Ppm Ethylene Oxide Research Articles

Skin Absorption of Ethylene Oxide Gas Following Exposures Relevant to HAZMAT Incidents.

Ethylene oxide (EO) is a reactive gas used by numerous industries and medical facilities as a sterilant, a fumigant, and as a chemical intermediate in chemical manufacturing. Due to its common use, EO has been involved in a number of leaks and explosive incidents/accidents requiring HAZMAT response. However, the extent of skin absorption under short-term HAZMAT conditions has not been directly assessed. Such data would assist decision making by first responders regarding skin decontamination in EO HAZMAT incidents. An in vitro test protocol with human skin was used for EO exposures at 800 ppm and 3000 ppm. No evidence of dermal penetration was seen for 800 ppm EO during a 30-min challenge. For 3000 ppm, EO penetration was observed after 20 min and was greater under higher temperature/humidity conditions. Fabric (heavy cotton) on skin enhanced penetration 5-fold compared with naked skin. Off gassing from exposed fabric was rapid. The results show dermal uptake of EO vapour from exposure at 3000 ppm is small but clothing may contribute to further dermal absorption/penetration over time. For exposed, but asymptomatic, persons in EO HAZMAT incidents first responders should remove bulky clothing to prevent potential skin damage and further uptake.

Dose and temporal evaluation of ethylene oxide-induced mutagenicity in the lungs of male big blue mice following inhalation exposure to carcinogenic concentrations.

Ethylene oxide (EO) is a direct acting alkylating agent; in vitro and in vivo studies indicate that it is both a mutagen and a carcinogen. However, it remains unclear whether the mode of action (MOA) for cancer for EO is a mutagenic MOA, specifically via point mutation. To investigate the MOA for EO-induced mouse lung tumors, male Big Blue (BB) B6C3F1 mice (10/group) were exposed to EO by inhalation, 6 hr/day, 5 days/week for 4 (0, 10, 50, 100, or 200 ppm EO), 8, or 12 weeks (0, 100, or 200 ppm EO). Lung DNA samples were analyzed for cII mutant frequency (MF) at 4, 8 and 12 weeks of exposure; the mutation spectrum was analyzed for mutants from control and 200 ppm EO treatments. Although EO-induced cII MFs were 1.5- to 2.7-fold higher than the concurrent controls at 4 weeks, statistically significant increases in the cII MF were found only after 8 and 12 weeks of exposure and only at 200 ppm EO (P ≤ 0.05), which is twice the highest concentration used in the cancer bioassay. Consistent with the positive response, DNA sequencing of cII mutants showed a significant shift in the mutational spectra between control and 200 ppm EO following 8 and 12 week exposures (P ≤ 0.035), but not at 4 weeks. Thus, EO mutagenic activity in vivo was relatively weak and required higher than tumorigenic concentrations and longer than 4 weeks exposure durations. These data do not follow the classical patterns for a MOA mediated by point mutations. Environ. Mol. Mutagen. 58:122-134, 2017. © 2017 Wiley Periodicals, Inc.

An electrochemical model for prediction of microvia filling process

The microvia filling process as encountered in the multi-layered printed circuit board manufacturing industry was investigated by electrochemical measurement and a multi-physics coupling technique in this paper. The effect of an accelerator on filling performance was investigated by cathode polarisation curves to obtain the suitable copper electroplating conditions. In the model, mass balance of adsorbed additives as a result of cathode surface shape change was considered. The electrodeposited layer thickness in the microvia from the additive-free solution and additive-assisted solution was calculated by the finite element method. The void-free microvia filling was finally achieved in acid copper electroplating solution consisting of base electrolyte, 200 ppm ethylene oxide–propylene oxide co-polymer and 1 ppm bis-(sodium-sulphopropyl)-disulphide, which was validated by experimental results.

Accidental exposure to gas emissions from transit goods treated for pest control.

