An eco-friendly solvent-free reaction based on peptide probes: design an extraction-free method for analysis of acrylamide under microliter volume

Acrylamide is a group 2A carcinogen and potential endocrine disruptor that can enter the ecosystem by various routes and has recently become a dangerous pollutant. This widely used chemical can enter the human body via air inhalation, food or water consumption, or skin contact. In this study, we developed a peptide probe for the detection of acrylamide by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) after its micro-tagging with a peptide. Direct detection of acrylamide by MALDI-TOF MS is not feasible due to its poor ionization in the MALDI interface, which hinders its analysis by the technique. After microwave irradiation for 2 min, the formed acrylamide-peptide derivative was detected easily by MALDI-TOF MS without the need for extraction procedures. The procedure does not involve organic solvents and a water-soluble peptide that allows detection of acrylamide in small sample volumes with a limit of detection (LOD) of 0.05 ng/μL. The relative standard deviation (RSD) and relative error (RE) of the measurements were < 6.7% for intra- and inter-day assays. Gel-washing solutions from a polyacrylamide gel experiment were used as a model to study the efficiency of the developed method. Finally, we used the proposed method for the detection of free acrylamide in small volumes of lung epithelial cells (a model to test the air inhalation of acrylamide under a tiny volume of sample) and human urine. The developed method will enable rapid acrylamide detection in environmental and biological samples via a green approach based on microwave-assisted derivatization in water alongside the use of a less toxic derivatization reagent, reusable target plate, and miniaturization protocols.

Are AAMA and GAMA Levels in Urine after Childbirth a Suitable Marker to Assess Exposure to Acrylamide from Passive Smoking during Pregnancy?-A Pilot Study

Introduction: Acrylamide (AA) is a “probably carcinogenic to humans” monomer that can form in heated starchy food and in tobacco smoke. N-Acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA), acrylamide metabolites in urine, are recognized as good markers of exposure to acrylamide. Aim: The aim of the study is a preliminary assessment whether the levels of AAMA and GAMA in urine after childbirth are good markers of acrylamide exposure due to passive smoking during pregnancy. Material and method: The study group consisted 67 non-smokers and 10 passive-smoker women during pregnancy. AAMA and GAMA levels in urine samples were determined using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Results: The median AAMA levels in urine of non-smoking and passively smoking women were 30.7 μg/g creatinine and 25.2 μg/g creatinine, respectively. Much lower values were determined for GAMA: 11.4 μg/g creatinine and 10.3 μg/g creatinine, respectively. There is no significant difference between AAMA and GAMA content in urine samples between both groups of women as well as in the anthropometric parameters of newborns between those two groups of mothers. Conclusion: Our pilot study did not confirm that postpartum AAMA and GAMA concentrations in urine are good markers of exposure to acrylamide from passive smoking during pregnancy. It is probably due to the different ways of acrylamide absorption from tobacco smoke by active and passive smokers. Exposure of pregnant women to acrylamide from passive smoking requires further research.

Rapid Simultaneous Determination of Cascade Metabolites of Acrylamide in Urine for Toxicokinetics Profiles and Short-Term Dietary Internal Exposure

The current study developed an ultrahigh-performance liquid chromatography tandem mass spectrometry method to simultaneously analyze cascade metabolites of acrylamide in urine of rats and humans, including acrylamide, glycidamide, N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA), N-acetyl-S-(2-carbamoylethyl)-l-cysteine-sulfoxide, N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-l-cysteine, and N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-l-cysteine. A tandem solid-phase extraction procedure was novelly used to purify all metabolites at once from human urine. The rapid analysis showed high sensitivity with LOD and LOQ ranges of 0.1-0.8 and 0.4-5.8 ng/mL, respectively, and achieved acceptable within-laboratory reproducibility (RSD < 12.0%) and spiking recovery (92.2%-117.3%) within 8 min per sample. Approximately 70.7 and 63.0% of ingested acrylamide were recovered during the toxicokinetics analysis from urine of male and female rats, respectively. For nonsmoking participants, the urinary levels of acrylamide and glycidamide were higher in men than women, whereas the urinary concentration of AAMA showed the opposite behavior. The current analysis provides methodological support of cascade metabolites of acrylamide for the dietary short-term internal exposure assessment of acrylamide.

