless it is well controlled medically and simulated cabin altitude is never greater than 8,000 ft), recent skull fracture, brain tumor, or history of violent or unpredictable behavior.
  • Hematologic—anemia (hemoglobin concentration of less than 8.5 g/dL or red-cell count of less than 3 million/mm3 in adults), sickle-cell disease (unless cruising altitude is never greater than 22,500 ft), or hemophilia.
  • Pregnancy—beyond 240 d or if miscarriage is threatened.
  • Miscellaneous—Scuba divers should not fly for at least 12 h after diving—24 h after repeated deep diving—before flying. The flight surgeon should be consulted if a patient requires intravenous fluids or special medical apparatus.


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