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A member of the Alkali Metals Group, sodium is not found as a free element in the Earth's crust due to its high reactivity. Oceans and other bodies of water owe their saline nature to the compound, sodium chloride (NaCl), known as "common salt."
From soaps to salt, glasses to textiles, photography to explosives, sodium compounds play a major role in industry. The element's abundance also extends beyond the Earth out into the universe, as it is a constituent of the light spectrum of our Sun and many other stars.
An essential element to the chemical industry and indispensable to the commercial world, sodium is also vital to the human body. Its varying concentration as an extracellular cation is responsible for the pulse signaling inside nerve cells. Interference with the mobility of Na+ ions can result in devastating neurological effects ranging from numbness to incoherent speech and even respiratory paralysis.
Paralytic shellfish poisoning (PSP) toxins can cause adverse neurological symptoms in humans. Saxitoxin is one PSP toxin that temporarily inhibits the permeability of sodium ions. The National Research Council Canada (NRC) discovered high levels of saxitoxin, normally found in shellfish, in pufferfish from Florida associated with a poisoning incident in April 2002. Researchers hypothesized that these normally non-toxic Atlantic puffers may have consumed saxitoxin-contaminated shellfish. Previously, NRC and its industrial partner, Jellet Biotek Ltd., had developed a field test kit for detecting these PSP toxins. This cost-effective, user-friendly kit was designed to allow shellfish farmers to pre-screen their product before harvesting, thereby increasing the safety of shellfish products going to the market and reducing production costs. The test kit is now being used by US agencies to screen Atlantic pufferfish for saxitoxin.