BackgroundInternational phytosanitary standards ISPM 15 require (since 2007) fumigation or heat treatment for shipping and storage. Those dealing with fumigated freight might be accidentally exposed. In this paper we report a series of three accidents of six storage room workers in a medium sized company regularly importing electronic production parts from abroad.MethodsPatients (n = 6, aged from 32–54 yrs.) and control group (n = 30, mean 40 yrs.) donated blood and urine samples. The fumigants: ethylene oxide, methyl bromide, chloropicrin, ethylene dichloride, other halo-alkanes and solvents were analyzed by headspace gas chromatography/mass spectrometry (GCMS). For the quantitation of long term exposure/s, macromolecular reaction products (hemoglobin adducts) were used (with GCMS) as molecular dosimeter; additionally 8-OHdG and circulating mtDNA (cmtDNA) were analyzed as nonspecific biological effect markers.ResultsThe hemoglobin adducts N-methyl valine (MEV) and N-(2-hydroxy ethyl) valine (HEV) were elevated after exposure to the alkylating chemicals methyl bromide and ethylene oxide. Under the consideration of known elimination kinetics and the individual smoking status (biomonitored with nicotine metabolite cotinine and tobacco specific hemoglobin adduct: N-(2 cyan ethyl) valines, CEV), the data allow theoretical extrapolation to the initial protein adduct concentrations at the time of the accident (the MEV/CEV levels were from 1,616 pmol/g globin to 1,880 pmol/g globin and HEV/CEV levels from 1,407 pmol/g globin to 5,049 pmol/g globin, and correlated with inhaled 0.4-1.5 ppm ethylene oxide. These integrated, extrapolated internal doses, calculated on the basis of biological exposure equivalents, confirmed the clinical diagnosis for three patients, showing severe intoxication symptoms. Both, cmtDNA and 8-OHdG, as non-specific biomarkers of toxic effects, were elevated in four patients.ConclusionThe cases reported here, stress the importance of a suitable risk assessment and control measures. We put emphasis on the necessity of human biomonitoring guidelines and the urgency for the relevant limit values.

Temporal Changes in K-ras Mutant Fraction in Lung Tissue of Big Blue B6C3F1 Mice Exposed to Ethylene Oxide

Ethylene oxide (EO) is a genotoxicant and a mouse lung carcinogen, but whether EO is carcinogenic through a mutagenic mode of action remains unclear. To investigate this question, 8-week-old male Big Blue B6C3F₁ mice (10 mice/group) were exposed to EO by inhalation-6 h/day, 5 days/week for 4 weeks (0, 10, 50, 100, or 200 ppm EO) and 8 or 12 weeks (0, 100, or 200 ppm EO). Lung DNA samples were analyzed for levels of 3 K-ras codon 12 mutations (GGT→GAT, GGT→GTT, and GGT→TGT) using ACB-PCR. No measureable level of K-ras codon 12 TGT mutation was detected (ie, all lung mutant fractions [MFs] ≤ 10⁻⁵). Four weeks of inhalation of 100 ppm EO caused a significant increase in K-ras codon 12 GGT→GTT MF relative to controls, whereas 50, 100, and 200 ppm EO caused significant increases in K-ras codon 12 GGT→GAT MF. In addition, significant inverse correlations were observed between K-ras codon 12 GGT→GTT MF and cII mutant frequency in the lungs of the same mice exposed to 50, 100, or 200 ppm EO for 4 weeks. Surprisingly, 8 weeks of exposure to 100 and 200 ppm EO caused significant decreases in K-ras MFs relative to controls. Thus, the changes in K-ras MF as a function of cumulative EO dose were nonmonotonic and were consistent with EO causing early amplification of preexisting K-ras mutations, rather than induction of K-ras mutation through genotoxicity at codon 12. The possibility that these changes reflect K-ras mutant cell selection under varying degrees of oxidative stress is discussed.

