Biomonitoring of volatile organic compounds and organophosphorus flame retardands in commercial aircrews after "fume and smell events"

Health risks to humans after "fume and smell events", short-term incidents on aircrafts that are accompanied by unpleasant odour or visible smoke, remain a subject of controversy. We assessed exposure to volatile organic compounds (VOC) and organophosphorus compounds (OPC) by biomonitoring in 375 aircrew members after self-reported "fume and smell events" and in 88 persons of the general population. A total of 20 parameters were analysed in blood and urine by gas chromatography and mass spectrometry. Median levels of acetone in blood and urine and 2-propanol in blood were elevated in aircrews compared to controls (p < 0.0001). Additionally, elevated peak exposures, best estimated by the 95th percentiles, were observed in aircrews for n-heptane and n-octane in blood, and acetone, 2,5-hexanedione and o-cresol in urine. Only the maximum observed levels of 2,5-hexandione in urine (768 μg/L) and toluene in blood (77 μg/L) in aircrew members were higher than the current biological exposure indices (BEI® levels) (500 and 20 μg/L, respectively) of the American Conference of Governmental Industrial Hygienists (US-ACGIH) for workers occupationally exposed to n-hexane and toluene, two well-accepted human neurotoxicants. Low-level exposures to n-hexane and toluene could be also observed in controls. The majority of OPC parameters in urine, including those of neurotoxic ortho-isomers of tricresylphosphate, were below the limit of quantitation in both aircrews and controls. Our comparative VOC and OPC analyses in biological samples of a large number of aircrew members and controls suggest that exposures are similar in both groups and generally low.

Human biomonitoring of neonicotinoid exposures: case studies after the use of a spray-agent to ornamental plants and a topical medication to pets

Acetamiprid (ACE) and imidacloprid (IMI) are insecticides of global importance and are used as spray and watering agents for ornamental plants to control biting and sucking insects or as topical medications on pets to remove and control fleas. Human biomonitoring data on ACE and IMI exposures when applying these products are limited. We investigated exposures to ACE and IMI in male volunteers after the domestic application of either an ACE-containing agent or an IMI-containing spot-on medication. Complete and consecutive urine samples were collected for up to 56 h after application. Urine samples were analyzed for ACE, IMI, and their respective metabolites (N-desmethyl-ACE, IMI-olefin, and sum of 4-/5-hydroxy-IMI) by liquid chromatography-tandem mass spectrometry. Fairly uniform concentrations of N-desmethyl-ACE could be observed before and after orchid treatment, so that an ACE exposure associated with orchid treatment can most likely be excluded. In contrast, after the application of the IMI-containing medication, elevated concentrations of IMI, 4-/5-hydroxy-IMI, and IMI-olefin were quantified in urine samples post-20 h with maximum concentrations of 3.1, 14.9, and 8.0 μg/g creatinine, respectively, well above general background levels. Nevertheless, the IMI intake (10.6 μg/kg bw), calculated from the excreted amounts, was around five times below the current European acceptable daily intake. Based on the case results here, household exposures to ACE and IMI after spray treatment of ornamental plants and anti-flea treatment of dogs can be regarded as low and safe. However, people regularly applying neonicotinoid-containing formulations, such as professional gardeners and employees in animal shelters, should be studied in more detail.

Use of Multiple Machine Learning Approaches for Selecting Urothelial Cancer-Specific DNA Methylation Biomarkers in Urine

Diagnosing urothelial cancer (UCa) via invasive cystoscopy is painful, specifically in men, and can cause infection and bleeding. Because the UCa risk is higher for male patients, urinary non-invasive UCa biomarkers are highly desired to stratify men for invasive cystoscopy. We previously identified multiple DNA methylation sites in urine samples that detect UCa with a high sensitivity and specificity in men. Here, we identified the most relevant markers by employing multiple statistical approaches and machine learning (random forest, boosted trees, LASSO) using a dataset of 251 male UCa patients and 111 controls. Three CpG sites located in ALOX5, TRPS1 and an intergenic region on chromosome 16 have been concordantly selected by all approaches, and their combination in a single decision matrix for clinical use was tested based on their respective thresholds of the individual CpGs. The combination of ALOX5 and TRPS1 yielded the best overall sensitivity (61%) at a pre-set specificity of 95%. This combination exceeded both the diagnostic performance of the most sensitive bioinformatic approach and that of the best single CpG. In summary, we showed that overlap analysis of multiple statistical approaches identifies the most reliable biomarkers for UCa in a male collective. The results may assist in stratifying men for cystoscopy.

Biomonitoring of polycyclic aromatic hydrocarbons in firefighters at fire training facilities and in employees at respiratory protection and hose workshops

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic to humans and are formed by incomplete combustion. PAHs are always present during firefighting operations, and fire department members can be exposed to them in the workplace.

