Toxicokinetics of Acrylamide in Humans after Ingestion of a Defined Dose in a Test Meal to Improve Risk Assessment for Acrylamide Carcinogenicity

Biomarker monitoring of controlled dietary acrylamide exposure indicates consistent human endogenous background

The aim of the present study was to explore the relation of controlled dietary acrylamide (AA) intake with the excretion of AA-related urinary mercapturic acids (MA), N-acetyl-S-(carbamoylethyl)-l-cysteine (AAMA) and N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-l-cysteine (GAMA). Excretion kinetics of these short-term exposure biomarkers were monitored under strictly controlled conditions within a duplicate diet human intervention study. One study arm (group A, n = 6) ingested AA via coffee (0.15–0.17 µg/kg bw) on day 6 and in a meal containing an upper exposure level of AA (14.1–15.9 μg/kg bw) on day 10. The other arm (group B) was on AA minimized diet (washout, 0.05–0.06 µg/kg bw) throughout the whole 13-day study period. On day 6, these volunteers ingested ¹³C₃D₃-AA (1 μg/kg bw). In both arms, urinary MA excretion was continuously monitored and blood samples were taken to determine hemoglobin adducts. Ingestion of four cups of coffee resulted in a slightly enhanced short-term biomarker response within the background range of group B. At the end of the 13-day washout period, group B excreted an AAMA baseline level of 0.14 ± 0.10 µmol/d although AA intake was only about 0.06 µmol/d. This sustained over-proportional AAMA background suggested an endogenous AA baseline exposure level of 0.3–0.4 µg/kg bw/d. The excretion of ¹³C₃D₃-AA was practically complete within 72–96 h which rules out delayed release of AA (or any other MA precursor) from deep body compartments. The results provide compelling support for the hypothesis of a sustained endogenous AA formation in the human body.

Protective effect of rosemary on acrylamide motor neurotoxicity in spinal cord of rat offspring: postnatal follow-up study

The direct interactive effects of rosemary and acrylamide on the development of motor neurons in the spinal cord remains unknown. Our goal is to confirm the protective effects of rosemary against motor neuronal degeneration induced by acrylamide in the developing postnatal rat spinal cord using a postnatal rat model. We assigned the offspring of treated female rats into control, rosemary; acrylamide group; and recovery groups. This work depended on clinical, histopathological, morphometrically, immunohistochemical and genetic methods. In the acrylamide group, we observed oxidation, motor neuron degeneration, apoptosis, myelin degeneration, neurofilament reduction, reactive gliosis. Whoever, concomitant rosemary intake and withdrawal of acrylamide modulate these effects. These findings proof that dietary rosemary can directly protect motor neuron against acrylamide toxicity in the mammalian developing spinal cord.

The genetic consequences of paternal acrylamide exposure and potential for amelioration

Acrylamide is a toxin that humans are readily exposed to due to its formation in many carbohydrate rich foods cooked at high temperatures. Acrylamide is carcinogenic, neurotoxic and causes reproductive toxicity when high levels of exposure are reached in mice and rats. Acrylamide induced effects on fertility occur predominantly in males. Acrylamide exerts its reproductive toxicity via its metabolite glycidamide, a product which is only formed via the cytochrome P450 detoxifying enzyme CYP2E1. Glycidamide is highly reactive and forms adducts with DNA. Chronic low dose acrylamide exposure in mice relevant to human exposure levels results in significantly increased levels of DNA damage in terms of glycidamide adducts in spermatocytes, the specific germ cell stage where Cyp2e1 is expressed. Since cells in the later stages of spermatogenesis are unable to undergo DNA repair, and this level of acrylamide exposure causes no reduction in fertility, there is potential for this damage to persist until sperm maturation and fertilisation. Cyp2e1 is also present within epididymal cells, allowing for transiting spermatozoa to be exposed to glycidamide. This could have consequences for future generations in terms of predisposition to diseases such as cancer, with growing indications that paternal DNA damage can be propagated across multiple generations. Since glycidamide is the major contributor to DNA damage, a mechanism for preventing these effects is inhibiting the function of Cyp2e1. Resveratrol is an example of an inhibitor of Cyp2e1 which has shown success in reducing damage caused by acrylamide treatment in mice.

