PFAS levels and determinants of variability in exposure in European teenagers - Results from the HBM4EU aligned studies (2014-2021).

BACKGROUND: Perfluoroalkyl substances (PFAS) are man-made fluorinated chemicals, widely used in various types of consumer products, resulting in their omnipresence in human populations. The aim of this study was to describe current PFAS levels in European teenagers and to investigate the determinants of serum/plasma concentrations in this specific age group. METHODS: PFAS concentrations were determined in serum or plasma samples from 1957 teenagers (12-18 years) from 9 European countries as part of the HBM4EU aligned studies (2014-2021). Questionnaire data were post-harmonized by each study and quality checked centrally. Only PFAS with an overall quantification frequency of at least 60% (PFOS, PFOA, PFHxS and PFNA) were included in the analyses. Sociodemographic and lifestyle factors were analysed together with food consumption frequencies to identify determinants of PFAS exposure. The variables study, sex and the highest educational level of household were included as fixed factors in the multivariable linear regression models for all PFAS and each dietary variable was added to the fixed model one by one and for each PFAS separately. RESULTS: The European exposure values for PFAS were reported as geometric means with 95% confidence intervals (CI): PFOS [2.13 µg/L (1.63-2.78)], PFOA ([0.97 µg/L (0.75-1.26)]), PFNA [0.30 µg/L (0.19-0.45)] and PFHxS [0.41 µg/L (0.33-0.52)]. The estimated geometric mean exposure levels were significantly higher in the North and West versus the South and East of Europe. Boys had significantly higher concentrations of the four PFAS compared to girls and significantly higher PFASs concentrations were found in teenagers from households with a higher education level. Consumption of seafood and fish at least 2 times per week was significantly associated with 21% (95% CI: 12-31%) increase in PFOS concentrations and 20% (95% CI: 10-31%) increase in PFNA concentrations as compared to less frequent consumption of seafood and fish. The same trend was observed for PFOA and PFHxS but not statistically significant. Consumption of eggs at least 2 times per week was associated with 11% (95% CI: 2-22%) and 14% (95% CI: 2-27%) increase in PFOS and PFNA concentrations, respectively, as compared to less frequent consumption of eggs. Significantly higher PFOS concentrations were observed for participants consuming offal (14% (95% CI: 3-26%)), the same trend was observed for the other PFAS but not statistically significant. Local food consumption at least 2 times per week was associated with 40% (95% CI: 19-64%) increase in PFOS levels as compared to those consuming local food less frequently. CONCLUSION: This work provides information about current levels of PFAS in European teenagers and potential dietary sources of exposure to PFAS in European teenagers. These results can be of use for targeted monitoring of PFAS in food.

A pilot study on the feasibility of European harmonized human biomonitoring: Strategies towards a common approach, challenges and opportunities.

In 2004 the European Commission and Member States initiated activities towards a harmonized approach for Human Biomonitoring surveys throughout Europe. The main objective was to sustain environmental health policy by building a coherent and sustainable framework and by increasing the comparability of data across countries. A pilot study to test common guidelines for setting up surveys was considered a key step in this process. Through a bottom-up approach that included all stakeholders, a joint study protocol was elaborated. From September 2011 till February 2012, 17 European countries collected data from 1844 mother-child pairs in the frame of DEMOnstration of a study to COordinate and Perform Human Biomonitoring on a European Scale (DEMOCOPHES).(1) Mercury in hair and urinary cadmium and cotinine were selected as biomarkers of exposure covered by sufficient analytical experience. Phthalate metabolites and Bisphenol A in urine were added to take into account increasing public and political awareness for emerging types of contaminants and to test less advanced markers/markers covered by less analytical experience. Extensive efforts towards chemo-analytical comparability were included. The pilot study showed that common approaches can be found in a context of considerable differences with respect to experience and expertize, socio-cultural background, economic situation and national priorities. It also evidenced that comparable Human Biomonitoring results can be obtained in such context. A European network was built, exchanging information, expertize and experiences, and providing training on all aspects of a survey. A key challenge was finding the right balance between a rigid structure allowing maximal comparability and a flexible approach increasing feasibility and capacity building. Next steps in European harmonization in Human Biomonitoring surveys include the establishment of a joint process for prioritization of substances to cover and biomarkers to develop, linking biomonitoring surveys with health examination surveys and with research, and coping with the diverse implementations of EU regulations and international guidelines with respect to ethics and privacy.

