Cesium-137 and Prussian blue: internal contamination

A 38-year-old man who makes a living selling scrap dismantles at home a heavy metal piece found on the grounds of a closed clinic. Inside, he finds a capsule with a powder that glows blue in the dark. Over four days, he, his 35-year-old wife and their two children, aged 9 and 3, handle the powder, show it to neighbors and eat with unwashed hands. The wife arrives at the health unit with nausea and a blister on her palm. The 9-year-old has diarrhea, and the father has vomiting and burns on his fingers. The health surveillance technician passes a detector near the family, and the device goes off. The scene is fictional and was written for teaching.

This text uses the case as a scenario for clinical reasoning for students and health professionals. The topic is internal contamination by cesium-137, as in the Goiânia accident in 1987, and treatment with insoluble Prussian blue. The focus is what the doctor decides in the first hours and weeks: separate irradiation from contamination, protect the team, decontaminate the skin, measure the internal burden and give the medication at the right dose for each age. It does not replace your service's protocol or contact with the radiation protection authority in your country. If you play the case of the day on NEXO, you will recognize the challenge: deciding with clues that arrive in sequence.

Key points

• Someone contaminated by cesium-137 has radioactive material on the skin and inside the body, and this changes team protection.
• Life-threatening injuries come before decontamination.
• Without treatment, cesium is excreted mainly in urine; with Prussian blue, fecal excretion becomes dominant.
• The Radiogardase label indicates 3 g three times a day for adults and adolescents and 1 g three times a day for ages 2 to 12.
• Treatment lasts at least 30 days, guided by whole-body counting and urine and fecal measurements.
• Radiogardase was approved by the FDA in 2003 and has no centralized authorization from the EMA.

Why this is a reasoning scenario

Lost or abandoned radioactive sources, called orphan sources, are still found in scrapyards, vacant lots and deactivated hospitals worldwide. The most studied case is Goiânia. A 50.9 TBq cesium chloride source was removed from the shielding of an abandoned radiotherapy device and opened (IAEA report on Goiânia). About 112,000 people were examined, and 249 were contaminated externally or internally (IAEA report on Goiânia). Four people died in the first four weeks of hospitalization (IAEA report on Goiânia). Some had very high internal and external contamination because they spread the powder on their skin and ate with contaminated hands (IAEA report on Goiânia).

The family's condition in the scene brings together almost everything the report describes: skin lesions, digestive symptoms, small children and household contamination. The post on signs, symptoms and history helps build the timeline of contact with the powder, and the post on clinical decision-making reminds us that each test must change a decision.

What the scene teaches

The scene trains six habits. The first is to think of a radioactive source when several people in the same household have burns without a thermal cause and digestive symptoms. The second is to call radiation protection early. The third is to treat what threatens life before decontaminating. The fourth is to remove clothing and store it in a bag. The fifth is to collect urine and feces to measure cesium. The sixth is to start Prussian blue without waiting for the final count result.

What is not at stake

The text does not cover in detail acute radiation syndrome, which was the topic of the first text in this series. It also does not cover other radionuclides, such as iodine, plutonium or americium, which require other antidotes. The post on diagnostic uncertainty helps at the beginning, when no one yet knows that a source exists.

Irradiation and contamination: the first distinction

Two different situations

In external exposure, the person receives radiation from a source outside the body, and no radioactive material is left on the skin or clothing (Kazzi et al., 2015). In contamination, the radioactive material stays on the skin, on clothing or inside the body, through inhalation, ingestion or wounds (Kazzi et al., 2015). The family at the scene has both. The source irradiated everyone for days, and the dust stayed on their hands, on clothing, in the house and inside the body.

