Chromium(III) sulfate, ([Cr(H2O)6]2(SO4)3), is the most efficient and effective tanning agent.
Chromium is present in the environment in different forms. Its most common stable valence states are Cr0, which is chromium as an elemental metal, and trivalent chromium or Cr3, and hexavalent chromium or Cr6.
Cr0 and Cr6 are generally produced by industrial processes such as the chrome plating of steel. Cr3 occurs naturally in the environment and is considered in the United States to be an essential nutrient. Cr3 is found in vegetables, meats, fruits, grains, and yeast, and it is essential for insulin, sugar, and lipid metabolism.
Cr6 has been clearly established to be toxic to humans and a carcinogen. Cr3 is significantly less toxic (about 1,000 times less toxic than Cr6).
Cr6 is commonly known as “the Erin Brockovich chemical”. In 1993 she was instrumental in building a case against Pacific Gas & Electric Company (PG&E) involving groundwater contamination in Hinkley, California. PG&E had been using Cr6 to prevent rust at its natural gas pumping station, but the waste Cr6 had seeped into the local groundwater and caused cancer in Hinkley’s residents.
The case was settled in 1996 for $333 million and was the largest settlement ever paid in a direct-action lawsuit in United States history to that date. The law firm she clerked for received $133.6 million, and Brockovich received $2.5 million as part of her fee.
In the 2000 movie named for her, Erin Brockovich was played by Julia Roberts. Julia Roberts won the 2001 best actress Oscar for her portrayal of the relentless and determined Brockovich.
Erin Brockovich —
Hinkley CA, near Barstow in Southern California’s Mojave Desert, is about 100 miles NE of Los Angeles —