Chromosomal aberrations and micronuclei in lymphocytes in relation to alkylation of hemoglobin in workers exposed to ethylene oxide and propylene oxide

Chromosomal aberrations and micronuclei in lymphocytes were measured in workers exposed to propylene oxide in a factory producing alkylated starch, and in workers exposed to ethylene oxide in connection with sterilization of medical equipment. Adduct levels in hemoglobin were determined as a measure of in vivo doses of the two compounds. The levels of hydroxypropylvaline in propylene oxide-exposed workers were correlated in estimated exposure doses. The levels of this adduct in the unexposed group were close to the detection limit of the method. The levels of hydroxyethylvaline, recorded in the propylene oxide-exposed group were consistent with earlier data on hemoglobin alkylation in occupationally unexposed subjects. The adduct measurements revealed increased levels of hydroxyethylvaline in the two subgroups of ethylene oxide-exposed workers, i.e., assemblers with a low and sterilizers with a high exposure. According to expectation the subgroups differed in adduct levels. The results of the cytogenetic study showed that the clastogenic potency of propylene oxide was lower than that of ethylene oxide, since the propylene oxide-exposed individuals had lower frequencies of micronuclei and chromosomal breaks compared to the assemblers despite a lower adduct level in the last group.

Associations between estimated acrylamide intakes, and hemoglobin AA adducts in a sample from the Malmö Diet and Cancer cohort

OBJECTIVE

To examine the coherence of estimated intakes of acrylamide (AA) from foods, with hemoglobin (Hb) AA adduct levels, an objective marker of environmental AA exposure.

DESIGN

A cross-sectional study.

SETTING

The Malmö Diet and Cancer study, a large population-based prospective cohort (n=28 098) in the south of Sweden.

SUBJECTS

A sample of non-smoking (n=70) and smoking (n=72) women and men selected to obtain large variation in Hb AA adducts.

METHODS

Self-reported data on the usual consumption of foods were combined with published data on the AA content in Swedish foods. The Hb AA adduct levels were determined by a modified Edman degradation method. Linear regression and correlation analysis examined associations between estimated AA intakes, and Hb AA adducts.

RESULTS

In randomly selected individuals (n=40), the estimated median AA intake was 28 mug per day. In linear regression models, adjusting for sex, significant associations were seen in non-smokers between Hb AA adducts and estimated AA from foods (P=0.006). In smokers both AA from foods (P=0.006) and the calculated amount of tobacco consumed (P=0.003) were significantly associated with Hb AA adducts. Positive partial correlations between dietary AA estimates and Hb AA adducts were seen in smoking men (r=0.37) and women (r=0.59), and in non-smoking men (r=0.60), but not in non-smoking women.

CONCLUSIONS

This study suggests that both diet and tobacco are important sources of the environmental AA exposure, although the lack of correlations in non-smoking women cast doubt on the validity of dietary AA intake estimates used in cancer epidemiology, or suggest that unrecognized factors may influence the internal dose measure of AA exposure.

Cobalamin as an analytical tool for analysis of oxirane metabolites of 1,3-butadiene: Development and validation of the method

The reduced form of vitamin B12 [cob(I)alamin] is known to be a supernucleophile, with the ability to react 10(5) times faster than standard nucleophiles. Procedures have been developed where cob(I)alamin is used as an analytical tool for the trapping of electrophilically reactive compounds. In the present work, a sensitive and accurate method for determination of reactive metabolites produced in vitro has been developed and validated. Diepoxybutane (DEB), a metabolite of 1,3-butadiene, was used as a model compound. The intermediate precursor 1,2-epoxybutene (EB) was incubated in a mouse liver S9 metabolic system and the formation of DEB was studied. Samples were taken at different times from the incubation mixture and added to the cob(I)alamin. The alkyl-cobalamins (alkyl-Cbl) formed were directly analysed by a miniaturized LC-MS/MS method and column switching. The assay was linear over the concentration range of 1.5-500 microM with acceptable precision and accuracy.

Human exposure and internal dose assessments of acrylamide in food

This review provides a framework contributing to the risk assessment of acrylamide in food. It is based on the outcome of the ILSI Europe FOSIE process, a risk assessment framework for chemicals in foods and adds to the overall framework by focusing especially on exposure assessment and internal dose assessment of acrylamide in food. Since the finding that acrylamide is formed in food during heat processing and preparation of food, much effort has been (and still is being) put into understanding its mechanism of formation, on developing analytical methods and determination of levels in food, and on evaluation of its toxicity and potential toxicity and potential human health consequences. Although several exposure estimations have been proposed, a systematic review of key information relevant to exposure assessment is currently lacking. The European and North American branches of the International Life Sciences Institute, ILSI, discussed critical aspects of exposure assessment, parameters influencing the outcome of exposure assessment and summarised data relevant to the acrylamide exposure assessment to aid the risk characterisation process. This paper reviews the data on acrylamide levels in food including its formation and analytical methods, the determination of human consumption patterns, dietary intake of the general population, estimation of maximum intake levels and identification of groups of potentially high intakes. Possible options and consequences of mitigation efforts to reduce exposure are discussed. Furthermore the association of intake levels with biomarkers of exposure and internal dose, considering aspects of bioavailability, is reviewed, and a physiologically-based toxicokinetic (PBTK) model is described that provides a good description of the kinetics of acrylamide in the rat. Each of the sections concludes with a summary of remaining gaps and uncertainties.

Reaction-kinetic parameters of glycidamide as determinants of mutagenic potency

Values for reaction-kinetic parameters of electrophiles can be used to predict mutagenic potency. One approach employs the Swain-Scott relationship for comparative kinetic studies of electrophilic agents reacting with nucleophiles. In this way glycidamide (GA), the putatively mutagenic/carcinogenic metabolite of acrylamide, was assessed by determining the rates of reaction with different nucleophiles. The rate constants (kNu) were determined using the "supernucleophile" cob(I)alamin [Cbl(I)] as an analytical tool. The Swain-Scott parameters for GA were compared with those of ethylene oxide (EO). The substrate constants, s values, for GA and for EO were found to be 1.0 and 0.93, respectively. The reaction rates at low values of nucleophilic strength (n=1-3), corresponding to oxygens in DNA, were determined to be 2-3.5 times higher for GA compared to EO. GA was also more reactive than EO towards other nucleophiles (n=0-6.4). The mutagenic potency of GA was determined in Chinese hamster ovary cells (hprt mutations in CHO-AA8 cells per dose unit with gamma-radiation as reference standard). The potency of GA was estimated to be about three mutations per 10(5) cells and mMh corresponding to about 40 rad-equ./mMh. A preliminary comparison of the mutagenic potency (per mMh and as rad-equivalents) of GA and EO shows an approximately seven times higher potency for GA. A higher mutagenic potency of GA compared to EO is compatible with expectation from reaction-kinetic data of the two compounds. The data confirmed that GA is not a strong mutagen, which is in line with what is expected for simple oxiranes. The present study shows the value of cob(I)alamin for the determination of reaction-kinetic parameters and their use for prediction of mutagenic potency.