Team protection

The team needs protection from secondary contamination and from the radionuclide entering their own bodies, with protective clothing, respiratory protection and gloves (Rump et al., 2018). Full heavy clothing for chemical, biological, radiological and nuclear threats is adequate, but it is not mandatory when caring for patients contaminated by radionuclides, unlike what happens with some chemical agents (Rump et al., 2018). Personal protective equipment protects against contamination, but not against the gamma radiation coming from the patient's body (Kazzi et al., 2015). That is why distance and contact time also matter (Kazzi et al., 2015). In Goiânia, radiological research on skin injuries showed dose rates of up to 15 mSv per hour, and a 6-year-old girl had an average of 3 mSv per hour on skin contact (IAEA report on Goiânia).

Life first

After stabilizing whatever threatens life, the patient undergoes contamination screening (Kazzi et al., 2015). Contaminated clothing is removed carefully and stored in a double bag for later analysis, and this already removes the contamination that was on it (Kazzi et al., 2015). The detector screening is repeated to locate contamination on the face, in body openings, on the skin and in wounds (Kazzi et al., 2015). The post about diagnostic pause helps avoid skipping this order when the detector goes off and everyone gets anxious.

How cesium-137 behaves in the body

Physics and biology

Cesium-137 has a physical half-life of about 30 years and emits beta and gamma radiation (Aaseth et al., 2019). Chemically, cesium resembles sodium and potassium (Aaseth et al., 2019). After entering the blood, it distributes evenly through the body's tissues and follows the movement of potassium (Radiogardase package insert, 08/2014). About 10 percent is eliminated with a biological half-life of 2 days, 90 percent with a half-life of 110 days and less than 1 percent with a half-life of about 500 days (Radiogardase package insert, 08/2014). The REMM radionuclide table gives a biological half-life of 70 days and renal excretion (REMM, internal contamination).

Circulation between liver and intestine

Cesium is excreted into the intestine, reabsorbed from the digestive tract into the blood and again into the bile (Radiogardase package insert, 08/2014). This is the cycle that Prussian blue interrupts. Without treatment, cesium leaves mainly through urine, about 80 percent in urine and 20 percent in feces (IAEA report on Goiânia). With oral Prussian blue, elimination through feces comes to dominate (Kazzi et al., 2015). The drug binds cesium in the intestine and reduces the time it stays in the body (Aaseth et al., 2019).

Effective half-life in Goiânia

The Radiogardase package insert uses data from 46 people treated in Goiânia (Radiogardase package insert, 08/2014). Treatment reduced the mean effective half-life of cesium-137 in the whole body by 69 percent in adults, 46 percent in adolescents and 43 percent in younger children (Radiogardase package insert, 08/2014). A 2022 review of past emergencies cites a reduction of 71 percent in adults, 46 percent in adolescents and 43 percent in children, and says the effect did not depend on the dose within the range used (Li et al., 2022). The small difference between the two sources comes from different analyses of the same patients; the text uses the number from the package insert.

The table summarizes the Goiânia data by age.

Group	Dose used in Goiânia	Reduction of effective half-life	Source
Adults	Initial dose of 3 g per day in three doses; 4 to 6 g per day with very high intake	69 percent	(IAEA report on Goiânia) (Radiogardase package insert from 08/2014)
Adolescents	Up to 10 g per day	46 percent	(Radiogardase package insert from 08/2014) (Li and colleagues, 2016)
Children aged 4 to 9	1 to 1.5 g per day in 2 to 3 doses	43 percent	(Li and colleagues, 2016) (Radiogardase package insert from 08/2014)
All	1 to 10 g per day, 46 people treated	Effect independent of dose within the range used	(IAEA report on Goiânia) (Li and colleagues, 2022)

Screening, tests and measurement of internal burden

The differential before the detector

Before the detector goes off, the family's picture can look like something else. Blisters on the hand can be a chemical burn, a thermal burn or contact dermatitis. Vomiting and diarrhea in several people in the same house suggest food poisoning, infection or pesticide poisoning. What changes the reasoning is the combination: a skin lesion with no reported thermal burn, digestive symptoms in several people and a strange object brought home days earlier. The post on differential diagnosis shows how to keep the hypotheses open until the decisive clue appears.