Study Design, Rationale and Procedures for Human Biomonitoring of Hazardous Chemicals from Foods and Cooking in Korea

Objectives: A nationwide biomonitoring program identified the long-term trends of environmental exposures to hazardous chemicals in the general population and found geographical locations where body burdens of an exposed group significantly differed from those of the general population. The purpose of this study is to analyze the hazardous compounds associated with foods and cooking in the nationwide general population for evaluation of the environmental exposures and health risk factors and for the establishment of the reference levels at the national level. Methods: During 2009–2010, the National Institute of Food and Drug Safety Evaluation (NIFDS) conducted a nationwide human biomonitoring study, including a questionnaire survey and environmental exposure assessments for specific hazardous compounds from foods and cooking among the general population in South Korea. Results: A total of 2139 individuals voluntarily participated in 98 survey units in South Korea, including 889 (41.6%) men and 1250 women (58.4%). Bio-specimens (serum and urine) and questionnaires were collected from the study population. Acrylamides, heterocyclic amines (HCAs), phenols, and phthalates were analyzed from urine, and perfluorinated compounds (PFCs) and organic chloride pesticides (OCPs) were analyzed from serum samples. The information on exposure pathway and geographical locations for all participants was collected by questionnaire interviews, which included demographic characteristics, socioeconomic status, history of family diseases, conditions of the indoor and outdoor environment, lifestyles, occupational history, and food and dietary information. Conclusion: We describe the design of the study and sampling of human biospecimen procedures including bio-sample repository systems. The resources produced from this nationwide human biomonitoring study and survey will be valuable for use in future biomarkers studies and for the assessment of exposure to hazardous compounds associated with foods and cooking.

Association of urinary acrylamide concentration with lifestyle and demographic factors in a population of South Korean children and adolescents

Acrylamide (AA) has been identified as probably carcinogenic to humans and thus represents a potential public health threat. This study aimed to determine the urinary concentrations of AA and N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) in a nationally representative sample (n = 1025) of children and adolescents (age range 3-18 years) in South Korea. The AA and AAMA detection rates and geometric mean concentrations were 97%, 19.1 ng/mL, and 98.7%, 26.4 ng/mL, respectively. Although urinary AA levels did not vary widely by age (17.2 ng/mL at 3-6 years, 19.9 ng/mL at 7-18 years), the urinary concentration of AAMA increased with age (18.3 ng/mL at 3-6 years, 30.4 ng/mL at 7-18 years). A multiple linear regression analysis revealed that the urinary levels of AA and AAMA varied significantly by sex, with the adjusted proportional changes indicating rates of 1.47- to 1.48-fold higher at 3-6 years and 1.36- to 1.68-fold higher at 7-18 years among males relative to females. Furthermore, the urinary levels of AA and AAMA correlated with the consumption of certain foods (doughnuts, hotdogs, popcorn, and nachos) among male subjects aged 7-18 years. The urinary concentrations of AA and AAMA increased significantly with the smoking status and passive smoking exposure, with adjusted proportional changes of 1.51 to 1.71-fold higher among smokers relative to non-smokers in the age range of 7-18 years. Exposure to smoking for > 30 min led to adjusted proportional increases in AA and AAMA of 1.51 and 1.77 times in the non-smoking group aged 3-6 years and a 1.52-fold increase in AAMA in the non-smoking group aged 7-18 years. In conclusion, the urinary levels of AA and AAMA were found to associate with age, sex, smoking, and food consumption in a population of Korean children and adolescents.