Interpreting biomarker data from the COPHES/DEMOCOPHES twin projects: Using external exposure data to understand biomarker differences among countries.

In 2011 and 2012, the COPHES/DEMOCOPHES twin projects performed the first ever harmonized human biomonitoring survey in 17 European countries. In more than 1800 mother-child pairs, individual lifestyle data were collected and cadmium, cotinine and certain phthalate metabolites were measured in urine. Total mercury was determined in hair samples. While the main goal of the COPHES/DEMOCOPHES twin projects was to develop and test harmonized protocols and procedures, the goal of the current paper is to investigate whether the observed differences in biomarker values among the countries implementing DEMOCOPHES can be interpreted using information from external databases on environmental quality and lifestyle. In general, 13 countries having implemented DEMOCOPHES provided high-quality data from external sources that were relevant for interpretation purposes. However, some data were not available for reporting or were not in line with predefined specifications. Therefore, only part of the external information could be included in the statistical analyses. Nonetheless, there was a highly significant correlation between national levels of fish consumption and mercury in hair, the strength of antismoking legislation was significantly related to urinary cotinine levels, and we were able to show indications that also urinary cadmium levels were associated with environmental quality and food quality. These results again show the potential of biomonitoring data to provide added value for (the evaluation of) evidence-informed policy making.

Gender differences in cadmium and cotinine levels in prepubertal children.

Susceptibility to environmental stressors has been described for fetal and early childhood development. However, the possible susceptibility of the prepubertal period, characterized by the orchestration of the organism towards sexual maturation and adulthood has been poorly investigated and exposure data are scarce. In the current study levels of cadmium (Cd), cotinine and creatinine in urine were analyzed in a subsample 216 children from 12 European countries within the DEMOCOPHES project. The children were divided into six age-sex groups: boys (6-8 years, 9-10 years and 11 years old), and girls (6-7 years, 8-9 years, 10-11 years). The number of subjects per group was between 23 and 53. The cut off values were set at 0.1 µg/L for Cd, and 0.8 µg/L for cotinine defined according to the highest limit of quantification. The levels of Cd and cotinine were adjusted for creatinine level. In the total subsample group, the median level of Cd was 0.180 µg/L (range 0.10-0.69 µg/L), and for cotinine the median wet weight value was 1.50 µg/L (range 0.80-39.91 µg/L). There was no significant difference in creatinine and cotinine levels between genders and age groups. There was a significant correlation between levels of cadmium and creatinine in all children of both genders. This shows that even at such low levels the possible effect of cadmium on kidney function was present and measurable. An increase in Cd levels was evident with age. Cadmium levels were significantly different between 6-7 year old girls, 11 year old boys and 10-11 year old girls. As there was a balanced distribution in the number of subjects from countries included in the study, bias due to data clustering was not probable. The impact of low Cd levels on kidney function and gender differences in Cd levels needs further investigation.

Urinary metabolites and health effects in workers exposed chronically to chloronitrobenzene.

For workers exposed to 4-chloronitrobenzene (4CNB), the major metabolites were determined. Urine were analysed before and after acid hydrolysis to qualify the free and conjugated metabolites of 4CNB. Three conjugated metabolites were identified in exposed workers: the mercapturic acid N-acetyl-S-(4-nitrophenyl)-L-cysteine (NANPC) was the only metabolite detected in non-hydrolysed urine, and accounted for approximately 51% of the total metabolites detected. The two remaining metabolites 4-chloroaniline (4CA) and 2-chloro-5-nitrophenol (CNP) were identified as cleavage products in hydrolysed urine, and accounted for approximately 18 and 30% of the total metabolites detected, respectively. No metabolites were found in factory controls within the limits of quantitation (LOQ) of the assay. There is a moderate correlation between NANPC and both 4CA and CNP. The correlation between 4CA and CNP is minor. The correlation between the total metabolites and both 4CA and CNP are good. The best correlation was found between the total metabolites and NANPC. There is a moderate inverse correlation between age and the creatinine levels. The raw metabolite levels CNP and NANPC decrease with age. The urine metabolites increase and correlate significantly with the creatinine levels. 4CA, NANPC and the total metabolite levels correlate with the haemoglobin adduct levels. NANPC is the most appropriate biomarker in the urine for a recent absorbed dose of 4CNB, since NANPC reflects the levels of 4CA and CNP and is the most prevalent metabolite detected in all the exposed workers.

