Compendium of the most significant studies with reference to properties, intake, effects.

Bailey AD, Zhang G, Murphy BP. Comparison of damage to human hair fibers caused by monoethanolamine- and ammonia-based hair colorants. J Cosmet Sci. 2014 Jan-Feb;65(1):1-9.

Abstract. The number of Level 3 hair color products that substitute 2-aminoethanol [monoethanolamine (MEA)] for ammonia is increasing. There is some anecdotal evidence that higher levels of MEA can be more damaging to hair and more irritating than a corresponding equivalent level of the typical alkalizer, ammonia (in the form of ammonium hydroxide). Our interest was to understand in more quantitative terms the relative hair damage from the two alkalizers, particularly at the upper limits of MEA on-head use. Limiting investigations of oxidative hair damage to increases in cysteic acid content (from cystine oxidation) can underreport the extent of total damage. Hence, we complemented Fourier transform infrared spectroscopy (FTIR) cysteic acid level measurement with scanning electron microscopy (SEM) photomicrographs to visualize cuticle damage, and protein loss to understand not only the oxidative damage but also the damage caused by other damage pathways, e.g., reaction of the more nucleophilic (than ammonia) MEA with hair protein. In fact, all methods show an increase in damage from MEA-based formulations, up to 85% versus ammonia in the most extreme case. Hence, if the odor of ammonia is a concern, a better approach may be to minimize the volatility of ammonia in specific chassis rather than replacing it with high levels of a potentially more damaging alkalizer such as MEA.

Ali N, Marsh J, Godfrey S, Williams DR. Aqueous MEA and Ammonia Sorption-Induced Damage in Keratin Fibers. ACS Omega. 2018 Oct 31;3(10):14173-14180. doi: 10.1021/acsomega.8b01189. 

Abstract. The sorption of aqueous monoethanolamine (MEA) and ammonia solutions in keratin fibers and its subsequent effect on their mechanical performance has been investigated. The diffusion kinetics of MEA into keratin fibers for 0.1, 1.0, and 5 v/v % MEA in water at 30 and 50 °C were found to exhibit two clear regimes of absorption behavior: a linear Fickian diffusion regime for initial times up to 100 min, after which a second slower uptake process was observed. Single fiber tensile tests showed that the Young's modulus and the tensile failure stress for 5% MEA-treated fibers, compared to untreated fibers, were 25% lower after 1 h of treatment and 50% lower after 9 h of treatment. Aqueous treatments of 0.1 and 1% MEA, as well as 0.6 and 3% aqueous ammonia, had no measurable effect on either Young's modulus or tensile failure stress for the fibers. Scanning electron microscopy images and protein content analysis confirmed that keratin fibers exposed to 5% MEA solution exhibited significant surface damage as well as high levels of protein loss. This study confirms for the first time the important damage hair treatments containing 5% aqueous MEA can cause on keratin fibers.

Sun, J. D., Beskitt, J. L., Tallant, M. J., & Frantz, S. W. (1996). In vitro skin penetration of monoethanolamine and diethanolamine using excised skin from rats, mice, rabbits, and humans. Journal of Toxicology: Cutaneous and Ocular Toxicology, 15(2), 131-146.

Abstract. Monoethanolamine (MEA; CAS No. 141-43-5) and diethanolamine (DEA; CAS No. 111-42-2) are used in a number of cosmetic formulations. Therefore, dermal absorption is an important route of potential human exposure to these compounds. Because of this, the skin penetration characteristics of these two alkanolamines were evaluated using an established in vitro technique. Full-thickness skin preparations from female CD rats, CD-1 mice, New Zealand White rabbits, and female mammoplasty patients were used. Using a dynamic, flow-through design, skin penetration apparatus, undiluted and aqueous solutions of [14C]MEA and [14C]DEA were applied to skin preparations from each species in an “infinite dose” manner at target doses of 4 mg/cm2 and 20 mg/cm2respectively. The time course of 14C penetration was then measured for 6 h. The results showed that undiluted MEA penetrated animal skin better than did undiluted DEA, but was approximately the same for human skin. For the aqueous applications of MEA and DEA, the penetration was similar to each species, except for rabbit skin, in which the permeability appeared to be less for aqueous MEA than it was for aqueous DEA. Comparing undiluted and water diluted doses of each compound, the results showed that there was generally less skin penetration of the undiluted material than that for the diluted test substances. Therefore, the total absorbed dose of MEA or DEA would be less for cutaneous exposures to undiluted MEA or DEA as compared to similar exposures to water solutions of either compound. A comparison of permeability constants among the species tested suggests that the general rank order of skin penetration for both chemicals, undiluted or diluted, as mouse > rabbit > rat > human skin. Therefore, the results from this in vitro study suggest that the potential percutaneous absorption of MEA or DEA would be less for humans than it would be for rats, rabbits, and mice.