Analysis of Protein Adducts as Biomarkers of Short-Term Exposure to Ethylene Oxide and Results of Follow-Up Biomonitoring

An accidental exposure of six workers to ethylene oxide (EO) provided the rationale for a biomonitoring and follow-up study, whose aim was to analyse protein adduct kinetics and examine the differentiation between accidental and environmental exposure, e.g., from tobacco smoke. For this purpose, the decrease in the concentration of the haemoglobin adduct N-2-hydroxyethylvaline (HEV) was followed during a five-month period after the accident, together with N-2-cyanoethylvaline (CEV) and urinary cotinine, two well-established biomarkers for smoking. The follow-up study showed that EO adduct concentrations significantly increased after a short but presumably high exposure. Initial biomonitoring revealed HEV levels above 500 pmol g(-1) globin in all cases, with a maximum of about 2,400 pmol g(-1) globin. This compares to a German EKA value (exposure equivalent for carcinogenic substances) for a daily 8-h-exposure to 1 ppm EO of 90 μg L(-1) blood (~3,900 pmol g(-1) globin). The adduct levels dropped in accordance with the expected zero-order kinetics for a single exposure. After the five-month observation interval, the HEV concentrations in blood reflected the individual background from tobacco smoking. The results of this study show that even a short exposure to ethylene oxide may result in a significant rise in haemoglobin adduct levels. Although protein adducts and their occupational-medical assessment values are considered for long-term exposure surveillance, they can also be used for monitoring accidental exposures. In these cases, the calculation of daily 'ppm-equivalents' may provide a means for a comparison with the existing assessment values.

Quantitative cancer risk assessment for ethylene oxide inhalation in occupational settings

The estimated occupational ethylene oxide (EO) exposure concentrations corresponding to specified extra risks are calculated for lymphoid mortality as the most appropriate endpoint, despite the lack of a statistically significant exposure-response relationship. These estimated concentrations are for occupational exposures--40 years of occupational inhalation exposure to EO from age 20 to age 60 years. The estimated occupational inhalation exposure concentrations (ppm) corresponding to specified extra risks of lymphoid mortality to age 70 years in a population of male and female EO workers are based on Cox proportional hazards models of the most recent updated epidemiology cohort mortality studies of EO workers and a standard life-table calculation. An occupational exposure at an inhalation concentration of 2.77 ppm EO is estimated to result in an extra risk of lymphoid mortality of 4 in 10,000 (0.0004) in the combined worker population of men and women from the two studies. The corresponding estimated concentration decreases slightly to 2.27 ppm when based on only the men in the updated cohorts combined. The difference in these estimates reflects the difference between combining all of the available data or focusing on only the men and excluding the women who did not show an increase in lymphoid mortality with EO inhalation exposure. The results of sensitivity analyses using other mortality endpoints (all lymphohematopoietic tissue cancers, leukemia) support the choice of lymphoid tumor mortality for estimation of extra risk.

Round‐robin evaluation of a solid‐phase microextraction–gas chromatographic method for reliable determination of trace level ethylene oxide in sterilized medical devices

Medical devices that are sterilized with ethylene oxide (EtO) retain small quantities of EtO residuals, which may cause negative systemic and local irritating effects, and must be accurately quantified to ensure non-toxicity. The goal of this round-robin study is to investigate the capability of a novel solid-phase microextraction-gas chromatographic (SPME-GC) method for trace-level EtO residuals analysis: three independent laboratories conducted a guided experiment using this SPME-GC method, in assessing method performance, ruggedness and the feasibility of SPME fibers. These were satisfactory across the independent laboratories, at the 0.05-5.00 ppm EtO range. This method was then successfully applied to analyze EtO residuals in several sterilized/aerated medical devices of various polymeric composition, reliably detecting and quantifying the trace levels of EtO residuals present ( approximately 0.05 ppm EtO). SPME is a feasible alternative for quantifying trace-level EtO residuals in sterilized medical devices, thereby lowering the limit of quantification (LOQ) by as much as two to three orders of magnitude over the current GC methodology of direct liquid injection.