Urine, feces and whole-body counting

In Goiânia, urine samples were collected from everyone with possible internal contamination and used for screening (IAEA report on Goiânia). Urine and feces were collected every day from those with internal contamination, and intake and committed dose were estimated with mathematical models adjusted for age (IAEA report on Goiânia). The efficacy of Prussian blue was assessed by the ratio of cesium in feces to cesium in urine, and a whole-body counter was set up in the city (IAEA report on Goiânia). The activity measured in urine can be compared with reference values, such as the clinical decision guide of the American radiation protection council, which translates intake into risk (Kazzi and colleagues, 2015). When intake exceeds the value in this guide, decorporation therapy can be used, if one exists for the radionuclide (Kazzi and colleagues, 2015).

Children in the count

Measuring small children is difficult, because the devices and protocols were made for adults (Li and colleagues, 2016). In Fukushima, a study of 32811 people used a detection limit of 300 Bq per body for cesium-134 and cesium-137 (Hayano and colleagues, 2013). After May 2012, cesium-137 was not detected in 10237 children (Hayano and colleagues, 2013). Another study in Iwaki also measured the internal dose in residents (Orita and colleagues, 2014). Fifteen years later, the authors of a report on whole-body examinations in Fukushima point to the lack of operating procedures for large-scale examinations as one of the challenges (Ohba and colleagues, 2026).

Arrival examinations

• Survey with a detector before and after undressing, with a map of the contaminated areas.
• New survey of the face, mouth and wounds, where dust tends to stay.
• 24-hour urine and feces to measure cesium, with the time of collection.
• Serial blood count, because the source also irradiated the body from outside.
• Electrolytes and potassium before starting Prussian blue.
• Pregnancy test in women of childbearing age.

The serial blood count is included because the family was irradiated from outside for days, and acute radiation syndrome can appear along with the contamination. The post on interprofessional clinical reasoning recalls that medical physics, nursing and the laboratory work together at this stage.

Management: decontamination and Prussian blue

Skin decontamination

In Goiânia, the skin of all patients was decontaminated with mild soap and water, acetic acid and titanium dioxide (IAEA report on Goiânia). Decontamination only worked in part, because sweat brought back to the skin the cesium that was inside the body (IAEA report on Goiânia). Cleaning should stop when contamination stops falling or when it starts to injure the skin, with redness or excoriation (Kazzi et al., 2015). Contaminated wounds are irrigated with saline without causing further tissue damage, and large foreign bodies are removed with tweezers (Kazzi et al., 2015).

Prussian blue: dose by age

The Radiogardase label states, for adults and adolescents, 3 g orally three times a day, and for children aged 2 to 12 years, 1 g orally three times a day (Radiogardase label of 08/2014). Treatment should start as soon as possible after suspected internal contamination with cesium or thallium (Radiogardase label of 08/2014). The expected duration is 30 days or more, with reassessment by whole-body counting or by measurement in samples (Radiogardase label of 08/2014). REMM notes that, in Goiânia, the regimen was 1 to 3 g three times a day, usually starting with 1 g three times a day, and reached 10 to 12 g per day in heavy contamination (REMM, Prussian blue). REMM also says that below 2 years of age use requires emergency authorization or a research protocol (REMM, Prussian blue). A review confirms the dose of 3 g every 8 hours for at least 30 days in adults (Aaseth et al., 2019).

In the family in the scene, this means 3 g three times a day for the father and mother and 1 g three times a day for the 9-year-old son. The 3-year-old son is also in the label's age range. If there were a baby under 2 years old, the decision would be made with the health authority (REMM, Prussian blue). The capsules can be opened and mixed with food for those who cannot swallow, and this leaves the mouth and teeth blue (Radiogardase label of 08/2014).

