Select Committee on Science and Technology Fifth Report


Principal health-related regulatory requirements

3.27 Although national and international regulations are intended primarily to ensure the safety of aircraft and their occupants, several of these impact directly on the health and comfort of passengers and crew. The requirements and rationale for each are discussed below, in most cases as a guide to more detailed discussion later in the Report.


3.28 Commercial aircraft cruise at up to around 40,000 feet where the external conditions would be lethal for unprotected humans. Atmospheric pressure[22] decreases with height and, at that altitude, is only about 20% of that at sea-level[23]. This thin air provides insufficient oxygen to support human life. Moreover, the air is very cold, at about minus 50-60ºC[24].

3.29 To provide an atmosphere with sufficient oxygen, aircraft cabins are pressurised in flight. Under normal operating conditions, the pressure inside the cabin - even at cruising altitudes - is not less than would be found outside the aircraft at 8,000 feet[25]. In fact, most modern aircraft have an effective cabin altitude of between 6,000-7,000 feet. Safety regulations also require that occupants are not exposed to a cabin pressure lower than would be found outside at 15,000 feet. If cabin pressure were suddenly lost at cruising height, the occupants would quickly lose consciousness. In such circumstances, there is a safety requirement for drop-down oxygen masks supplying 100% oxygen to cabin occupants until the aircraft has descended to a safe altitude.

3.30 The physiology of human respiratory needs is discussed in Chapter 4 as one of the aspects of healthy cabin air. The mechanics of pressurisation (and temperature control) are discussed in Chapter 5 as part of the practical provision of such air. Both those sections also discuss the health issues arising.

3.31 As discussed in paragraphs 5.41ff, rates of change of pressurisation on ascent and descent have some implications for comfort and health. These rates are not, however, subject to regulation.

3.32 The material structure of the cabin, its doors, its windows, and partitions between pressurised and non-pressurised parts of the aircraft must be strong enough to withstand any pressure differential they may encounter, and light enough to meet aerodynamic requirements. All the design and operating standards and features necessary to meet these structural needs throughout the life of the aircraft are laid down, controlled and monitored by the regulating aviation authorities (FAR/JAR 25).


3.33 Until 1996, both FAA and JAA had the same basic requirement for cabin ventilation rates. FAR 25.831 and JAR 25.831 required a minimum supply of 10 cubic feet per minute (cfm)[26] [27] of fresh air per flight crew member, which "must be free from harmful or hazardous concentrations of gases or vapours" with specific maximum concentrations for:

  • carbon dioxide at 5,000 parts per million by volume (ppm)[28];
  • carbon monoxide at 50 ppm; and
  • ozone at 0.1 ppm (short-term emergency maximum 0.25 ppm).

3.34 The FAR required that ventilation would "provide reasonable passenger comfort" but the JAR made no reference to passenger requirements. In June 1996, FAA introduced Amendment 87, by which the ventilation design requirement of 10 cfm of fresh air would be required "per occupant", as opposed to "per flight crew member". However, JAA did not follow suit because of industry concerns about the ability of new aircraft to meet the new regulation in some cases. For the same reason, US industry petitioned FAA against the Amendment. FAA/JAA harmonisation on regulation 25.831 is being attempted but, as JAA noted, is proving contentious, particularly in relation to the ventilation air supply parameter "per occupant" or "per flight crew member" (p 130).

3.35 The current regulatory position is that, while FAA currently requires 10 cfm of fresh air per cabin occupant, JAA has no passenger cabin ventilation requirement other than a guideline figure cited by Airbus Industrie[29] of "0.4 lb/min (7.3 cfm at the maximum effective cabin altitude) of fresh air per passenger as a minimum comfort level when only one air-conditioning pack is operative". This latter guidance is expressed differently by JAA as a recommendation for "improbable failure conditions" of "not less than 0.4 pounds of fresh air per minute per crew member for any period exceeding five minutes" (p 130).

3.36 To summarise, for the main purpose of airworthiness certification, JAA currently has no specific cabin air supply requirements for passengers, and the FAA requirement is seen by manufacturers as, in some cases, impossible or impracticable. Because of the intrinsic importance of the matter and also to clarify matters which, as our evidence has shown (Appendix 4), cause great public concern, we recommend the Government, CAA and JAA to find a practicable way forward as soon as possible.