Comparison of biomarkers in workers exposed to 2,4,6-trinitrotoluene.

2,4,6-Trinitrotoluene (TNT) is an important occupational and environmental pollutant. In TNT-exposed humans, notable toxic manifestations have included aplastic anaemia, toxic hepatitis, cataracts, hepatomegaly, and liver cancer. Therefore, methods were developed to biomonitor workers exposed to TNT. The workers were employed in a typical ammunition factory in China. The external dose (air levels and skin exposure), the internal dose (urinary metabolites), the biologically effective dose (haemoglobin adducts, urinary mutagenicity), biological effects (chromosomal aberrations and health effects), and individual susceptibility (genotypes of xenobiotic-metabolizing enzymes) were determined. Haemoglobin-adducts of TNT, 4-amino-2,6-dinitrotoluene (4ADNT) and 2-amino-4,6-dinitrotoluene (2ADNT), and the urinary metabolites of TNT, 4ADNT and 2ADNT, were found in all workers and in some controls. The levels of the haemoglobin-adducts or the urinary metabolites correlated weakly with the skin or air levels of TNT. The urinary mutagenicity determined in a subset of workers correlated strongly with the levels of 4ADNT and 2ADNT in urine. The haemoglobin-adducts correlated moderately with the urinary metabolites and with the urinary mutagenicity. The genotypes of glutathione S-transferases (GSTM1, GSTT1, GSTP1) and N-acetyltransferases (NAT1, NAT2) were determined. In general, the genotypes did not significantly influence the haemoglobin-adduct levels and the urine metabolite levels. However, TNT-exposed workers who carried the NAT1 rapid acetylator genotype showed an increase in urinary mutagenicity and chromosomal aberrations as compared with slow acetylators. The haemoglobin adduct 4ADNT was significantly associated with a risk of hepatomegaly, splenomegaly and cataract; urine metabolites and genotypes were not associated with health effects. These results indicate that a set of well-selected biomarkers may be more informative regarding exposure and effect than routinely performed chemical measurements of pollutants in the air or on the skin.

Urinary metabolites of workers exposed to nitrotoluenes.

Nitrotoluenes are important intermediates in the chemical industry. 2,6-Dinitrotoluene (26DNT), 2,4-dinitrotoluene (24DNT) and 2-nitrotoluene (2NT) are carcinogenic in animals and possibly carcinogenic in humans. Thus, it is important to develop methods to biomonitor workers exposed to such chemicals. The authors have monitored the air and urine metabolite levels for a group of workers in China exposed to 24DNT, 26DNT, 2NT and 4-nitrotoluene (4NT). The metabolites 2,4-dinitrobenzylalcohol (24DNBAlc), 2-amino-4-nitrobenzoic acid (2A4NBA), 4-amino-2-nitrobenzoic acid (4A2NBA) and 2,4-dinitrobenzoic acid (24DNBA) resulting from exposure to 24DNT were found in 89, 88, 91 and 78% of the exposed workers, respectively. The metabolites 2,6-dinitrobenzylalcohol (26DNBAlc) and 2,6-dinitrobenzoic acid resulting from 26DNT exposure were found in 99 and 86% of the exposed workers, respectively. Quantitatively, 2A4NBA, 4A2NBA and 26DNBAlc were the major metabolites. The nitrobenzoic acids were the major metabolites resulting from exposure to 2NT and 4NT and were present in 96 and 73% of the exposed workers, respectively. Air concentrations of DNT and 2NT did not correlate with the levels of metabolites in the urine. In conclusion, the dinitrobenzyl alcohols and aminonitrobenzoic acids determined in the urine provided a good marker for recently absorbed dose and were intrinsically related to the bioactivation and detoxification pathways of DNT. Air measurements were not a good measure to predict internal exposure.