Seroprevalence of Dictyocaulus viviparus in first grazing season calves in Sweden

A serological survey was carried out to determine the prevalence and geographical distribution of Dictyocaulus viviparus in calves after their first grazing season in Sweden. A total of 754 animals from 76 randomly selected herds in seven geographical regions were examined between September 24 and December 19, 2001. To get an indication about the geographical distribution of the infection 41 herds with beef-suckler calves were investigated. On each farm, blood was collected from 8 to 10 animals after an average of 26 +/- 24 days post-housing to determine specific IgG1 levels against a possible lungworm sperm antigen that is highly specific against patent infections of D. viviparus. We also investigated the seroprevalence of lungworm infection in relation to cattle management. In one region additional samples were analysed from 35 herds either with: (a) beef-suckling calves that were dewormed at housing, (b) untreated organically raised dairy calves, and finally from conventionally raised dairy calves either, (c) with or, (d) without a prophylactic anthelmintic treatment programme against gastrointestinal parasites on pasture. A questionnaire was used to obtain information about herd size and management, including measures to control nematode parasites on the farm. A total of 86 (11.8%) out of 754 animals had antibodies against D. viviparus, and at least one infected individual was detected in 30 (39.5%) of the 76 herds examined. Lungworm infected animals were found throughout the country and there was no significant differences between regions, although in southern and southwestern Sweden 70.0% of the herds were infected. Furthermore, there were no major differences in the seroprevalence in relation to management. Between 40.0 and 44.4% of the herds were infected irrespective of management, with the exception of calves from organic herds where no seropositive samples were found (0%). This result is in contrast to previous findings of lungworms in Sweden, and indicates that the parasite status on organic farms is diverse.

Adducts of N-terminal valines in hemoglobin with isoprene diepoxide, a metabolite of isoprene

Isoprene (2-methylbuta-1,3-diene) is a multi-site carcinogen in rodents. To evaluate the role of the diepoxide metabolite (1,2:3,4-diepoxy-2-methylbutane) in carcinogenesis, measurements of in vivo doses of the diepoxide are needed. The in vivo dose may be inferred from levels of reaction products with hemoglobin (Hb adducts). This report presents in vitro studies of the adduct formation by the diepoxide of isoprene with valinamide and oligopeptides as model compounds of N-terminal valines in hemoglobin (Hb). In the reaction with valinamide it was shown that isoprene diepoxide forms as the main product a ring-closed adduct, which is a pyrrolidine derivative [N,N-(2,3-dihydroxy-2-methyl-1,4-butadiyl)valinamide, MPyr-Val]. The analysis was performed by gas chromatography/mass spectrometry (GC/MS) (EI and PICI) after acetylation. The ring-closed adduct was also identified by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) as the main product in the reaction between isoprene diepoxide and standard hepta- or (2H8)octapeptides, corresponding to the N-terminal peptides of the alpha-chains in mouse and rat Hb. These peptides, alkylated with isoprene diepoxide, to be used as internal standards and calibration standards for quantification of MPyr-adduct levels in vitro and in vivo, were analyzed with respect to the degree of MPyr-alkylation by two independent methods, amino acid analysis and HPLC-UV; similar results were obtained using these methods. A method for measurement of Hb adducts as modified peptides, used earlier to measure a similar adduct to N-terminal valines in Hb from the diepoxide of 1,3-butadiene, has in the present work been tested for application to isoprene diepoxide. The method is based on tryptic degradation of globin and LC/ESI-MS analysis of N-terminal Pyr-heptapeptides of the Hb alpha-chain enriched by HPLC. MPyr-adduct levels in isoprene diepoxide alkylated hemolysate from mouse erythrocytes incubated with different concentrations of isoprene diepoxide (2 and 10 mM) for 1 h were quantified. The adduct level was about 50 nmol/g alpha-chain Hb per mM x h. From the adduct levels the rate constant of isoprene diepoxide for reaction with N-terminal valine was calculated to be about 1.6 times faster than for diepoxybutane.

Acrylamide and N-methylolacrylamide poisoning in a herd of Charolais crossbreed cattle

Seven beef cattle from a herd accidentally exposed to acrylamide and N-methylolacrylamide while grazing were observed for eight months. They showed clinical signs of impaired nerve function, mainly in the hindlegs, with varying degrees of weakness and ataxia. The animals were irritable, nervous and hypersensitive to touch. Both pupils of the most badly affected animal were dilated and it had poor pupillary light responses; it also showed signs of axonal neuropathy. Selected haematological and clinical chemistry variables were normal. The severity of the neurological signs was correlated with the concentrations of haemoglobin adducts of acrylamides. The animals recovered substantially after their exposure. The gestations of four of the animals which were in calf proceeded normally.

Estimation of cancer risk caused by environmental chemicals based on in vivo dose measurement

Methods for estimating the risks, that is, the probabilities of contracting a disease, are required as a basis of decision-making regarding the needs for protection and risk reduction. A mechanism-based model has been developed for estimating the cancer risks from genotoxic chemicals using adducts to macromolecules for determining the in vivo dose. On the assumption that cancer is caused by an increased frequency of mutations in tissues, interacting with inherited or acquired growth-promoting factors, a simplified model has been proposed for estimating cancer risks from chemically reactive, that is, mutagenic agents. According to a multiplicative model, the risk increment (deltaP) is deltaP = beta x D x P0, proportional to the background incidence (P0) and linearly dependent on dose at low to intermediate doses (D); beta is the risk coefficient, which is approximately the same for different tumor sites and, probably, different species. This model is already in use for ionizing radiation and has been validated for a few mutagenic and carcinogenic chemical compounds. Inherent in this method is the measurement of dose. Sensitive chemical methods have been developed for determining reactive compounds and intermediates in vivo through their stable reaction products (adducts) with proteins, particularly hemoglobin. In humans or animals, the doses of genotoxic agents can be derived from measured levels of adducts and rates of adduct formation. This approach has been applied to various exposures such as air pollutants in occupational settings, carcinogens in foods, and tobacco smoke. By such methods, exposures to previously unknown mutagens and carcinogens may be detected and assessed in humans. Examples of this are epoxides (from endogenously produced alkenes) and compounds (such as acrylamide) formed in cooking foodstuffs.

Health effects of occupational exposure to acrylamide using hemoglobin adducts as biomarkers of internal dose

OBJECTIVES

This study assessed the health effects of occupational acrylamide exposure using hemoglobin (Hb) adducts as biomarkers of internal dose.