Formation of DNA adducts and induction of mutagenic effects in rats following 4 weeks inhalation exposure to ethylene oxide as a basis for cancer risk assessment

Ethylene oxide (EO) is mutagenic in various in vitro and in vivo test systems and carcinogenic in rodents. EO forms different adducts upon reaction with DNA, N7-(2-hydroxyethyl)guanine (N7-HEG) being the main adduct. The major objectives of this study were: (a) to determine the formation and persistence of N7-HEG adducts in liver DNA of adult male rats exposed to 0, 50, 100 and 200 ppm by inhalation (4 weeks, 5 days/week, 6 h/day) and (b) to assess dose–response relationships for Hprt gene mutations and various types of chromosomal changes in splenic lymphocytes. N7-HEG adducts were measured 5, 21, 35 and 49 days after cessation of exposure. By extrapolation, the mean concentrations of N7-HEG immediately after cessation of exposure (‘day 0’) to 50, 100 and 200 ppm were calculated as 310, 558 and 1202 adducts/10 8 nucleotides, respectively, while the mean concentration in control rats was 2.6 adducts/10 8 nucleotides. At 49 days, N7-HEG values had returned close to background levels. The mean levels of N-(2-hydroxyethylvaline) adducts in haemoglobin were also determined and amounted 61.7, 114 and 247 nmol/g globin, respectively. Statistically significant linear relationships were found between mean N7-HEG levels (‘day 0’) and Hprt mutant frequencies at expression times 21/22 and 49/50 days and between mean N7-HEG (‘day 0’) and sister-chromatid exchanges (SCEs) or high frequency cells (HFC) measured 5 days post-exposure. At day 21 post-exposure, SCEs and HFCs in-part persisted and were significantly correlated with persistent N7-HEG adducts. No statistically significant dose effect relationships were observed for induction of micronuclei, nor for chromosome breaks or translocations. In conclusion, this study indicates that following sub-chronic exposure, EO is only weakly mutagenic in adult rats. Using the data of this study to predict cancer risk in man resulting from low level EO exposures in conjunction with other published data, i.e., those on (a) genotoxic effects of EO in humans and rats, (b) DNA binding of other carcinogens, (c) natural background DNA binding and (d) genotoxic potency of low energy transfer (LET) radiation, it is not expected that long term occupational exposure to airborne concentrations of EO at or below 1 ppm EO produces an unacceptable increased risk in man.

Ethylene Oxide Dosimetry in the Mouse

Ethylene oxide (EO) is a direct-acting mutagen and animal carcinogen used as an industrial intermediate and sterilant with a high potential for human exposure. Understanding the exposure–dose relationship for EO in rodents is critical for developing human EO exposure–dose models. The study reported here examined the dosimetry of EO in male B6C3F1 mice by direct determination of blood EO concentrations. Steady-state blood EO concentrations were measured during a single 4-h nose-only inhalation exposure (0, 50, 100, 200, 300, or 400 ppm EO). In addition, glutathione (GSH) concentrations were measured in liver, lung, kidney, and testis to assess the role of the GSH depletion in the saturable metabolism previously observed in mice (Brownet al., Toxicol. Appl. Pharmacol.136, 8–19, 1996). Blood EO concentrations were found to increase linearly with exposure concentration up to 200 ppm. Markedly sublinear blood dosimetry was observed at exposure concentrations exceeding 200 ppm. An EO exposure concentration-dependent reduction in tissue GSH levels was observed, with both liver and lung GSH levels significantly depressed at EO exposure concentrations of 100 ppm or greater. Our results also indicate that depletion of GSH is likely responsible for nonlinear dosimetry of EO in mice and that GSH depletion corresponds with reports of dose–rate effects in mice exposed to EO.

