Aircrew dose limits: the 20 mSv/yr ICRP rule explained

Aircrew radiation dose is the most heavily regulated category of in-flight exposure. The framework stacks several different reference numbers from several different bodies on top of each other, and most casual writing about aircrew dose confuses them. Three distinctions do most of the work: a limit may not be exceeded; an action level triggers investigation when crossed; a reference level is a benchmark, not enforced. Every number below fits one of those three buckets.

The ICRP-103 occupational limit: 20 mSv/yr averaged over 5 years

The headline number is ICRP Publication 103's recommendation that the effective dose for an occupationally exposed adult shall not exceed an average of 20 millisieverts per year, averaged over five consecutive years (i.e. 100 mSv across any five years), with the additional restriction that no single year shall exceed 50 mSv ^[1]. This recommendation has been carried into national regulation by most countries that operate radiation-protection frameworks.

For the equivalent dose to specific organs, ICRP-103 also specifies:

• 20 mSv/yr averaged over 5 years to the lens of the eye (revised from 150 mSv/yr by ICRP-118 in 2011)
• 500 mSv/yr to the skin (averaged over any 1 cm² area)
• 500 mSv/yr to the hands and feet

For aircrew in-flight exposure, the relevant figure is effective dose; the dose distribution is broadly whole-body for the cosmic-ray cascade.

How ICRP-103 differs from ICRP-60 on dose limits

The 20 mSv/yr averaged over 5 years figure is unchanged between ICRP-60 (1990) and ICRP-103 (2007); what changed are the tissue weighting factors used to compute effective dose. The numerical impact on a typical aircrew dose figure is on the order of 10–15%; the direction depends on the radiation-field composition. We always use ICRP-103 weighting in our reports.

The FAA position: 6 mSv/yr action level (NCRP 132 / AC 120-61B)

The US FAA does not regulate aircrew dose. There is no enforceable cap in 14 CFR; the FAA's position is set out in Advisory Circular 120-61B (2014), which recommends that air carriers provide aircrew with information about galactic-cosmic-radiation exposure and adopt an action level of 6 mSv per year at which the carrier reviews the crew member's flying pattern and considers schedule modification ^[2]. The 6 mSv figure originated in NCRP Report 132 (2000) and represents 30% of the ICRP-103 occupational limit; it is intended as an early-warning indicator, not a cap.

Because AC 120-61B is advisory rather than regulatory, US carrier compliance varies. Larger network carriers typically maintain dosimetry programs that meet the AC; smaller carriers may not. There is no requirement in US regulation to record or report aircrew dose to any government register.

The EU position: EURATOM Basic Safety Standards (Directive 2013/59/Euratom)

The EU regulates aircrew radiation. The Basic Safety Standards Directive (2013/59/Euratom), transposed into member-state law by 2018, requires operators of aircraft routinely flying above 8 km altitude (FL260+) to ^[3]:

• Assess crew exposure.
• Take into account assessed exposure when organising work schedules with a view to reducing the doses of highly exposed crew.
• Inform the workers concerned of the health risks their work involves.
• Provide special protection during pregnancy for female crew (the ICRP-132 1 mSv fetal dose ceiling applies).
• Apply the same general dose limits as for any radiation worker (20 mSv/yr averaged over 5 years, 50 mSv in any single year).

EURATOM does not assign a separate action level analogous to the FAA 6 mSv figure; the regulatory architecture is to monitor against the ICRP-103 limits directly. In practice EU carriers' dose-assessment programs use codes equivalent to CARI-7 (PCAIRE, EPCARD, and the EURADOS-recommended methodology).

Where does typical aircrew dose sit?

Real-world aircrew dose depends heavily on route mix. Some indicative ranges from the EURADOS and FAA dosimetry literature ^[4]:

Crew type	Typical annual flight hours	Typical annual effective dose (mSv)
Short-haul European or US domestic narrow-body	600–800	1.5–3.0
Medium-haul mixed (transcon + Europe)	700–900	2.5–4.5
Long-haul transatlantic / Asia-Europe network	700–900	3.5–6.0
Polar-heavy long-haul (e.g. transpolar Asia-North America)	600–800	5.0–8.0
Cargo long-haul polar (high cruise altitude, near-continuous polar work)	600–800	7.0–10.0

The top of the range exceeds the FAA 6 mSv/yr action level but remains well below the ICRP-103 20 mSv/yr ceiling. In published aircrew dosimetry programs we are not aware of any cohort whose median dose has approached 20 mSv/yr; the ceiling is comfortably above any realistic civil-aviation flying pattern.