Carcinogenic risk of toluene diisocyanate and 4,4'-methylenediphenyl diisocyanate: epidemiological and experimental evidence.

Diisocyanates are highly reactive compounds widely used, for example, in the production of polyurethane foams, elastomers, paints, and adhesives. The high chemical reactivity of these compounds is also reflected in their toxicity: diisocyanates are one of the most important causes of occupational asthma but also other adverse effects, such as irritation and toxic reactions, have been described in exposed subjects. One of the open questions is whether occupational isocyanate exposure is a carcinogenic hazard. The few epidemiological studies available have been based on young cohorts and short follow-up and are not conclusive. Toluene diisocyanate (TDI) has been classified as carcinogenic in animals on the basis of gavage administration studies, but no conclusions are available on inhalation exposure. For 4,4'-methylene diphenyldiisocyanate (MDI) there is suggestive evidence for carcinogenicity in rats. The possible carcinogenic mechanism of TDI and MDI is not clear. Both chemicals have been positive in a number of short-term tests inducing gene mutations and chromosomal damage. The reactive form could be either the diisocyanate itself or may derive from the metabolic activation of the aromatic diamine derivatives formed by hydrolysis. TDI and MDI react with DNA in vivo and in vitro. However, the structure of the adducts has not been identified. Especially from the in vivo experiment it is not known if the adducts are a product from the reaction with the isocyanate or the corresponding amine. In conclusion, both TDI and MDI are highly reactive chemicals that bind to DNA and are probably genotoxic. The alleged animal carcinogenicity of TDI and MDI would suggest that occupational exposure to these compounds is a carcinogenic risk. The few epidemiological studies available have not, however, been able to clarify if TDI and MDI are occupational carcinogens.

Should control measures be based on air measurements or biological/biological effect monitoring?

The setting of, and the review of, exposure limits takes into account toxicological, occupational hygiene and epidemiological data. The COSHH Regulations 1994 define a hierarchical approach to controlling workplace exposures with a particular emphasis on the measurement and control of airborne substances. Absorption via the lungs is considered the most important route of entry in the workplace, however, percutaneous absorption must not be overlooked. Biomarkers are used extensively in the surveillance of workers' exposure to metals and organic chemicals. In addition, Genetic polymorphism for xenobiotic metabolism has been widely studied. The selection, validation and application of any biomarker is a complicated process and requires careful consideration prior to any application.

Should we be frightened of bracken? A review of the evidence.

OBJECTIVE: To assess the risk to human health of the plant bracken (Pteridium sp). DESIGN: An evaluation of studies of human and animal populations exposed to bracken, together with a review of expert reports and advice to the public. MAIN RESULTS: Bracken induced disease has been demonstrated in animals in both laboratory and field studies. Depending on the species, diseases in animals associated with the plant have included; cancers of the alimentary and urogenital tract, lung and breast; haematuria; retinal degeneration; and, thiamine deficiency. Potential exposure of human populations is through: food either directly (people in some parts of the world eat bracken as a traditional dish) or indirectly by consuming animals fed on bracken; milk; water; inhalation and ingestion of spores; and insect vectors. Four studies of human populations (two analytical and two observational) failed to assess adequately confounding factors and other sources of bias, so that conclusions about a risk to human health from bracken cannot firmly be drawn. Establishing exposure is also extremely difficult in populations (such as the United Kingdom) where direct consumption of bracken is rare. CONCLUSION: Bracken is a common plant worldwide. It is toxic to many animal species and to several organ systems. There is no tumour (or other disease) that is pathognomic of exposure in animals, though cancers of the alimentary and urogenital tract seem to be the most commonly associated. It is not possible to extrapolate from animal models to humans. Studies of human populations, do not establish a clear risk of bracken to human health, largely because of methodological problems. Testing the evidence against traditional criteria of causality only fulfils the criterion of biological plausibility. Despite this, current public information implies a serious risk to human health from bracken, and increasing media coverage of the subject is likely to lead to greater public concern. Further epidemiological studies are required.