METHODS

Two hundred and ten tunnel workers exposed for about 2 months to a chemical-grouting agent containing acrylamide and N-methylolacrylamide underwent a health examination. Blood samples were drawn for the analysis of Hb adducts of acrylamide. Fifty workers claiming recently developed or deteriorated symptoms of the peripheral nervous system (PNS) were referred to a neurophysiological examination. Workers with Hb-adduct levels exceeding 0.3 nmol/g globin attended follow-up examinations 6, 12, and 18 months after exposure cessation.

RESULTS

Forty-seven workers had Hb-adduct levels within the normal background range (0.02-0.07 nmol/g globin), while the remaining 163 had increased levels up to a maximum of 17.7 nmol/g globin. Clear-cut dose-response associations were found between the Hb-adduct levels and PNS symptoms. Thirty-nine percent of those with Hb-adduct levels exceeding 1 nmol/g globin experienced tingling or numbness in their hands or feet. A no-observed adverse effect level of 0.51 nmol/g globin was estimated for numbness or tingling in the feet or legs. For 23 workers there was strong evidence of PNS impairment due to occupational exposure to acrylamide. All but two had recovered 18 months after the cessation of exposure.

CONCLUSIONS

Occupational exposure to a grouting agent containing acrylamide resulted in PNS symptoms and signs. The use of Hb adducts of acrylamide as a biomarker of internal dose revealed strong dose-response associations. The PNS symptoms were, however, generally mild, and in almost all cases they were reversible.

Studies of dose distribution, premutagenic events and mutation frequencies for benzo[a]pyrene aiming at low dose cancer risk estimation

Cancer risk assessment of polycyclic aromatic hydrocarbons (PAH) is complicated by several of these compounds exerting a promoter action leading to high tumour incidences at high doses. Cancer risks at low doses corresponding to the uptake from air and food in the general environment would best be estimated on the basis of measurement of in vivo target doses of genotoxic (mutagenic) intermediates and a determination of mutation frequency per unit of dose. In experiments ultimately aiming at a risk assessment of environmental PAH from in vivo doses benzo[a]pyrene (BaP) was chosen as a model. gamma-Radiation has earlier been used as a reference standard in cancer risk estimation of genotoxic chemicals where dose equivalents (rad-equivalents) have been shown to give reliable risk estimates for several alkylating agents. Variation in dose of BaP diolepoxide between organs was studied by measurement of deoxyguanosine-N(2) adducts in DNA after administration of BaP by gavage to mice of a strain with reduced DNA repair (Xpa(-/-)). The adduct levels in spleen, forestomach, stomach and small intestine were approximately the same; with the adduct level in spleen as reference it was twice as high in liver and lung and about half as high in colon tissue. A chemical or radiation dose is proportional to the cumulative frequency of putatively premutagenic changes (premutagenic hits) in DNA. The mutation frequency per premutagenic hit (genotoxic chemicals) and per unit of dose (gamma-radiation) were calculated from acutely exposed V79 cells in order to determine the mutagenic effectiveness of each agent. Based on the mutagenic effectiveness determined in this study 10(-4) Gy can be regarded equally effective in causing phenotypically expressed HPRT mutations as the dose of BaP which causes the formation of one deoxyguanosine-N(2) adduct per cell.

Comparison of exhaust emissions from Swedish environmental classified diesel fuel (MK1) and European Program on Emissions, Fuels and Engine Technologies (EPEFE) reference fuel: a chemical and biological characterization, with viewpoints on cancer risk

Diesel fuels, classified as environmentally friendly, have been available on the Swedish market since 1991. The Swedish diesel fuel classification is based upon the specification of selected fuel composition and physical properties to reduce potential environmental and health effects from direct human exposure to exhaust. The objective of the present investigation was to compare the most stringent, environmentally classified Swedish diesel fuel (MK1) to the reference diesel fuel used in the "European Program on Emissions, Fuels and Engine Technologies" (EPEFE) program. The study compares measurements of regulated emissions, unregulated emissions, and biological tests from a Volvo truck using these fuels. The regulated emissions from these two fuels (MK1 vs EPEFE) were CO (-2.2%), HC (12%), NOx (-11%), and particulates (-11%). The emissions of aldehydes, alkenes, and carbon dioxide were basically equivalent. The emissions of particle-associated polycyclic aromatic hydrocarbons (PAHs) and 1-nitropyrene were 88% and 98% lower than those of the EPEFE fuel, respectively. The emissions of semi-volatile PAHs and 1-nitropyrene were 77% and 80% lower than those from the EPEFE fuel, respectively. The reduction in mutagenicity of the particle extract varied from -75 to -90%, depending on the tester strain. The reduction of mutagenicity of the semi-volatile extract varied between -40 and -60%. Furthermore, the dioxin receptor binding activity was a factor of 8 times lower in the particle extracts and a factor of 4 times lower in the semi-volatile extract than that of the EPEFE fuel. In conclusion, the MK1 fuel was found to be more environmentally friendly than the EPEFE fuel.

The multiplicative model for cancer risk assessment: applicability to acrylamide

According to a multiplicative model for prediction of cancer risk for genotoxic agents the incremental cancer risk is, for low-intermediate exposures, proportional to target doses of the genotoxic substance and to the background risk in control groups. This model has been applied to evaluate cancer tests of acrylamide in rodents. Because of its reactivity toward DNA, glycidamide is assumed to be the causative genotoxic metabolite of acrylamide. Evaluation of experimental data according to the multiplicative model shows that mice, compared with rats, are of the order of 10 times more sensitive per administered dose of acrylamide. The US EPA procedure would, however, generally predict rats to be about twice as sensitive as mice to carcinogenic chemicals, because their estimates are based on scaling of the dose per square meter body surface area, as a surrogate for metabolic differences between the species. The comparison of rats and mice with respect to observed cancer incidence is at a key position in the evaluation of the usefulness of risk models for extrapolation between species. In the present study mice and rats were compared, with respect to in vivo doses of acrylamide and the metabolite glycidamide, after exposure to acrylamide. The relative in vivo doses were inferred from levels of hemoglobin adducts. The adduct levels from glycidamide were, per administered dose of acrylamide, approximately 3-10 times higher in mice than in rats. In combination with the above mentioned higher sensitivity of mice than rats in cancer tests of acrylamide this is compatible with the concept that glycidamide is the key genotoxic factor in acrylamide exposure. Furthermore, it is shown that the multiplicative, i.e. relative, risk model and measurements of the dose of the genotoxic factor give good prediction of the observed risk from acrylamide in cancer tests with rats and mice.

