Many of the recommendations that we have encountered from the medical profession for decades has been based on bad data.
Additives to Iodized Table Salt
Iodine:
Iodine is often added in the form of potassium iodide, sodium iodide, or sodium iodate.
Dextrose (a sugar) is added to stabilize the iodine.
Sodium fluoride: Sodium fluoride is a chemical added to prevent dental caries. While many claims about it strengthening tooth enamel, this would be true if we are sharks (Ca5(PO4)3F). Human enamel doesn't. The chemical breakdown of the inorganic components of teeth is Ca10(PO4)6·2(OH) and small quantities of other elements such as Na, Cl and Mg. The formula of Sodium fluoride is NaF. In other words, while perhaps the Na component of Sodium fluoride is of some use, it really has nothing to do with the chemical composition of human teeth. As a poison fluoride is symptomatic as low as 0.1 to 0.3 milligrams of fluoride for every kilogram of bodyweight. The concentration of fluoride is .1 milligrams per gram of toothpaste.
Iron: "Doubly-fortified" salt is available for iron deficient diets. It contains both iron salts and iodide. In small amounts most things are safe but this should only be used by people low in iron.
Folic acid (Vitamin B9). Folic acid helps prevent neural tube defects for pregnant women. Unfortunately it is added to multiple foods. It is associated with gluten intolerance, cancer and heart disease. Too much of a good thing can be bad.
Table salt has anti-caking agents to prevent the grains from sticking together. This includes:
Calcium aluminosilicate (CaAl2Si2O8): While there is no clear understanding of the role that aluminum has with Alzheimer's some research shows that it is associated with the development of the amyloid precursor protein. My own spin on this is that the kidney normally removes aluminum from the body. Insulin resistance impairs proper kidney function as it intermediates in low grade infections through the production of several adipocyte-derived pro-inflammatory bioactive proteins.
Calcium carbonate: Calcium carbonate is not very dangerous (it is found in antacid tablets) but long term use can harm kidney function
Calcium silicate: Silica is an important element for good health. Just as sodium is necessary it must be balanced with potassium. Where calcium and silica have been seen in arterial plaques it possibly is a lack of Vitamin K2 that causes an imbalance.
Fatty acid salts (acid salts): Is not shown to have any risks for humans
Magnesium carbonate: At the level found as a salt additive has a low risk for humans.
Magnesium oxide: Not recommended to breath it as will cause irritation.
Silicon dioxide: Is not shown to have any risks for humans
Sodium aluminosilicate: Only the same concern as Calcium aluminosilicate (be wary if there is kidney damage)
Sodium ferrocyanide or yellow prussiate of soda: Ferrocyanides do not appear to accumulate in the human body so limited exposure to the chemical should be not a problem.
Tricalcium phosphate: Both calcium and phosphorus are critical nutrients. As all things are healthy if kept in balance.
Himalayan Salt
While it contains a healthy amount of sodium chloride as well as sulphate, magnesium, calcium, potassium, bicarbonate, bromide, borate, strontium, and fluoride.
Sea Salt
Where the salts are harvested from regardless of the type will cause a variation in composition. "Celtic Sea Salts" have been found to have the following elements:
Chloride
Sodium
Sulfur
Magnesium
Potassium
Calcium
Silicon
Carbon
Iron
Aluminum
Praseodymium
Strontium
Zinc
Copper
Erbium
Tin
Manganese
Cerium
Fluoride
Rubidium
Gallium
Boron
Titanium
Bromine
This information was taken from Celtic Sea Salts Analysis which also has additional information about the value/hazard of each element.