The Grease Thickeners Category includes 11 substances comprised of the lithium and calcium salts of fatty acids. These salts are used to thicken mineral oil and create greases. For this use they are not synthesized as the “pure” compounds and seldom exist except in the presence of the oil matrix. One or more fatty acids are dissolved in mineral oil and then a metal hydroxide such as calcium hydroxide or lithium hydroxide is added. The metal hydroxide and fatty acid react to form the insoluble metal salt of the fatty acid. The resulting compounds gel the mineral oil into a functional grease. Greases typically contain from 1 to 14 % thickener by mass. Greases are used in the lubrication of bearings and other moving parts in virtually every segment of transportation and industry. Most finished lubricants are mixtures of oils and additives but greases are one of the few types of lubricants that involve an actual chemical reaction during their manufacture.  

To meet the HPV Challenge, the Testing Group has thoroughly evaluated grease thickeners and has made all of the reliable human health and ecological hazard data available to the public. Since the fatty acids used to make the salts in this category are edible themselves or closely related to edible fats and oils, hazard characterization is focused on the metal ions, calcium and lithium. However, greases thickened with aluminum, calcium or lithium soaps have been widely and safely used in industry for several decades.

• The Category Assessment Document (CAD) for Grease Thickeners submitted to EPA by API which includes the final chemical hazard characterization and considers any new testing and analysis carried out for substances within the category.

• The Robust Summary for Grease Thickeners  submitted to EPA by the American Petroleum Institute (API) which summarizes the available reliable data on physic-chemical properties, environmental fate and transport pathways, ecotoxicity, and human health toxicity.

• The EPA Screening-Level Hazard Characterization  for Grease Thickeners which summarizes EPA’s views on the available data for the category and on the need for additional studies to fill data gaps.

• The API Petroleum HPV Testing Group’s response  to the EPA Screening-Level Hazard Characterization.