Synthesis and quantification of DNA adducts of 4,4'-methylenedianiline.

4,4'-Methylenedianiline (MDA) is used as a hardener in the manufacture of plastics and polyurethanes. MDA has been classified as a carcinogen in animals and is a suspected human carcinogen. Assuming that MDA would yield similar DNA adducts to other arylamines, we synthesized the following C-8 guanine adducts: N'-acetyl-N-(deoxyguanosin-8-yl)-MDA, N-(deoxyguanosin-8-yl)-MDA, N-(deoxyguanosin-8-yl)-4MA, and their corresponding 3'-monophosphate derivatives. We developed methods to identify these adducts of MDA in liver DNA using 32P-postlabeling, HPLC, and GC-MS techniques. Liver DNA was obtained from rats treated with radiolabeled MDA (1.11 and 116.5 mumol/kg body weight). The total radioactivity bound to the DNA corresponded to 0.06 and 2.7 adducts per 10(7) nucleotides [covalent binding index (CBI = (mumol of adduct per mol of nucleotide)/(mmol of compound per kg body weight)) of 1.05 and 2.3]. This DNA-binding potency is in the range of weakly genotoxic compounds. The liver DNA was analyzed for the presence of the synthesized adducts by the following methods: (I) HPLC analysis of nucleotides and purines after enzymatic and acid hydrolysis, and (II) 32P-postlabeling after enzymatic hydrolysis. The major adducts found in vivo did not correspond to the synthesized standards. Further work was carried out to determine the structure of the unidentified adducts. It was possible to release MDA and MDA-d4 from DNA of rats dosed with MDA and/or MDA-d4 and from the synthesized adducts using strong base hydrolysis. Liver of two female Wistar rats given 500 mumol/kg MDA-2HCl was hydrolyzed in 0.1 M NaOH overnight at 110 degrees C. GC-MS analysis of the heptafluorobutyric anhydride derivatized dichloromethane extracts detected 428 +/- 40 fmol of MDA/mg of DNA. In the control animals no MDA was found. The experiment was repeated with livers from animals dosed 500 mumol/kg MDA-d4.2DCl. In these rats 488 +/- 19 fmol MDA-d4 was found to be bound at liver DNA. Taking into account a 68% yield of the method, the CBI found in these cases was 0.82 and 1.0, respectively.

Biomonitoring human exposure to environmental carcinogenic chemicals.

A coordinated study was carried out on the development, evaluation and application of biomonitoring procedures for populations exposed to environmental genotoxic pollutants. The procedures used involved both direct measurement of DNA or protein damage (adducts) and assessment of second biological effects (mutation and cytogenetic damage). Adduct detection at the level of DNA or protein (haemoglobin) was carried out by 32P-postlabelling, immunochemical, HPLC or mass spectrometric methods. Urinary excretion products resulting from DNA damage were also estimated (immunochemical assay, mass spectrometry). The measurement of adducts was focused on those from genotoxicants that result from petrochemical combustion or processing, e.g. low-molecular-weight alkylating agents, PAHs and compounds that cause oxidative DNA damage. Cytogenetic analysis of lymphocytes was undertaken (micronuclei, chromosome aberrations and sister chromatid exchanges) and mutation frequency was estimated at a number of loci including the hprt gene and genes involving in cancer development. Blood and urine samples from individuals exposed to urban pollution were collected. Populations exposed through occupational or medical sources to larger amounts of some of the genotoxic compounds present in the environmental samples were used as positive controls for the environmentally exposed population. Samples from rural areas were used as negative controls. The project has led to new, more sensitive and more selective approaches for detecting carcinogen-induced damage to DNA and proteins, and subsequent biological effects. These methods were validated with the occupational exposures, which showed evidence of DNA and/or protein and/or chromosome damage in workers in a coke oven plant, garage workers exposed to diesel exhaust and workers exposed to ethylene oxide in a sterilization plant. Dose reponse and adduct repair were studied for methylated adducts in patients treated with methylating cytostatic drugs. The biomonitoring methods have also demonstrated their potential for detecting environmental exposure to genotoxic compounds in nine groups of non-smoking individuals, 32P-postlabelling of DNA adducts being shown to have the greatest sensitivity.