3.37 While the regulatory situation as far as passengers' needs are concerned is chaotic, the vast majority of aircraft operate at a cabin fresh air supply rate of 10 cfm or more per person. This is an average rate and, because the supply air flow per unit length of the aircraft is the same throughout all cabins, economy class has a lower air flow per passenger than in classes with less dense seating. Nevertheless, Boeing drew our attention to the fact that, even if one of their standard aircraft was configured for maximum density seating throughout, the fresh air flow would still be between 6.5 and 8.0 cfm per passenger[30] (p 204). As noted in paragraph 4.7, this volume of air supplies at least 30 times more oxygen than needed for normal respiration.

3.38 As will be discussed in paragraphs 5.4 and 5.5, modern passenger aircraft are ventilated with a mix of fresh and re-circulated air. Regardless of the regulatory muddle, the major aircraft manufacturers work to a design cabin air supply requirement of 20 cfm of air either "per person" or "per passenger" of which at least 10 cfm is fresh air. In supplementary material (Q 427), Airbus Industrie stated that all its current production aircraft provided 12 cfm of fresh air per person plus 8 cfm (40%) re-circulated air, while Boeing (p 204) provides 10 cfm of fresh air plus another 10 cfm (50%) of re-circulated air, both giving the same cabin air supply of 20 cfm per person.

3.39 The regulations do not make detailed specifications for such re-circulatory systems, except to require that the design fresh air provision can be maintained if the re-circulatory systems are shut down for any reason. In particular (as discussed in paragraphs 5.18ff), there is no requirement for filtration. However, where re-circulatory systems and filters are installed, operators are required either to use and maintain them in accordance with the manufacturer's specifications or to secure CAA agreement to different arrangements.

3.40 It is also required that: to avoid contamination, air must be ducted through compartments inaccessible during flight; the minimum fresh air must be capable of being supplied when one source is lost; and ventilation and temperature controls for all compartments of the aircraft must be accessible to the flight crew. JAA also requires that, for safety reasons, the flight crew compartment conditioned air supply must be separated from the general cabin air supply, and consist only of fresh air (p 130, Q 363). While FARs regulate for thermal conditions in the cabin (relating temperature and humidity to exposure time), JARs do not.

3.41 Ventilation is discussed further in Chapter 5 as one aspect of providing a healthy cabin atmosphere.


3.42 For clarity throughout this Report, we use:

    (a)  "aircrew" to refer to all the personnel employed to work in aircraft;

    (b)  "flight crew" to refer to pilots and flight engineers employed only on the flight-deck; and

    (c)  "cabin crew" to refer to those working only in the passenger cabin and associated areas such as galleys.

3.43 ICAO, JAA and FAA require only flight crew to be subjected to regular medical examination[31], in order to maintain the validity of their flying licences. The purpose of medical certification is to ensure that the licensed person is medically fit to "exercise the privileges of" the licence. The examination is concerned with individuals' health only insofar as it might interfere with the safe performance of their duties, or render them likely to become suddenly unable to operate aircraft safely or to perform assigned duties safely. The qualifications of the medical examiner, the examination procedures to be used, the standards required, and the frequency of examinations, are all laid down in the relevant regulations. The medical examiners appointed by CAA are aviation medicine specialists, known as Authorised Medical Examiners (AMEs).

3.44 Between licence examinations, flight crew are responsible for assessing their own fitness to fly. They can ground themselves with or without medical advice if they think they are unfit for any reason. They inform their employing airline and CAA accordingly, and the latter may require re-certification by an AME before restoring flying privileges. Although the AME may in some cases additionally be an airline employee, airlines normally have no direct jurisdiction over the medical fitness to fly of their flight crew.

3.45 The important points about these procedures are:

    (a)  an airline may have no information about the health of its flight crew other than their medical certification as fit to operate;

    (b)  CAA is not concerned with the general and long-term health of flight crew unless it impacts on their medical certification; and

    (c)  although an individual's general practitioner (GP) may have information about the person's health, because of medical confidentiality requirements, the GP will not normally release such information to airlines or to CAA without the individual's permission.