Feasibility of using urinary N7-(2-carbamoyl-2-hydroxyethyl) Guanine as a biomarker for acrylamide exposed workers

Acrylamide (AA), a probable human carcinogen, is a widely-used industrial chemical but is also present in tobacco smoke and carbohydrate-rich foods processed at high temperatures. AA is metabolized to glycidamide (GA) to cause the formation of DNA adducts. N7-(2-carbamoyl-2-hydroxyethyl) guanine (N7-GAG), the most abundant DNA adduct induced by GA, was recently detected in urine of smokers and non-smokers. In this study, we assessed the variability of AA exposure and biomarkers of AA exposure in urine samples repeatedly collected from AA-exposed workers and explored the half-life of N7-GAG. A total of 8 AA-exposed workers and 36 non-exposed workers were recruited. Pre-shift and post-shift urine samples were collected from the exposed group in parallel with personal sampling for eight consecutive days and from the control group on day 1 of the study. Urinary N7-GAG and the mercapturic acids of AA and GA, namely N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R,S)-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) were analyzed using on-line solid phase extraction-liquid chromatography-electrospray ionization/tandem mass spectrometry methods. We found that N7-GAG levels in urine were significantly higher in exposed workers than in controls and that N7-GAG level correlated positively with AAMA and GAMA levels. Results from this study showed that AAMA and GAMA possibly remain the more preferred biomarkers of AA exposure and that N7-GAG levels could be elevated by occupational exposures to AA and serve as a biomarker of AA-induced genotoxicity for epidemiological studies.

Exposure assessment of process-related contaminants in food by biomarker monitoring

Exposure assessment is a fundamental part of the risk assessment paradigm, but can often present a number of challenges and uncertainties. This is especially the case for process contaminants formed during the processing, e.g. heating of food, since they are in part highly reactive and/or volatile, thus making exposure assessment by analysing contents in food unreliable. New approaches are therefore required to accurately assess consumer exposure and thus better inform the risk assessment. Such novel approaches may include the use of biomarkers, physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry, and/or duplicate diet studies. This review focuses on the state of the art with respect to the use of biomarkers of exposure for the process contaminants acrylamide, 3-MCPD esters, glycidyl esters, furan and acrolein. From the overview presented, it becomes clear that the field of assessing human exposure to process-related contaminants in food by biomarker monitoring is promising and strongly developing. The current state of the art as well as the existing data gaps and challenges for the future were defined. They include (1) using PBK modelling and duplicate diet studies to establish, preferably in humans, correlations between external exposure and biomarkers; (2) elucidation of the possible endogenous formation of the process-related contaminants and the resulting biomarker levels; (3) the influence of inter-individual variations and how to include that in the biomarker-based exposure predictions; (4) the correction for confounding factors; (5) the value of the different biomarkers in relation to exposure scenario's and risk assessment, and (6) the possibilities of novel methodologies. In spite of these challenges it can be concluded that biomarker-based exposure assessment provides a unique opportunity to more accurately assess consumer exposure to process-related contaminants in food and thus to better inform risk assessment.

Occupational exposure to acrylamide in closed system production plants: air levels and biomonitoring

The aim of this study was to evaluate biomarkers of acrylamide exposure, including hemoglobin adducts and urinary metabolites in acrylamide production workers. Biomarkers are integrated measures of the internal dose, and it is total acrylamide dose from all routes and sources that may present health risks. Workers from three companies were studied. Workers potentially exposed to acrylamide monomer wore personal breathing-zone air samplers. Air samples and surface-wipe samples were collected and analyzed for acrylamide. General-area air samples were collected in chemical processing units and control rooms. Hemoglobin adducts were isolated from ethylenediamine teraacetic acid (EDTA)-whole blood, and adducts of acrylamide and glycidamide, at the N-terminal valines of hemoglobin, were cleaved from the protein chain by use of a modified Edman reaction. Full work-shift, personal breathing zone, and general-area air samples were collected and analyzed for particulate and acrylamide monomer vapor. The highest general-area concentration of acrylamide vapor was 350 μg/cm(3) in monomer production. Personal breathing zone and general-area concentrations of acrylamide vapor were found to be highest in monomer production operations, and lower levels were in the polymer production operations. Adduct levels varied widely among workers, with the highest in workers in the monomer and polymer production areas. The acrylamide adduct range was 15-1884 pmol/g; glycidamide adducts ranged from 17.8 to 1376 p/mol/g. The highest acrylamide and glycidamide adduct levels were found among monomer production process operators. The primary urinary metabolite N-acetyl-S-(2-carbamoylethyl) cysteine (NACEC) ranged from the limit of detection to 15.4 μg/ml. Correlation of workplace exposure and sentinel health effects is needed to determine and control safe levels of exposure for regulatory standards.

