Sodium benzoate (potassium benzoate)
Described also as benzoate of sodium and usually listed as E211, sodium benzoate is the sodium salt of benzoic acid. It’s the oldest chemical preservative to be used in the cosmetic, personal care product, food, and pharmaceutical industry, and the first preservative to be approved by the US Food and Drug Administration for use in foods. It’s industrially produced by reacting sodium hydroxide with benzoic acid, or adding benzoic acid to a hot sodium bicarbonate solution. Note that potassium benzoate can be used as a sodium benzoate substitute.
Exposure - via skin contact, inhalation, or ingestion - is generally believed to be safe. However, it’s been linked with a number of health concerns, including asthma attack, anaphylactic shock, hay fever (rhinitis), and hives (urticaria). These symptoms usually appear, even at low concentrations, shortly after exposure and disappear within a few hours. Sodium benzoate can also create free radicals and damage mitochondrial DNA which may trigger cell mutation, cancer, and speed up the aging process. Acute toxicity is generally low within the healthy, general population but it can cause contact dermatitis, a condition that can be exacerbated in asthmatics. The chemical’s been linked with developmental abnormalities as well as hyperactivity in children.
Sodium benzoate doesn’t contain benzene, a cancer-causing agent associated with increased risk of leukemia and other blood cancers. However, when it combines with vitamin C (ascorbic acid) or citric acid (in orange for example), it forms benzene. You can reduce your exposure to benzene by limiting the consumption of soft drinks and consumer items that contain both sodium benzoate and vitamin C.
Sodium benzoate is a known neurotoxin, i.e. it can act on the nervous system and damage nerves or nerve tissue. Significant amounts are released into the environment - through the regular use of personal care products, cosmetics, food, and dentifrices - causing harm to aquatic and terrestrial organisms.