Methods

In this study, we analyzed 1-hydroxypyrene (1-OHP) in 36 urine samples from nine firefighters, collected before and after fire training sessions, and 32 urine samples from eight employees at respiratory protection and hose workshops. To assess breakthrough PAH exposure through personal protective equipment and potential dermal uptake, some of the workshop employees wore cotton garments under their regular workwear. Cotton samples were then examined for the presence of 17 semi-volatile and low-volatility PAHs.

Results

After firefighting exercises, we observed approximately a fivefold increase in mean 1-OHP concentrations in samples from firefighters, from 0.24 μg/L to 1.17 μg/L (maximum: 5.31 μg/L). In contrast, 1-OHP levels in workshop employees were found to be low, with the majority of urine samples yielding concentrations below the limit of quantification (LOQ: 0.05 μg/L, maximum: 0.11 μg/L). Similarly, low PAH levels were found on the workshop employees' cotton undergarments, with maximum concentrations of 250 and 205 ng/g for pyrene and benzo[a]pyrene, respectively.

Discussion

In conclusion, significant increases in 1-OHP in urine were observed in firefighters after training sessions, whereas work-related exposure remained low among workshop employees.

Quantitative Metabolism and Urinary Elimination Kinetics of Seven Neonicotinoids and Neonicotinoid-Like Compounds in Humans

Reverse dosimetry, i.e., calculating the dose of hazardous substances that has been taken up by humans based on measured analyte concentrations in spot urine samples, is critical for risk assessment and requires metabolic and kinetic data. We quantitatively studied the metabolism of seven major neonicotinoid and neonicotinoid-like compounds (NNIs) after single oral doses in male volunteers and determined key kinetic parameters and urinary elimination for NNIs together with their metabolites. Complete and consecutive urine samples were collected over 48 h. All samples were analyzed by tandem mass spectrometry, following liquid or gas chromatographic separation. Single- and group-specific NNI metabolites were quantified, i.e., hydroxylated and N-dealkylated NNIs and NNI-associated carboxylic acids and their glycine derivatives. Large, substance-dependent variations of key toxicokinetic parameters were observed. Mean times of concentration maxima (tmax) in urine varied between 2.0 (imidacloprid) and 25.8 h (N-desmethyl-clothianidin), whereas mean urinary elimination half-times (t1/2) were between 2.5 (acetamiprid) and 49.5 h (sulfoxaflor). Mean 48 h excretion fractions (Fue's) were between 0.03% (2-chloro-1,3-thiazole-5-carboxylic acid glycine) and 84% (clothianidin). In contrast, the interindividual differences of Fue's between the volunteers for each of the NNIs and their metabolites remained low (below a factor of 2 between the maximum and minimum derived Fue with the exception of 6-chloronicotinic acid in the acetamiprid dose study). The obtained quantitative data enabled choosing appropriate biomarkers for exposure assessment and, at the same time, for risk assessment by reverse dosimetry at current environmental exposures, i.e., comparing the calculated doses that have been taken up to currently available acceptable daily intakes of NNIs.

Quantitation of 6-chloronicotinic acid and 2-chloro-1,3-thiazole-5-carboxylic acid and their glycine conjugates in human urine to assess neonicotinoid exposure

Neonicotinoids and neonicotinoid-like compounds (NNIs) are widely used insecticides and their ubiquitous occurrence in the environment requires methods for exposure assessment in humans. The majority of the NNIs can be divided into 6-chloropyridinyl- and 2-chlorothiazolyl-containing compounds, suggesting the formation of the group-specific metabolites 6-chloronicotinic acid (6-CNA), 2-chloro-1,3-thiazole-5-carboxylic acid (2-CTA), and their respective glycine derivatives (6-CNA-gly, 2-CTA-gly). Here, we developed and validated an analytical method based on gas chromatography coupled to mass spectrometry (GC-MS/MS) to simultaneously analyze these four metabolites in human urine. As analytical standards for the glycine conjugates were not commercially available, we synthesized 6-CNA-gly, 2-CTA-gly, and their ¹³C₂,¹⁵N-labeled analogs for internal standardization and quantitation by stable isotope dilution. We also ensured chromatographic separation of 6-CNA and its isomer 2-CNA. Enzymatic cleavage during sample preparation was proven unnecessary. The limits of quantitation were between 0.1 (6-CNA) and 0.4 μg/L (2-CTA-gly) and the repeatability was satisfactory (coefficient of variation was <19% over the calibration range). We analyzed 38 spot urine samples from the general population and were able to quantify 6-CNA-gly in 58% of the samples (median 0.2 μg/L). In contrast, no 6-CNA could be detected. The results are in line with well-known metabolic pathways specific in humans, that, compared to rodents, favor the formation and excretion of phase-II-metabolites (glycine derivatives) rather than phase-I metabolites (free carboxylic acids). Nevertheless, the exact source of exposure (i.e., the specific NNI) remains elusive in the general population, may even vary quantitatively between different NNIs, and also might be regional specific based on the respective use of individual NNIs. In sum, we developed a robust and sensitive analytical method for the determination of four group-specific NNI metabolites.