Albumin adducts, hemoglobin adducts and urinary metabolites in workers exposed to 4,4'-methylenediphenyl diisocyanate.

4,4'-Methylenediphenyl diisocyanate (MDI) is the most widely used isocyanate in the manufacture of polyurethanes. MDI has been implicated as one of the major causes of occupational asthma. Hydrolysis of MDI can yield 4,4'-methylenedianiline (MDA), which is a suspected human carcinogen. Thus the need to monitor occupational exposure to MDI is of great significance. The use of air monitors alone has been found to be insufficient and there is a need for sensitive markers of recent and long-term exposure. We obtained biological samples from a group of 20 workers exposed to MDI vapor during the manufacture of polyurethane products. The air levels of MDI in the factory were measured using personal, work room and work station monitors. In most cases the levels were below detection limits. The blood and urine samples were analyzed for the presence of adducts and metabolites using GC-MS methods. Urinary base-extractable metabolites were found above control levels in 15 of the 20 workers and ranged from 0.035 to 0.83 pmol MDA/ml. The level of the acetylated metabolite N'-acetyl-4,4'-methylenedianiline (AcMDA) ranged from 0.13 to 7.61 pmol/ml. The amount of MDA released after acid hydrolysis was on average 6.5 times higher than the amount of free MDA and AcMDA present in urine. MDA was detected as a hemoglobin (Hb) adduct in all of the 20 subjects. The level ranged from 70 to 710 fmol/g Hb. In one individual the Hb adduct of AcMDA was detected. This is the first time a Hb adduct of AcMDA has been detected after occupational exposure to MDI. This is a further piece of evidence for the biological availability of the suspected human carcinogen MDA from in vivo hydrolysis of MDI. Plasma albumin conjugates of MDI can cause the onset of respiratory disorders in both man and animal models. Thus we investigated the presence of plasma protein adducts. The plasma MDA levels ranged from 0.25 to 5.4 pmol/ml. Up to 120 fmol/mg were found to be covalently bound to albumin.

Hemoglobin adducts and urine metabolites of 4,4'-methylenedianiline after 4,4'-methylenediphenyl diisocyanate exposure of rats.

4,4'-Methylenediphenyl diisocyanate (MDI) is a very important component in the production of polyurethane. In a long-term experiment, designed to determine the carcinogenic and toxic effects of MDI, rats were exposed chronically for 3 and 12 months, to 0.0 (control), 0.26, 0.70 and 2.06 mg MDI/m3 as aerosols. Hemoglobin adducts and urine metabolites of MDI were determined at the different doses in order to develop methods to biomonitor workers exposed to MDI and to assess a risk resulting from such exposure. Hemoglobin adducts and urine metabolites of 4,4'-methylenedianiline (MDA) were found in all rats, including controls. MDA and N-acetyl-MDA (AcMDA) were quantified by GC-MS after derivatization with heptafluorobutyric anhydride. The dose-response relationships for hemoglobin adducts and urine metabolites were non-linear over this dose range. In urine, free AcMDA and MDA were found after base extraction. The amount of MDA present in urine and to a lesser extent the AcMDA found in urine correlate well with the corresponding amount determined as hemoglobin adducts for all dose groups. In order to release MDA from possible conjugates of MDA and AcMDA, urine was treated under strong acidic conditions. Following this procedure higher MDA levels were found than the sum of MDA and AcMDA from mild base hydrolysis. Similar results were obtained with the rats exposed for 3 and 12 months, indicating that a steady state had been reached by 3 months. In order to perform further investigations of the bronchoalveolar lavage fluid one group of animals was given a 1 week recovery period before sacrifice. Hemoglobin adducts from these animals showed a decrease of approximately 40% for all dose groups. According to the lifetime of rat erythrocytes the levels of hemoglobin adducts should have decreased by only 22%. This suggests that the erythrocytes with modified hemoglobin have a shorter lifespan. In order to exclude the possibility that hemoglobin adducts may have resulted from ingestion of hydrolyzed MDI via licking of the fur, a single dose experiment with rats exposed through the nose only or with the whole body was carried out. The only difference observed between these two exposure regimes was that the hemoglobin adduct levels of AcMDA after nose only exposure were significantly higher than after total body exposure. The presence of AcMDA in urine and as a hemoglobin adduct indicates that MDA was bioavailable after MDI exposure. The presence of MDA may contribute significantly to the carciongenic potential of MDI, since MDA has been shown to be carcinogenic in animals.