What "averaged over 5 years" means in practice

The averaging mechanism matters because aircrew flying patterns can be uneven. A crew member might fly a polar-heavy schedule for two years (8 mSv/yr) and then transition to short-haul (2 mSv/yr) for three years. Their five-year average is 4.4 mSv/yr, comfortably below both the FAA action level and the ICRP ceiling. The averaging is designed exactly to accommodate this kind of legitimate variation.

The 50 mSv-in-any-single-year cap exists to prevent the averaging from being used to mask a single highly-exposed year. For aircrew this is almost never the binding constraint; the only way to exceed 50 mSv in a single year is to be exposed to a major SPE under specific operating conditions.

How an action level differs from a regulatory cap

Three different ways a dose number can function:

• Regulatory limit. Cannot be exceeded; the operator faces consequences if it is. ICRP-103 occupational 20 mSv/yr is this kind of number under EURATOM Basic Safety Standards.
• Action level. Triggers investigation and possible schedule modification when crossed. The FAA 6 mSv/yr from AC 120-61B is this kind of number.
• Reference level. A benchmark for thinking, not enforced. The ICRP-103 1 mSv/yr public limit, when applied to non-occupational fliers, is this kind of number; there is no enforcement mechanism for passenger dose.

Reading any dose-limit number, the first question is always: which of the three is this?

Pregnancy: a special case

Once an occupationally-exposed worker declares her pregnancy, ICRP-103 §5.4.2 and ICRP-132 recommend the conceptus be protected to approximately 1 mSv across the remainder of pregnancy ^{[1, 5]}. This is far below the worker's own 20 mSv/yr limit, reflecting the special protection ICRP applies to the conceptus as a member of the public rather than as a worker. EU carriers under EURATOM must accommodate this; US carriers under AC 120-61B are recommended to. For more detail see our pregnancy guide.

How this maps to non-occupational fliers

If you are not aircrew, no occupational limit applies to you. The ICRP-103 1 mSv/yr public limit is a reference for controllable sources (e.g. nuclear power) and explicitly excludes natural background, including cosmic radiation. There is no regulatory dose limit for a passenger. The dose numbers nonetheless matter (they put your total annual exposure in context), but the framework around them is different from the aircrew framework. Compare your annual dose against the ICRP-103 references but understand they are benchmarks, not caps.

Our frequent-flyer dose math guide works through what realistic non-occupational flying patterns produce in annual dose, and where on the limit chart they sit.

The honest summary

The 20 mSv/yr ICRP-103 occupational limit is a real, enforceable number (in EURATOM jurisdictions) that sits well above any realistic civil-aviation flying pattern. The FAA 6 mSv/yr action level is a more directly relevant number for US aircrew and indicates the point at which a carrier should investigate a crew member's schedule. Pregnancy invokes a much tighter 1 mSv protection target. Non-occupational frequent fliers face no regulatory limit at all but can use the ICRP-103 figures as benchmarks. For most of the population, passenger or crew, the system is conservative enough that the binding constraint is operational economics, not dose.

How carrier dosimetry programs work in practice

A modern carrier dosimetry program does not put physical dosimeters on every crew member. The numbers are too small, the workforce is too large, and the underlying dose is well-modelled by codes like CARI-7. Instead, the typical program:

• Records each crew member's flight log automatically from operations data.
• Runs each segment through a CARI-class code (CARI-7A, PCAIRE, or EPCARD).
• Adds the per-segment doses to produce a rolling annual total and a rolling five-year total.
• Flags any crew member approaching the action level (FAA 6 mSv/yr) or the regulatory limit (EURATOM 20 mSv/yr averaged over 5 years).
• For pregnant crew, applies the ICRP-132 1 mSv ceiling and modifies schedule accordingly.
• Adds per-event SPE estimates for any flight during a logged solar particle event.

The system is the same one we use to produce a FlightRadiation report (same model, same limits, same approach) applied at carrier scale rather than to an individual passenger.

Historical context: how the 20 mSv/yr number got there

The ICRP occupational limit of 20 mSv/yr (averaged) was introduced in ICRP Publication 60 (1990) as a reduction from the previous 50 mSv/yr limit that had been in place since ICRP Publication 26 (1977). The reduction reflected the increased confidence in epidemiological evidence from the atomic-bomb-survivor lifespan studies and the resulting upward revision of risk coefficients per sievert. ICRP-103 (2007) retained the 20 mSv/yr figure; subsequent ICRP statements have not indicated any plan to reduce it further ^[1].

Last reviewed 30 June 2026 · See our methodology and sources.