REVIEW Naphthenic acid (NAs) is the name for an unspecific mixture of several cyclopentyl and cyclohexyl carboxylic acids with molecular weight of 120 to well over 700 atomic mass units. The main fraction are carboxylic acids with a carbon backbone of 9 to 20 carbons. McKee et al. claim that "naphthenic acids (NAs) are primarily cycloaliphatic carboxylic acids with 10 to 16 carbons." Salts of naphthenic acids, which are naphthenates, are widely used as hydrophobic sources of metal ions in diverse applications.
Richard H. McKee, Colin M. North, Paula Podhasky, Jeffrey H. Charlap, Adam Kuhl (February 2014). "Acute and Subchronic Mammalian Toxicity of Naphthenic Acids from Oil Sands Tailings". International Journal of Toxicology 33 (1): 347-355.