Determination of hydroxyalkyl derivatives of cobalamin (vitamin B12) using reversed phase high performance liquid chromatography with electrospray tandem mass spectrometry and ultraviolet diode array detection

Electrospray ionization tandem mass spectrometry (ESI-MS/MS) and ultraviolet diode array detection (UV-DAD), coupled on-line to reversed phase high performance liquid chromatography (HPLC), was used for the characterization of hydroxyalkyl derivatives of cob(I)alamin. The reduced form of vitamin B12, cob(I)alamin, denoted a supernucleophile due to its high nucleophilic strength, has shown promise as an analytical tool in studies of electrophilically reactive compounds in vitro and in vivo. A method for analysis of DNA-phosphate adducts was developed earlier utilizing the supernucleophilicity of cob(I)alamin to transfer alkyl groups from the phosphotriester configuration in DNA, with the formation of a Co-substituted alkyl-cobalamin (alkyl-Cbl) complex. For the purpose of identification and quantification of alkyl-Cbls at high sensitivity, an MS/MS method has been developed with application to a number of 2-hydroxyalkyl-cobalamins (OHalkyl-Cbls). The precursor oxiranes were reacted with cob(I)alamin, followed by clean-up and mass spectrometric analysis of the resulting OHalkyl-Cbls. It was found that ionization was highly dependent on solvent composition. By using acetonitrile/water/trifluoroacetic acid (TFA) (eluent I), the base peak was the doubly protonated molecule [M + 2H](2+), whereas acetonitrile/water/1-methylpiperidine (eluent II) yielded the singly protonated molecule [M + H](+) as the base peak. Excellent separation was obtained with eluent II, with good separation between stereoisomers, thus enabling the characterization of these by means of UV spectra. Limits of quantitation for 2-hydroxypropyl-cobalamin (OHPr-Cbl) were 0.2 and 2 pg/microL (or 0.1 and 1 fmol/microL) using selected ion recording (SIR) with eluent I and II, respectively. The obtained detection level should be sufficient for analysis of alkyl-Cbls from a wide range of toxicological applications.

Heating of food and haemoglobin adducts from carcinogens: possible precursor role of glycidol

Studies of adducts from reactive compounds to haemoglobin (Hb) by gas chromatography-tandem mass spectrometry according to the N-alkyl Edman method reveals the occurrence of N-(2,3-dihydroxypropyl)valine (diHOPrVal) at levels of 1-2 pmol/g Hb, in persons without known exposure. The hypothesis that this background originates from glycidol or related compounds during heating of food was tested in experiments with rats. Animals fed fried animal feed for 30 or 72 days showed an increase of the diHOPrVal level by about 50% compared with controls. Several arguments, such as the formation of reactive oxiranes by heat-induced dehydration of glycol configurations in glycerol and sugars, support the idea that glycidol (or e.g. glycidyl esters) are precursors of the adduct. In Hb samples, reduced for stabilisation of aldehyde adducts, relatively high levels of adducts determined as diHOPrVal were found, although without significant relation to frying of the feed. There is thus no indication that reduction in vivo of, for example, the Schiff base from glyceraldehyde, is a pathway for formation of the diHOPrVal. The background level of diHOPrVal in humans Hb is low, and the cancer risk associated with exposure to the specific alkylator-probably glycidol-formed in cooking, is therefore presumably low. The result implies, however, that low-molecular mass mutagenic oxiranes formed during the heating of food should be studied further.

Effects of selenium deficiency on the formation and detoxification of endogenous electrophiles in rats

Selenium deficiency could be expected to lead to enhanced lipid peroxidation through loss of selenium-dependent glutathione peroxidase activity. Such a relation has, however, been difficult to verify. In the present study, the influence of selenium deficiency in rats on in vivo doses of some endogenously occurring low-molecular mass aldehydes and epoxides was determined. In vivo doses were measured by mass-spectrometric analysis according the N-alkyl Edman method of reaction products (adducts) with N-terminal valines in hemoglobin. Despite variations between experiments, the adduct levels of acetaldehyde and malonaldehyde were shown to be significantly higher in rats fed a selenium-deficient diet than in controls fed a selenium-adequate diet. No significant effect was found for the other aldehydes measured. In contrast, the in vivo doses of endogenous ethylene oxide and propylene oxide were lowered in selenium-deficient rats, indicating a 1.7-times faster detoxification rate. This was verified by the lower adduct levels in selenium-deficient rats following intraperitoneal administration of these epoxides at moderate doses. In conclusion, the results seem to reflect the complex changes of induced and reduced enzyme activities in response to selenium deficiency. Measurement of reactive compounds through their adducts to hemoglobin has shown its ability to elucidate the effects of selenium deficiency per se.

Acrylamide: a cooking carcinogen?

Exposure to acrylamide (AA) has been monitored by mass spectrometric detection of the adduct, N-(2-carbamoylethyl)valine (CEV), to the N-termini of hemoglobin (Hb), according to the N-alkyl Edman method. In these studies, a conspicuous background level, about 40 pmol/g of globin, of apparently the same adduct was regularly observed in Hb from persons without known exposure to AA. For testing of the hypothesis that this adduct originates from AA formed in cooking, rats were fed fried animal standard diet for 1 or 2 months. These animals exhibited a strong increase of the level of the studied Hb adduct, compared to control rats fed unfried diet. By gas chromatography/tandem mass spectrometry, the identity with CEV was confirmed by the concordance of the product ion spectrum of the studied adduct with that of a verified standard and by interpretation of the fragment ions. Further support of the chemical structure, at the same time pinpointing AA as the causative reactive factor, was obtained through the demonstration that AA is formed in the heating of the feed and that the level of AA in the fried feed is compatible with the measured levels of the CEV adduct. The raised CEV adduct levels observed in experimental animals are of a magnitude that is similar to the background level in nonsmoking humans. These data render it likely that cooking of food is a major source of the background dose of AA also in humans. An evaluation of cancer tests of AA and available data for its metabolism leads to the estimation that the background dose of AA is associated with a considerable cancer risk.

Transalkylation of phosphotriesters using Cob(I)alamin: toward specific determination of DNA-phosphate adducts

The supernucleophilic cobalt compound, cob(I)alamin, has been kinetically characterized with respect to its ability to bring about transalkylation of adducts to DNA phosphates (phosphotriesters). The reactivity of cob(I)alamin toward different phosphotriesters (model compounds and methylated DNA), as well as its specificity toward DNA-phosphate adducts, has been investigated. Through nucleophilic displacement on the alkyl by cob(I)alamin, the alkyl groups (methyl and ethyl) were transferred from phosphotriesters within minutes at room temperature. In contrast, methylated nucleosides (base adducts) were stable in the presence of cob(I)alamin.