Monitoring urinary mercapturic acids as biomarkers of human dietary exposure to acrylamide in combination with acrylamide uptake assessment based on duplicate diets

The present human intervention study investigated the relation between the intake of acrylamide (AA) in diets with minimized, low, and high AA contents and the levels of urinary exposure biomarkers. As biomarkers, the mercapturic acids, N-acetyl-S-(carbamoylethyl)-L-cysteine (AAMA), and N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) were monitored. The study was performed with 14 healthy male volunteers over a period of 9 days, under controlled conditions excluding any inadvertent AA exposure. Dietary exposure to AA was measured by determining AA contents in duplicates of all meals consumed by the volunteers. The study design included an initial washout period of 3 days on AA-minimized diet, resulting in dietary AA exposure not exceeding 41 ng/kg bw/d. Identical washout periods of 2 days each followed the AA exposure days (day 4, low exposure, and day 7, high exposure). At the respective AA intake days, volunteers ingested 0.6-0.8 (low exposure) or 1.3-1.8 (high exposure) μg AA/kg bw/d with their food. Both low and high AA intakes resulted in an AAMA output within 72 h corresponding to 58 % of the respective AA intake. At the end of the initial 3-day washout period, an AAMA baseline level of 93 ± 31 nmol/d was recorded, suggestive for an assumed net AA baseline exposure level of 0.2-0.3 μg AA/kg bw/d.

Trigonella foenum-graecum ameliorates acrylamide-induced toxicity in rats: Roles of oxidative stress, proinflammatory cytokines, and DNA damage

Acrylamide is a hazardous substance inducing oxidative stress. Based on some evidence on the antioxidant properties of fenugreek, Trigonella foenum-graecum, this study was conducted to investigate the protective effect of fenugreek seed oil against acrylamide toxicity. Thirty-two male Wistar rats were randomly assigned into four groups. The control group was given normal saline. The second group was administered acrylamide (20 mg/kg bw orally). The third and fourth groups were administered acrylamide (20 mg/kg bw) and supplemented with 2.5% and 5% fenugreek seed oil in their diets, respectively. Acrylamide intoxication significantly increased serum levels of LDH, AST, ALT, APL, γ-GT, cholesterol, uric acid, urea, creatinine, 8-oxo-2'-deoxyguanosine, interleukin 1 beta, interleukin 6, and tumor necrosis factor α. Moreover, it increased hepatic, renal, and brain lipid peroxidation, while it impaired the activities and concentrations of the antioxidant biomarkers. Fenugreek oil supplementation normalized the altered serum parameters, prevented lipid peroxidation, and enhanced the antioxidant biomarker concentrations and activities in the hepatic, renal, and brain tissues of acrylamide-intoxicated rats in a dose-dependent manner. Thus, these results indicate that Trigonella foenum-graecum oil has a protective effect against acrylamide-induced toxicity through its free radical scavenging and potent antioxidant activities.

Dietary acrylamide and human cancer: a systematic review of literature

Cancer remains the second leading cause of death in the United States, and the number of cases is expected to continue to rise worldwide. Cancer prevention strategies are crucial for reducing the cancer burden. The carcinogenic potential of dietary acrylamide exposure from cooked foods is unknown. Acrylamide is a by-product of the common Maillard reaction where reducing sugars (i.e., fructose and glucose) react with the amino acid, asparagine. Based on the evidence of acrylamide carcinogenicity in animals, the International Agency for Research on Cancer has classified acrylamide as a group 2A carcinogen for humans. Since the discovery of acrylamide in foods in 2002, a number of studies have explored its potential as a human carcinogen. This article outlines a systematic review of dietary acrylamide and human cancer, acrylamide exposure and internal dose, exposure assessment methods in the epidemiologic studies, existing data gaps, and future directions. A majority of the studies reported no statistically significant association between dietary acrylamide intake and various cancers, and few studies reported increased risk for renal, endometrial, and ovarian cancers; however, the exposure assessment has been inadequate leading to potential misclassification or underestimation of exposure. Future studies with improved dietary acrylamide exposure assessment are encouraged.

