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10 CFR 20 (specifically Subpart C) sets the legal occupational radiation dose limits for anyone working under an NRC or Agreement State license — the numbers a radiation safety program is built around, and the numbers ALARA sits on top of, not instead of. This guide lays out the actual limits as a reference table: total effective dose equivalent, the organ/tissue alternative, lens of the eye, extremities, minors, and the declared pregnant worker — plus the monitoring threshold that determines who actually needs to wear a dosimetry badge.
Adult Occupational Dose Limits — 10 CFR 20.1201
20.1201(a) sets the annual limit for adults as the more limiting of two calculations, plus two separate tissue-specific limits that apply regardless of which of the first two governs:
| Limit type | Annual value | What it covers |
|---|---|---|
| Total effective dose equivalent (TEDE) | 5 rem (0.05 Sv) | Combined external + internal whole-body dose — the primary limiting figure for most research radioisotope work |
| Deep-dose + committed dose equivalent (organ/tissue) | 50 rem (0.5 Sv) | Alternative sum to any individual organ or tissue other than the lens of the eye; TEDE governs unless this alternative calculation is more restrictive |
| Lens of the eye (eye dose equivalent) | 15 rem (0.15 Sv) | Separate limit — relevant to fluoroscopy, PET/SPECT work, and any procedure with sustained eye proximity to a source |
| Skin of the whole body, or any extremity (shallow-dose equivalent) | 50 rem (0.5 Sv) | Hands, forearms, feet, ankles — the limit that matters most for bench work with unshielded beta/gamma emitters like 32P or 125I |
These are annual limits, not lifetime limits, and they apply to occupational dose — dose received in the course of licensed work. They exclude background radiation, dose from a person’s own medical procedures, and (in most circumstances) voluntary participation in medical research as a subject rather than a worker.
Limits for Minors — 10 CFR 20.1207
20.1207 sets the annual occupational dose limit for a minor (an individual under 18) at 10 percent of the adult 20.1201 limits — so a TEDE ceiling of 0.5 rem (5 mSv) per year, with the organ/tissue, lens-of-eye, and extremity limits scaled down proportionally in the same way. Minors working under a research license are uncommon but not unheard of (undergraduate research assistants under 18, some high-school outreach programs) — the lower threshold is the reason most radiation safety programs default to age-gating any role with routine source access.
Limits for a Declared Pregnant Worker — 10 CFR 20.1208
20.1208 applies once a worker has formally declared her pregnancy to the licensee in writing — the lower limit is not automatic on becoming pregnant, it is triggered by the declaration. Once declared:
- The dose equivalent to the embryo/fetus for the entire pregnancy must not exceed 0.5 rem (5 mSv) — a single figure covering the whole gestation period, not an annual allowance.
- The licensee must make a reasonable effort to avoid substantial variation above a uniform monthly exposure rate, so the full 0.5 rem isn’t received in one or two months.
- If the declaration is made after some occupational dose has already been received during the pregnancy, the regulation is satisfied as long as the dose equivalent to the embryo/fetus for the remainder of the pregnancy does not exceed an additional 0.05 rem (0.5 mSv).
Declaration is voluntary and can be withdrawn at any time; a lab’s radiation safety program should have a documented process for it, typically routed through the Radiation Safety Officer.
ALARA vs. the Limit: Two Different Things
10 CFR 20 limits and ALARA are frequently conflated, and the distinction matters operationally:
- The dose limits above are a legal ceiling. Exceeding them is a reportable regulatory violation regardless of circumstances, cost, or how far under the limit the rest of the facility’s staff are running.
- ALARA (As Low As Reasonably Achievable), under 20.1101, is a separate, affirmative obligation to stay well below the limit whenever that’s achievable without unreasonable cost or burden. A radiation safety program that lets doses drift up toward the 20.1201 ceiling while remaining technically compliant is not meeting its ALARA obligation, even though it isn’t violating the numeric limit.
In practice this means the limits in the table above are the number a compliance audit checks against, while ALARA is the number a well-run program actually manages to — typically a small fraction of the regulatory limit. For the practical, bench-level mechanics of keeping dose down through time, distance, and shielding, see Time, Distance, Shielding: Applying ALARA Principles in Everyday Radioisotope Work.
The Monitoring Threshold: Who Actually Needs a Dosimetry Badge
Not every person who works near a radiation source is required to wear a dosimeter. 10 CFR 20.1502 sets the trigger:
- Adults: monitoring is required for anyone likely to receive, in one year, a dose in excess of 10 percent of the 20.1201(a) limits — in practice, 0.5 rem (5 mSv) TEDE from external sources.
- Minors: a lower, absolute threshold — 0.1 rem (1 mSv) deep-dose equivalent, 0.15 rem (1.5 mSv) lens dose equivalent, or 0.5 rem (5 mSv) shallow-dose equivalent to skin/extremities.
- Declared pregnant workers: monitoring is required if she is likely to receive, from external sources over the entire pregnancy, a deep-dose equivalent in excess of 0.1 rem (1 mSv).
This is a “likely to receive” test applied prospectively, based on job duties and source access — not a rule that only kicks in retroactively once someone’s dose crosses the line. A Radiation Safety Officer typically makes this determination per role during badge issuance, not per individual after the fact. See How Dosimetry Badges Work for what happens after monitoring is assigned — exchange schedules and how to read the resulting exposure report.
Where These Limits Fit in a Compliant Radiation Safety Program
The limits above are enforced through the same institutional structure regardless of which specific number applies to a given role: a Radiation Safety Officer holds license authority and day-to-day responsibility for keeping doses under both the regulatory limits and the facility’s own ALARA targets, reporting to the institution’s Radiation Safety Committee, which sets policy and reviews dose records. Radioactive material that isn’t yet disposed of also carries its own handling rules distinct from personnel dose limits — see Radioactive Waste Disposal in the Lab for that separate compliance track.
Frequently Asked Questions
What is the annual radiation dose limit for a radiation worker?
5 rem (0.05 Sv) total effective dose equivalent per year under 10 CFR 20.1201(a), unless the alternative organ/tissue calculation (50 rem to a single organ) is more restrictive for that individual’s specific exposure pattern.
What is TEDE in radiation safety?
Total Effective Dose Equivalent — the combined external and internal whole-body dose used as the primary annual limiting figure under 10 CFR 20.1201. It is the number most routine dosimetry badge reports are measured against.
What is the dose limit for the lens of the eye?
15 rem (0.15 Sv) per year under 10 CFR 20.1201(a)(2) — a separate limit from TEDE, most relevant to procedures with sustained eye proximity to a source, such as fluoroscopy.
What is the radiation dose limit for a declared pregnant worker?
0.5 rem (5 mSv) to the embryo/fetus for the entire pregnancy under 10 CFR 20.1208, applying only after the worker has formally declared the pregnancy in writing to the licensee, with a requirement to avoid substantial month-to-month variation.
At what dose does an employee need to wear a dosimetry badge?
An adult must be monitored if likely to receive more than 10 percent of the 20.1201 limits in a year (in practice roughly 0.5 rem/5 mSv TEDE from external sources); minors and declared pregnant workers have lower, fixed thresholds under 10 CFR 20.1502.
Is ALARA the same as the 10 CFR 20 dose limit?
No. The 10 CFR 20 figures are a hard regulatory ceiling; ALARA (20.1101) is a separate, ongoing obligation to keep actual doses well below that ceiling whenever reasonably achievable, not a target to approach.