Impact of diesel exhaust exposure on urinary 1-hydroxypyrene in underground salt and potash workers

BACKGROUND

Diesel engine exhaust (DEE) and some of the polycyclic aromatic hydrocarbons (PAH) it contains are carcinogenic to humans (for example benzo(a)pyrene) and can cause lung cancer in workers. The objective of this study was to assess exposures to DEE and its component PAH and the potential associations between these two health hazards in a salt and potash mining population.

METHODS

Between 2017 and 2019, 1003 underground workers (mining n = 801, maintenance n = 202) and 243 above-ground facility workers from two German mines participated. Personal exposure to DEE was assessed in air as elemental carbon for diesel particulate matter (EC-DPM), whereas exposure to PAH was assessed in pre- and post-shift urine samples in terms of 1-hydroxypyrene (1-OHP). Associations between EC-DPM and 1-OHP were studied using linear regression models.

RESULTS

The highest EC-DPM exposures were measured in mining workers (median 0.06 mg/m³) followed by workers in the maintenance (0.03 mg/m³) and facility areas (<0.02 mg/m³). Exposures above the current German occupational threshold level of 0.05 mg/m³ were observed in 56%, 17%, and 5% of mining, maintenance and facility workers, respectively. 1-OHP increased statistically significantly across a work shift in underground workers but not in facility workers. Regression analyses revealed an increase of post-shift 1-OHP by almost 80% in mining and 40% in maintenance compared with facility workers. 1-OHP increased with increasing EC-DPM among underground workers. However, internal exposure of 1-OHP mainly remained at levels similar to those of the German general population in more than 90% of the urine samples.

CONCLUSIONS

While exposures to DEE above the current German OEL for EC-DPM are quite common in the studied population of underground salt and potash miners (39.5% overall), urinary concentrations of 1-OHP did not reflect these findings.

Expression of DNA mismatch repair proteins in melanoma patients treated with immune checkpoint inhibitors

PURPOSE

To investigate the protein expression of DNA mismatch repair (MMR) proteins in patients with cutaneous melanoma (CM) under immune checkpoint inhibitor (ICI) therapy.

METHODS

Immunohistochemistry was performed on tumor tissue for MMR proteins MLH1, MSH2, MSH6, and PMS2 in 50 metastatic CM patients treated with ICI (ipilimumab, nivolumab, pembrolizumab).

RESULTS

Best overall response (BOR) rate was 48% (24/50). Reduced MMR protein expression (nuclear expression in < 80% of tumor cells) was observed in 8 patients (16%). Compared to other clinical parameters, baseline neutrophil/lymphocyte ratio and reduced intratumoral MMR protein expression (P = 0.0033) were determined as the only parameters significantly associated with favorable BOR. However, in this small study population, reduced MMR protein expression did not reach statistical significance in multivariate analysis.

CONCLUSION

Reduced MMR protein expression is observed in CM and might predict favorable BOR in patients treated with ICI, as was observed for other entities. However, these findings need to be substantiated in larger patient cohorts.

Exposure to polycyclic aromatic hydrocarbons assessed by biomonitoring of firefighters during fire operations in Germany

BACKGROUND

Firefighters are exposed to a variety of hazardous substances including carcinogens such as polycyclic aromatic hydrocarbons (PAH) during firefighting. In order to minimize the uptake of such substances into the body, firefighters wear personal protective equipment. Only few data exist from real-life firefighting missions and under common although highly variable exposure scenarios such as fighting fires in residential buildings, outdoor, and vehicle fires. The aim of this study is to assess the levels of 1-Hydroxypyrene (1-OHP) as marker for incorporated PAH during firefighting operations in Germany using biomonitoring methods.

METHODS

We analyzed urine samples for 1-OHP from 77 firefighters who reported firefighting operations (with and without creatinine adjustment). Urine samples were collected before (baseline) and, where applicable, after firefighting operations at three time points subsequent (2-4, 6-8, and 12 h).