In vivo mutagenicity of ethylene oxide at the hprt locus in T-lymphocytes of B6C3F1 lacI transgenic mice following inhalation exposure

Ethylene oxide (EO) is a direct-acting alkylating agent with the potential to induce cytogenetic alterations, mutations, and cancer. In the present study, the in vivo mutagenicity of EO at the hypoxanthine guanine phosphoribosyltransferase ( hprt) locus of T-lymphocytes was evaluated following inhalation exposure of male B6C3F1 lacI transgenic mice. For this purpose, groups of male Big Blue ® mice at 6–8 ( n=4/group) and 8–10 ( n=5/group) weeks of age were exposed to 0, 50, 100, or 200 ppm EO for 4 weeks (6 h/day, 5 days/week). At necropsy, T-cells were isolated from thymus and/or spleen and cultured in the presence of concanavalin A, IL-2, and 6-thioguanine [Skopek, T.R., V.E. Walker, J.E. Cochrane et al. (1992) Proc. Natl. Acad. Sci. USA, 89, 7866–7870]. The time course for expression of hprt-negative lymphocytes in thymus was determined in mice necropsied 2 h, 2 weeks, and 8 weeks after exposure to 200 ppm EO. The dose-response for hprt mutant T-cells in thymus and spleen was defined in mice necropsied 2 and 8 weeks post-exposure, respectively. The hprt mutant frequency (M f) in thymus of exposed mice was increased 2 h after exposure and reached a maximum of 7.5±0.9×10 −6 (average M f±SE) at 2 weeks post-exposure, compared with 2.3±0.8×10 −6 in thymus of control mice. Dose-related increases in hprt M fs were found in thymus from mice exposed to 100 and 200 ppm EO. In addition, a nonlinear dose-dependent increase in hprt M fs was observed in splenic T-cells, with greater mutagenic efficiency (mutations per unit dose) found at higher concentrations than at lower concentrations of EO. Average induced M fs (i.e. induced M f=treatment M f−background M f) in splenic T-cells were 1.6, 4.6, and 11.9×10 −6 following exposures to 50, 100, or 200 ppm EO, respectively, while the average control M f value was 2.2±0.3×10 −6. In aliquots of lymphocytes (both B- and T-cells) isolated from spleen for analysis of lacI mutations in the same animals, only two of three EO-exposed mice at the 200 ppm exposure level demonstrated an elevated lacI M f and these elevations were apparently due to the in vivo replication of preexisting mutants and not due to the induction of new mutations associated with EO exposure [Sisk, S., L.J. Pluta, K.G. Meyer and L. Recio (1996) Mutation Res., submitted]. These data demonstrate that repeated inhalation exposures to high concentrations of EO produce dose-related increases in mutations at the hprt locus of T-lymphocytes in male lacI transgenic mice of B6C3F1 origin.

Assessment of the in vivo mutagenicity of ethylene oxide in the tissues of B6C3F1 lacI transgenic mice following inhalation exposure

In the present study, the lacI mutant frequency was determined in the tissues of B6C3F1 lacI transgenic mice exposed by inhalation to ethylene oxide (EO). Groups of 15 male transgenic lacI B6C3F1 mice were exposed to either 0, 50, 100, or 200 ppm EO for 4 weeks (6 h/day, 5 days/week) and were sacrificed at 0, 2, or 8 weeks after the last EO exposure. The lacI transgene was recovered from lung, bone marrow, spleen, and germ cells for determination of the lacI mutant frequency. The tissues selected for analysis were tumor target site tissues in chronic bioassays (lung tumors and lymphomas) and germ cells. The lacI mutant frequency in lung was significantly increased at 8 weeks post exposure to 200 ppm EO (6.2±2.2 vs. 9.1±1.5, p=0.046). In contrast, the lacI mutant frequency in spleen and bone marrow at 2 and 8 weeks was not significantly increased in mice exposed to 200 ppm EO. The lacI mutant frequencies in male germ cells for 200 ppm EO-exposed mice were not increased compared to air controls at 2 and 8 weeks post-exposure. In a spleen cell fraction two of three EO-exposed mice at the 200 ppm exposure level demonstrated an elevated lacI mutant frequency. The increased lacI mutant frequency in these animals was likely due to mutant siblings that contained background G:C→A:T transitions at CpG sites. These results demonstrate that a 4-week inhalation exposure to EO is mutagenic in lung. However, EO did not increase the frequency of mutations recovered at the lacI transgene in other tissues examined under the conditions used in the present studies. Since the mutational spectrum for EO in other systems consists of an increased proportion of large deletions, the lack of a mutagenic response in the tissues examined is likely due to the lack of recovery of large deletions in lambda-based shuttle vector systems. These data indicate that a primary mechanism of EO-induced mutagenicity in vivo is likely through the induction of deletions, not specific point mutations.