Adverse effects and precautions

Constipation was reported in 10 of 42 treated patients, about 24 percent, and the label calls for monitoring and treatment (Radiogardase label of 08/2014). Prussian blue can bind to electrolytes in the intestine, and the label calls for monitoring electrolytes during treatment (Radiogardase label of 08/2014). Stools turn blue (Radiogardase label of 08/2014). A study in a digestive model showed that binding to cesium is minimal at pH 1 to 2 and maximal near pH 7 to 7.5 (Martínez-Alonso et al., 2025). The authors note that neither the European nor the American label gives guidance for people with low stomach acidity, such as those using a proton pump inhibitor (Martínez-Alonso et al., 2025). This is laboratory data, with no dose change yet.

Pregnancy and breastfeeding

Prussian blue is not absorbed by the intestine, and so no effect on the fetus is expected (Radiogardase label of 08/2014). But cesium-137 crosses the placenta (Radiogardase label of 08/2014). Cesium also passes from mother to baby through milk, and the label advises that women with internal cesium contamination not breastfeed (Radiogardase label of 08/2014).

Long-term follow-up

In Goiânia, a victim care center was created in 1987 and offers monitoring, diagnosis, treatment and follow-up (Li et al., 2022). An ecological study did not associate radiation with the incidence of breast cancer in the city (Lage et al., 2020). Another study found an increase in small variations in DNA copy number in the children of people exposed to low doses (Costa et al., 2018). The topic of follow-up will be covered in another text in this series.

Regulatory status: FDA and EMA

FDA

Radiogardase, insoluble Prussian blue capsules, has NDA 021626 at the FDA (Drugs@FDA, NDA 021626). The original approval was on 10/02/2003, as a new molecular entity, with priority review and orphan drug designation (Drugs@FDA, NDA 021626). A label revision was approved on 08/25/2008, and the current label, in the new format, was approved on 08/20/2014 (Drugs@FDA, NDA 021626) (Radiogardase label from 08/2014). The manufacturer is HEYL, from Berlin (Radiogardase label from 08/2014). Prussian blue is in the United States strategic national stockpile (REMM, Prussian blue), and the program of the American institute of infectious diseases funds new countermeasures for this stockpile (Rios and colleagues, 2014).

EMA

As of the 24 October 2026 search, there was no European public assessment report for Radiogardase or for Prussian blue at the EMA, meaning the drug has no centralized authorization. The study on pH cites a European label, which suggests national authorizations (Martínez-Alonso and colleagues, 2025). Availability outside the United States therefore depends on each country's rules.

How NEXO helps train this reasoning

In NEXO, the case of the day is fictional, with a real clinical presentation and up to six progressive clues, and you propose the diagnosis by searching for the ICD-10 code. Cesium contamination is a good exercise because the decisive clue, the object brought home, usually appears late in the story. The post on case-based learning explains why this format fixes knowledge.

Three exercises with cases

Change the age. Say what changes if the family had a 10-month-old baby.

Change the route. Say what changes if the father had an open wound contaminated with the powder.

Change the stomach. Say what you would monitor if the mother took a proton pump inhibitor every day.

The post on simulation of care helps train the arrival of a contaminated family as a team, and the post on clinical deterioration in the ward helps recognize worsening in the following weeks.

The limits of use of the game are described on the NEXO economy page. If you research teaching of clinical reasoning, the page for researchers explains how to get in touch. Professionals who write or review cases find information on curation and on creators, and institutions can learn about the proposal on the for partnerships page.

Frequently asked questions

Is a patient contaminated with cesium dangerous to the team?

They can contaminate the team and emit gamma radiation. Protection against contamination, distance and short contact time resolve most of the risk (Kazzi and colleagues, 2015) (Rump and colleagues, 2018).

Do I need to wait for the whole-body count to give Prussian blue?

No. The label advises starting as soon as possible after suspicion (Radiogardase label from 08/2014).

What is the dose for a 5-year-old child?

Per the label, 1 g orally three times a day (Radiogardase label from 08/2014).

How long does treatment last?

At least 30 days, with reassessment by count and by samples (Radiogardase label from 08/2014).

Can a contaminated mother breastfeed?

No. Cesium passes into milk (Radiogardase label from 08/2014).

