Acute effects of radiation appear above a threshold whole-body dose and grow more severe as the dose rises: from no symptoms at the lowest band to almost certain death within hours to days at the highest. Published dose tables differ in their details, so every band here is a rough guide for a short, penetrating whole-body exposure and must never be used to make a medical decision about an individual.
Part of Radiation Safety
A dose threshold is the whole-body dose above which a given acute effect starts to appear. Cancer risk is treated differently, as having no assumed threshold.
What The Bands Mean And What They Cover
The table below is the parent article’s, Nuclear Safety. It is reproduced as written, in sieverts of whole-body dose received over a short time, with no figure altered.
| Dose (Sv) | Effects (parent article) | Prognosis (parent article) |
|---|---|---|
| 0-0.25 | No symptoms | Full recovery, slightly increased cancer risk |
| 0.25-1 | Mild nausea, fatigue, reduced blood cell counts | Full recovery within weeks |
| 1-2 | Nausea, vomiting, fatigue within hours; blood counts drop significantly over weeks | Recovery likely with supportive care |
| 2-4 | Severe nausea and vomiting within hours; hair loss, haemorrhaging, infection risk | 50% mortality without medical care |
| 4-6 | Vomiting within minutes; severe bone marrow damage | 50-90% mortality even with care |
| 6-10 | Vomiting immediately; gut-tract destruction | Near 100% fatal within 2 weeks |
| 10+ | Immediate disorientation; cardiovascular collapse | Fatal within hours to days |
These apply to a dose received in a short time to most of the body from penetrating radiation. They do not apply to doses spread over weeks, to a dose to one part of the body, or to swallowed or inhaled material.
Three Places Where Sources Disagree
- Units. Acute effects are properly described in grays of absorbed dose. The parent table uses sieverts, which for gamma and beta are numerically close to grays; for alpha or neutron they are not. See Units of Measurement.
- Where the 50 percent point sits. The parent table puts 50 percent mortality without medical care in the 2-4 Sv band. Other published tables put the median lethal dose for untreated whole-body exposure somewhat higher. This guide does not pick between them. The safer reading is the lower figure: treat the bottom of the 2-4 band as the point from which survival is in real doubt.
- Vomiting timing. The parent article’s rule that vomiting within 1 hour means a potentially lethal dose does not match its own table, which has vomiting “within hours” at 1-4 Sv. The consistent reading is relative: earlier vomiting means a higher dose, and neither the 1-hour rule nor the table is a measurement. See Acute Radiation Syndrome.
Dose Rate, Protraction And Partial Body Change The Outcome
The same total dose is less damaging when it arrives slowly, because the body repairs some damage in between, and a dose to a hand is not a dose to the marrow. No factor for either is supplied here, since none is sourced. The only safe use of this limit is the conservative one: treat any short, whole-body, penetrating exposure that might have reached the upper bands as serious.
Cancer Risk Has No Threshold In The Standard Model
Below the bands that cause illness, the parent table says “slightly increased cancer risk”. Standard radiation protection assumes cancer risk rises in proportion to dose with no safe level; see Chronic Exposure.
What These Numbers Cannot Do
You cannot use them without a dose. A dose can be found only from a calibrated instrument and a record of time, neither of which an improvised electroscope provides; see Improvised Detectors. Without a measurement the thresholds give you the shape of the problem and nothing about any particular person’s exposure.
Common Mistakes
- Reading the bands as limits one may approach. They describe injury, not tolerable exposure.
- Comparing a dose rate with a threshold. The bands are totals; a reading per hour must be multiplied by exposure time, with the rate falling as isotopes decay.
- Using the bands to decide who to treat. Choices about scarce care are for the community, not for this table.
Safety
These are doses that injure or kill
The bands are not exposure targets. If an emergency requires someone to take a dose, the only defensible rule here is to keep it as small as the task allows and to record time in the field. This guide supplies no permitted-dose figure for emergency work.
What’s Next
- Learn next: Treatment Protocols — what can be done for an exposed person
- Combine with: Chronic Exposure — long-term cancer risk