RESULTS

Compared to the baseline measurements, mean 1-OHP concentrations after firefighting missions were doubled (0.14 vs. 0.31 μg/L urine, 0.13 μg/g vs. 0.27 μg/g creatinine) and this increase was observed 2-4 h after firefighting. Firefighting in residential buildings (N = 54) and of outdoor and vehicle fires (N = 17) occurred most frequently, whereas blazes, vegetation fires, and fires in underground facilities (N = 6) were rarely encountered. For residential building fires, a 3-fold increase in mean 1-OPH concentrations was observed, whereas no increase could be observed for outdoor and vehicle fires. The highest increase was observed for firefighters with interior attack missions (0.11 μg/L vs. 0.48 μg/L 1-OHP) despite the use of self-contained breathing apparatus (SCBA). During the suppression of outdoor or vehicle fires using SCBA, again, no increase was observed. Although PAH are taken up during certain firefighting missions, the 1-OHP levels almost entirely remained (in 64 of the 77 reported missions) within the normal range of the German general population, i.e., below the reference levels (95th percentiles) of smokers (0.73 μg/g creatinine) and non-smokers (0.30 μg/g creatine).

CONCLUSION

Under study conditions, properly applied protective clothing and wearing of SCBA led to a significant reduction of PAH exposure levels. But there are individual situations in which PAH are increasingly incorporated since the incorporation depends on several factors and can be extremely variable. In contrast to many workplaces with high occupational exposure levels, firefighters are not exposed to PAH on a daily basis. Nevertheless, the possibility of an individual increased cancer risk for a particular firefighter cannot completely be ruled out.

Rapid quantification of seven major neonicotinoids and neonicotinoid-like compounds and their key metabolites in human urine

Neonicotinoids and neonicotinoid-like compounds (NNIs) are frequently used insecticides worldwide and exposure scenarios can vary widely between countries and continents. We have developed a specific and robust analytical method based on liquid chromatography-electrospray tandem mass spectrometry coupled to online-SPE (online-SPE-LC-ESI-MS-MS) to analyze the seven most important NNIs from a global perspective together with nine of their key metabolites in human urine. The method also includes the neonicotinoid-like flupyradifurone (FLUP), an important future substitute for classical neonicotinoids, and two of its major human metabolites, 5-hydroxy- and N-desfluoroethyl-FLUP. Validation of the method was carried out using pooled urine samples from low-dose human metabolism studies and spiked urine samples with a wide range of creatinine concentrations. Depending on the analyte, the limits of quantitation were between 0.06 and 2.1 µg L^-1, the inter-day and intra-day imprecisions ≤6%, and the mean relative recoveries between 89% and 112%. The method enabled us to successfully quantify NNIs and their metabolites at current environmental exposures in 34 individuals of the German general population and 43 pregnant women from Brazil with no known occupational exposures to NNIs.

Protein expression of prognostic genes in primary melanoma and benign nevi

PURPOSE

To evaluate the protein expression characteristics of genes employed in a recently introduced prognostic gene expression assay for patients with cutaneous melanoma (CM).

METHODS

We studied 37 patients with CM and 10 with benign (melanocytic) nevi (BN). Immunohistochemistry of primary tumor tissue was performed for eight proteins: COL6A6, DCD, GBP4, KLHL41, KRT9, PIP, SCGB1D2, SCGB2A2.

RESULTS

The protein expression of most markers investigated was relatively low (e.g., DCD, KRT9, SCGB1D2) and predominantly cytoplasmatic in melanocytes and keratinocytes. COL6A6, GBP4, and KLHL41 expression was significantly enhanced in CM when compared to BN. DCD protein expression was significantly correlated with COL6A6, GBP4, and KLHL41. GBP4 was positively correlated with KLHL41 and inversely correlated with SCGB2B2. The latter was also inversely correlated with serum S100B levels at time of initial diagnosis. The presence of SCGB1D2 expression was significantly associated with ulceration of the primary tumor. KRT9 protein expression was significantly more likely found in acral lentiginous melanoma. The presence of DCD expression was less likely associated with superficial spreading melanoma subtype but significantly associated with non-progressive disease. The absence of SCGB2A2 expression was significantly more often observed in patients who did not progress to stage III or IV.

CONCLUSIONS

The expression levels observed were relatively low but differed in part with those found in BN. Even though we detected some significant correlations between the protein expression levels and clinical parameters (e.g., CM subtype, course of disease), there was no major concordance with the protective or risk-associated functions of the corresponding genes included in a recently introduced prognostic gene expression assay.

Sensitivity and Specificity in Urine Bladder Cancer Markers – Is it that Simple?

Marker research and, in particular urine bladder cancer marker research throughout the past three decades, devours enormous scientific resources in terms of manpower (not to mention time spent on reviewing and editorial efforts) and financial resources finally generating large numbers of manuscripts without affecting clinical decision making. This is mirrored by the fact that current guidelines do not recommend marker use due to missing level 1 evidence. Although we recognize the problems and obstacles, the authors of this commentary feel that the time has come to abandon the current procedures and move on to prospective trial designs implementing marker results into clinical decision making. Our thoughts and concerns are summarized in this comment.