Current issues in dietary acrylamide: formation, mitigation and risk assessment

Acrylamide (AA) is known as a neurotoxin in humans and it is classified as a probable human carcinogen by the International Agency of Research on Cancer. AA is produced as by-product of the Maillard reaction in starchy foods processed at high temperatures (>120 °C). This review includes the investigation of AA precursors, mechanisms of AA formation and AA mitigation technologies in potato, cereal and coffee products. Additionally, most relevant issues of AA risk assessment are discussed. New technologies tested from laboratory to industrial scale face, as a major challenge, the reduction of AA content of browned food, while still maintaining its attractive organoleptic properties. Reducing sugars such as glucose and fructose are the major contributors to AA in potato-based products. On the other hand, the limiting substrate of AA formation in cereals and coffee is the free amino acid asparagine. For some products the addition of glycine or asparaginase reduces AA formation during baking. Since, for potatoes, the limiting substrate is reducing sugars, increases in sugar content in potatoes during storage then introduce some difficulties and potentially quite large variations in the AA content of the final product. Sugars in potatoes may be reduced by blanching. Levels of AA in different foods show large variations and no general upper limit is easily applicable, since some formation will always occur. Current policy is that practical measures should be taken voluntarily to reduce AA formation in vulnerable foods since AA is considered a health risk at the concentrations found in foods.

Neuroprotective effect of geraniol and curcumin in an acrylamide model of neurotoxicity in Drosophila melanogaster: relevance to neuropathy

Chronic exposure of acrylamide (ACR) leads to neuronal damage in both experimental animals and humans. The primary focus of this study was to assess the ameliorative effect of geraniol, (a natural monoterpene) against ACR-induced oxidative stress, mitochondrial dysfunction and neurotoxicity in a Drosophila model and compare its efficacy to that of curcumin, a spice active principle with pleiotropic biological activity. Adult male flies (8-10 days) were exposed (7 days) to ACR (5 mM) with or without geraniol and curcumin (5-10 μM) in the medium. Both phytoconstituents significantly reduced the incidence of ACR-induced mortality, rescued the locomotor phenotype and alleviated the enhanced levels of oxidative stress markers in head/body regions. The levels of reduced glutathione (GSH) and total thiols (TSH) resulting from ACR exposure was also restored with concomitant elevation in the activities of detoxifying enzymes. Interestingly, ACR induced mitochondrial dysfunctions (MTT reduction, activities of SDH and citrate synthase enzymes) were alleviated by both phytoconstituents. While ACR elevated the activity of acetylcholinesterase in head/body regions, marked diminution in enzyme activity ensued with co-exposure to phytoconstituents suggesting their potency to mitigate cholinergic function. Furthermore, phytoconstituents also restored the dopamine levels in head/body regions. The neuroprotective effect of geraniol was comparable to curcumin in terms of phenotypic and biochemical markers. Based on our evidences in fly model we hypothesise that geraniol possess significant neuromodulatory propensity and may be exploited for therapeutic application in human pathophysiology associated with neuropathy. However, the precise mechanism/s by which geraniol offers neuroprotection needs to be investigated in appropriate neuronal cell models.

