Magnesium sulfate can even pollute water if used in excessive amounts.Magnesium sulfate was historically used as a treatment for lead poisoning prior to the development of chelation therapy, as it was hoped that any lead ingested would be precipitated out by the magnesium sulfate and subsequently purged from the digestive system. This application saw particularly widespread use among veterinarians during the early-to-mid 20th century; Epsom salt was already available on many farms for agricultural use, and it was often prescribed in the treatment of farm animals that inadvertently ingested lead. Food preparation
Magnesium sulfate is used as

Brewing salt in making beer. coagulant for making tofu. Salt substitute. Chemistry
Anhydrous magnesium sulfate is commonly used as a desiccant in organic synthesis owing to its affinity for water and compatibility with most organic compounds. During work-up, an organic phase is treated with anhydrous magnesium sulfate. The hydrated solid is then removed by filtration, decantation, or by distillation (if the boiling point is low enough). Other inorganic sulfate salts such as sodium sulfate and calcium sulfate may be used in the same way. Construction
Magnesium sulfate is used to prepare specific cements by the reaction between magnesium oxide and magnesium sulfate solution, which are of good binding ability and more resistance than Portland cement. This cement is mainly adopted in the production of lightweight insulation panels. Weakness in water resistance limits its usage.
It decomposes without melting at 1124 °C into magnesium oxide (MgO) and sulfur trioxide (SO3). Heptahydrate
The heptahydrate takes its common name "Epsom salt" from a bitter saline spring in Epsom in Surrey, England, where the salt was produced from the springs that arise where the porous chalk of the North Downs meets the impervious London clay. The heptahydrate readily loses one equivalent of water to form the hexahydrate. It is a natural source of both magnesium and sulphur. Epsom salts are commonly used in bath salts, exfoliants, muscle relaxers and pain relievers. However, these are different from Epsom salts that are used for gardening, as they contain aromas and perfumes not suitable for plants. Monohydrate
Magnesium sulfate monohydrate, or kieserite, can be prepared by heating the heptahydrate to 120 °C. Further heating to 250 °C gives anhydrous magnesium sulfate. Undecahydrate
The undecahydrate MgSO4·11H2O, meridianiite, is stable at atmospheric pressure only below 2 °C. Above that temperature, it liquefies into a mix of solid heptahydrate and a saturated solution. It has a eutectic point with water at −3.9 °C and 17.3% (mass) of MgSO4. Large crystals can be obtained from solutions of the proper concentration kept at 0 °C for a few days.At pressures of about 0.9 GPa and at 240 K, meridianiite decomposes into a mixture of ice VI and the enneahydrate MgSO4·9H2O. Enneahydrate
The enneahydrate MgSO4·9H2O was identified and characterized only recently, even though it seems easy to produce (by cooling a solution of MgSO4 and sodium sulfate Na2SO4 in suitable proportions).