Strontium

Strontium has a bad reputation because of its radioactive isotopes: Sr 89 (52 day half-life), Sr 90 (28 year half-life), Sr 91 (10 hour half-life), etc. These radioactive isotopes arise from nuclear fission of uranium and plutonium. In past years, atmospheric testing of nuclear devices resulted in contamination of grazing lands and the food chain with radioactive strontium. It is emphasized that the Sr level reported here does not reflect exposure to radioactive Sr.

Sr is chemically similar to calcium and is assimilated by plants and animals along with calcium. Studies with chicks show that vitamin D controls Sr assimilation just as it does for calcium. It is very probable that Sr assists in bone and calciferous tissue formation in humans, and clinical studies have been reported about treatment of osteoporosis with low doses of stable strontium. Controlled studies with animals have shown stimulation of bone formation with low levels of Sr in drinking water.

Elevated strontium in whole blood may reflect problems with calcium assimilation, parathyroid function, or vitamin D activity. Calcium and parathyroid hormone levels and vitamin D activity should be checked to directly assess such problems. Blood Sr levels may rise in osteoporosis (due to bone loss); calcium levels may also rise but may not be as pronounced.

A common reason for elevated whole blood Sr (with normal Ca, parathyroid, and vitamin D) is a high concentration of Sr in drinking water. This varies geographically; two areas having high Sr water are northwest Florida and southeast Wisconsin. Other environmental and occupational sources of Sr are: fireworks and road flares, a dental desensitizer ”Elecol”, diagnostic barium preparations used as radiopaque ”cocktails”, depilatories and luminous paints. Stable strontium has very low toxicity as an element, although there are toxic or corrosive Sr compounds such as Sr(OH)2.

Strontium incorporates into hydroxyl crystal lattice of bone, stimulates new cortical and cancellous bone formation, and decreases bone resorption by inhibiting osteoclastic activity. There are a number of stable isotopes of strontium, including 84Sr, 86Sr, 87Sr, and 88Sr. Radioactive strontium, 90Sr, is a nuclear waste product and a human carcinogen. Serum strontium levels have been evaluated during therapy to establish GI absorption. Strontium has been shown to concentrate in hair with increased environmental exposure. Like calcium and magnesium, strontium is deposited in bone. Conversely, it is mobilized from bone when blood calcium levels fall.