A liquid chromatography tandem mass spectrometric method for in vivo dose monitoring of diepoxybutane, a metabolite of butadiene

1,3-Butadiene, a common air pollutant formed in the combustion of organic matter, has been assessed by the U.S. EPA to be a strongly carcinogenic compound. This risk assessment is very uncertain because of the lack of information on the dose of the powerful carcinogenic metabolite diepoxybutane (DEB). This report presents an analytical method for in vivo dose monitoring of a unique marker for DEB. For a large number of alkylating agents in vivo doses are monitored by measurement by gas chromatography/mass spectrometry (GC/MS) of adducts to N-terminal valine in hemoglobin (Hb), using a modified Edman degradation method. This method is applicable to monofunctional epoxides from butadiene. However, in reaction with N-terminal valine, DEB forms an adduct which is ring-closed to a pyrrolidine, N,N-(2,3-dihydroxy-1,4-butadiyl)valine, with a tertiary amino group that prevents detachment of the alkylated valine by the Edman reagent. Therefore a method has been developed based on the analysis by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) of the N-modified N-terminal peptides enriched after trypsin digestion of globin. In this study Hb samples from mice injected intraperitoneally with (+/-)-DEB were examined qualitatively and quantitatively with regard to the ring-closed adduct. The N-terminal pyrrolidine-heptapeptide was identified in treated mice. The highest adduct levels were obtained in samples from animals given the highest dose of DEB and the adduct levels were below the detection level in control mice.

A new approach for measuring protein adducts from benzo[a]pyrene diolepoxide by high performance liquid chromatography/tandem mass spectrometry

The long-range goal of the present study is the development of a general approach for in vivo dosimetry of reactive metabolites of polycyclic aromatic hydrocarbons (PAHs), to be used as a tool in cancer risk assessment. With benzo[a]pyrene (BaP) chosen as indicator and a model of PAHs this study aims at the development of a method for the determination of adducts to histidine (His) in hemoglobin (Hb) and serum albumin (SA) of reactive metabolites of BaP. The predominantly mutagenic metabolite of BaP has been shown to be a diolepoxide isomer, +(anti)r-7, t-8-dihydroxy-t-9,10-epoxy-7,8, 9,10-tetrahydrobenzo[a]pyrene (+BPDE). In comparison with other methods for protein degradation, hydrazinolysis was found to be sufficiently effective and mild. The His adduct isolated after protein hydrazinolysis, with protection by tert-butyloxycarbonyl (Boc) of the hydrazide and alpha-amino groups, was shown to be N(im)- +/- (r-7, t-8, t-9-trihydroxy-7, 8, 9, 10-tetrahydrobenzo[a]pyren-c-10-yl)-N(alpha), N(2)-bis(tert-butyloxycarbonyl)-L-histidinehydrazide. Isomers of this compound, used as references, were synthesized and characterized by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Adducts in Hb and SA from in vitro treatment with BPDE were characterized after hydrazinolysis by HPLC-UV/MS, muHPLC/MS/MS and gas chromatography/mass spectrometry (GC/MS). Approximately 70 and 10% of the isolated BPDE adducts from SA and Hb, respectively, were His adducts. Other products were released as BaP tetrols and BaP triols. For the purpose of enrichment/purification of BPDE-His adducts, C(18) and cation exchange solid phase extraction (SPE) were utilized. The sensitivity obtained by this new approach, based on hydrazinolysis of protein, enrichment by SPE and analysis with muHPLC/MS/MS (APCI), is in the low-fmole range.

Measurement of HPRT mutations in splenic lymphocytes and haemoglobin adducts in erythrocytes of Lewis rats exposed to ethylene oxide

Young adult male Lewis rats were exposed to ethylene oxide (EO) via single intraperitoneal (i.p.) injections (10-80 mg kg-1) or drinking water (4 weeks at concentrations of 2, 5, and 10 mM) or inhalation (50, 100 or 200 ppm for 4 weeks, 5 days week-1, 6 h day-1) to measure induction of HPRT mutations in lymphocytes from spleen by means of a cloning assay. N-ethyl-N-nitrosourea (ENU) and N-(2-hydroxyethyl)-N-nitrosourea (HOENU) were used as positive controls. Levels of N-(2-hydroxyethyl)valine (HOEtVal) adducts in haemoglobin (expressed in nmol g-1 globin) were measured to determine blood doses of EO (mmol kg-1 h, mM h). Blood doses were used as a common denominator for comparison of mutagenic effects of EO administered via the three routes. The mean HPRT mutant frequency (MF) of the historical control was 4.3 x 10(-6). Maximal mean MFs for ENU (100 mg kg-1) and HOENU (75 mg kg-1) were 243 x 10(-6) and 93 x 10(-6), respectively. In two independent experiments, EO injections led to a statistically significant dose-dependent induction of mutations, with a maximal increase in MF by 2.3-fold over the background. Administration of EO via drinking water gave statistically significant increases of MFs in two independent experiments. Effects were, at most, 2.5-fold above the concurrent control. Finally, inhalation exposure also caused a statistically significant maximal increase in MF by 1.4-fold over the background. Plotting of mutagenicity data (i.e., selected data pertaining to expression times where maximal mutagenic effects were found) for the three exposure routes against blood dose as common denominator indicated that, at equal blood doses, acute i.p. exposure led to higher observed MFs than drinking water treatment, which was more mutagenic than exposure via inhalation. In the injection experiments, there was evidence for a saturation of detoxification processes at the highest doses. This was not seen after subchronic administration of EO. The resulting HPRT mutagenicity data suggest that EO is a relatively weak mutagen in T-lymphocytes of rats following exposure(s) by i.p. injection, in drinking water or by inhalation.

Short-term exposure of rodents to diesel exhausts: usefulness for studies of genotoxic and immunotoxic effects

An exposure facility was tested with regard to the information obtainable from short-term animal experiments for the assessment of health hazards from automotive engine exhausts. Indicators of immunotoxicity and genotoxicity were studied in guinea pigs and mice, respectively, exposed for 2 weeks, 8 h/day, to ten times diluted exhausts from a one-cylinder research diesel engine running at constant load. Regulated and non-regulated pollutants were determined. Besides increased number of lavageable cells in the airways, exposed guinea pigs exhibited, after immunization and challenge to ovalbumin, reduced leukotrienes B4 and C4 in lavage fluid and reduced anti-ovalbumin IgG in serum. Absence of increased CYP1A activity indicated that the exposure was below the threshold for induction of these enzymes. Instead a certain reduction of this activity indicated interaction with active enzyme sites. In vivo doses of some reactive metabolites of low molecular mass were measured by adducts to hemoglobin. Doses from aliphatic epoxides were low, in accordance with low hydrocarbon levels in the exhaust. The levels of hemoglobin adducts from aldehydes showed no clearcut influences of exposure. Genetic effects determined by DNA fingerprint analysis were indicated. It is concluded that repeated dose inhalation exposure of small numbers of animals is a useful mode of exposure for studying parameters that may elucidate toxic effects of air pollutants emitted from automotive engines, with a possibility to evaluate engine and fuel with regard to health hazards.