Urinary biomarkers of smokers' exposure to tobacco smoke constituents in tobacco products assessment: a fit for purpose approach

There are established guidelines for bioanalytical assay validation and qualification of biomarkers. In this review, they were applied to a panel of urinary biomarkers of tobacco smoke exposure as part of a "fit for purpose" approach to the assessment of smoke constituents exposure in groups of tobacco product smokers. Clinical studies have allowed the identification of a group of tobacco exposure biomarkers demonstrating a good doseresponse relationship whilst others such as dihydroxybutyl mercapturic acid and 2-carboxy-1-methylethylmercapturic acid - did not reproducibly discriminate smokers and non-smokers. Furthermore, there are currently no agreed common reference standards to measure absolute concentrations and few inter-laboratory trials have been performed to establish consensus values for interim standards. Thus, we also discuss in this review additional requirements for the generation of robust data on urinary biomarkers, including toxicant metabolism and disposition, method validation and qualification for use in tobacco products comparison studies.

Thermally induced process-related contaminants: the example of acrolein and the comparison with acrylamide: opinion of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG)

α,β-Unsaturated aliphatic carbonyl compounds are naturally widespread in food, but are also formed during the thermal treatment of food. This applies, for example, to the genotoxic carcinogen acrylamide (AA), but also to acrolein (AC), the simplest α,β-unsaturated aldehyde. First observations indicate that human exposure to AC may be higher than the exposure to AA. The DFG Senate Commission on Food Safety therefore compared data on AC and AA available in the scientific literature, evaluating current knowledge on formation, occurrence, exposure, metabolism, biological effects, toxicity, and carcinogenicity and defined knowledge gaps as well as research needs in an opinion on November 19, 2012, in German. The English version was agreed on April 17, 2013.

Urinary levels of N-acetyl-S-(2-carbamoylethyl)-cysteine (AAMA), an acrylamide metabolite, in Korean children and their association with food consumption

Acrylamide (AA), a probable human carcinogen, is present in high-temperature-processed foods, and has frequently been detected in humans worldwide. In the present study, the levels of a major AA metabolite, N-acetyl-S-(2-carbamoylethyl)-cysteine (AAMA) were measured in urine samples collected in two separate events with 3d interval from Korean children (n=31, 10-13 years old), and their diets were surveyed for 4d period prior to the second urine sampling. Daily AA intake was estimated from AAMA urinary levels and the influence of food consumption on urinary AAMA levels was investigated. The concentrations of metabolite AAMA in urine ranged between 15.4 and 196.3 ng/mL, with a median level of 68.1 ng/mL, and the levels varied by day considerably even in a given child. Children who were exposed to environmental smoke at home exhibited significantly higher levels of AAMA in urine, suggesting the importance of passive smoking as a source of AA exposure among children. Median (95th percentile) values of daily AA intake in Korean children were 1.04 (2.47)μg/kgbodyweight/day, which is higher than those reported elsewhere. After adjustment for gender, body mass index, and smoking status of family members, the consumptions of cracker and chocolate were identified to be significantly associated with the concentrations of AAMA in urine. The result of this study will provide information useful for developing public health and safety management for AA.

N7-glycidamide-guanine DNA adduct formation by orally ingested acrylamide in rats: a dose-response study encompassing human diet-related exposure levels