Final checklist

• I treated what threatened life first.
• I called radiation protection and health surveillance.
• I removed the clothing and stored it in a double bag.
• I decontaminated the skin until the count stopped falling.
• I collected urine, feces and a blood count with a scheduled time.
• I gave Prussian blue at the age-appropriate dose.
• I monitored constipation and potassium.
• I gave guidance on breastfeeding and planned follow-up.

Want to practice reasoning with progressive clues? Play the case of the day.

References

1. Aaseth J, Nurchi VM, Andersen O. Medical Therapy of Patients Contaminated with Radioactive Cesium or Iodine. Biomolecules. 2019. PMID 31835766.
2. Costa EOA, Pinto IP, Gonçalves MW, et al. Small de novo CNVs as biomarkers of parental exposure to low doses of ionizing radiation of caesium-137. Sci Rep. 2018. PMID 29651024.
3. Food and Drug Administration. Drugs@FDA: FDA-Approved Drugs. NDA 021626, Radiogardase. Accessed on 24/10/2026. Official source.
4. Hayano RS, Tsubokura M, Miyazaki M, et al. Internal radiocesium contamination of adults and children in Fukushima 7 to 20 months after the Fukushima NPP accident as measured by extensive whole-body-counter surveys. Proc Jpn Acad Ser B Phys Biol Sci. 2013. PMID 23574806.
5. HEYL Chemisch-pharmazeutische Fabrik. RADIOGARDASE (prussian blue insoluble) capsules, for oral use. Leaflet revised in 08/2014. Official source.
6. International Atomic Energy Agency. THE RADIOLOGICAL ACCIDENT IN GOIANIA. Vienna: IAEA, 1988. Official source.
7. Kazzi Z, Buzzell J, Bertelli L, et al. Emergency department management of patients internally contaminated with radioactive material. Emerg Med Clin North Am. 2015. PMID 25455668.
8. Lage LB, Freitas-Junior R, Corrêa RDS, et al. Evaluation of ionizing radiation as a risk factor for the incidence of breast cancer: long-term analysis after the cesium-137 accident in Goiânia, Brazil. An ecological study. Sao Paulo Med J. 2020. PMID 32813846.
9. Li C, Alves Dos Reis A, Ansari A, et al. Public health response and medical management of internal contamination in past radiological or nuclear incidents: A narrative review. Environ Int. 2022. PMID 35378442.
10. Li C, Ansari A, Etherington G, et al. Managing Internal Radiation Contamination Following an Emergency: Identification of Gaps and Priorities. Radiat Prot Dosimetry. 2016. PMID 27521210.
11. Martínez-Alonso B, Torrado Durán G, Pardo Laurel H, et al. Prussian Blue Tablets for Cesium Decorporation: pH-Dependent Performance Under Normogastric and Hypochlorhydric Conditions in an In Vitro Gastrointestinal Model. Pharmaceuticals (Basel). 2025. PMID 41304948.
12. Ohba T, Amir I, Yoshida K, et al. Challenges and perspectives for internal radiation exposure examinations using the whole-body counting system following the Fukushima Daiichi nuclear power plant accident. Front Public Health. 2026. PMID 42577197.
13. Orita M, Hayashida N, Nukui H, et al. Internal radiation exposure dose in Iwaki city, Fukushima prefecture after the accident at Fukushima Dai-ichi Nuclear Power Plant. PLoS One. 2014. PMID 25478794.
14. Radiation Emergency Medical Management. Managing Internal Radiation Contamination. Accessed on 24/10/2026. Official source.
15. Radiation Emergency Medical Management. Prussian Blue. Accessed on 24/10/2026. Official source.
16. Rios CI, Cassatt DR, Dicarlo AL, et al. Building the strategic national stockpile through the NIAID Radiation Nuclear Countermeasures Program. Drug Dev Res. 2014. PMID 24648046.
17. Rump A, Becker B, Eder S, et al. Medical management of victims contaminated with radionuclides after a "dirty bomb" attack. Mil Med Res. 2018. PMID 30086798.