Strontium behaves like calcium and collects in bone; food safety interest centers on radioactive strontium-90 after nuclear releases, while stable strontium is mostly studied as a dietary and geographic tracer.
- Role: An alkaline earth element that substitutes for calcium in bone mineral, present in soils, crops, water and salt.
- Main exposure: Plant foods, drinking water and salt carry stable strontium; fallout can add strontium-90 to soil, crops, tea, mushrooms and fish.
- Key distinction: Radioactive strontium-90 is a radiation dose concern regulated through radiocesium screening; stable strontium has no toxicity threshold in the cited evidence.
This page draws on 20 peer-reviewed studies. The complete citation list is at the bottom of the page.
Overview
Strontium is an alkaline earth element that the body handles much like calcium, so it is taken up into bone and tooth mineral in place of calcium 1 2. The papers cited here split into two very different bodies of work. A smaller group deals with strontium-90, a radioactive fission product with a physical half-life of about 28.8 years that was released, in small amounts relative to radiocesium, by the Fukushima Daiichi accident 3 4. A larger group uses stable strontium, and especially the ratio of strontium-87 to strontium-86, as a natural tracer of where foods, animals and people come from, because the ratio in plants and skeletal tissue reflects the local geology of the food and water consumed 5 6 7.
For food safety, the practical questions are how much strontium-90 reaches staple foods after a nuclear release, how stable strontium moves from soil into crops, and which foods and waters are strontium-rich. The cited evidence answers the first two in part for Japan and gives scattered measurements for the third. It does not supply a human toxicity assessment for stable strontium.
Toxicology
The cited evidence does not establish a human dose-response relationship or toxicity threshold for stable strontium. The concern raised in the radiostrontium papers is radiological: strontium-90 accumulates in bone and is described as a potential cause of leukemia or bone cancer, a statement those papers make in their introductions rather than test 4 3. For dose assessment, Japanese surveillance work used an adult committed effective dose coefficient of 2.8 x 10^-5 mSv per becquerel of strontium-90 3.
The only direct toxicity data in the cited set are for plants. In spiked farm-soil microcosms, strontium chloride at 5 to 40 mM reduced germination vigor and growth of red fescue and red clover, with pre-germination exposure most damaging to red fescue; for example, red fescue shoot weight fell from 0.54 mg per plant in controls to 0.21 to 0.30 mg per plant across 5 to 40 mM 8. These doses are far above normal agricultural conditions.
Rodent studies in the set used stable strontium chloride as a stand-in for radiostrontium and focused on absorption, not harm 9 2. In one of them, kidney mineralization appeared in rats fed a 10 percent sodium alginate diet, which the authors attribute to excess sodium rather than to strontium 9.
Typical exposure routes
Food and drinking water are the routes the cited studies describe. Isotope studies across several regions rest on the observation that the strontium in bones and teeth comes from what an animal or person ate and drank while the tissue formed 5 6. Analysis of a single cattle tooth concluded that enamel strontium was wholly diet-derived, whereas lead in the same tooth also reflected release from the animal’s own skeleton 10.
Water can matter when its strontium content is high. In controlled rat feeding, Zurich tap water held 0.29 mg/L strontium while a commercial strontium-rich mineral water held 8.6 mg/L, about 30 times more, and rats given the mineral water had measurably different bone and incisor isotope ratios from rats on the same diet with tap water 11. In a marine fish, water supplied about 83 percent of the strontium in the ear stones and food only about 17 percent 12; this reflects fish physiology and cannot be carried over to people.
Salt is a further route. Two archaeological studies of cremated human bone from Belgium and the Netherlands found higher bone strontium in Roman-period groups, especially urban and military groups in the Netherlands, and linked it to salt-preserved and salt-rich foods 13 14.
For strontium-90, the cited route is fallout settling onto soil and vegetation and then entering crops and other foods 4 3.
