Methodology

Every number on a FlightRadiation report is produced by running each flight segment through the FAA CARI-7 / CARI-7A cosmic-radiation transport model and weighting the output with ICRP Publication 103 tissue weighting factors. This page documents the model, the inputs, the derived metrics, and the uncertainty bounds.

1. The transport model: CARI-7 / CARI-7A

CARI-7 is the seventh-generation cosmic-radiation transport code published by the FAA's Civil Aerospace Medical Institute (CAMI) in Oklahoma City. It replaced CARI-6, which had been the regulatory reference since the late 1990s. CARI-7 differs from CARI-6 in that it uses Monte Carlo particle transport (MCNPX-based) and includes secondary particle production (neutrons, muons, electromagnetic cascade) explicitly rather than via tabulated parameterisation.

The publicly maintained interactive version, CARI-7A, accepts origin and destination airports (IATA or ICAO), a cruise flight level, departure date, and aircraft type. It returns effective dose for that single segment in microsieverts. We use CARI-7A as the reference implementation for individual segments; for batch processing of flight logs we use the same physics tables and the great-circle routing logic documented in Copeland's CARI-7 / CARI-7A documentation (see sources).

2. The dose quantity: effective dose (E), ICRP-103 weighted

The CARI series outputs effective dose, denoted E, in sieverts. Effective dose is not a measurement; it is a calculated whole-body equivalent that accounts for (a) the radiation type's biological effectiveness via radiation weighting factor w_R, and (b) the differential radio-sensitivity of organs via tissue weighting factor w_T. We use ICRP Publication 103 (2007) w_T values, which superseded ICRP Publication 60 (1990).

The key ICRP-103 w_T revisions from ICRP-60: gonads dropped from 0.20 to 0.08, breast rose from 0.05 to 0.12, brain raised explicitly to 0.01 (was in the remainder under ICRP-60). For typical cruise altitudes and mixed cosmic-ray fields, ICRP-103 weighting yields E values within roughly 10–15% of ICRP-60 weighting for the same physical fluence, but the direction of the correction depends on the radiation field composition. We always cite ICRP-103.

3. Inputs we accept

• Origin and destination. IATA airport codes; we map to ICAO and to lat/long internally using a static OpenFlights-derived table.
• Cruise altitude. Either you enter a flight level (FL250–FL420), or we infer one based on aircraft type and route distance using a static lookup (e.g. transatlantic Boeing 787 → typical step climb FL350 → FL390).
• Departure date. Used to retrieve the heliocentric potential for the corresponding month (CARI uses monthly-averaged Climax neutron monitor data via the Oulu Cosmic Ray Station to derive the proxy used in the model).
• Number of segments per year. A simple multiplier for annualising.
• Passenger profile. Adult / child / pregnant. Adult is the default ICRP-103 reference person. Pregnant invokes the 1 mSv gestational limit and a recommendation to consult an obstetrician.

4. Derived metrics on the report

The PDF contains the following derived quantities, each computed as documented below:

Metric	How we compute it
Per-segment effective dose (µSv)	Direct CARI-7A output for that O/D + FL + date.
Annual effective dose (mSv)	Sum of per-segment doses across the analysis window, scaled to 12 months if the input window is shorter or longer than 12 months.
Polar-route attribution (%)	Sum of dose from segments whose great-circle path crosses ≥60° geomagnetic latitude, divided by total annual dose.
ICRP-103 limit comparisons	Bar chart of annual dose against (a) ICRP-103 public limit 1 mSv/yr, (b) FAA aircrew action level 6 mSv/yr (NCRP Report 132 / FAA AC 120-61B), (c) ICRP-103 occupational 5-yr averaged limit 20 mSv/yr, (d) US surface background of 0.39 mSv/yr from cosmic + terrestrial (NCRP Report 160).
30-year projection (mSv)	Annual dose × 30, holding flight pattern constant. Linear projection only; does not model solar cycle modulation across decades.
Gestational dose (mSv)	For pregnant subject: dose accrued across the 40 weeks of pregnancy at the same flying cadence as the analysis window, compared against the ICRP-103 fetus limit of 1 mSv across the remainder of pregnancy once it is declared (ICRP-103 §5.4.2).

5. What we deliberately do NOT compute

• Individual cancer risk. Lifetime attributable risk (LAR) per Sv is published in BEIR VII (NAS, 2006) and ICRP-103, but applying a single LAR coefficient to an individual is statistically unsound and we will not do it. Risk depends on age at exposure, sex, dose rate, prior exposures, and competing causes of death.
• SPE dose. Solar particle events can deliver doses comparable to weeks of flying in a few hours, but the magnitude depends on the specific event spectrum and the aircraft's location at the time. We flag any user-supplied flight dates that overlap a NOAA SWPC-listed SPE and recommend the operator's incident report be consulted.
• Aircraft shielding differences. CARI-7 assumes a generic civil-aviation airframe. Differences between, say, an A220 and an A380 at the same FL are within the model's stated uncertainty band and we do not break them out.

6. Known uncertainty bounds

The CARI series has been validated against a large set of in-flight neutron and ionising-radiation measurements (Friedberg & Copeland and colleagues, multiple decades of papers; see sources). The model's stated uncertainty for galactic cosmic-ray-driven effective dose at typical cruise altitudes is on the order of ±25% (2σ) when compared to instrumented measurements. We carry this band through the report: a value of "5.4 mSv/yr" should be read as "approximately 4 to 7 mSv/yr at the 2σ level". The polar-route attribution metric is less precise because the geomagnetic-cutoff transition is gradual rather than a hard 60° step, but the qualitative finding (polar segments dominate transatlantic dose) holds across implementations.

7. Data refresh cadence

The CARI-7A heliocentric-potential tables are updated by FAA CAMI as new neutron-monitor data become available. We pull the latest published tables monthly. The ICRP-103 weighting factors are static; ICRP-103 has been the operative recommendation since 2007 and a successor publication is not yet in force. NCRP Report 160 background-dose values reflect 2006 US-population averages and have not been formally superseded.

8. Reproducibility

Every report PDF lists the exact CARI-7A version used, the heliocentric potential table month, and the ICRP-103 w_T set. A reader with access to the public CARI-7A web tool can reproduce every per-segment number on the report.

Last reviewed 30 June 2026 · See our sources