Expression of Mismatch Repair Proteins in Merkel Cell Carcinoma

Simple Summary

Merkel cell carcinoma (MCC) is a rare and highly malignant skin cancer with neuroendocrine differentiation. About 80% are Merkel cell polyomavirus (MCPyV) positive. The aim of this work was to immunohistochemically investigate the expression of mismatch repair proteins (MSH2, MSH6, MLH1, and PMS2) in MCC (n = 56). In a second step, tumors with a low expression were tested for microsatellite instability. Microsatellite instability in MCC could have an impact on immune checkpoint inhibitor therapy (ICI) outcome. This study showed a significant association between low expression of mismatch repair proteins and a negative MCPyV status. Microsatellite instability was detected in only one case. Future studies will establish whether this subset of MCC patients respond better to ICI.

Abstract

We aimed to assess for the first time the mismatch repair (MMR) protein expression in Merkel cell carcinoma (MCC). Immunohistochemistry was performed for MLH1, MSH2, MSH6, and PMS2 on patients’ tumor tissue (n = 56), including neighbored healthy control tissue. In cases with low-level MMR expression (<10th percentile), we performed multiplex PCR in combination with high-resolution capillary electrophoresis in order to confirm microsatellite instability (MSI). Microscopic evaluation revealed a high median expression for all MMR proteins studied (91.6–96.3%). However, six patients (56/10.7%) had low-level MLH1 expression, six (55/10.9%) had low-level MSH2 expression, five (56/8.9%) had low-level MSH6 expression, and six (54/11.1%) had low-level PMS2 expression. Together, we observed nine (56/16.1%) patients who had low-level MMR expression of at least one protein. Of the patients with low-level MMR expression, MSI evaluation was possible in five cases, revealing one case with high-level MSI. In all MMR proteins assessed, low-level expression was significantly (p = 0.0004 to p < 0.0001) associated with a negative Merkel cell polyomavirus (MCPyV) status. However, the expression profiles of the MMR proteins did not correlate with clinical outcome measures such as disease relapse or death (p > 0.05). MCC appears to be a malignancy characterized by low-level MMR rather than completely deficient MMR in a subset of cases, predominantly affecting MCPyV-negative tumors. Future studies will establish whether this subset of MCC patients respond better to immune checkpoint inhibitor therapy.

Expression of Hedgehog signalling molecules in microcystic adnexal carcinoma

BACKGROUND

Microcystic adnexal carcinoma (MAC) is a rare skin neoplasm that has not been characterized on a molecular basis.

AIM

To assess expression profiles of Hedgehog (HH) signalling molecules in MAC and control tumours.

METHODS

Immunohistochemistry was performed for Sonic Hedgehog (SHH), Indian Hedgehog (IHH), Patched 1 (PTCH1) and Smoothened (SMO) on patient MAC tissue (n = 26) and control tumour tissue, including syringoma (SyG; n = 11), trichoepithelioma (TE; n = 11) and basal cell carcinoma (BCC; n = 12) tissues.

RESULTS

Patched 1 and SMO immunoreactivity was significantly higher in BCC than in SyG, TE or MAC (P < 0.001 and P < 0.03, respectively). The highest IHH expression was observed in BCC and TE compared with SyG and MAC (P < 0.04). Notably, the highest SHH protein expression was observed in SyG compared with MAC, TE and even BCC (P < 0.001). In patients with MAC, SMO immunoreactivity significantly (r = 0.51; P < 0.01) correlated with PTCH1 expression. Further correlation studies did not show significant associations between the HH expression markers assessed (P > 0.05).

CONCLUSION

Our results indicate that alterations of the HH signalling are unlikely to play a major role in the pathogenesis of MAC, which is in contrast to the morphologically similar BCC and TE. Our observation provides additional information to the limited molecular pathology knowledge on this rare tumour.

In-Vitro Identification and In-Vivo Confirmation of DNA Methylation Biomarkers for Urothelial Cancer

We identified DNA methylation targets specific for urothelial cancer (UC) by genome-wide methylation difference analysis of human urothelial (RT4, J82, 5637), prostate (LNCAP, DU-145, PC3) and renal (RCC-KP, CAKI-2, CAL-54) cancer cell lines with their respective primary epithelial cells. A large overlap of differentially methylated targets between all organs was observed and 40 Cytosine-phosphate-Guanine motifs (CpGs) were only specific for UC cells. Of those sites, two also showed high methylation differences (≥47%) in vivo when we further compared our data to those previously obtained in our array-based analyses of urine samples in 12 UC patients and 12 controls. Using mass spectrometry, we finally assessed seven CpG sites in this “bladder-specific” region of interest in urine samples of patients with urothelial (n = 293), prostate (n = 75) and renal (n = 23) cancer, and 143 controls. DNA methylation was significantly increased in UC compared to non-UC individuals. The differences were more pronounced for males rather than females. Male UC cases could be distinguished from non-UC individuals with >30% sensitivity at 95% specificity (Area under the curve (AUC) 0.85). In summary, methylation sites highly specific in UC cell lines were also specific in urine samples of UC patients showing that in-vitro data can be successfully used to identify biomarker candidates of in-vivo relevance.

