Diethanolamine

Diethanolamine (DEA) is produced by the reaction of ethylene oxide with ammonia, which simultaneously yields mono-, di-, and triethanolamine; the ratio of products is controlled by adjusting the reaction conditions. [1] It is a high-production-volume chemical (hundreds of millions of pounds per year in the US) with applications spanning industrial gas scrubbing (DEA solutions absorb acid gases like CO₂ and H₂S in natural gas sweetening and refinery operations), metalworking fluids (corrosion inhibitor, pH buffer), agricultural emulsifiers, and — most significantly for consumer exposure — cosmetics and personal care products, where DEA and its fatty acid esters (DEA-cocoamide, lauramide DEA) are used as surfactants, foam stabilizers, and pH adjusters in shampoos, body washes, liquid soaps, and lotions. [2] NTP dermal application studies found clear evidence of liver carcinogenicity (hepatocellular carcinomas) in B6C3F1 mice, including at low doses that simulated consumer product exposure levels, prompting a 1998 NTP finding and FDA consumer advisory recommending reduction of DEA in rinse-off cosmetic products. [3] The carcinogenic mechanism is thought to involve depletion of choline — DEA competes with choline for incorporation into phosphatidylcholine, depleting a critical nutrient important for DNA methylation and liver cell maintenance. This mechanism is non-genotoxic and may not apply equally to humans. Nevertheless, DEA remains on the list of chemicals under scrutiny, and its use in cosmetics has declined in some markets while remaining prevalent in others.

Consumer dermal exposure from cosmetic and personal care products (shampoos, lotions, liquid soaps) is the dominant pathway for the general public — these products are applied directly to skin and sometimes scalp. Industrial workers in natural gas processing, petroleum refining, metalworking, and chemical manufacturing have occupational inhalation and dermal exposures. Agricultural workers handling DEA-emulsified pesticide formulations have skin exposure.

The NTP finding of hepatocellular carcinomas at low dermal doses in mice raised specific concern because the doses used were in a range potentially relevant to repeated consumer product use. [3] The choline-depletion mechanism is biologically plausible. While FDA has not required DEA removal from cosmetics, the NTP recommended that consumers choose DEA-free products where possible, especially for products that remain on the skin (leave-on products vs. rinse-off products). Acute toxicity at typical consumer exposure concentrations is low; DEA is a mild skin sensitizer in some individuals.

Industrial workers in gas sweetening and metalworking fluid operations face the highest occupational exposures. Consumers who regularly use DEA-containing leave-on personal care products (lotions, creams) have more sustained skin contact than those using rinse-off products. Infants and children who are regularly bathed with DEA-containing baby products have elevated exposure relative to their body weight.

1. Choose DEA-free personal care products — many brands now formulate without DEA. 2. For rinse-off products (shampoo, body wash), exposure is lower than for leave-on products; prioritize DEA-free formulations for products left on the skin. 3. Check cosmetic ingredient labels for DEA, cocamide DEA, lauramide DEA, TEA-lauryl sulfate, and related alkylamide ethanolamines. 4. Industrial workers in gas sweetening and metalworking should use closed systems and appropriate PPE for DEA solutions. 5. The EU has restricted DEA in cosmetics due to nitrosamine formation concerns (DEA + nitrosating agents → carcinogenic nitrosamines in the product).