📍 How to read a radiation map

The key points from the outset

The number shown on the map reflects only part of the radiation hazard — the portion the instrument can detect.
Real harm is more often caused not by sudden spikes but by quiet, long-term exposure that builds up over years.
Even in a "green" area, risk may still exist due to invisible sources: radon, water, food and air.
A map is a guide, not a guarantee. It helps you think but does not replace common sense.

🟩
0–11

Green zone

"Generally safe — but stay attentive"

0–11 microroentgens per hour — close to natural background.

you can usually live here permanently
drink the water
grow and eat local produce
this does not mean radiation is absent
it means levels are about what the body is used to
⚠ hidden risks still exist: indoor radon; radioactive impurities in water; accumulation of radionuclides in food and tobacco

🟨
11–30

Yellow zone

"Pay attention and find out why"

11–30 microroentgens per hour. Usually no immediate danger, but a yellow patch inside green is a reason to pause.

possible causes: radon; alpha or beta contamination the dosimeter only partially sees; localised sources
sensible steps: test water and food; identify the source; measure indoor radon
harm can build up over time, even if you feel fine now

🟥
30–100

Red zone

"Without checks, it is not worth the risk"

30–100 microroentgens per hour — no longer a normal level.

avoid: living here permanently; regularly drinking local water; relying on local food
possible causes: man-made radionuclides; contaminated soil; high radon in homes and water
recommended: drink water only after testing; eat food after checks; live here only with full awareness of the risks

⬛
100+

Black zone

"Extended exposure is unsafe"

Over 100 microroentgens per hour — a serious level of exposure.

risk fronts: external irradiation; radionuclides entering the body; potential skin damage
food and water may contain hazardous substances even if they look and smell normal
🔹 exceptions (brief skin exposure): air travel; high-altitude locations

🔍 What a dosimeter shows — and what it misses

Typically detected:

gamma radiation
sometimes part of beta radiation

Often missed:

alpha radiation (especially dangerous once inside the body)
radon — a gas we breathe and drink with water
tritium in water and air
radionuclides in food
neutrons (rare, but extremely dangerous)
👉 a "green" reading does not equal full safety.

🧬 How radiation actually enters the body

The most dangerous routes are quiet and long

Through breathing — radon, dust, smoke → lungs
Through water — tritium and dissolved isotopes → whole body
Through food — mushrooms, greens, milk → accumulation in tissues
Through smoking — tobacco readily absorbs radionuclides

Less dangerous:

brief external exposure
one-off contact

⏳ Time is the main risk factor

Radiation is dangerous because of prolonged exposure. Moderate doses taken continuously can be more harmful than a short spike. The body can eliminate radionuclides, but with constant exposure and other stresses those systems get overloaded.

👥 Who is affected more severely

Higher risk for: older people; those with chronic illnesses. What one body tolerates without consequences may cause serious problems for another.

⚛️ Radioactive "disguise"

Some radionuclides resemble ordinary substances to the body: tritium — like water; carbon-14 — like normal carbon; potassium-40 — like potassium; strontium, radium — like calcium. Cells do not recognise the substitution and incorporate them. Damage and mutations are possible even when the dosimeter reads "normal."

🗺️ Why a map should not be trusted blindly

Even a perfectly green map reflects only part of reality. Hidden factors are not shown. 👉 A map is a hint, not a pardon. You still need to think, check, and ask questions yourself.

Safecast New Map – Global map of radioactivity

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Common Isotope Peaks Reference

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