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).

Determination and quantification of urinary metabolites after dietary exposure to acrylamide

It is known that heat-treated carbohydrate-rich foods may contain high levels of acrylamide (AA) and up to 4000 microg kg-1 in potato crisps and 2000 microg kg-1 in French fries have been reported. In order to obtain more information on the human exposure to and metabolism of AA, a method for the determination of known urinary metabolites from the dietary exposure of AA using solid-phase extraction and liquid chromatography with positive electrospray MS/MS detection was developed. The validated assay range was from 8.6 to 342.9 microg l-1. The urinary metabolites were synthesized and their structures determined by NMR and MS. To test the method, a pilot study was conducted in which all urine during 48 h starting with 24 h fasting was collected. The two urinary metabolites, N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)cysteine (MA-GA3) and N-acetyl-S-(3-amino-3-oxopropyl)cysteine (MA-AA), were found to be above the detection limit. Fasting during 1 day caused about a 50% decrease in the total level of the metabolites, but after 1 day of a normal diet, the metabolite levels increased back to pre-fasting levels. The total amount of AA in the form of urinary metabolites excreted over the period was estimated to be about 40 microg AA day-1 for the average non-smoker.

Simultaneous determination of mercapturic acids derived from ethylene oxide (HEMA), propylene oxide (2-HPMA), acrolein (3-HPMA), acrylamide (AAMA) and N,N-dimethylformamide (AMCC) in human urine using liquid chromatography/tandem mass spectrometry

Mercapturic acids are highly important and specific biomarkers of exposure to carcinogenic substances in occupational and environmental medicine. We have developed and validated a reliable, specific and very sensitive method for the simultaneous determination of five mercapturic acids derived from several high-production chemicals used in industry, namely ethylene oxide, propylene oxide, acrylamide, acrolein and N,N-dimethylformamide. Analytes are enriched and cleaned up from urinary matrix by offline solid-phase extraction. The mercapturic acids are subsequently separated by means of high-performance liquid chromatography on a Luna C8 (2) column and specifically quantified by tandem mass spectrometric detection using isotopically labelled analytes as internal standards. The limits of detection (LODs) for N-acetyl-S-2-carbamoylethylcysteine (AAMA) and N-acetyl-S-2-hydroxyethylcysteine (HEMA) were 2.5 microg/L and 0.5 microg/L urine, while for N-acetyl-S-3-hydroxypropylcysteine (3-HPMA), N-acetyl-S-2-hydroxypropylcysteine (2-HPMA) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) it was 5 microg/L. These LODs were sufficient to detect the background exposure of the general population. We applied the method on spot urine samples of 28 subjects of the general population with no known occupational exposure to these substances. Median levels for AAMA, HEMA, 3-HPMA, 2-HPMA and AMCC in non-smokers (n = 14) were 52.6, 2.0, 155, 7.1 and 113.6 microg/L, respectively. In smokers (n = 14), median levels for AAMA, HEMA, 3-HPMA, 2-HPMA and AMCC were 243, 5.3, 1681, 41.7 and 822 microg/L, respectively. Due to the simultaneous quantification of these mercapturic acids, our method is well suited for the screening of workers with multiple chemical exposures as well as the determination of the background excretion of the general population.

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.

Searching for novel biomarkers of centrally and peripehrally-acting neurotoxicants, using surface-enhanced laser desorption/ionisation-time-of-flight mass spectrometry (SELDI-TOF MS)