Haemoglobin adducts from isoprene and isoprene monoepoxides

1. Isoprene is metabolised in vitro by oxygenation of either double bond to 2-ethenyl-2-methyloxirane (epoxide A) and 2-(1'-methylethenyl)oxirane (epoxide B). The reactivity in vitro and formation in vivo of the monoepoxides of isoprene were studied by the formation of adducts to N-terminal valines in haemoglobin (Hb). These adducts were analysed by mass spectrometry after cleavage and derivatization by a modified Edman degradation method. 2. When red blood cells were incubated with commercial isoprene oxide (about 95% epoxide A, < or = 5% epoxide B) adducts from both epoxides were formed. 3. It is confirmed that epoxide A is hydrolysed much faster than epoxide B. The rates are enhanced by phosphate buffer (epoxide A), probably through acid catalysis, and by the presence of red blood cells (both epoxides), due to enzymatic detoxification. 4. Comparison of total valine adduct levels in Hb from isoprene and isoprene oxide injected i.p. led to the conclusion that 23 and 1% of injected isoprene was metabolized to the epoxides in mouse and rat, respectively.

Studies of transalkylation of phosphotriesters in DNA: reaction conditions and requirements on nucleophiles for determination of DNA adducts

Reactive compounds form adducts at several sites in DNA. One of these sites, the phosphate groups, forms phosphotriesters (PTE) which are both chemically stable and little repaired. A measurement of PTE in DNA could therefore be advantageous for the determination of doses in vivo of mutagens/cancer initiators. In this paper, the possibilities of utilizing the weakly alkylating properties of PTE for the transfer of adducts to strong nucleophiles have been investigated. Model compounds, thymidine 3'-[thymidine 5'-(methyl phosphate)], TpMeT, and thymidine 3'-[thymidine 5'-(2-hydroxyethyl phosphate)], TpHOEtT, were incubated with thiosulfate, a relatively strong nucleophile and the formation of dealkylated model PTE, thymidine 3'-(thymidine 5'-phosphate), TpT, was followed by HPLC. Transalkylation to thiosulfate or aniline of methyl PTE in DNA alkylated by [3H]N-methyl-N-nitrosourea was demonstrated. The methyl groups transferred, forming methyl thiosulfate and N-methylaniline, respectively, were determined by HPLC. These experiments demonstrate that it is possible to transfer alkyls from DNA phosphate to nucleophiles. Kinetic aspects of the transalkylation and requirement on nucleophiles for a practically useful method for determination of DNA adducts are discussed. Constants of reaction rates are presented.

In vivo dosimetry of ethylene oxide and propylene oxide in the cynomolgus monkey

In mammals, including the cynomolgus monkey, a striking difference between the potencies of ethylene oxide (EO)* and propylene oxide (PO) with respect to induction of certain clastogenic effects has previously been observed. In order to clarify to what extent such differences can be ascribed to a difference in detoxification rate, cynomolgus monkeys were administered an equimolar mixture of the two epoxides at two dose levels, and the blood doses were determined by measurement of the degree of alkylation of N-terminal valines in hemoglobin (Hb). For the highest exposure a saturation in the detoxification of PO was evident from a marked increase in adduct level. At the lower exposure, the dose in blood resulting from exposure to PO was about one fourth of that from EO. Although playing a great role, differences in detoxification rate, therefore, cannot fully account for the much lower clastogenic potency of PO, which has been found in earlier studies. Furthermore, the determination of doses in blood gives data on relationship between in vivo dose and exposure dose (accounting for detoxification), with relevance for risk estimation.

Relationship between dose in vivo of ethylene oxide and exposure to ethene studied in exposed workers

1. In vivo doses of ethylene oxide, arising from ethene exposure, in plastic industry workers were estimated through hemoglobin adducts. The ethene exposure was assessed through person-worn monitors. The metabolic conversion of ethene to ethylene oxide was estimated from the exposure dose/in vivo dose ratio. 2. Two studies were done: In the first study hemoglobin adducts were determined in samples collected on one occasion in exposed groups and exposure doses were estimated by using exposure data from the hygienic surveillance program. The second study applies a newly developed study design with repeated blood sampling in a few persons combined with a complete personal exposure monitoring during the study period. This makes it possible to relate adduct formation with individual short-time exposure doses, which in theory should overcome the problems with exposure history dependence of the adduct level in a single blood sample. The results of the second study shows that it is possible, through the proposed method, to utilize occupational exposure situations for this kind of studies even if the exposure pattern is irregular and highly variable. Both studies show a metabolic conversion of ethene to ethylene oxide of only 0.5%, which is unexpectedly low. 3. The cancer risk associated with the ethene exposure in the highly exposed group (3.6 p.p.m. 40 h/week) is estimated by applying the radiation-dose-equivalence approach. The result of this evaluation leads to a risk corresponding to a radiation dose of 4 mSv/year which is about a factor 3 below the current dose limit for radiological work recommended by ICRP.

Adducts to N-terminal valines in hemoglobin from butadiene metabolites

In order to identify a hemoglobin adduct useful for monitoring of doses of butadiene metabolites, particularly the strongly genotoxic, bifunctional diepoxybutane (DEB), the reaction of DEB with valinamide, a relevant model of globin N-termini, was studied. A preliminary kinetic analysis showed that the primary reaction product of DEB with valine-N gives, as was expected, rise to a ring-closed pyrrolidine-structured compound, N,N-(2,3-dihydroxybuta-1,4-diyl)valine (PYRV), in a reaction which is fast when compared to hydrolysis of the second oxirane ring with formation of N-(2,3,4-trihydroxybutyl)valine (THBV). The ring closure is also fast when compared to the rate of formation of a cross-linked divaline product. PYRV can therefore be used as a specific marker of in vivo doses of DEB whereas THBV may be applied for the dosimetry of the metabolite (1,2-dihydroxyethyl)oxirane. The latter is formed by half-hydrolysis of DEB or oxygenation of 1,2-dihydroxy-3-butene. The N-alkyl Edman method, used for specific cleavage and gas chromatographic/mass spectrometric (GC/MS) determination of adducts to N-terminal valine in hemoglobin, could be used for measurement of THBV, as shown in alkylation experiments with blood. However, the adduct specific for DEB, PYRV, requires-due to its tertiary amine structure-other techniques. The reaction products were identified by GC/MS, PYRV by 13C and 1H NMR, and THBV because of its formation by reduction of the Schiff bases of threose and erythrose with hemoglobin.