Geier J, Lessmann H, Dickel H, Frosch PJ, Koch P, Becker D, Jappe U, Aberer W, Schnuch A, Uter W. Patch test results with the metalworking fluid series of the German Contact Dermatitis Research Group (DKG). Contact Dermatitis. 2004 Sep;51(3):118-30. doi: 10.1111/j.0105-1873.2004.00416.x. 

Abstract. Based on the information of the interdisciplinary task force on allergy diagnostics in the metal branch, in 2001, the German Contact Dermatitis Research Group (DKG) compiled two metalworking fluid (MWF) test series with currently and previously used components, respectively. After 2 years of patch testing, we present results obtained with these series, based on data of the Information Network of Departments of Dermatology (IVDK). 251 metalworkers who were patch tested because of suspected MWF dermatitis in 2002 and 2003 were included in this retrospective data analysis. Of these, 206 were tested with the current MWF series and 155 with the historical MWF series. Among the current MWF allergens, monoethanolamine ranked 1st with 11.6% positive reactions. Diethanolamine (3.0%), triethanolamine (1.1%), and diglycolamine (1.9%) elicited positive reactions far less frequently. Allergic reactions to p-aminoazobenzene were frequently observed (6.0%), but the relevance of these reactions is still obscure. Positive reactions to biocides ranged from 4.5% for Bioban CS 1135 to 0.5% for iodopropynyl butylcarbamate and 2-phenoxyethanol. Concomitant reactions to formaldehyde, which caused positive reactions in 3.3%, and formaldehyde releasers occurred to varying extents without conclusive pattern. No positive reactions were seen to dibutyl phthalate, di-2-ethylhexyl phthalate, tricresyl phosphate, isopropyl myristate or benzotriazole. With the historical MWF test series, positive reactions to methyldibromo glutaronitrile (MDBGN) were observed most frequently. However, sensitization via allergen sources other than MWF seems likely, as MDBGN, during the study period, has been one of the most frequent preservative allergens in cosmetics and body care products. Other historical MWF allergens comprised morpholinyl mercaptobenzothiazole (3.3%), benzisothiazolinone (BIT; 2.0%) and Bioban P 1487(1.3%). BIT is currently used in MWF again, so it was shifted to the current MWF test series. As decreasing reaction frequencies to former MWF allergens that are no longer used can be expected, the historical series should be re-evaluated after some years. The test series with current MWF allergens has to be kept up-to-date based on information from industry and to be kept concise by eliminating test substances which never cause positive reactions.

Seo JA, Bae IH, Jang WH, Kim JH, Bak SY, Han SH, Park YH, Lim KM. Hydrogen peroxide and monoethanolamine are the key causative ingredients for hair dye-induced dermatitis and hair loss. J Dermatol Sci. 2012 Apr;66(1):12-9. doi: 10.1016/j.jdermsci.2011.12.015. 

Abstract. Background: Hair dyes are being commonly used to change the color of hair for cosmetic reason. However, concern is growing over the dermatitis and subsequent hair loss associated with the repeated use of hair dye products, yet the causative ingredients have not been elucidated. Objective: Here we investigated hair dye-induced dermatitis and hair loss using in vivo mouse model to uncover the causative ingredients....Conclusion: These results suggest that H(2)O(2) and MEA may be the key causative ingredients for hair dye-associated dermatitis and hair loss. Copyright © 2012 Japanese Society for Investigative Dermatology. 

Libralato, G., Ghirardini, A. V., & Avezzù, F. (2010). Seawater ecotoxicity of monoethanolamine, diethanolamine and triethanolamine. Journal of hazardous materials, 176(1-3), 535-539.

Abstract. Monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) are compounds with potential acute, sub-chronic and chronic toxicity effects towards aquatic species. A literature review highlighted the existence of a gap in the knowledge on their toxicity with saltwater testing species. A battery of toxicity tests including the alga Phaeodactylum tricornutum Bohlin, the bivalve molluscs Crassostrea gigas (Thunberg) and Mytilus galloprovincialis (Lmk), and the crustacean Artemia franciscana, was considered to update and improve the existing ecotoxicological information. Data were provided as the Effective Concentration that induces a 50% effect in the observed population (EC50), Lowest Observed Effect Concentration (LOEC) and No Observed Effect Concentration (NOEC). EC50, LOEC and NOEC values were compared with a reviewed database containing the existing ecotoxicological data from saltwater organisms.