Food sources
Strontium-90 in foods after Fukushima
Japan’s national food surveillance detected strontium-90 in 25 of 40 foods that also carried accident-derived radiocesium and in 8 of 13 that did not, at 0.028 to 0.87 Bq/kg fresh weight and 0.42 to 3.7 Bq/kg dry weight in the radiocesium-positive group 3. Levels in rice, wheat, soybeans, beef, freshwater fish and mushrooms fell within ranges recorded before the accident, so the survey found no clear accident-related increase 3. Bran fractions and dried leaf products carried the higher values, and a whole marbled flounder analyzed with its bones held about twice the strontium-90 of earlier muscle-only sea fish data 3.
| Study / location | Material / design | Metal species | Value (units and basis) | n | Interpretation / limitation |
|---|---|---|---|---|---|
| 1 Japan, 2011 to 2013 | Brown rice, radiocesium-positive | 90Sr | 0.036 to 0.071 Bq/kg fresh weight | 4 (3 detected) | Within pre-accident range; lowest LOD 0.02 Bq/kg |
| 1 Japan | Rice bran; wheat bran | 90Sr | 0.27 Bq/kg; 0.57 Bq/kg fresh weight | 1 each | Bran fractions higher than whole grain |
| 1 Japan | Crude wheat; soybean | 90Sr | 0.057 and 0.16 Bq/kg; 0.28 Bq/kg | 2; 1 | Soybean without accident radiocesium 0.15 Bq/kg |
| 1 Japan | Beef, radiocesium-positive | 90Sr | 0.028 and 0.081 Bq/kg | 5 (2 detected) | Only slightly above LOD |
| 1 Japan | Whole pond smelt and loach | 90Sr | 0.073 to 0.15 Bq/kg (positive); 0.028 to 0.17 Bq/kg (negative) | 4; 3 | Bones included; similar with or without accident radiocesium |
| 1 Japan | Dried mulberry leaf tea | 90Sr | 3.7 Bq/kg (positive); 2.0 to 5.5 Bq/kg (negative), dry weight | 1; 3 | Highest values; high even without accident radiocesium, consistent with older fallout |
| 1 Japan | Dried shiitake harvested 2010 | 90Sr | 0.88 Bq/kg dry weight | 1 | Pre-accident sample, shows background fallout |
| 2 eastern Japan, 2011 to 2012 | Soil and vegetation at hot spots | 90Sr | up to about 1 Bq/g | not stated in text | 1 to 4 powers of ten below cesium-137; per-sample data in supplement |
Strontium-90 was also detected in green tea (0.60 Bq/kg dry weight) and in wild mushrooms such as kuritake (0.52 Bq/kg) 3.
Stable strontium in crops, feeds, water and salt
A survey of 142 Japanese farm fields found a geometric mean of 78 mg/kg stable strontium in soil (range 12 to 360 mg/kg) and 1.6 mg/kg dry weight in the edible parts of crops (range 0.13 to 88 mg/kg, n = 146) 15. Leafy vegetables had the highest transfer factors and brown rice the lowest: geometric mean transfer factors were 0.27 for spinach, 0.17 for cabbage, 0.048 for tomato, 0.020 for potato, 0.014 for wheat and 0.0032 for brown rice 15. Crop calcium, not soil strontium, best explained how much strontium a crop held 15.
| Study / location | Material / design | Metal species | Value (units and basis) | n | Interpretation / limitation |
|---|---|---|---|---|---|
| 3 Japan, 142 fields | Agricultural soil, 0 to 20 cm | stable Sr | GM 78 mg/kg (12 to 360) | 142 | Background levels; analytical details in a separate report |
| 3 Japan | Edible crop parts, 25 crop types | stable Sr | GM 1.6 mg/kg dry weight (0.13 to 88) | 146 | Dry basis; several crops with 1 or 2 samples |
| 4 Switzerland and Germany, laboratory | Pelleted animal diets (insect, plant, meat meal) | stable Sr | 11.7, 19.6 and 26.4 µg/g | 9 aliquots each | Laboratory feeds, not human foods |
| 4 Zurich | Municipal tap water; commercial mineral water | stable Sr | 0.29 mg/L; 8.6 mg/L | 14; 2 | Single city and single product |
| 10 Scotland, microcosm | Red clover shoots, unspiked control; 40 mM spiked | stable Sr | 0.036 g/kg; 17.4 g/kg | 9; 3 | Forage legume; spiked doses far above field levels |
| 6 Belgium (literature values quoted) | Marine and rock salts | stable Sr | 10 to 153 ppm | 15 salts | Secondary values cited by the authors, not measured in that study |
The salt values in the last row, and the authors’ citation of up to 4.6 ppm in salted hams against 0.1 to 1.1 ppm in pork, are quoted from earlier studies and should be checked against the primary sources before use 13. They still indicate that salt, and particularly sea salt, can be a notable strontium source. An older paleodiet synthesis describes maize (corn) as a low-strontium food whose adoption lowered bone strontium in prehistoric Ontario 1.