Acrylamide (AA) is formed during the heating of food and is classified as a genotoxic carcinogen. The margin of exposure (MOE), representing the distance between the bench mark dose associated with 10% tumor incidence in rats and the estimated average human exposure, is considered to be of concern. After ingestion, AA is converted by P450 into the genotoxic epoxide glycidamide (GA). GA forms DNA adducts, primarily at N7 of guanine (N7-GA-Gua). We performed a dose-response study with AA in female Sprague-Dawley (SD) rats. AA was given orally in a single dosage of 0.1-10 000 μg/kg bw. The formation of urinary mercapturic acids and of N7-GA-Gua DNA adducts in liver, kidney, and lung was measured 16 h after application. A mean of 37.0 ± 11.5% of a given AA dose was found as mercapturic acids (MAs) in urine. MA excretion in urine of untreated controls indicated some background exposure from endogenous AA. N7-GA-Gua adduct formation was not detectable in any organ tested at 0.1 μg AA/kg bw. At a dose of 1 μg/kg bw, adducts were found in kidney (around 1 adduct/10(8) nucleotides) and lung (below 1 adduct/10(8) nucleotides) but not in liver. At 10, respectively, 100 μg/kg bw, adducts were found in all three organs, at levels close to those found at 1 μg AA/kg, covering a range of about 1-2 adducts/10(8) nucleotides. As compared to DNA adduct levels from electrophilic genotoxic agents of various origin found in human tissues, N7-GA-Gua adduct levels within the dose range of 0.1-100 μg AA/kg bw were at the low end of this human background. We propose to take the background level of DNA lesions in humans more into consideration when doing risk assessment of food-borne genotoxic carcinogens.

The carcinogenicity of dietary acrylamide intake: a comparative discussion of epidemiological and experimental animal research

Since 2002, it is known that the probable human carcinogen acrylamide is present in commonly consumed carbohydrate-rich foods, such as French fries and potato chips. In this review, the authors discuss the body of evidence on acrylamide carcinogenicity from both epidemiological and rodent studies, including variability, strengths and weaknesses, how both types of evidence relate, and possible reasons for discrepancies. In both rats and humans, increased incidences of various cancer types were observed. In rats, increased incidences of mammary gland, thyroid tumors and scrotal mesothelioma were observed in both studies that were performed. In humans, increased risks of ovarian and endometrial cancers, renal cell cancer, estrogen (and progesterone) receptor-positive breast cancer, and oral cavity cancer (the latter in non-smoking women) were observed. Some cancer types were found in both rats and humans, e.g., endometrial cancer (observed in one of the two rat studies), but there are also some inconsistencies. Interestingly, in humans, some indications for inverse associations were observed for lung and bladder cancers in women, and prostate and oro- and hypopharynx cancers in men. These latter observations indicate that genotoxicity may not be the only mechanism by which acrylamide causes cancer. The estimated risks based on the epidemiological studies for the sites for which a positive association was observed were considerably higher than those based on extrapolations from the rat studies. The observed pattern of increased risks in the rat and epidemiological studies and the decreased risks in the epidemiological studies suggests that acrylamide might influence hormonal systems, for which rodents may not be good models.

Expression of CYP450-2E1 and formation of 2,3-epoxymethacrylic acid (2,3-EMA) in human oral cells exposed to dental materials

OBJECTIVES

Methacrylate-based (co)monomers released from dental composites can be, metabolized in vivo to methacrylic acid (MA). MA can be further oxidized to the toxic 2,3-epoxymethacrylic acid (2,3-EMA) by cytochrome P450 (CYP450) enzymes. The subform CYP450-2E1, can metabolize xenobiotics with low-molecular weight to epoxides. Oral cells are highly exposed to (co)monomers released from composites. Therefore in this study the, expression of CYP450-2E1 in human oral (and other) cells was investigated as well as the formation of 2,3-EMA in cells exposed to MA.

METHODS

Following human oral cells were used: human gingiva fibroblasts (HGF), human pulp fibroblasts (HPF), and human tumor buccal keratinocytes (SqCC/Y1). As negative control V79 cells without CYP450-2E1 expression were used. As positive controls V79 cells with CYP450-2E1 expression (V79-CYP450-2E1) and pooled human liver microsomes were used. The expression of CYP450-2E1 in cells was analyzed with the real-time polymerase chain reaction (RT-PCR). 2,3-EMA was quantified by the use of the method of gas chromatography/mass spectrometry (GC/MS).

RESULTS

The highest expression of CYP450-2E1 was found in human liver microsomes, followed by SqCC/Y1 cells, V79-CYP450-2E1 cells, HGF, and HPF. The highest amount of 2,3-EMA (μmol/L; mean±SEM, n=3) was found in human liver microsomes (5.0±1.0), followed by SqCC/Y1 cells (2.5±0.8), V79-CYP450-2E1 cells (1.5±0.6), HPF (0.3±0.3), and HGF (0.2±0.2).