Developmental toxicity of inhaled ethylene oxide in rats following short-duration exposure.

The developmental toxicity of ethylene oxide (EtO) was examined in Sprague-Dawley rats following inhalation exposure during Days 6 to 15 of gestation. Two different exposure regimens were used: (1) exposure for 0.5 hr once a day to 0, 400, 800, or 1200 ppm EtO; or (2) exposure for 0.5 hr three times a day to 0, 200, or 400 ppm EtO or 0, 800, or 1200 ppm EtO. Repeated brief exposures (3 x 0.5 hr/day) to EtO caused fetal toxicity indicated by reduced fetal weight at 800 and 1200 ppm, and overt maternal toxicity manifested as reduced body weight gain at 1200 ppm. Neither embryolethality nor teratogenicity occurred following any exposure regimen.

Neurophysiological and neuropathological evaluation of primates exposed to ethylene oxide and propylene oxide.

Over 500,000 workers in the United States are exposed to ethylene oxide and propylene oxide. These two solvents are used as chemical intermediates, as well as components in the manufacture of fumigants and food preparation. The neurophysiologic and neuropathologic effects of these two organic oxides were investigated in five groups of 12 primates after exposure to 50 or 100 ppm ethylene oxide, 100 or 300 ppm propylene oxide, or no chemical (sham-exposed). Animals were exposed for 7 h/day, 5 days/wk for 24 months. Body weights, electroencephalograms, and motor nerve conduction velocities of the sciatic and ulnar nerves were assessed six times throughout the exposure period. Although the monkeys exposed to 100 ppm ethylene oxide had significantly lower mean weights, nerve conduction velocities did not differ significantly among the groups. Following termination of exposures, ten animals (two from each exposure group) were sacrificed for neuropathological examinations. Multiple axonal bodies were found in the nucleus gracilis in seven of eight oxide-exposed animals, and demyelination was found in two monkeys exposed to ethylene oxide. In contrast, a single axonal body was found in one of the two sham-control monkeys. However, the lack of a dose-response relationship suggests that this effect may not be related to oxide exposure. In a follow-up study, nerve conduction velocity and neuropathology were assessed in the remaining monkeys seven years after exposure terminated, but again, treatment-related effects could not be detected.

In Vivoandin VitroKinetics of Ethylene Oxide Metabolism in Rats and Mice

Ethylene oxide (EO) is a direct-acting mutagen and animal carcinogen used as an industrial intermediate and sterilant with a high potential for human exposure. Kinetics of EO metabolism in rodents can be used to develop human EO dosimetry models. This study examined the kinetics of EO metabolismin vivoandin vitroin male and female F-344 rats and B6C3F1 mice.In vivostudies measured blood and tissue EO levels during and 2–20 min following whole-body inhalation exposure (4 hr, 100 or 330 ppm EO). At 100 ppm EO, the half-life of elimination (t1/2) in rats was 13.8 ± 0.3 (mean ± SD) and 10.8 ± 2.4 min for males and females, respectively, compared to at1/2in mice of 3.12 ± 0.2 and 2.4 ± 0.2 min in males and females, respectively. On exposure to 330 ppm EO, thet1/2in mice increased approx twofold, while no change int1/2was observed in rats.In vitrokinetic parameters (VmaxandKM) of EO metabolism were determined using tissue cytosol and microsomes. EO metabolismin vitrooccurred primarily via cytosolic glutathioneS-transferase-mediated EO–GSH conjugation (cGST–EO), with highest activity in the liver. Liver cGST–EO activity (Vmax) was 258 ± 86.9 and 287 ± 49.0 nmol/mg protein/min (mean ± SD) in male and female mice, respectively, compared to 52.7 ± 10.8 and 29.3 ± 4.9 in male and female rats, respectively. In rats, but not mice, there was a statistically significant (p< 0.05) gender difference in theVmaxfor liver cGST. TheKMfor liver cGST–EO was approximately 10 mMin both species. The higherVmaxvalues observed in mice are consistent with the more rapid elimination of EO observed for this speciesin vivocompared to rats.

