Atomic Elements, Human, Non-Essential or Toxic Elements

Strontium (Sr)

23
May

Strontium (Sr) is a naturally occurring chemical element found in the environment and certain foods, but unlike essential minerals like calcium or magnesium, its role in the human body is limited and not fully understood. While it shares some properties with calcium, strontium’s health effects, both potential benefits and risks, have sparked interest. This article provides a clear, engaging, and scientifically accurate overview of strontium, empowering you to understand its properties, sources, and practical steps to manage exposure for better health.

What Is Strontium?

Basic Chemical and Physical Properties

  • Atomic Number: 38
  • Symbol: Sr
  • Appearance: Strontium is a soft, silvery-white or yellowish metal that tarnishes quickly in air.
  • Classification: An alkaline earth metal in the periodic table, often found in minerals like celestite (strontium sulfate) and strontianite (strontium carbonate).
  • Properties: Strontium is reactive, similar to calcium, and forms compounds used in fireworks, ceramics, and medical applications. Its radioactive isotopes, like strontium-90, are a health concern due to environmental contamination.

Strontium’s similarity to calcium allows it to interact with biological systems, but its role in human health is complex and not essential.

Where Is Strontium Found?

Natural Occurrence and Common Sources

  • Environmental Presence: Strontium is naturally present in the Earth’s crust, primarily in minerals like celestite and strontianite. It’s released through weathering, volcanic activity, and human activities like mining or nuclear fallout (for radioactive strontium-90).
  • Exposure Routes:
    • Dietary Sources:
      • Leafy greens (e.g., spinach, kale), grains, and root vegetables grown in strontium-rich soils.
      • Dairy products (e.g., milk, cheese) and seafood, which may contain trace amounts.
      • Drinking water, especially from groundwater in areas with high strontium levels.
    • Environmental Sources:
      • Soil and dust in regions with naturally high strontium or near industrial sites.
      • Air and water contaminated by radioactive strontium-90 from nuclear testing or accidents (e.g., Chernobyl, Fukushima).
    • Other Sources:
      • Occupational exposure in industries like ceramics, glass manufacturing, or pyrotechnics.
      • Medical applications, such as strontium ranelate (used in some countries for osteoporosis) or strontium-89 for cancer treatment.
      • Consumer products like fireworks or specialty glass containing strontium compounds.

Most dietary strontium comes from plant-based foods and water, with exposure varying by region and soil composition.

Strontium in the Human Body

Biological Importance and Functions

  • Limited Role: Strontium is not an essential nutrient, but it can incorporate into bones and teeth due to its chemical similarity to calcium.
  • Metabolism: Strontium is absorbed in the gut (about 20–30% of ingested strontium), binds to proteins in blood, and is deposited in bones or excreted via urine and feces. Its half-life in bones is several years.
  • Potential Effects: At low levels, stable strontium may support bone density in specific medical contexts, but excessive or radioactive forms are harmful.

How It Affects the Body

  • Strontium mimics calcium, incorporating into bone tissue and potentially affecting bone formation or remodeling.
  • Radioactive strontium-90 is particularly dangerous, as it emits beta radiation, damaging bone marrow and increasing cancer risk.

Health Impacts of Strontium Exposure

Health Benefits and Deficiency Symptoms

  • Potential Benefits:
    • Therapeutic Uses: Strontium ranelate, a prescription drug in some countries, has been used to treat osteoporosis by promoting bone formation and reducing bone loss. However, its use is limited due to cardiovascular risks.
    • No nutritional benefits are associated with dietary strontium, as it’s not essential.
  • Deficiency Symptoms:
    • No deficiency state exists, as strontium is not required for human health.
    • Lack of strontium has no adverse effects, as the body relies on calcium for similar functions.

Health Risks and Toxicity

Stable strontium is generally safe at low dietary levels, but excessive or radioactive exposure poses risks. The International Agency for Research on Cancer (IARC) classifies radioactive strontium-90 as a carcinogen.

  • Bone Health:
    • High doses of stable strontium may disrupt bone mineralization, leading to rickets-like symptoms or weakened bones, especially in children or those with low calcium intake.
  • Cancer:
    • Radioactive strontium-90 exposure increases the risk of bone cancer and leukemia due to its accumulation in bone marrow.
  • Cardiovascular Effects:
    • Strontium ranelate is linked to increased risk of heart attack and blood clots, limiting its medical use.
  • Other Effects:
    • Chronic high exposure to stable strontium may impair kidney function or cause skin rashes.