Abstract A01: Environmentally prevalent polycyclic aromatic hydrocarbons elicit cocarcinogenic properties in human and mouse lung cells

Rationale: Polycyclic aromatic hydrocarbons (PAHs) are prevalent contaminants in our environment, workplace, and in first- and secondhand smoke from both cigarettes and marijuana. The toxicity of low molecular weight (LMW) PAHs compared to high molecular weight PAHs (e.g., benzo[a]pyrene, B[a]P) is not well studied in lung cells. Our overall hypothesis was that LMW PAHs act as cocarcinogens in the presence of a known carcinogen (B[a]P) in human and mouse lung epithelial cells. Gap junctions are commonly suppressed during tumor promotion, while DNA-adduct formation and micronuclei (MN) are observed during the initiation stage of cancer. We used these endpoints together as markers of carcinogenicity in Beas2B and C10 cells.

Methods: Beas2B, a human bronchial epithelial cell line, and C10 cells, a nontumorigenic type II alveolar pneumocyte cell line, were used. LMW PAHs (1-methylanthracene, 1-MeA, and fluoranthene, Flthn) were applied in a 1:1 ratio mixture based on previous studies and B[a]P as a classic carcinogen. Cells were treated for 30 min.-24 h with the LMW PAH mixture, B[a]P, or both, and assessed for the following endpoints: cytotoxicity, genotoxicity (MN), apoptosis, proliferation, gap junctional intercellular communication (GJIC) by the lucifer yellow scalpel-loaded/dye-transfer assay, and DNA adducts of B[a]P by HPLC with fluorescence detection in C10 cells.

Results: LMW PAHs are more cytotoxic in the human Beas2B cells than the mouse C10 cells. Significant toxicity is observed in Beas2B cells at 0.3 uM B[a]P combined with the LMW PAH mixture (0.1-1 uM), while no toxicity is observed in C10 cells at identical doses. No significant apoptosis was observed in Beas2B cells while significant increases in S-phase were observed in response to B[a]P combined with LMW PAH mixture compared to B[a]P alone. B[a]P in combination with the LMW PAH mixture significantly inhibited GJIC in C10 and Beas2B cells compared to B[a]P or the LMW PAH mixture alone, supporting a role for GJIC suppression in cancer development. B[a]P diol-epoxide (BPDE)-DNA adduct levels were also significantly induced in C10 cells at 1.0 uM B[a]P with the LMW PAH mixture at several doses (less than or equal to 1.0 uM) and significant increases in BPDE-DNA adduct formation compared to B[a]P alone were observed. Lastly, MN were also observed in both cell lines and significantly differed between B[a]P alone and in combination with the LMW PAH mixture. DNA adduct formation and genotoxicity coincided with GJIC inhibition.

Conclusion: These studies provide evidence that LMW PAHs in combination with B[a]P can elicit increased carcinogenic potential in human and mouse cells.

Support: Flight Attendant Medical Research Institute (CIA130022, AKB); the National Institute for Environmental Health Sciences (R15ES024893, AKB).

Citation Format: Alison K. Bauer, Katelyn J. Siegrist, Sabine Plöttner, Thomas Brüning, Heiko U. Käfferlein. Environmentally prevalent polycyclic aromatic hydrocarbons elicit cocarcinogenic properties in human and mouse lung cells [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A01.

Toward noninvasive follow-up of low-risk bladder cancer - Rationale and concept of the UroFollow trial

BACKGROUND

Follow-up recommendations for patients with nonmuscle invasive bladder cancer (NMIBC) are largely based upon expert opinion. A growing body of evidence suggests that current follow-up strategies for bladder cancer patients with low and intermediate risk represent overdiagnosis and may lead to overtreatment. The goal of this study is to explore the options of a noninvasive follow-up in patients with pTa G1-2/low-grade NMIBC.

METHODS

The risks and options for a urine marker-guided, noninvasive follow-up of patients with pTa G1-2/low-grade NMIBC were defined and the study design for a prospective randomized trial (UroFollow) was developed based upon the current literature.

RESULTS

The investigators postulated that follow-up of patients with pTa G1-2/low-grade NMIBC requires a high sensitivity of urinary tumor markers. However, data from prospective studies with prediagnostic urine samples are scarce, even for approved markers, and cross-sectional studies with symptomatic patients overestimate the sensitivity. So far, cell-based markers (e.g., uCyt+ and UroVysion) in urine appeared to have higher sensitivities and specificities in low-grade NMIBC than urine cytology and markers analyzing soluble tumor-associated antigens. Marker panels are more sensitive than single-marker approaches at the expense of a lower specificity. Given a prospective randomized comparison with a marker sensitivity of 80% compared to usual care with cystoscopy, the sample size calculation yielded that 62 to 185 patients under study per arm are needed depending on different recurrence rates.