SIGNIFICANCE

It is concluded that the formation of the toxic epoxide 2,3-EMA, as intermediate in the metabolism of dental materials, can occur also in human oral cells which can express the CYP450-2E1 enzyme system.

Development of a physiologically-based toxicokinetic model of acrylamide and glycidamide in rats and humans

Physiologically-based toxicokinetic ("pharmacokinetic") (PBPK or PBTK) modeling can be used as a tool to compare internal doses of acrylamide (AA) and its metabolite glycidamide (GA) in humans and rats. An earlier PBTK model for AA and GA in rats was refined and extended to humans based on new data. With adjustments to the previous parameters, excellent fits to a majority of the data for male Fisher 344 rats were obtained. Kinetic parameters for the human model were estimated based on fit to available human data for urinary metabolites of AA, and levels of hemoglobin adducts of AA and GA measured in studies in which human volunteers ingested known doses of AA. The simulations conducted with the rat and human models predicted that rats and humans ingesting comparable levels of AA (in mg/kg day) would have similar levels of GA in blood and tissues. This finding stands in contrast to the default approach that assumes a 3.2-fold increase in human risk due to pharmacokinetic differences between rats and humans. This model was used in a companion paper to estimate safe levels of ingested AA.

Cytotoxicity and chromosomal aberrations induced by acrylamide in V79 cells: role of glutathione modulators

Acrylamide (AA) is a suspected human carcinogen found to be generated during the heating of carbohydrate-rich foodstuffs. AA exhibits 'Michael-type' reactivity towards reduced glutathione (GSH), resulting in vivo in the urinary excretion of mercapturic acid conjugates. GSH is a key factor for mammalian cell homeostasis, with diverse functions that include, among others, the conjugation of electrophilic compounds and the detoxification of products generated by oxidative stress. Therefore, studies focusing on the modulation of GSH are of great importance for the understanding of the mechanisms of AA-induced toxicity. This report addresses this issue by analyzing cytotoxicity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) reduction assay) and clastogenicity (chromosomal aberrations) as endpoints in V79 cells after exposure to AA. The experiments described herein include the evaluation of the effect of buthionine sulfoximine (BSO), an effective inhibitor of GSH synthesis, GSH-monoethyl ester (GSH-EE), a compound that is taken up by cells and intracellularly hydrolysed to GSH, and also GSH exogenously added to culture medium. Pre-treatment with BSO increased the cytotoxicity and the frequency of aberrant cells excluding gaps (ACEG) induced by AA. While pre-treatment with GSH-EE did not modify the cytotoxicity or the frequency of ACEG induced by AA, co-treatment with AA and GSH decreased both parameters, rendering the cells less prone to the toxic effects of AA. In vitro studies in a cell-free system, using monochlorobimane (MCB), a fluorescent probe for GSH, were also performed in order to evaluate the role of AA in GSH depletion. The results show that spontaneous conjugation of AA with GSH in the extracellular medium is involved in the protection given by GSH. In summary, these results reinforce the role of GSH in the modulation of the cytotoxic and clastogenic effects induced by AA, which may be relevant in an in vivo exposure scenario.