Ethylene oxide: evaluation of genotoxicity data and an exploratory assessment of genetic risk

A risk estimate of the heritable effects of ethylene oxide exposure, using the parallelogram approach, as suggested by Frits Sobels, is described. The approach is based on available data on the ethylene oxide-induced responses for the same genetic endpoint in somatic cells of both laboratory animals and humans, and for germ cell mutations in the same laboratory animal. Human germ cell effects are estimated. The available data sets for this approach were evaluated. We consider this as complementary to the genetic risk assessment carried out by U.S. EPA scientists, in which the risk from heritable (reciprocal) translocations induced by ethylene oxide was estimated. In the present study we restricted our assessment to dominant mutations. The sensitivity factor relating mouse to man was based on ethylene oxide-induced HPRT mutant frequencies in lymphocytes in vivo. From this comparison, it could be concluded that occupational exposure for 1 year to 1 ppm ethylene oxide would lead to a risk of a dominantly inherited disease in the offspring of 4 × 10 −4 above the background level. The uncertainty interval of this figure is quite large (0.6–28) × 10 −4. The values are compatible with the existing estimates of the corresponding risk from exposure to low LET radiation when the genotoxic potency ratio of ethylene oxide and radiation is considered. This risk estimation approach has allowed us to identify additional data that are required for a more complete risk estimation of the heritable effects of ethylene oxide, or indeed any mutagenic chemical.

Molecular Dosimetry of DNA and Hemoglobin Adducts in Mice and Rats Exposed to Ethylene Oxide

Experiments involving ethylene oxide (ETO) have been used to support the concept of using adducts in hemoglobin as a surrogate for DNA adducts in target tissues. The relationship between repeated exposures to ETO and the formation of N-(2-hydroxyethyl)valine (HEtVal) in hemoglobin and 7-(2-hydroxyethyl)guanine (7-HEG) in DNA was investigated in male rats and mice exposed by inhalation to 0, 3, 10, 33, or 100 ppm ETO for 6 hr/day for 4 weeks, or exposed to 100 ppm (mice) or 300 ppm (rats) for 1, 3, 5, 10, or 20 days (5 days/week). HEtVal was determined by Edman degradation, and 7-HEG was quantitated by HPLC separation and fluorescence detection. HEtVal formation was linear between 3 and 33 ppm ETO and increased in slope above 33 ppm. The dose-response curves for 7-HEG in rat tissues were linear between 10 and 100 ppm ETO and increased in slope above 100 ppm. In contrast, only exposures to 100 ppm ETO resulted in significant accumulation of 7-HEG in mice. Hemoglobin adducts were lost at a greater rate than predicted by normal erythrocyte life span. The loss of 7-HEG from DNA was both species and tissue dependent, with the adduct half-lives ranging from 2.9 to 5.8 days in rat tissues (brain, kidney, liver, lung, spleen, testis) and 1.0 to 2.3 days in all mouse tissues except kidney (t1/2 = 6.9 days). The concentrations of HEtVal were similar in concurrently exposed rats and mice, whereas DNA from rats had at least 2-fold greater concentrations of 7-HEG than DNA from mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular dosimetry of DNA and hemoglobin adducts in mice and rats exposed to ethylene oxide.