Biomonitoring of epichlorohydrin by hemoglobin adducts

A gas chromatographic mass spectrometric method for monitoring exposure to epichlorohydrin (ECH) by means of quantitative analysis of N-(2,3-dihydroxypropyl)valine in hemoglobin has been developed. The analysis is based on the modified Edman method for measurement of adducts to the N-terminal valine, one of the reactive sites of the globin chains. The presence of two hydroxyl groups in the adduct to be analyzed required special precautions to be introduced into the method, such as acetylation of the Edman derivative. An in vitro treated globin with [2H5]N-2,3-dihydroxypropyl adducts was used as internal standard. The limit of detection achieved is 4 fmol in analysis by tandem mass spectrometry. Adduct levels found in smokers (15 to 20 cigarettes per day) were between 6.5 and 11.2 pmol/g globin and for nonsmokers the adduct levels were close to the detection limit (about 2 pmol/g globin). In two rats, treated ip with 40 mg ECH/kg body wt and sacrificed after 30 days, the average adduct level was 44 pmol/g globin and that for two nonexposed rats was close to the detection level. The method will be useful for monitoring of exposure and for cancer risk estimation of ECH.

Macromolecule adducts as biomarkers of exposure to environmental mutagens in human populations

A cancer epidemiologist recently said that "adduct measurement has so far been of little use to epidemiological research." This remark gives us a starting point for the discussion of the purposes of measuring macromolecule adducts that originate from electrophilic compounds or metabolites in humans and animals. Historically, methods for adduct monitoring were developed as a means of determining target doses that, combined with measurements of genotoxic potencies, could be used for risk assessment. With mass spectrometric methods, adducts can be quantified at levels that are thousands of times lower than those in which the cancer incidence associated with this exposure is detectable in disease-epidemiological studies. Furthermore, mass spectrometric techniques permit identification of the chemical structure of the adduct, particularly in the case of hemoglobin adducts. Adduct measurement therefore constitutes not only a means of risk estimation but it may be used as a complement of disease epidemiology in situations in which, for statistical reasons, the risk is too low to be detectable--which does not signify that the risk is acceptably low. It also gives a possibility of identification of the dangerous components in mixed exposures and of the relevant reactive intermediates in cases of complex metabolism.

Changes of visual function and visual ability in daily life following cataract surgery

We conducted a prospective study of 56 patients aged 70 to 79 years undergoing cataract surgery, in order to determine the impact of surgery on subjective and objective measurements of visual ability. In 46 cases we could obtain all necessary data. Binocular visual acuity, near vision and contrast sensitivity improved due to surgery. Self-assessed ability to perform visually related tasks was examined in form of a questionnaire. The results show that there was no simple relationship between objective measurements and perceived visual ability. An impairment in preoperative visual acuity cannot be related to a specific loss of visual ability. In order to increase the quality of cataract surgery more subtly, subjective aspects of vision must be taken into consideration when operation is decided upon and in the evaluation of the results.

Oxazolidonylethyl adducts to hemoglobin and DNA following nornitrogen mustard exposure

Formation of adducts to hemoglobin (Hb) and DNA of nornitrogen mustard (NNM) was studied with the aim of developing a method for monitoring exposure to NNM. Adducts to N-terminal valines in Hb were studied by the N-alkyl Edman method using pentafluorophenyl isothiocyanate (PFPITC) as the derivatizing reagent. In preliminary studies five major Hb adducts were shown to be formed in reaction of NNM with red cell hemolysate in vitro. Following treatment with PFPITC three of these were found to be pentafluorophenylthiohydantoins (PFPTHs) of N-alkylated valines and the fourth probably originates from NNM esters in which PFPITC had reacted with the nitrogen of N-chloroethylaminoethyl. A PFPTH was found to originate from N-2-(3-oxazolidonyl)ethylvaline, Val-OZ. Val-OZ is formed in reaction, with ring closure to oxazolidone, of CO2 with the 2-chloroethylamino group in the primary valine-N adduct. Besides a few other adducts, Val-OZ was also observed in mouse Hb following injection of NNM, and also after injection of cyclophosphamide. Following reaction in vitro of NNM with DNA, three major adducts to guanine-N-7 were observed; one of them, 7-(N'-(2-chloroethyl)-2-aminoethyl]-guanine (NNMCl), was converted by carbonate to 7-(2-3-oxazolidonyl)ethyl]guanine (Gua-OZ). In mice treated with NNM, Gua-Oz was the only DNA adduct observed. Val-Oz is a chemically stable Hb adduct, potentially useful for monitoring exposures to NNM and cyclophosphamide.

Hemoglobin adducts for in vivo dose monitoring and cancer risk estimation

For the estimation of cancer risks from environmental chemicals, knowledge of the target dose is essential, dose being defined as the time integral of concentration in target tissues. In vivo doses from chronic or intermittent exposures are best determined from established steady-state levels of macromolecule adducts of reactive compounds or intermediates. For dose monitoring, hemoglobin (Hb) is preferred to DNA for several reasons: accessibility in large amounts, availability of methods for chemical identification, and well-determined life span due to absence of repair. For these reasons, and because of the proportionality of rates of DNA and Hb adduct formation, Hb adduct levels give better information on cumulative DNA adduct levels than do direct measurement of DNA adducts. The scientific background of Hb adduct measurement, target dose determination, and risk estimation based on the relative genotoxic potency, with gamma-radiation as reference standard, is reviewed and exemplified. The sensitivity of the method for Hb adduct measurement permits determination of exposures where the associated annual cancer risk is less than 1 per million. Besides application for studies of metabolism by determination of in vivo doses in exposed animals and humans, as a basis for risk estimation, Hb adduct measurement is used for hygienic surveillance of occupational exposures. Determination of Hb adducts by mass-spectrometric techniques gives a tool for identification of reactive metabolites, not only in individuals with known exposure, but also for characterization of adducts to Hb from compounds acting as mutagens (initiators) in the background carcinogenesis. This is the large fraction of the total number of cancer cases that occur among individuals without known exposure.

The research background for risk assessment of ethylene oxide: aspects of dose

Data for relationships between in vivo doses inferred from levels of hemoglobin (Hb) or DNA adducts and administered (by inhalation or injection) doses of ethylene oxide (EO) in mice, rats and humans are reviewed. At low absorbed doses or dose rates these relationships appear to be linear, whereas at higher dose rates deviations from linearity due to saturation kinetics of detoxification and of DNA repair as well as certain toxic effects have to be allowed for. If these factors are taken into consideration, a rather consistent picture is obtained for animal studies, with a variation by less than a factor 2 between estimates of adduct level increments or in vivo dose increments per unit of administered dose. Although the value for in vivo dose per unit of exposure dose (ppm-hour) in humans is uncertain because of unreliable data for the time-weighted average exposure level, the most likely value for this relationship, supported by data for ethene, agrees with data for the rodents. In the animal species testis doses are approximately one-half of the blood doses inferred from Hb adducts.