Hellwig, J., & Liberacki, A. B. (1997). Evaluation of the pre-, peri-, and postnatal toxicity of monoethanolamine in rats following repeated oral administration during organogenesis. Fundamental and Applied Toxicology, 40(1), 158-162.

Abstract Pregnant Wistar rats (40/group) were administered monoethanolamine (MEA) as an aqueous solution by gavage at dose levels of 0, 40, 120, and 450 mg/kg/day on days 6 through 15 of gestation. On day 20 of gestation, 25 dams/group were euthanized and the fetuses were delivered by cesarean section, weighed, sexed, and examined for external, visceral, and skeletal alterations. The remaining dams (15/group) were allowed to litter and rear their pups to day 21 postpartum. The dams and pups were then euthanized and examined for gross pathologic changes. Gavage administration of 450 mg MEA/kg/day to pregnant rats resulted in maternal toxicity as evidenced by statistically significant (α = 0.05) decreases in feed consumption on gestation days 6–8 and 17–20 and on postpartum days 0–4. Additionally, statistically significant decreases in mean maternal body weights were observed on gestation days 15, 17, and 20 and on lactation days 0, 4, 7, and 21. Body weight gains of the 450 mg/kg/day dams were also significantly decreased (13% relative to controls) on gestation days 15–20. There was no evidence of maternal toxicity at 40 or 120 mg/kg/day of MEA. Despite the maternal effects observed at 450 mg/kg/day, no significant fetal effects were observed at this or any dose level tested, nor were there any indications of a treatment-related effect on postnatal growth or on the viability of offspring. Thus, it was concluded that MEA was not developmentally toxic to Wistar rats following repeated oral administration, even at maternally toxic dose levels as high as 450 mg/kg/day.

Hawthorne, S. B., Kubátová, A., Gallagher, J. R., Sorensen, J. A., & Miller, D. J. (2005). Persistence and biodegradation of monoethanolamine and 2-propanolamine at an abandoned industrial site. Environmental science & technology, 39(10), 3639-3645.

Abstract. Soil and groundwater samples were collected at the site of a former chemical processing plant in areas impacted by accidental releases of MEA (monoethanolamine) and IPA (2-propanolamine or isopropanolamine). Although their use had ceased ca. 10 years before sample collection, soils collected at contamination sites had MEA concentrations ranging from ca. 400 to 3000 mg/kg and IPA concentrations from ca. 30 to 120 mg/kg. Even though alkanolamines are miscible in water, transport to groundwater was slow, apparently because they are present in soil as bound cations. Only one groundwater sample (near the most highly contaminated soil) from wells directly adjacent to and down-gradient from the contaminated soils had detectable MEA, and none had detectable IPA. However, ammonia was found in the soil samples collected in the MEA-contaminated areas (ca. 500−1400 mg/kg) and the groundwater (80−120 mg/L), as would be consistent with bacterial degradation of MEA to ammonia, followed by transport of ammonia into the groundwater. Counts for bacteria capable of using MEA or IPA as a sole carbon source were ca. 5 × 106 and 1 × 106 (respectively) per gram in uncontaminated site soil, but no such organisms were found in highly contaminated soils. Similarly, bacterial degradation of MEA in slurries of highly contaminated soils was slow, with ca. 8−20 days required for half of the initial concentrations of MEA to be degraded at 20 °C and 30−60 days at 10 °C. In contrast, bacterial degradation studies using uncontaminated site soils spiked with ca. 1300 mg/L either MEA or IPA showed very rapid degradation of both compounds, with more than 99% degradation occurring in less than 3 days with quantitative conversion to ammonia, followed by slower conversion to nitrite and nitrate. The results obtained in the site soils, the groundwater samples, and from the biodegradation studies demonstrate that MEA and IPA can persist for decades on soil at high (hundreds of mg/kg) concentrations without significant migration into groundwater, despite the fact that they are miscible in water. Since MEA and IPA exist primarily as cations at the pH of site soils, their persistence apparently results from strong binding to soil, as well as inhibition of natural bioremediation in highly contaminated field soils.