Formation and inhibition of N-nitrosodiethanolamine in cosmetics under pH, temperature, and fluorescent, ultraviolet, and visual light

N-nitrosodiethanolamine (NDELA), a type of nitrosamine, is a possible human carcinogen that may form in cosmetic products. The aim of this study was to examine the formation and inhibition of NDELA through chemical reactions of secondary amines including mono-ethanolamine, di-ethanolamine (DEA), and tri-ethanolamine (TEA), and sodium nitrite (SN) under varying conditions such as pH, temperature, and fluorescent, ultraviolet (UV), and visual light (VIS) using liquid chromatography-mass spectroscopy. In a mixture of TEA and SN under acidic conditions pH 2, residual NDELA concentrations rose significantly under various storage conditions in the following order: 50°C > 40°C > UV (2 W/m²) > VIS (4000 lux) > fluorescent light > 25°C > 10°C. In a mixture of DEA and SN under the same acidic pH 2 conditions, NDELA formation was significantly elevated in the following order: UV (2 W/m²) > VIS (4000 lux) > 50°C > 40°C > fluorescent light > 25°C > 10°C. Inhibition of NDELA formation by d-mannitol, vitamin C (Vit C), or vitamin E (Vit E) was determined under varying conditions of pH, temperature, and fluorescent, UV, and VIS. At high concentrations of 100 or 1000 µg/ml, Vit E significantly decreased residual NDELA compared with control levels under acidic pH 2, but not under basic pH 6. Among various antioxidants, Vit E reacted more effectively with many nitrosating agents such as nitrate and nitrite found in cosmetic products. Therefore, to reduce NDELA, it is recommended that cosmetics be stored under cool/amber conditions and that Vit E or Vit C inhibitors of nitrosation be optimally added to cosmetic formulations at concentrations between 100 and 1000 µg/ml.

Comparison of N-nitrosodiethylamine degradation in water by UV irradiation and UV/O3: efficiency, product and mechanism

N-nitrosodiethylamine (NDEA) is a member of nitrosamines, which is strong carcinogenic. In order to explore an effective treatment method for NDEA removal from water, sole UV irradiation and UV/O(3) were carried out in this study. The removal efficiency, degradation products and pathways were compared between those two processes. Results showed that NDEA removal efficiency achieved 99% within 15 min by both UV and UV/O(3). Degradation reaction well followed pseudo-first-order kinetics. Water pH had different effect on NDEA degradation in those two processes. Acidic and neutral conditions were good for NDEA degradation by sole UV irradiation. However, NDEA underwent rapid degradation under various pH conditions in the UV/O(3) process. Though the ozone introduction in the UV/O(3) process had little effect on NDEA degradation efficiency, it had significant effect on its degradation products and pathways. Methylamine, dimethylamine, ethylamine and diethylamine were observed as aliphatic amine products of NDEA degradation in both two processes. They were assumed to arise due to N-N bond fission under UV irradiation, or due to the reaction of NDEA and hydroxyl radicals in the UV/O(3) process.

Effect of 50 Hz sinusoidal electromagnetic field on the kinetics of 14CO2 exhalation after [14C]-N-nitrosodiethylamine administration in mice

N-Nitrosodiethylamine (NDEA) has been identified as a typical environmental carcinogen. Its metabolism was studied in mice under the influence of an electromagnetic field (EMF). After intraperitoneal administration of [14C]-NDEA, 0.2 microCi/100 g body weight resulted in 22.8% of the total radioactivity exhaled as 14CO2 within 1 h. Mice were exposed to a 50 Hz, 2 mT (rms) electromagnetic field, 8 h/day for 8 weeks. There was a significant increase in the metabolic turnover of [14C]-NDEA into 14CO2 at the end of both 6 and 8 weeks of field exposure, i.e., 26.9% and 37.4% respectively. The enhanced capacity of mice to metabolize NDEA after the exposure to EMF may result in animals with a smaller amount of the bioactive carcinogen burden, thereby indicating a protective role of 2 mT EMF in a whole animal study.

Synergistic action of N-nitrosodialkylamines and near-UV in the induction of chromosome aberrations in Chinese hamster lung fibroblasts in vitro

N-Nitrosodialkylamines are promutagens and proclastogens, requiring metabolic activation for their actions. Previously, we showed that direct-acting bacterial mutagens can be formed from N-nitrosodialkylamines on exposure to near-UV. We have now found that N-nitrosodialkylamines with near-UV irradiation are clastogenic to Chinese hamster lung cells. When the cells in culture were irradiated with near-UV for 3 h in the presence of N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosopiperidine (NPIP) or N-nitrosomorpholine (NMOR), and then further incubated for a total period of 24 h with the N-nitrosodialkylamines, chromosome aberrations were induced. Neither the N-nitrosodialkylamine nor near-UV alone were clastogenic. Severe clastogenicity (> 50% of cells examined showing aberrations) was observed for 0.5 mM NDEA, NPYR and NPIP. The order of the clastogenic activity was NDEA, NPYR > NPIP, NDMA > NMOR. This order differed from that of bacterial mutagenicity previously reported for these N-nitrosodialkylamines plus near-UV, in which NMOR gave the strongest activity. The chromosome aberrations induced by the NPYR and NDEA plus near-UV in CHL-cells were inhibited by superoxide dismutase, glutathione and L-cysteine. Dimethylsulfoxide or D-mannitol, scavengers of hydroxy radical, and L-histidine, a scavenger of single oxygen, were ineffective. These results suggest that superoxide formed by a synergistic action of an N-nitrosodialkylamine and near-UV is the cause of the chromosome aberrations observed, an assumption consistent with the known ability of superoxide to cleave DNA.

Formation of 2-nitro-3-methylimidazo[4,5-f]quinoline, a directly mutagenic product, by near-ultraviolet irradiation of a mixture of 2-amino-3-methylimidazo[4,5-f]quinoline and N-nitrosodimethylamine

Direct-acting mutagens to Salmonella typhimurium TA98 were found to be formed from heterocyclic amines on exposure to near-ultraviolet light in the presence of N-nitrosodialkylamines. We have isolated the mutagenic photoproduct formed from 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and N-nitrosodimethylamine, and the product was identified as 3-methyl-2-nitroimidazo[4,5-f]quinoline (IQ(NO2]. The yield of IQ(NO2) from IQ was estimated to be 17%. Similar light-dependent activation of IQ was noted with 4 different nitrosodialkylamines other than nitrosodimethylamine. Furthermore, MeIQ and MeIQx were also activated with nitrosamine and light. These reactions represent an example of interaction between 2 different classes of mutagens.