Uptake, distribution, and formation of hemoglobin and DNA adducts after inhalation of C2-C8 1-alkenes (olefins) in the rat

Absorption, distribution, elimination and hemoglobin and DNA adduct formation were studied in the rat after inhalation of individual C2-C8 1-alkenes (olefins) at 300 p.p.m., 12 h a day for 3 consecutive days. The concentrations of olefins were measured in blood, lung, brain, liver, kidney and perirenal fat immediately after each exposure and 12 h after the third exposure. DNA adducts were determined by 32P-postlabeling in liver, and lymphocytes sampled immediately after the last exposure. Hemoglobin adducts were determined by GC/MS and GC/MS/MS in erythrocytes sampled immediately after the last exposure. Concentrations of 1-alkenes in blood and organs reached a steady-state level after the first 12 h exposure, and the concentrations 12 h after the last exposure were generally low, except in fat tissue. Concentrations of 1-alkenes in blood and the different tissues increased with increasing number of carbon atoms. In contrast, levels of hemoglobin and DNA adducts decreased with increasing number of carbon atoms. The decrease was most pronounced from C2 to C3. The decrease through the whole homologous series from ethene to 1-octene was most pronounced for hemoglobin adducts followed by the DNA adducts in the lymphocytes. All 1-alkenes caused formation of detectable levels of hemoglobin and DNA adducts, although the levels of hemoglobin adducts after C4-C8 exposure were low. The project illustrates important aspects of the use of biomarkers. The structure-activity approach gives possibilities for extrapolation within the homologous series.

Effects of variation in detoxification rate on dose monitoring through adducts

1. Föst et al. (Human & Experimental Toxicology 1991; 10: 25) have shown that ethylene oxide (EO) added to human blood gave rise to a higher level of adducts to haemoglobin (Hb) when the donors were deficient in an erythrocytic glutathione S-transferase (GST, later found to be GST-theta) than in blood from persons possessing this enzyme, and drew the conclusion that this polymorphism in detoxification rendered Hb adducts less suitable for biological monitoring. 2. By fitting a kinetic model to the data, the present study shows that the Hb adduct level gives a correct measure of the dose (concentration integrated over time) relevant to risk estimation. 3. It does illustrate, however, the importance of knowing an individual's detoxification efficiency, when Hb adduct measurements are used to assess environmental exposure, for example in occupational surveillance.

Is ambient ethene a cancer risk factor?

Ethene is, on a molar basis, a major urban air pollutant. It has been shown beyond doubt that a fraction of inhaled ethene is metabolized in mammals (including humans) via ethylene oxide, an electrophilic reagent that has been shown to be mutagenic and carcinogenic. To the extent that the linearity hypothesis for dose-response relationships at low levels is accepted, exposure to ethene is therefore expected to lead to a risk increment. In order to judge whether ethene as a single compound should be considered a risk factor, it has to be evaluated whether this risk increment is negligibly small or of concern to individuals or societies. The magnitude of the cancer risk from ethene cannot be inferred from animal experiments. Because of saturation of the metabolism of ethene, sufficient statistical power cannot be attained in long-term animal tests with about 100 animals per dose. By application of the radiation-dose equivalent of the unit of target dose of ethylene oxide and using the best (although still uncertain) value for the conversion factor (about 5%), exposure to 10 ppb ethene--a level occurring in urban areas--is expected to lead to a lifetime risk of cancer death amounting to approximately 70 per 100,000. According to a recent estimate the average exposure in Sweden to ethene is some six times lower. These figures are uncertain by a factor of at least three. They indicate ethene to be a risk factor of concern.

On cancer risk estimation of urban air pollution

The usefulness of data from various sources for a cancer risk estimation of urban air pollution is discussed. Considering the irreversibility of initiations, a multiplicative model is preferred for solid tumors. As has been concluded for exposure to ionizing radiation, the multiplicative model, in comparison with the additive model, predicts a relatively larger number of cases at high ages, with enhanced underestimation of risks by short follow-up times in disease-epidemiological studies. For related reasons, the extrapolation of risk from animal tests on the basis of daily absorbed dose per kilogram body weight or per square meter surface area without considering differences in life span may lead to an underestimation, and agreements with epidemiologically determined values may be fortuitous. Considering these possibilities, the most likely lifetime risks of cancer death at the average exposure levels in Sweden were estimated for certain pollution fractions or indicator compounds in urban air. The risks amount to approximately 50 deaths per 100,000 for inhaled particulate organic material (POM), with a contribution from ingested POM about three times larger, and alkenes, and butadiene cause 20 deaths, respectively, per 100,000 individuals. Also, benzene and formaldehyde are expected to be associated with considerable risk increments. Comparative potency methods were applied for POM and alkenes. Due to incompleteness of the list of compounds considered and the uncertainties of the above estimates, the total risk calculation from urban air has not been attempted here.

Uptake and metabolism of ethene studied in a smoke-stop experiment

Knowledge of the relationships between exposure levels and levels of hemoglobin adducts are essential when the latter are to be used for exposure monitoring or risk estimation, the hygienic control being based on measurements of exposure. These ratios are mostly very uncertain, mainly due to difficulties of determining the time-weighted average exposure concentration. A solution to this problem has been suggested involving adduct measurement before and after two consecutive periods of about 1 week, the first with absence from exposure, the second with careful measurement of exposure. This model was tested in two smokers who abstained from smoking for one week. Analysis of inhaled ethene and of adducts from ethylene oxide (EO) to N-terminal valine of hemoglobin are compatible with metabolism of 2% of inhaled ethene to EO and a detoxification rate of 1 h-1 of EO.

Biological monitoring of workers occupationally exposed to ethylene oxide

Ethylene oxide (EtO) is an important intermediate industrial chemical which is also used for sterilizing medical products and hospital equipment. In the present study we have evaluated some biological markers, such as chromosomal aberrations, micronuclei and EtO-hemoglobin adducts in the peripheral blood cells, and micronuclei in buccal exfoliated cells of 22 controls and 75 workers employed in an industry in Brazil using EtO as an intermediate. Measurements of EtO in the general area showed that workers were exposed to 2-5 ppm time-weighted average (TWA) for an 8-h working day, during the 3-month sampling. Our results indicate that exposure to EtO resulted in a statistically significant enhancement of chromosomal aberrations (P = 0.01) and of micronuclei in binucleated lymphocytes (P < 0.001). For the frequencies of micronucleated cells in buccal mucosa there was no statistically significant difference between exposed and control groups. The mean values of hemoglobin adduct (HOEtVal) measurements obtained from a selected group of exposed and unexposed donors were statistically different.