Exposure to toluenediamines from polyurethane-covered breast implants.

Toluenediamines (TDA) were monitored in blood, urine and redon drainage following implantation of polyurethane (PU)-covered breast prostheses. In the redon drainage TDAs showed an initial steep drop. The levels did not fall below detection limits but formed a plateau, which suggests a continued degradation of the PU foam. Urinary metabolite levels were above pre-operation background in all samples collected. In plasma there is an initial lag period of 20-30 days, where little above background TDA was found, after which levels rose to above 4.0 and 1.5 ng/ml plasma for 2,4-toluenediamine (24TDA) and 2,6-toluenediamine (26TDA), respectively. Elevated levels were found up to 2 years post-operation. Acid hydrolysis of precipitated plasma proteins released equivalent amounts of TDA as from total plasma, TDA being covalently bound to both albumin and globulin fractions. Urinary and plasma levels from these patients are in the same range detected from occupational exposure to toluene diisocyanate.

Biomonitoring of workers exposed to 4,4'-methylenedianiline or 4,4'-methylenediphenyl diisocyanate.

4,4'-Methylenedianiline (MDA) and 4,4'-methylenediphenyl diisocyanate (MDI) are important intermediates in the production of polyurethanes. In order to biomonitor people exposed to low levels of MDA or MDI we have developed sensitive methods to measure hemoglobin (Hb) adducts and urine metabolites. Adducts and metabolites from 33 workers exposed to MDA and 27 workers exposed to MDI were analyzed by gas chromatography-mass spectrometry after hydrolysis, extraction and derivatization with heptafluorobutyric anhydride. Hb adducts of MDA were detected in 31 out of the 33 MDA workers and both MDA and N-acetyl-MDA (AcMDA) were found in 20 of these individuals. The detection limit for MDA was 20 fmol and for AcMDA 100 fmol/sample, which correspond to an absolute detection limit of approximately 1 fmol MDA and 5 fmol AcMDA, respectively. In the urine of workers exposed to MDA both MDA and AcMDA were found in all samples, with the exception of five where only MDA was detected. Acid hydrolysis of the urine samples yielded an approximately 3-fold higher concentration of MDA than the sum of MDA and AcMDA found after base hydrolysis. MDA but not AcMDA found in urine and in Hb correlate well, except for three outliers. In one workers the Hb adduct level of MDA was very low compared to the urine levels. Two workers had very high levels of MDA as Hb adducts but very low levels as urine metabolites. The former case indicates that the workers were recently exposed to higher levels of MDA. The latter case suggests a relatively low recent exposure. The air levels of MDA, monitored using personal air monitors, were below the detection limit. It was possible, however, to determine exposure to MDA for all workers with the methods presented in this publication. Workers exposed exclusively to MDI were studied. Exposure levels, as monitored using personal air samplers, were below the detection limit of 3 micrograms/m3, with the exception of three individuals. In 10 of the MDI workers, hydrolyzable Hb adducts of MDA (57-219 fmol/g Hb) were found. Except for four subjects, the presence of MDA (0.007-0.14 nmol/l) and AcMDA (0.08-3 nmol/l) was detected in all urine samples after base treatment. Following acid hydrolysis of the urine, higher levels of MDA (0.7-10 nmol/l) were found than the sum of free MDA and AcMDA. According to the present data, it was possible to detect exposure to MDI in a greater number of individuals by analyzing urinary metabolites than by measuring Hb adducts or air monitoring.