CONCLUSIONS

Based upon these findings the UroFollow trial has been designed as a prospective randomized study comparing a noninvasive marker-based (UroVysion, NMP22, urine cytology, and ultrasound) follow-up with the current standard of care over a period of 3 years.

Expression of Lefty predicts Merkel cell carcinoma-specific death

BACKGROUND

Lefty and Nodal are transforming growth factor β-related proteins, which, beside their role in determination of laterality during embryogenesis, have also been linked with cancer progression.

OBJECTIVES

Prompted by the observed significant left-sided laterality of Merkel cell carcinoma (MCC), we addressed whether Lefty and Nodal are expressed in MCC and correlated expression patterns with clinical parameters such as MCC laterality and patient outcome.

METHODS

Expression of Lefty and Nodal in primary MCC was assessed in 29 patients by immunohistochemistry. The histology (H-)score was calculated and correlated with clinical parameters.

RESULTS

The median (range) H-score of Lefty and Nodal was 17.6 (0-291) and 74.9 (0.7-272), respectively. There was a significant correlation between Lefty expression and Nodal expression (correlation coefficient of 0.60, P = 0.0006). There was no significant correlation between Lefty expression and Nodal expression with either tumour laterality, gender, age, Merkel cell polyomavirus status, disease stage, anatomical localization of primary tumours or disease relapse. On univariate analysis, low Lefty expression and Nodal expression were significantly associated with MCC-specific death (P = 0.010 and P = 0.019, respectively). On univariate analysis, low Lefty expression was the only significant independent predictor for MCC-specific death (P = 0.025) as indicated by an odds ratio of 14 (95% CI: 1.43-137.33).

CONCLUSIONS

Lefty and Nodal are frequently expressed in MCC, but not correlated with tumour laterality. Importantly, our data suggest that a low level of Lefty expression in primary MCC is a strong predictor of MCC-specific death.

TGFBI Protein Is Increased in the Urine of Patients with High-Grade Urothelial Carcinomas, and Promotes Cell Proliferation and Migration

Here, we discovered TGFBI as a new urinary biomarker for muscle invasive and high-grade urothelial carcinoma (UC). After biomarker identification using antibody arrays, results were verified in urine samples from a study population consisting of 303 patients with UC, and 128 urological and 58 population controls. The analyses of possible modifying factors (age, sex, smoking status, urinary leukocytes and erythrocytes, and history of UC) were calculated by multiple logistic regression. Additionally, we performed knockdown experiments with TGFBI siRNA in bladder cancer cells and investigated the effects on proliferation and migration by wound closure assays and BrdU cell cycle analysis. TGFBI concentrations in urine are generally increased in patients with UC when compared to urological and population controls (1321.0 versus 701.3 and 475.6 pg/mg creatinine, respectively). However, significantly increased TGFBI was predominantly found in muscle invasive (14,411.7 pg/mg creatinine), high-grade (8190.7 pg/mg) and de novo UC (1856.7 pg/mg; all p < 0.0001). Knockdown experiments in vitro led to a significant decline of cell proliferation and migration. In summary, our results suggest a critical role of TGFBI in UC tumorigenesis and particularly in high-risk UC patients with poor prognosis and an elevated risk of progression on the molecular level.

Noninvasive diagnosis of urothelial cancer in urine using DNA hypermethylation signatures-Gender matters

Urothelial cancer (UCa) is the most predominant cancer of the urinary tract and noninvasive diagnosis using hypermethylation signatures in urinary cells is promising. Here, we assess gender differences in a newly identified set of methylation biomarkers. UCa-associated hypermethylated sites were identified in urine of a male screening cohort (n = 24) applying Infinium-450K-methylation arrays and verified in two separate mixed-gender study groups (n = 617 in total) using mass spectrometry as an independent technique. Additionally, tissue samples (n = 56) of mixed-gender UCa and urological controls (UCt) were analyzed. The hypermethylation signature of UCa in urine was specific and sensitive across all stages and grades of UCa and independent on hematuria. Individual CpG sensitivities reached up to 81.3% at 95% specificity. Albeit similar methylation differences in tissue of both genders, differences were less pronounced in urine from women, most likely due to the frequent presence of squamous epithelial cells and leukocytes. Increased repression of methylation levels was observed at leukocyte counts ≥500/μl urine which was apparent in 30% of female and 7% of male UCa cases, further confirming the significance of the relative amounts of cancerous and noncancerous cells in urine. Our study shows that gender difference is a most relevant issue when evaluating the performance of urinary biomarkers in cancer diagnostics. In case of UCa, the clinical benefits of methylation signatures to male patients may outweigh those in females due to the general composition of women's urine. Accordingly, these markers offer a diagnostic option specifically in males to decrease the number of invasive cystoscopies.