3.46 We asked the main staff organisations representing UK pilots and cabin crew for their views on the monitoring of aircrew health as opposed to their fitness to fly. The British Air Line Pilots Association (p 213) stated that there had not been a great deal of data collected on the long term health of flight crew, and they indicated that one of the difficulties CAA expressed on this matter was that that pilots are lost to CAA's medical data bank when they retire. The Transport and General Workers Union (p 287) said that they were not aware of any existing studies or data that might be of help to us but did enclose a cabin crew survey, of the self-reporting type on which we comment in paragraph 8.22. On behalf of Cabin Crew '89, the Amalgamated Engineering and Electrical Union stated that it would be in everyone's interest to have an independent scientific study on passenger cabin air quality, although they were unaware of any clearly proven problems. We received no views at all from aircrew or their representatives about medical needs for the protection and preservation of their long term health. Indeed, JAA said that pilots' unions actually disagreed with the giving of preventive medical advice to pilots by their certifying medical examiners (p 130). This attitude compounds the dearth of information on aircrew health indicated in the immediately preceding paragraphs.

3.47 Cabin crew are not required to be subject to licence procedures, and thus are not subject to regular medical examinations[32]. They are required, however, to pass an initial medical assessment as part of the recruitment process to ensure that they are fit to carry out their duties (JAR-OPS 1.995), and they must ensure that they remain medically fit to discharge them.

3.48 We were surprised at the lack of attention - by regulators, airlines, and aircrew trade unions - to the health of aircrew. We are aware that there are serious issues of medical confidentiality and job security involved. Nevertheless, we recommend that the present rules, agreements, and attitudes regarding the monitoring and recording of the general health of aircrew, over and above their fitness to operate, should be reconsidered urgently. This would benefit aircrew themselves and would also provide a sound body of evidence on which to judge the impact of the aircraft cabin environment on health[33]. In the case of pilots, who are already subject to regular medical examinations, including blood tests where appropriate, we recommend that, if the AME finds evidence significant ill-health not necessarily affecting a pilot's fitness certification, this should be recorded and reported both to CAA and to the affected person's general practitioner.


3.49 CAA's Airworthiness Notice 64 includes several minimum dimensions between seats. The one of most significance to health and comfort is a minimum distance of 26 inches between the back support cushion of a seat and the back of the seat or other fixed structure in front of it. The dimensions and other regulations are intended to ensure that the majority of passengers can sit upright, stand up from the seat, and move to the aisle without undue difficulty. Every aircraft's seating configuration has to be agreed by CAA.

3.50 JAA and CAA require seats to be designed to help protect passengers from injuries caused by air turbulence, high acceleration and deceleration events, and crash conditions. The requirements do not include any consideration of passenger comfort, and there is no regulation to relate either passenger numbers or seat spacing to the type of operation concerned. Whatever the room intended to be available between seats, the space available for movement of feet and legs is sometimes reduced by the safety requirement that hand-baggage not stored in overhead bins must be placed beneath the seat in front, at least during take-off and landing.

3.51 CAA requires operators to demonstrate that, for safety purposes, everyone in an aircraft can be disembarked within 90 seconds. We were pleased to hear about new CAA research into people's size and the reduction in mobility after long flights to ensure that the emergency evacuation requirements are in line with modern circumstances (Q 13). Given changes over the years in the length of flights and in the sizes, ages and health states of people undertaking them, we recommend that this research be completed urgently.

3.52 Seating and space are discussed further in paragraphs 6.33ff.


3.53 All civil passenger aircraft under JAA (and FAA) jurisdiction are required to carry basic first aid equipment and the airlines are required to train their aircrew in first aid procedures. As noted by the Consumers' Association and the Aerospace Medical Association (AsMA), they have also to carry an additional kit for professional medical use in emergency (pp 59 & 198).

3.54 The handling of in-flight medical emergencies is considered further in paragraphs 7.76ff.


3.55 Control of exposure to cosmic and other ionising[34] radiation in aircraft is a recent addition to the regulatory arrangements. Drawing principally on material submitted by the UK National Radiological Protection Board (NRPB) (p 146, QQ 391ff), British Airways (p 99) and the Mullard Space Science Laboratory (p 253), this section deals with the possible hazards to crew and passenger health from radiation.

3.56 The principal source of ionising radiation in the aircraft cabin is cosmic radiation, which comes from both outer space and, less significantly (except under rare conditions mentioned in 3.64), the sun. Cosmic radiation is absorbed as it passes through the Earth's atmosphere, but the energy of the radiation means that there is no practicable way of preventing it passing through an aircraft at altitude. Flying exposes passengers and crew to more radiation than generally experienced at ground level but the doses received are of very little significance to health, as discussed in paragraphs 3.59ff.

