Ethoxylated fatty methyl esters (EFME) are nonionic surfactants obtained by direct insertion of ethylene oxide to fatty methyl esters in the presence of a composite metal oxide catalyst. Results of cumulative skin irritation testing of EFME on guinea pigs indicate that EFME are less irritating compared to ordinary alcohol ethoxylates (AE). Good skin compatibility of EFME is further illustrated by an in vitro hemolysis test and an in vitro cytotoxicity test. From the standpoint of environmental properties, EFME are readily biodegradable and are less toxic than AE . These results indicate the outstanding dermatological compatibility and good environmental compatibility of EFME. JSD 1, 93-97 (1998).KEY WORDS: Acute toxicity to fish, Al-Mg composite oxide catalyst, biodegradation, ecotoxicity, ethoxylate, ethoxylated fatty methyl ester, fatty methyl ester, skin compatibility.Many studies on characteristics of alkylene oxide-based nonionic surfactants, represented by alcohol ethoxylates (AE) and nonyl phenol ethoxylate, have been done since the 1950s. Today, vigorous studies on the effects of surfactants on organisms and the environment are being done owing to increased global environmental protection.Ethoxylated fatty methyl esters (EFME) are nonionic surfactants obtained by direct insertion of ethylene oxide (EO) to fatty methyl esters in the presence of a composite metal oxide catalyst (1-4). Fatty methyl ester precursors are important derivatives from natural oils and fats. EFME have been compared to common AE with respect to surface-chemical and physico-chemical properties. Compared to AE, EFME exhibit better foam-breaking, and the gelling region of EFME aqueous solutions is smaller (5-7). EFME and AE have similar surface tension-lowering characteristics (5-7).In this paper, in vivo and in vitro results for evaluating skin compatibility of EFME are reported. Biodegradability and ecotoxicity are discussed as well.
EXPERIMENTAL PROCEDURESMaterials. EFME, listed in Table 1, were synthesized by the method of Hama et al. (4) from fatty methyl esters having various alkyl chain lengths 10,12,14,16; Lion Corp., Tokyo, Japan) and EO (Mitsubishi Chemical, Tokyo, Japan) in the presence of the surface-modified Al-Mg composite oxide catalyst. The following materials were used as controls for each test-lauryl alcohol ethoxylates: C 12 AE (Emalex series; Nihon Emulsion Corp., Tokyo, Japan); alkyl polyglycosides (APG): C 8-12 APG and C 12 APG (Henkel KGaA, Düsseldorf, Germany); sodium N-lauroyl-N-methyl-β-alaninate: LMA (Mitsui Toatsu Chemicals, Inc., Tokyo, Japan); and sodium N-lauroyl-L-glutamate: LG (Ajinomoto Co., Inc., Tokyo, Japan).Cumulative skin irritation test. Five solutions [20% (vol/vol) aqueous] of EFME test material were applied on the intact, shaved dorsal skin (2 × 2 cm) of three albino guinea pigs, Hartley strain, females. A dose of 0.3 mL was administered daily for 3 d by painting without occlusion. On each day of treatment and after application, erythema (score 0-4) and edema (score 0-4) were assessed acco...