The neurotoxicity of chemicals to humans is difficult to monitor as there are no suitable methods of detecting early neuronal dysfunction. Here, a proof of principle study was designed to assess the potential of identifying protein biomarkers in accessible biofluids for this purpose. Groups of rats were treated with a range of doses of the model neurotoxicants, acrylamide (0, 2, 10, 50mg/kg) and methylmercury (0, 0.2, 1, 5mg/kg) for up to 3 weeks and samples of serum, urine, and cerebral spinal fluid analysed by surface-enhanced laser desorption/ionisation-time-of-flight mass spectrometry. There was no neuropathology up to the highest dose tested. Protein profiles were obtained from all samples and changes in the levels of many proteins were detected in both serum and urine, although not cerebral spinal fluid. In serum, the combination of three protein ion levels with m/z values of 4968, 9402 and 12,948 was able to correctly classify the treatment groups thus: 88% control, 100% acrylamide, 92% methylmercury. In urine, three protein ions with m/z values of 4944, 12,966 and 21,992 classified correctly the groups: 67% control, 94% acrylamide, 97% methylmercury. Similar classifications using other serum and urinary protein ions were also possible. This indicates the potential of serum and urine protein biomarkers for the assessment of sub-clinical neurotoxicity.

Urinary acrylamide metabolites as biomarkers for short-term dietary exposure to acrylamide

It has previously been reported that heat-treated carbohydrate rich foods may contain high levels of acrylamide resulting in consumers being inadvertently exposed to acrylamide. Acrylamide is mainly excreted in the urine as mercapturic acid derivatives of acrylamide and glycidamide. In a clinical study comprising of 53 subjects, the urinary excretion of these metabolites was determined using solid-phase extraction and liquid chromatography with positive electrospray MS/MS detection. The median (range) total excretion of acrylamide in urine during 24 h was 16 (7-47) microg acrylamide for non-smokers and 74 (38-106) microg acrylamide for smokers, respectively. It was found that the median intake estimate in the study based on 24 h dietary recall was 21 (13-178) and 26 (12-67) for non-smokers and smokers, respectively. The median dietary exposure to acrylamide was estimated to be 0.47 (range 0.17-1.16) microg/kg body weight per day. In a multiple linear regression analysis, the urinary excretion of acrylamide metabolites correlated statistically significant with intake of aspartic acid, protein, starch and coffee. Consumption of citrus fruits correlated negatively with excretion of acrylamide metabolites.

Urinary excretion of acrylamide and metabolites in Fischer 344 rats and B6C3F1 mice administered a single dose of acrylamide

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in mice and rats. AA is also formed during cooking in many commonly consumed starchy foods. Our previous toxicokinetic investigations of AA and its genotoxic metabolite, glycidamide (GA), in rodents showed that AA is highly bioavailable from oral routes of administration, is widely distributed to tissues, and that the dietary route, in particular, favors metabolism to GA. Formation and accumulation of mutagenic GA-DNA adducts in many tissues support the hypothesis that AA is carcinogenic in rodent bioassays through metabolism to GA. The current investigation describes the quantification of 24 h urinary metabolites, including free AA and GA and their mercapturic acid conjugates (AAMA and GAMA, respectively), using LC/MS/MS in F344 rats and B6C3F(1) mice following a dose of 0.1 mg/kg bw given by intravenous, gavage, and dietary routes of administration. Similar groups of rodents were used previously for serum/tissue toxicokinetic and adduct determinations (DNA and hemoglobin). The goal was to investigate relationships between urinary and circulating biomarkers of exposure, toxicokinetic parameters for AA and GA, and tissue GA-DNA adducts in rodents from single doses of AA. Significant linear correlations were observed between urinary levels of AA with AAMA and GA with GAMA in the current data sets for rats and mice. Concentrations of AA and AAMA correlated significantly with average AUC values determined previously for AA in groups of rats and mice similarly dosed with AA. Urinary GA and GAMA concentrations showed significant correlations with average AUC values for GA and liver GA-DNA adducts determined previously in rats and mice similarly dosed with AA. Despite statistical significance, considerable inter-animal variability was observed in all urinary measurements, which limited the degree of correlation with either average toxicokinetic or biomarker data collected from different groups of animals. These results suggest that urinary measurements of AA and its metabolites may be useful for prediction of internal exposures to AA and GA.