Rapid and sensitive HILIC-ESI-MS/MS quantitation of polar metabolites of acrylamide in human urine using column switching with an online trap column

The carcinogen acrylamide (AA) is formed during the processing of food. AA is metabolized to mercapturic acids, which are excreted with urine. A hydrophilic interaction liquid chromatography tandem mass spectrometry method (HILIC-MS/MS) using a zwitterionic stationary phase (Zic-HILIC) was developed and validated to quantitate the mercapturic acids of AA (AAMA) and glycidamide (GAMA), and AAMA-sulfoxide in human urine. In contrast to reversed phases, the application of Zic-HILIC resulted in efficient retention and separation of these highly polar compounds. Off-line sample workup was avoided by application of column switching with a Stability BS-C17 trap column prior to the analytical column, thus minimizing interferences with the urinary matrix. Limit of quantification values (LOQs) were 0.5 microg/L (AAMA), 2.0 microg/L (AAMA-sulfoxide), and 1.0 microg/L (GAMA) in human urine. Median concentrations in urine samples ( n = 54) of six nonsmoking human subjects were 24.0 microg/L (AAMA, 7.8-79.8 microg/L), 16.7 microg/L (AAMA-sulfoxide, 6.8-70.1 microg/L), and 3.82 microg/L (GAMA, 1.0-23.6 microg/L).

Carcinogenicity of acrylamide: a computational study

This paper reports a series of ab initio, density functional theory (DFT), and semiempirical molecular orbital (MO) calculations concerning the reaction between the ultimate carcinogen of acrylamide and guanine. Acrylamide--a product of the Maillard reaction--is present in a variety of fried and oven-cooked food. After intake, it is epoxidized by cytochrome P450 2E1 to yield the ultimate carcinogen--glycidamide. Effects of solvation were considered using the Langevin dipoles (LD) model of Florian and Warshel and the solvent reaction field (SCRF) model of Tomasi and co-workers. In silico activation free energies are in very good agreement with the experimental value of 22.8 kcal/mol. This agreement presents strong evidence in favor of the validity of the proposed S N2 reaction mechanism and points to the applicability of quantum chemical methods to studies of reactions associated with carcinogenesis. In addition, insignificant stereoselectivity of the studied reaction was predicted. Finally, the competing reaction of glycidamide with adenine was simulated, and the experimentally observed regioselectivity was successfully reproduced.

Hemoglobin adducts and mercapturic acid excretion of acrylamide and glycidamide in one study population

The aim of this study was to determine the relationship between the oxidative and reductive metabolic pathways of acrylamide (AA) in the nonsmoking general population. For the first time both the blood protein adducts and the urinary metabolites of AA and glycidamide (GA) were quantified in an especially designed study group with even distribution of age and gender. The hemoglobin adducts N-carbamoylethylvaline (AAVal) and N-( R, S)-2-hydroxy-2-carbamoylethylvaline (GAVal) were detected by GC-MS/MS in all blood samples with median levels of 30 and 34 pmol/g of globin, respectively. Concentrations ranged from 15 to 71 pmol/g of globin for AAVal and from 14 to 66 pmol/g of globin for GAVal. The ratio GAVal/AAVal was 0.4-2.7 (median = 1.1). The urinary metabolites were determined by LC-MS/MS. Of all urine samples examined 99% of N-acetyl- S-(2-carbamoylethyl)- l-cysteine (AAMA) levels and 73% of N-( R/ S)-acetyl- S-(2-carbamoyl-2-hydroxyethyl)- l-cysteine (GAMA) levels were above the LOD (1.5 microg/L). Concentrations ranged from <LOD to 229 microg/L (median = 29 microg/L) for AAMA and from <LOD to 85 microg/L (median = 7 microg/L) for GAMA. The ratio of GAMA/AAMA varied from 0.004 to 1.4 (median = 0.3). Using hemoglobin adduct levels in blood and mercapturic acid excretion in urine for calculation of daily AA intake gave practically identical values. The median daily intakes were 0.43 (0.21-1.04) microg/kg of body weight(bw)/day using Hb adducts and 0.51 (<LOD-2.32) microg/kg of bw/day using mercapturic acids for calculations. Children take up approximately 1.3-1.5 times more AA per kilogram of body weight than adults. The ratio GAMA/AAMA is significantly higher in the group of young children (6-10 years) with a median level of 0.5. A gender-related difference in internal exposure and metabolism was not observed.