Radiation & cancer

NASA risk title (verbatim)

Risk of Radiation Carcinogenesis

NASA short title: Carcinogenesis · HRP element: Space Radiation (SR) · Status: Active [current research ongoing] [1]

What it is

Beyond Earth’s protective magnetic field, crews are exposed to galactic cosmic rays (GCR) and solar particle events (SPEs). NASA’s concern is that this exposure raises a person’s chance of developing, or dying from, cancer later in life [1]. Unlike X-rays or gamma rays on Earth, space radiation includes high-energy protons, heavy ions and neutrons. These particles leave dense tracks of damage in cells that are hard to repair [1].

Current evidence

• There are no epidemiological data for people exposed to space radiation. Estimates are built from Earth-based radiation-exposed groups and then adjusted for space radiation using animal and cell experiments [1].
• Animal and cell studies suggest particle radiation may cause more cancer-related effects than X-rays or gamma rays, such as tumors appearing sooner or being more malignant [1].
• NASA’s model (NASA Space Cancer Risk, NSCR) expresses risk as the risk of exposure-induced death (REID). It uses Monte Carlo simulation to carry uncertainty about radiation quality, dose rate and the Earth-based data into the estimate [1].
• The space radiation field is roughly 87% protons, 12% helium nuclei and 1% heavier, high-energy ions (HZE). Spacecraft shielding against it is still imperfect [1].
• The Mars Science Laboratory measured a dose equivalent of 0.66 ± 0.12 sievert for the shortest Mars round trip possible with current propulsion and comparable shielding [4].
• A 2021 National Academies report reviewed how NASA manages and communicates these cancer risks [5].

NASA’s risk posture

NASA scores each risk for each design reference mission (DRM) as likelihood × consequence (LxC). Both run from 1 (lowest) to 5 (highest) on the HSRB’s 5×5 matrix [1][3]. Each score comes with a disposition, such as “Accepted”, “Requires Characterization” or “Requires Mitigation”. These ratings were last approved by NASA’s Human System Risk Board (HSRB) (see note) [1].

NASA notes that these ratings were set under the HSRB’s previous 3×4 matrix and are due to be re-rated on the current 5×5 matrix [1]. In-flight (operations) risk is rated very low. The concern is long-term health.

Copied from the Human Research Roadmap on 2026-10-14. Ratings change. Check the live record before citing.

Open knowledge gaps

NASA lists 12 knowledge gaps for this risk, 12 of them open as of 2026-10-14 [1]. Each gap ID links to its page on the Human Research Roadmap (HRR).

See also Open questions.

Active countermeasure research

• Ground radiobiology at the NASA Space Radiation Laboratory (NSRL). Studies began with single-ion beams. Newer GCR-simulator beams now approximate the mixed radiation field inside a spacecraft [1].
• Tissue-specific research. NASA Specialized Centers of Research study lung, breast, colon, blood and lymphatic, liver and brain cancers. They are also looking for biomarkers that could catch pre-malignant disease early [1].
• Better risk models. New data-driven computational models aim to translate ground results into human risk [1].
• Operational protection, in place now. Dose limits and ALARA keep exposure down. NASA-STD-3001 sets a career limit of less than 600 mSv effective dose (see Requirements referenced below). No medical countermeasure that lowers cancer risk from space radiation has been validated [1].

Project-level detail, including status, investigators and results, is in the NASA Task Book and on each HRR gap page.

Clinical articles

For practical, clinic-facing guidance, see:

• Space Radiation: Exposure Limits, Dosimetry & Shielding
• Postflight Recovery, Rehabilitation & Long-term Health Surveillance