Quantitation of mercapturic acids from acrylamide and glycidamide in human urine using a column switching tool with two trap columns and electrospray tandem mass spectrometry

A sensitive and specific electrospray tandem mass spectrometry method using a column switching unit with two trap columns was established to quantify the mercapturates (MAs) of acrylamide (AA) and glycidamide (GA) in human urine. A specially endcapped material was applied for trapping the hydrophilic MAs and a pre-trap column was used to remove lipophilic compounds from the directly injected urine to protect the trap column. The limits of quantitation for AA-MA and GA-MA in urine were 0.5 microg/L and 1 microg/L, respectively. Urine was spiked with deuterated internal standards and injected directly into LC-MS/MS. Urine of smokers (n=13) revealed the highest concentrations of AA-MA and GA-MA in the range of 61-706 microg/L and 5-54 microg/L, respectively. Lower levels for AA-MA (14-102 microg/L) and GA-MA (1-11 microg/L) were detected in non-smokers (n=13).

Kinetics of elimination of urinary metabolites of acrylamide in humans

Acrylamide (AM), used in the manufacture of polyacrylamide and grouting agents, is produced during the cooking of foods. Workplace exposure to AM can occur through the dermal and inhalation routes. The objective of this study was to define the kinetics of elimination of AM and its metabolites following oral and dermal administration. This is the second part of a study in which metabolites and hemoglobin adducts of AM were determined in people (Fennell et al., 2005, Toxicol. Sci. 85, 447-459). (1,2,3-(13)C(3))AM was administered in an aqueous solution orally (single dose of 0.5, 1.0, or 3.0 mg/kg) or dermally (three daily doses of 3.0 mg/kg) to sterile male volunteers. Urine samples were collected at 0-2, 2-4, 4-8, 8-16, and 16-24 h following administration orally, or at 0-2, 2-4, 4-8, 8-16, and 16-24 h following each of three daily dermal doses. (13)C(3)-AM and its metabolites in urine, (13)C(3)-glycidamide, (13)C(3)-N-acetyl-S-(3-amino-3-oxopropyl)cysteine and its S-oxide, and (13)C(3)-N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)cysteine, were quantitated using liquid chromatography-tandem mass spectrometry. The recovered urinary metabolites accounted for 45.6, 49.9, and 39.9% of a 0.5, 1.0, and 3.0 mg/kg oral dose (0-24 h), respectively, and for 4.5% of the dose after 3 mg/kg was administered daily for 3 days dermally (0-4 days). These results indicate that after oral administration AM is rapidly absorbed and eliminated. The half-life estimated for elimination of AM in urine was 3.1-3.5 h. After dermal administration, AM uptake is slow. This study indicated that skin provides a barrier that slows the absorption of AM, and results in limited systemic availability following dermal exposure to AM.

Excretion of mercapturic acids of acrylamide and glycidamide in human urine after single oral administration of deuterium-labelled acrylamide

We investigated the human metabolism of AA to the mercapturic acids N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R/S)-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L: -cysteine (GAMA) which are derived from AA itself and from its oxidative genotoxic metabolite glycidamide (GA), respectively. A healthy male volunteer received a single dose of about 1 mg deuterium-labelled acrylamide (d(3)-AA), representing 13 microg/kg body weight, in drinking water. Urine samples before dosing and within 46 h after the dose were analysed for d(3)-AAMA and d(3)-GAMA by LC-ESI-MS/MS. A first phase of increase in urinary concentration was found to last 18 h with a broad plateau between 8 and 18 h for AAMA, and 22 h for GAMA. Elimination half-lives of both AAMA and GAMA were estimated to be approximately 3.5 h for the first phase and more than 10 h up to few days for the second phase. Total recovery in urine after 24 h was about 51% as the sum of AAMA and GAMA and hereby well in accordance with former studies in rats. After 2 days AAMA, accounting for altogether 52% of the total AA dose, was the major metabolite of AA in humans. GAMA, accounting for 5%, appeared as a minor metabolite of AA. In humans we found a urinary ratio of 0.1 for GAMA/AAMA compared to previously reported values of 0.2 for rats and 0.5 for mice. Therefore, the metabolic fate of AA in humans was more similar to that in rats than in mice as already demonstrated in terms of the haemoglobin adducts. Consequently a genotoxic potency of AA mediated by GA could be supposed to be comparable in rats and humans.