The cited evidence contains no measured stable strontium concentrations in retail foods such as seaweed, milk or fish, and no total diet study.
Strontium isotopes and food origin
Strontium isotope ratios can verify where a food was produced. A New Zealand isotope map predicted the farm origin of 33 cow milk samples with closest predictions averaging 7.05 km from the true location 16. Overlapping isotope signatures between candidate regions can, however, prevent a confident assignment, as a reanalysis of archaeological maize from Chaco Canyon showed 17.
Regulatory limits
The cited evidence states no regulatory limit for stable strontium in food or water.
For radioactive strontium, Japan’s standards that took effect on 1 April of 2012 limit radiocesium to 100 Bq/kg in foods other than drinking water, milk and infant foods, and were set so that the dose from the target radionuclides, including strontium-90, would not exceed 1 mSv per year 3. Strontium-90 is not measured directly under this scheme; its contribution was built in through assumed ratios to cesium-137, reflecting an assumption that strontium-90 activity stays at or below 10 percent of cesium-137 4. Field and food data supported that assumption for the samples tested: no soil or vegetation sample exceeded the 10 percent ratio 4, and the highest committed effective dose ratio of strontium-90 to radiocesium in foods was 0.063 against the 0.5 assumed when setting the limit 3. The one exception was whole freshwater fish, whose observed strontium-90 to cesium-137 ratios of 0.0039 to 0.025 exceeded the estimated 0.000024; recalculating with the highest ratio did not change the derived radiocesium limit, because consumption of such fish is low 3.
Testing
Strontium-90 is a pure beta emitter and requires radiochemical separation before counting, which makes it slow and costly to measure compared with gamma-emitting radiocesium 3 4. Japanese food surveillance ashed samples at 600 degrees C, separated strontium by cation exchange or ferric chloride co-precipitation, and counted the yttrium-90 daughter on a low-background gas-flow counter, correcting for chemical recovery (mostly above 75 percent) and validating with IAEA reference materials; the lowest detection limit was 0.02 Bq/kg 3. Soil and vegetation work used a strontium-selective extraction resin and liquid scintillation counting with a strontium-85 recovery tracer (92.4 to 98.2 percent recovery) 4.
Stable strontium concentrations in the cited studies were measured by ICP-MS (limit of quantification 0.05 ppb in mouse bone digests) 2, by ICP-OES in plant tissue, water and skeletal samples 8 11 18, and by graphite furnace atomic absorption spectrometry in binding experiments 9. Isotope ratios were measured by multi-collector ICP-MS or thermal ionization mass spectrometry against the NIST SRM 987 standard 14 6.
One analytical caution applies to laboratories measuring rubidium: strontium-87 overlaps rubidium-87 in ICP-MS, and a reaction-cell method with fluoromethane gas was developed to remove this interference 19.
Microbiome effects
The cited evidence does not establish any effect of strontium on the gut microbiome. The only microbiological use in the set is strontium chloride as a selective ingredient in laboratory enrichment broth for isolating Salmonella, which says nothing about gut exposure 20.
Vulnerable populations
The cited evidence does not identify populations at higher risk from strontium. None of the papers measured strontium-90 or stable strontium intake in children, pregnant women or other groups, and the animal absorption studies were done in young male rodents 9 2.
Mitigation
Two animal studies tested foods and food additives that reduce strontium uptake from the gut. In rats fed diets with 10 percent sodium or calcium alginate for two weeks, plasma strontium fell to 63 to 77 percent of control, and the peak plasma concentration after an oral strontium chloride dose fell from 108 ng/mL in controls to 58 and 37 ng/mL; calcium alginate was judged safer because sodium alginate caused kidney mineralization 9. That paper also reports an IAEA recommendation of 4 g per person per day of sodium alginate for patients exposed to large amounts of radioactive strontium 9. In mice given a single oral strontium dose, kelp, its polysaccharide laminaran, and calcium alginate lowered femur strontium to 92.1, 80.2 and 75.4 percent of control after 24 hours, while a single dose of sodium alginate had no effect 2. Neither study establishes effective human doses.