Experiments involving ethylene oxide (ETO) have been used to support the concept of using adducts in hemoglobin as a surrogate for DNA adducts in target tissues. The relationship between repeated exposures to ETO and the formation of N-(2-hydroxyethyl)valine (HEtVal) in hemoglobin and 7-(2-hydroxyethyl)guanine (7-HEG) in DNA was investigated in male rats and mice exposed by inhalation to 0, 3, 10, 33, or 100 ppm ETO for 6 hr/day for 4 weeks, or exposed to 100 ppm (mice) or 300 ppm (rats) for 1, 3, 5, 10, or 20 days (5 days/week). HEtVal was determined by Edman degradation, and 7-HEG was quantitated by HPLC separation and fluorescence detection. HEtVal formation was linear between 3 and 33 ppm ETO and increased in slope above 33 ppm. The dose-response curves for 7-HEG in rat tissues were linear between 10 and 100 ppm ETO and increased in slope above 100 ppm. In contrast, only exposures to 100 ppm ETO resulted in significant accumulation of 7-HEG in mice. Hemoglobin adducts were lost at a greater rate than predicted by normal erythrocyte life span. The loss of 7-HEG from DNA was both species and tissue dependent, with the adduct half-lives ranging from 2.9 to 5.8 days in rat tissues (brain, kidney, liver, lung, spleen, testis) and 1.0 to 2.3 days in all mouse tissues except kidney (t1/2 = 6.9 days). The concentrations of HEtVal were similar in concurrently exposed rats and mice, whereas DNA from rats had at least 2-fold greater concentrations of 7-HEG than DNA from mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Levels of Epoxides in Blood During Inhalation of Alkenes and Alkene Oxides

AbstractWe previously reported that propylene oxide levels in the blood of rats exposed to propylene spiked 5–10 min into the exposure and that hepatic and nasal cytochrome P-450 concentrations decreased relative to control values after the occurrence of the propylene oxide spike. These results can be explained by the inactivation of enzymes both efficient at propylene epoxidation and susceptible to inactivation by terminal alkene metabolites. To further examine this phenomenon, we exposed rats to ethylene, a known cytochrome P-450 inactivator; to cyclohexene, an alkene that does not inactivate cytochrome P-450; and to the epoxides of ethylene, cyclohexene, and propylene. During a 600-ppm ethylene exposure, blood ethylene oxide levels rapidly increased for the first 5–10 min and then rapidly declined to remain relatively constant for the duration of a 60-min exposure. Hepatic cytochrome P-450 decreased throughout the ethylene exposure. During exposure to 5 ppm ethylene oxide, blood epoxide concentrations ...

Rapid axonal transport velocity is reduced in experimental ethylene oxide neuropathy.

Chronic exposure of rats to ethylene oxide (EO) causes distal axonal neuropathy of lumbosacral primary sensory neurons. To study the pathogenesis of this neuropathy, we measured rapid axonal transport in peripheral nerves. Rats were exposed for 6 h to 500 ppm EO in a chamber three times a wk for 15 wk. Rapid axonal transport and quantitative histological alterations of peripheral nerves were studied. After [35S]methionine injection into the dorsal root ganglion, the velocity of rapid anterograde axonal transport of radioisotope-labeled protein was measured. The velocity in the rats exposed to EO was 33% less than that in control rats exposed to filtered room air. However, histological differences were slight. Morphometric studies showed that in EO-exposed rats, only the distal portions of the sural nerve had significantly greater incidental degeneration of myelinated fibers than did controls. There were significantly fewer large myelinated fibers only in the distals peroneal nerve. Therefore, a decrease in the velocity of anterograde axonal transport, related to these slight histological abnormalities of the peripheral nerve, may play a causative role in the development of the distal axonal neuropathy owing to chronic EO exposure.