Mercapturic acids of acrylamide and glycidamide as biomarkers of the internal exposure to acrylamide in the general population

Acrylamide (AA), a widely used industrial monomer which is categorised to be carcinogenic, was found to be generated in starch-containing foods during the heating process. This discovery has caused reasonable concern about possible health risks to humans due to dietary acrylamide uptake. In order to gain more information on human metabolism of acrylamide and to contribute to the assessment of the human carcinogenic risk due to AA uptake we measured the mercapturic acid of AA and its epoxide glycidamide (GA) i.e. N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R,S)-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) in human urine. The relation between AAMA and GAMA is important in this context because GA is thought to be the ultimate carcinogenic metabolite of AA. The median levels in smokers (n=13) were found to be about four times higher than in non-smokers (n=16) with median levels of 127 microg/l versus 29 microg/l for AAMA and 19 microg/l versus 5 microg/l for GAMA. Therefore cigarette smoke proved to be an important source of acrylamide exposure. The level of AAMA in the occupationally non-exposed collective (n=29) ranged from 3 to 338 microg/l, the level of GAMA from <LOD to 45 microg/l. The ratio of GAMA:AAMA varied from 0.03 to 0.53, median was 0.16 which is in reasonable agreement with results of different studies on rats. Thus the metabolic conversion of acrylamide to its genotoxic epoxide glycidamide seems to occur to a comparable extent in rats and humans. Consequently, risk estimations by various authorities based on experimental data obtained in rats are supported by our findings. Besides we also measured the haemoglobin adducts of AA and GA in the blood of 26 participants. From these results compared to the mercapturic acids, we deduce a steady state for AA uptake, and we demonstrate a higher reactivity of GA in comparison to AA towards haemoglobin compared to glutathione in humans.

Acrylamide: increased concentrations in homemade food and first evidence of its variable absorption from food, variable metabolism and placental and breast milk transfer in humans

We have developed a liquid chromatography/mass spectrometry (LC-MS/MS) assay to determine acrylamide in various body fluids. The assay also allows the reliable quantitation of acrylamide in food. In a total of 11 healthy male and female subjects, we were able to show that acrylamide from food given to humans is in fact absorbed from the gut. The half-lives determined in two male subjects were 2.2 and 7 h. Acrylamide was found in human breast milk and penetrated the human placenta (n = 3). The variability of acrylamide concentrations found in this investigation is most likely caused by variable intersubject bioavailability and metabolism. This may be an important indication that the assessment of the risk from acrylamide for the individual may be very difficult without knowing the concentrations of acrylamide in the body. This should be considered in the design of any risk assessment study or post hoc analysis of earlier studies. At this time, we suggest that pregnant women and breast-feeding mothers avoid acrylamide-containing food.

Role of cytochrome P450 2E1 in the metabolism of acrylamide and acrylonitrile in mice

Acrylonitrile (AN) and acrylamide (AM) are commonly used in the synthesis of plastics and polymers. In rodents, AM and AN are metabolized to the epoxides glycidamide and cyanoethylene oxide, respectively. The aim of this study was to determine the role of cytochrome P450 in the metabolism of AM and AN in vivo. Wild-type (WT) mice, WT mice pretreated with aminobenzotriazole (ABT, 50 mg/kg ip, 2 h pre-exposure), and mice devoid of cytochrome P450 2E1 (P450 2E1-null) were treated with 50 mg/kg [(13)C]AM po. WT mice and P450 2E1-null mice were treated with 2.5 or 10 mg/kg [(13)C]AN po. Urine was collected for 24 h, and metabolites were characterized using (13)C NMR. WT mice excreted metabolites derived from the epoxides and from direct GSH conjugation with AM or AN. Only metabolites derived from direct GSH conjugation with AM or AN were observed in the urine from ABT-pretreated WT mice and P450 2E1-null mice. On the basis of evaluation of urinary metabolites at these doses, these data suggest that P450 2E1 is possibly the only cytochrome P450 enzyme involved in the metabolism of AM and AN in mice, that inhibiting total P450 activity does not result in new pathways of non-P450 metabolism of AM, and that mice devoid of P450 2E1 do not excrete metabolites of AM or AN that would be produced by oxidation by other cytochrome P450s. P450 2E1-null mice may be an appropriate model for the investigation of the role of oxidative metabolism in the toxicity or carcinogenicity of these compounds.