Identification of endogenous electrophiles by means of mass spectrometric determination of protein and DNA adducts.

Monitoring exposure to alkylating agents may be achieved by quantitatively determining the adduct levels formed with nucleic acids and/or proteins. One of the most significant results arising from the application of this approach has been the discovery in control populations of "background" levels of alkylated nucleic acid bases or alkylated proteins, in particular hemoglobin (Hb). In the case of Hb, a wide variety of such adducts have been detected and quantitated by mass spectrometric techniques, with methylated, 2-carboxyethylated, and 2-hydroxyethylated modifications being most abundant. Although the source of these alkylation products is unknown, both endogenous and exogenous sources may be proposed. We have recently confirmed the presence of the N-terminal hydroxyethylvaline adduct in control human Hb using tandem mass spectrometry (MS-MS) and have now established background levels using GC-MS in more than 70 samples. Smoking raises the levels of the adduct up to 10-fold and occupational exposure to ethylene oxide up to 300-fold. Background levels of alkylated nucleic acids may be studied by analysis of N7-alkylated guanine or N3-alkylated adenine, which are excised from nucleic acids after their formation and are excreted in urine. Although the presence of some of these urinary constituents may be accounted for by their natural occurrence in RNA or diet, the endogenous or exogenous source of others is unknown. Quantitative methods using MS-MS have now been developed for five of the observed urinary alkylguanines [N7-methyl-, N2-methyl-, N2-dimethyl-, N7-(2-hydroxyethyl)-, and N2-ethylguanine].(ABSTRACT TRUNCATED AT 250 WORDS)

Monitoring of exposure to styrene oxide by GC-MS analysis of phenylhydroxyethyl esters in hemoglobin.

Styrene oxide, which is the genotoxically active metabolite of styrene, reacts in vivo with carboxylic acid residues in hemoglobin forming phenylhydroxyethyl esters. Mild alkali hydrolysis cleaves these ester adducts, yielding styrene glycol, which in human blood labelled in vitro with 14C-styrene oxide accounted for 15% of the total radioactivity covalently bound to the protein. A quantitative assay procedure has been developed for measuring the base released styrene glycol in globin. The method utilizes solvent extraction followed by trimethylsilyl ether derivatization and separation and quantitation by capillary gas chromatography with selective ion recording mass spectrometry. Globin labelled in vitro with d8-styrene oxide was used as the internal standard. The method was used to establish a dose-response relationship in rats given single i.p. doses of styrene oxide (83.3-833 mumol/kg body wt). The method, which allows quantitation of the adducts down to levels of 15 pmol/g globin, has the potential to act as a dosimeter for industrial workers exposed to styrene or styrene oxide.

Identification of metabolites of 4,4'-diaminodiphenylmethane (methylene dianiline) using liquid chromatographic and mass spectrometric techniques.

The in vitro metabolism of 4,4'-diaminodiphenylmethane (methylene dianiline, MDA) was investigated using rabbit liver microsomes. Minimal clean-up of the microsomal incubations was carried out using zinc sulphate precipitation followed by solid-phase extraction on Sep-Pak C18 cartridges. Three metabolites were detected in hepatic microsomal incubations, namely the azodiphenylmethane (azo) azoxydiphenylmethane (azoxy) and 4-nitroso-4'-aminodiphenylmethane (nitroso) compounds. The azo and azoxy metabolites were produced enzymatically whereas the nitroso compound may have been formed via a non-enzymatic process. Reversed-phase high-performance liquid chromatography-plasma spray mass spectrometry was used to initially detect these metabolites. Fast atom bombardment mass spectrometry and fast atom bombardment tandem mass spectrometry were utilized to further structurally characterise these compounds. Comparison of mass spectral data obtained from synthesised standards with data obtained on the putative metabolites substantiated the characterisation of these compounds.