For soils, red clover moved strontium into its shoots at translocation factors of 2.65 to 25.3, far more than red fescue, and its authors propose it for phytoremediation of contaminated ground 8. The same property means clover grown as forage on contaminated land would carry strontium into feed, a link the study did not test.
The cited evidence does not establish food processing steps that reduce strontium. Higher strontium-90 in rice and wheat bran than in whole grain suggests that the outer layers carry more of it, but no paper measured removal by milling or cooking 3.
Open questions
- No toxicity assessment or reference value for stable strontium in people appears in the cited evidence; Toxicology rests on plant data and background statements.
- No regulatory limit for stable strontium in food, water or supplements is stated in the cited papers.
- No measured stable strontium concentrations in retail foods, total diets or dietary supplements; Food sources relies on Japanese crops, laboratory feeds, two waters and literature values quoted for salt.
- No strontium-90 food data outside Japan, and no intake estimates from measured diets.
- Effects of strontium on the gut microbiome are not addressed.
- Vulnerable populations are not addressed; no data on children, pregnancy or bone-disease groups.
- Whether milling, washing or cooking removes strontium-90 or stable strontium from grains and leaves has not been measured.
- Human efficacy and safe doses of alginate or kelp as strontium-uptake countermeasures are unknown.
- Per-sample strontium-90 values for Fukushima soil and vegetation are only in an unarchived supplement.
What remains uncertain
Most of the 25 cited papers are archaeological or geological studies that use strontium isotope ratios as a tracer. They are strong evidence that skeletal strontium comes from food and water and that isotope ratios can verify geographic origin, but they say little about how much strontium people consume today or whether any intake is harmful.
The food-safety evidence that does exist is concentrated in Japan after Fukushima and in one national soil-to-crop survey. Strontium-90 levels in foods were low and close to pre-accident fallout ranges, many results sat near detection limits, and comparison groups differed in commercial status as well as contamination. Stable strontium crop data are on a dry-weight basis with limited samples for many crops.
Mitigation evidence comes from small rodent studies using large single or dietary doses of stable strontium. Two co-authors of the rat alginate study worked for the company that supplied the alginate, and the mouse study used alginates from the same supplier, so independent replication would strengthen confidence.
References
Works cited in this page’s text, in first-appearance order. See Sources for this page’s source inventory. Each title links to a source record with bibliographic details, reported findings, and document provenance.
- Paleonutrition in Southern Ontario: Evidence from strontium and stable isotopesPeer-reviewed
- Exploration of food materials and components showing the suppressing effect on absorption of strontium and the promoting effect on excretion of cesium in vivoPeer-reviewed
- Surveillance of Strontium-90 in Foods after the Fukushima Daiichi Nuclear Power Plant AccidentPeer-reviewed
- Concentration of Strontium-90 at Selected Hot Spots in JapanPeer-reviewed
- A strontium isoscape for the Conchucos region of highland Peru and its application to Andean archaeologyPeer-reviewed
- Bioavailable soil and rock strontium isotope data from IsraelPeer-reviewed
- The IRHUM (Isotopic Reconstruction of Human Migration) database: bioavailable strontium isotope ratios for geochemical fingerprinting in FrancePeer-reviewed
- Toxicological response and bioaccumulation of strontium in Festuca rubra L. (red fescue) and Trifolium pratense L. (red clover) in contaminated soil microcosmsPeer-reviewed
- Alginate Enhances Excretion and Reduces Absorption of Strontium and Cesium in RatsPeer-reviewed
- Sequential multi-isotope sampling through a Bos taurus tooth from Stonehenge, to assess comparative sources and incorporation times of strontium and leadPeer-reviewed
- Strontium Uptake and Intra-Population 87Sr/86Sr Variability of Bones and Teeth: Controlled Feeding Experiments With Rodents (Rattus norvegicus, Cavia porcellus)Peer-reviewed
- Water, not food, contributes the majority of strontium and barium deposited in the otoliths of a marine fishPeer-reviewed
- Strontium isotopes and concentrations in cremated bones suggest an increased salt consumption in Gallo-Roman dietPeer-reviewed
- Global tastes, local choices: Strontium isotope and concentration evidence for changing dietary input in Roman Nijmegen, the NetherlandsPeer-reviewed
- A Statistical Approach to Estimating Soil-to-Plant Transfer Factor of Strontium in Agricultural FieldsPeer-reviewed
- A bioavailable strontium (87Sr/86Sr) isoscape for Aotearoa New Zealand: Implications for food forensics and biosecurityPeer-reviewed
- Strontium Isotopes and the Reconstruction of the Chaco Regional System: Evaluating Uncertainty with Bayesian Mixing ModelsPeer-reviewed
- Strontium isotope analysis on human skeletal remains from the Hobi and Ikawazu shell-mounds in Aichi Prefecture, JapanPeer-reviewed
- Determination of Rubidium by ID-ICP-QMS/QMS with Fluoromethane as the Reaction Cell Gas to Separate Spectral Interference from StrontiumPeer-reviewed
- An evaluation of strontium chloride, Rappaport and strontium selenite enrichment for the isolation of salmonellas from man, animals, meat products and abattoir effluentsPeer-reviewed
Sources
- Strontium-90 in Japanese foods after Fukushima (2015; peer-reviewed): measured strontium-90 in 53 foods and the design basis of Japan’s radionuclide food limits.