3.57 The amount of exposure depends not only on the length of flight but, as cosmic radiation is affected by the Earth's magnetic field, also on the altitudes and latitudes which the aircraft traverses. Increased cosmic radiation exposure at altitude is counterbalanced to some extent by reduced exposure to sources of background radiation at ground level. Although there may be some additional radiation within the aircraft cabin (e.g. from radioactive materials in smoke detectors and sign lights), their contribution to the overall cabin radiation level is very small (Q 391).

3.58 Ionising radiation, including cosmic radiation, is measured in a unit called the Sievert (Sv). This summates the effect on the body of radiation exposure taking into account the type and energy of the radiation. Doses of radiation received from cosmic sources and the many ground sources, including natural background radiation, are so small that they are expressed in milli- (one thousandth) or micro- (one millionth) Sieverts: mSv or µSv respectively.

3.59 The annual radiation dose which the average member of the UK population receives from natural and artificial sources at ground level is about 2.25 mSv. Individuals may receive anything between 2 and 8 mSv depending on their jobs and recreation, the medical procedures they may have undergone and, in particular, the part of the country where they live (Q 393). The International Commission on Radiological Protection (ICRP) sets dose limits in the light of two main risks - the induction of cancer and inheritable mutations in germ cells - and assumes (a) that both risks increase proportionally with dose and (b) that there is no dose below which there is no risk (Q 299). ICRP's current recommendations are that exposure over and above that received from normal background sources should not exceed:

  • mSv per year for the general public;
  • mSv for the foetus during pregnancy; and
  • mSv for persons occupationally exposed to radiation by their jobs - which includes aircrew.

3.60 Radiation levels typically found in aircraft cabins during flight at cruising altitudes are around 5 µSv per hour at polar latitudes, and about half that at the equator[35]. An individual would need to fly for about 200 hours at polar latitudes or 400 hours at the equator to reach the general public allowed annual dose, and could take about 40 transatlantic flights a year by Concorde without exceeding the general public limit. (A simple comparison of cosmic radiation exposure from flying with exposure from background radiation is given in paragraph 3.66.)

3.61 The ICRP recommended limits have been incorporated into both European and United Kingdom legislation[36], but not yet into US legislation (QQ 407-409). NRPB has examined the ICRP limits in relation to airline passengers and crew and is satisfied that, with the exception of a very few frequent flyers, passengers are at no risk of exceeding the general public limit. Although frequent flyers who routinely fly as a major part of their jobs would appear to be occupationally exposed, they are not included in either the European Directive or the United Kingdom's legislation. Nevertheless, NRPB considers that a risk assessment on them should be undertaken by their employers (Q 405)

3.62 Although aircrew are defined as occupationally exposed under the Directive, they are not so defined under the United Kingdom's Air Navigation Order as it presently stands. Nevertheless, some airlines are using the requirements of the Ionising Radiations Regulations as if they applied to aircrew (pp 99, 104, 107 & 229). The Regulations set a working action level of 6 mSv per year, and if any workers are liable to exceed this level, special measures must be taken to monitor, control and limit their exposure. If they are liable to receive between 1 mSv (the general public limit) and 6 mSv per year they are required to have their exposure assessed and work schedules organised to keep annual exposure below 6 mSv per year. In addition, occupationally-exposed workers must be informed of the health risks involved. The Ministry of Defence's Defence Evaluation Research Agency (DERA) brought to our attention a personal cosmic radiation dosimeter it has developed for military aircrew whose operational flying experiences are, by their nature, unpredictable (p 250).

3.63 Measurement and calculation show that the vast majority of aircrew do not exceed about 4 mSv per year, and the NRPB stated that the average annual dose for all aircrew is about 2 mSv[37] (p 146). The only crew members who might exceed the 6 mSv level would be those who fly only ultra-long-haul transpolar routes, but this can be avoided by appropriate crew scheduling. The ANO already incorporates requirements for cosmic radiation exposure records, and UK airlines are now monitoring and recording the cosmic radiation exposure of all affected aircrew. It is common airline practice to ground female aircrew on declaration of pregnancy, and this would ensure compliance with the foetus protection limit.

3.64 The only situation in which aircrew could receive cosmic radiation doses in excess of the limits would be in the event of a large solar flare during the most active part of the solar cycle, which peaks every 11 years. Such a flare may yield a burst of high-energy radiation over a period of a few hours which reaches Earth at flying altitudes. These are very rare events. For example, although Concorde has radiation monitoring equipment on board to warn of such events, none has been recorded in its lifetime. (pp 99 & 146). The evidence from members of the Mullard Space Science Laboratory noted a possible such event in April 2000 (p 253), but we understand from the NRPB that this event did not affect cosmic radiation levels at cruising altitudes.