Symptoms of Acute Exposure

  • High-level exposure to stable strontium (e.g., from medications) may cause:
    • Nausea, diarrhea, or abdominal discomfort.
    • Skin irritation or rashes.
  • Acute exposure to radioactive strontium-90 is rare but may cause radiation sickness (e.g., nausea, fatigue, or bone marrow suppression).

Symptoms of Chronic Exposure

  • Low-level, long-term exposure to stable strontium may result in:
    • Bone pain or weakened bones.
    • Kidney dysfunction or fatigue.
  • Chronic exposure to strontium-90 may lead to:
    • Bone marrow damage, anemia, or increased cancer risk.

Strontium in Supplements or Nutrition

Limited Use in Supplements

  • Strontium is not a standard ingredient in dietary supplements due to its non-essential status and potential risks.
  • Strontium ranelate or citrate is sometimes marketed for bone health, but these are not widely recommended due to safety concerns. Choose supplements from reputable brands with third-party testing to avoid contamination.
  • Trace contamination may occur in supplements derived from plants grown in strontium-rich soils.

Recommended Intake and Exposure Limits

No Recommended Intake

  • Strontium is not a nutrient, so there’s no dietary requirement.
  • Health organizations set tolerable exposure limits for stable strontium:
    • The World Health Organization (WHO) suggests a tolerable daily intake of 0.13 mg/kg body weight for stable strontium (e.g., ~9 mg/day for a 70 kg adult).
    • No safe level exists for radioactive strontium-90, as even low exposure increases cancer risk.
  • The U.S. Environmental Protection Agency (EPA) sets a drinking water limit of 4 mg/L for stable strontium.

Typical Exposure

  • Dietary intake typically ranges from 1–5 mg/day, primarily from plant-based foods and water, well within safe limits for stable strontium.
  • Radioactive strontium-90 exposure is minimal in most populations but higher in areas affected by nuclear fallout.

Minimizing Exposure

  • Dietary Choices:
    • Ensure adequate calcium intake to reduce strontium absorption, as they compete for uptake.
    • Wash produce thoroughly to remove soil containing strontium.
    • Diversify diet to limit reliance on foods from strontium-rich regions.
  • Home Safety:
    • Test well water for strontium in areas with high natural levels or near industrial sites.
    • Avoid using ceramics or glass with strontium-based glazes for food storage.
  • Lifestyle:
    • Avoid exposure to radioactive strontium by following local advisories in areas affected by nuclear contamination.
    • Use caution with strontium-containing supplements unless prescribed by a healthcare provider.
  • Supplements:
    • Choose brands with third-party testing for heavy metal and radioactive contamination.

Safety Considerations and Toxicity Risks

Safety Profile

  • Stable strontium is safe in small dietary amounts but can be harmful in excess, particularly in children or those with low calcium intake.
  • Radioactive strontium-90 is highly dangerous due to its carcinogenic properties.
  • Populations at higher risk include:
    • Residents in areas with strontium-rich soils or nuclear fallout.
    • Individuals using strontium-based medications without medical supervision.
    • Workers in industries like ceramics or pyrotechnics.

Toxicity Thresholds

  • Stable Strontium: Harmful effects, like bone disruption, may occur at intakes above 10–20 mg/day over time.
  • Radioactive Strontium-90: Even low-level exposure increases cancer risk due to its radioactive nature.
  • Acute Poisoning: Rare for stable strontium but possible with high doses from medications, causing gastrointestinal or skin issues.

Interactions

  • Strontium competes with essential nutrients:
    • Calcium: Adequate calcium intake reduces strontium absorption and mitigates bone-related risks.
    • Phosphorus: Balanced phosphorus supports bone health and may limit strontium’s effects.
    • Vitamin D: Enhances calcium absorption, further reducing strontium uptake.
  • A nutrient-rich diet with sufficient calcium, phosphorus, and vitamin D can help protect against strontium toxicity.

Fun Fact

Did you know strontium gives fireworks their vibrant red color? Strontium compounds, like strontium carbonate, are used in pyrotechnics to create dazzling red hues, lighting up celebrations worldwide while being carefully managed to avoid environmental harm!

Empowering Your Health Choices

Strontium, while not essential, is a part of your diet and environment, and understanding its role can help you manage exposure wisely. By prioritizing calcium-rich foods, testing water sources, avoiding unnecessary strontium supplements, and following safety guidelines in contaminated areas, you can keep your exposure within safe bounds. If you suspect strontium exposure, especially to radioactive forms, consult a healthcare provider for testing and guidance. Stay informed and keep your health in balance!