- Strontium-90 at Fukushima hot spots (2013; peer-reviewed): strontium-90 in soil and vegetation relative to cesium-137 and the 10 percent screening assumption.
- Soil-to-crop strontium transfer in Japan (2009; peer-reviewed): stable strontium in 142 farm soils and crops with crop-specific transfer factors.
- Rodent controlled feeding and strontium uptake (2020; peer-reviewed): strontium in laboratory feeds and two drinking waters and their effect on skeletal isotope ratios.
- Water versus food strontium in fish ear stones (2006; peer-reviewed): water supplied most otolith strontium in a marine fish.
- Cremated bone strontium and Roman salt use (2022; peer-reviewed): higher Roman-period bone strontium linked to salt; quotes literature values for salts and meats.
- Bone strontium in Roman Nijmegen (2026; peer-reviewed): bone strontium by period and context, consistent with salt-rich foods.
- Alginate and strontium absorption in rats (2013; peer-reviewed): dietary alginate lowered strontium absorption; supplier co-authors.
- Kelp, laminaran and strontium uptake in mice (2016; peer-reviewed): food materials that lowered femur strontium after an oral dose.
- Strontium in red fescue and red clover (2023; peer-reviewed): plant toxicity and shoot accumulation in spiked soils.
- New Zealand strontium isoscape and milk origin (2022; peer-reviewed): isotope map validated on cow milk origin.
- Strontium isoscape for highland Peru (2021; peer-reviewed): food and water as the source of skeletal isotope signatures.
- Bioavailable strontium isotopes in Israel (2020; peer-reviewed): soil and rock isotope baselines for provenance work.
- French bioavailable strontium isotope database (2014; peer-reviewed): isotope baselines for France, including food provenance uses.
- Bone strontium and paleodiet in Ontario (1986; peer-reviewed): bone strontium as a diet indicator; maize as a low-strontium food.
- Strontium and lead in a Stonehenge cattle tooth (2025; peer-reviewed): enamel strontium tracked diet while lead also reflected skeletal stores.
- Strontium isotopes in Jomon shell-mound burials (2022; peer-reviewed): calcium to strontium ratios measured by ICP-OES in archaeological skeletons.
- Strontium interference in rubidium ICP-MS (2018; peer-reviewed): off-topic for dietary exposure: an analytical method in which strontium is only an interferent.
- Strontium chloride broth for Salmonella (1972; peer-reviewed): off-topic for dietary exposure: strontium salts used as culture-medium ingredients.
- Uncertainty in strontium sourcing of Chaco maize (2014; peer-reviewed): limits of isotope-based food origin assignment.
- Strontium isotopes and Iron Age sheep in Catalonia (2018; peer-reviewed): off-topic for dietary exposure: archaeological livestock provenance from isotope ratios.
- Strontium isotopes and Neanderthal land use (2019; peer-reviewed): off-topic for dietary exposure: paleolithic mobility from isotope ratios.
- Strontium isotopes in Mesolithic fish teeth (2021; peer-reviewed): off-topic for dietary exposure: archaeological fish provenance.
- Strontium and oxygen isotopes in Neolithic Syria (2025; peer-reviewed): off-topic for dietary exposure: human mobility from isotope ratios.
- Strontium-containing phosphate glass (2024; peer-reviewed): off-topic for dietary exposure: materials properties of a glass.
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