3.65 Cosmic radiation is different from other aspects of the aircraft cabin environment since exposure is intrinsic to air travel rather than a consequence of design considerations. Exposure to radiation and the consequent risks of cancers or inheritable mutations can be an emotive topic, although very few concerns were raised with us during this Inquiry. The topic was not mentioned by either BALPA (p 213) or the International Association of Flight Attendants (AFA - p 245). The International Air Passenger Association (IAPA) noted it as an issue on which it did not have a position (p 243). Mr Kahn of the Aviation Health Institute raised extensive concerns in respect of passengers and crew (p 44). His points seem effectively rebutted by the sources noted by Varig (p 288).

3.66 The extensive written and oral evidence from NRPB (p 146, QQ 378-424) is, in our view, highly reassuring. However, while it is technically correct to talk of risks in terms of "so many per million"[38], these are not easy for non-specialists to appreciate and put into context. NRPB confirmed our proposed simplification that, because the radiation from the earth's crust in Wales is a quarter of that in Cornwall (although of no significance to health in either place), a day a week at cruising height has the same consequences as living permanently in Cornwall rather than Central Wales (Q 421). We invite NRPB to explore other ways of making these important points more accessible and understandable for the public.

3.67 In the meantime, we are assured that the health risk from cosmic radiation exposure during flight represents an insignificantly small addition to the range of other factors that could lead to cancer or inheritable mutations. In view of this and the legislative controls currently coming into force, we conclude that the matter does not require further comment or recommendations in this Report.

22   A manifestation of the air's density or number of gas molecules per unit volume. Back

23   The standard atmospheric pressure at sea level is, as in some of the evidence submitted to us sometimes referred to as either 1 atmosphere (atm) or 760 mmHg, the latter being the height of mercury (Hg) in an old-fashioned barometer. Back

24   A domestic deep freeze operates at about minus 18ºC. Back

25   JAR 25.841 Back

26   JAA's volume measures are applied at the standard effective cabin altitude. Back

27   As FAA uses a weight of air measurement unit (which removes the need for defining the effective altitude), its FAR 25.831 expresses this as 0.55 pounds per minute (lb/min).  Back

28   "Parts per million" (ppm) are the conventional way of referring to low concentrations. 1 ppm is equal to 0.0001%. Back

29   Airbus Industrie, in response to Q 427, and Boeing, with its evidence on page 204, submitted a number of articles from company publications on cabin air on which we have drawn in this Report. We refer to these as supplementary evidence from Airbus Industrie and Boeing. Back

30   This was presumably one reason why manufacturers petitioned against FAA Amendment 87, as noted in paragraph 3.34. Back

31   Under JAR-FCL 3, flight crew are subject to licence medicals annually up to the age of 40 and 6-monthly thereafter.  Back

32   The European agreement noted in paragraph 3.17 offers the prospect of some change in due course. Back

33   A point we discuss further in paragraph 8.23. Back

34   High energy radiation which can damage body cells and other molecular structures. Back

35   At Concorde's higher cruising altitudes, the levels are about twice these - although this is effectively cancelled out by the shorter journey time. Private business jets are outside the scope of our Inquiry, but we understand from the NRPB that they routinely fly at very high altitudes, approaching those used by Concorde (p 146). Being subsonic, they also spend longer at those heights. Back

36   EC Directive 96/29/EURATOM 1996 and UK Ionising Radiations Regulations 1999. Article 42 of the Directive applies to aircrew as occupationally exposed workers, but the UK regulations do not apply to aircrew. Article 42 is being incorporated into the Air Navigation Order but, with the exception of protection of the foetus (see paragraph 3.59), dose limits for aircrew exposure are not specified, largely because it is difficult to envisage anyone being in the air long enough to exceed a dose of even 10 mSv.  Back

37   Concorde crew doses might be a little higher but do not reach the 6mSv level. Back

38   For example that, compared to the overall lifetime risk of developing a fatal cancer of 1 in 4 (Q 424), the additional lifetime risk from a 20 hour return flight is about 1 in 1 million (Q 418). Back

previous page contents next page

House of Lords home page Parliament home page House of Commons home page search page enquiries index

© Parliamentary copyright 2000