LIPG-promoted lipid storage mediates adaptation to oxidative stress in breast cancer

Endothelial lipase (LIPG) is a cell surface associated lipase that displays phospholipase A1 activity towards phosphatidylcholine present in high‐density lipoproteins (HDL). LIPG was recently reported to be expressed in breast cancer and to support proliferation, tumourigenicity and metastasis. Here we show that severe oxidative stress leading to AMPK activation triggers LIPG upregulation, resulting in intracellular lipid droplet accumulation in breast cancer cells, which supports survival. Neutralizing oxidative stress abrogated LIPG upregulation and the concomitant lipid storage. In human breast cancer, high LIPG expression was observed in a limited subset of tumours and was significantly associated with shorter metastasis‐free survival in node‐negative, untreated patients. Moreover, expression of PLIN2 and TXNRD1 in these tumours indicated a link to lipid storage and oxidative stress. Altogether, our findings reveal a previously unrecognized role for LIPG in enabling oxidative stress‐induced lipid droplet accumulation in tumour cells that protects against oxidative stress, and thus supports tumour progression.

What's new?

Endothelial lipase (LIPG), a cell surface‐associated lipase with multifaceted roles, is expressed on breast cancer cells, but its molecular function and clinical relevance remain unknown. Here the authors uncover a link between oxidative stress and LIPG upregulation and show that high LIPG expression is associated with shorter metastasis‐free survival in women with node‐negative breast cancer. The authors speculate that LIPG may favor metastasis by enabling stress adaptation through lipid droplet formation and protection of mitochondria.

Total synthesis of 13 C2 ,15 N-imidacloprid with three stable isotopes in the pyridine ring

Imidacloprid (IC) is an important crop-protecting insecticide worldwide and commonly used for seed treatment. However, only few data are available on human toxicity of IC. Having in view the metabolic studies at low doses in humans and residue analysis of IC in food and consumer products, we elaborated the synthesis and prepared ¹³ C₂ ,¹⁵ N-IC with three stable isotopes of the "heavy" atoms in positions 1, 2, and 3 of the pyridine ring. By using readily available and affordable starting materials, ¹⁵ NH₄ Cl and ¹³ C₄ -acetic anhydride, the target compound has been prepared in eight steps with an overall yield of 13%.

Environmentally prevalent polycyclic aromatic hydrocarbons can elicit co-carcinogenic properties in an in vitro murine lung epithelial cell model

Low molecular weight (LMW) polycyclic aromatic hydrocarbons (PAH) are the most abundant PAHs environmentally, occupationally, and are in cigarette smoke; however, little is known about their carcinogenic potential. We hypothesized that LMW PAHs act as co-carcinogens in the presence of a known carcinogen (benzo[a]pyrene (B[a]P)) in a mouse non-tumorigenic type II cell line (C10 cells). Gap junctions are commonly suppressed and inflammation induced during tumor promotion, while DNA-adduct formation is observed during the initiation stage of cancer. We used these endpoints together as markers of carcinogenicity in these lung adenocarcinoma progenitor cells. LMW PAHs (1-methylanthracene and fluoranthene, 1-10 µM total in a 1:1 ratio) were used based on previous studies as well as B[a]P (0-3 µM) as the classic carcinogen; non-cytotoxic doses were used. B[a]P-induced inhibition of gap junctional intercellular communication (GJIC) was observed at low doses and further reduced in the presence of the LMW PAH mixture (P < 0.05), supporting a role for GJIC suppression in cancer development. Benzo[a]pyrene diol-epoxide (BPDE)-DNA adduct levels were significantly induced in B[a]P-treated C10 cells and additionally increased with the LMW PAH mixture (P < 0.05). Significant increases in cyclooxygenase (Cox-2) were observed in response to the B[a]P/LMW PAH mixture combinations. DNA adduct formation coincided with the inhibition of GJIC and increase in Cox-2 mRNA expression. Significant cytochrome p4501b1 increases and connexin 43 decreases in gene expression were also observed. These studies suggest that LMW PAHs in combination with B[a]P can elicit increased carcinogenic potential. Future studies will further address the mechanisms of co-carcinogenesis driving these responses.

Altered Global 5-Hydroxymethylation Status in Hidradenitis Suppurativa: Support for an Epigenetic Background

BACKGROUND

The pathogenesis of hidradenitis suppurativa (HS), with its complex inflammatory network, is still elusive. Imbalances in DNA methylation can lead to genome destabilization and have been assumed to play a role in inflammatory diseases. Global DNA methylation and hydroxymethylation have not been studied in HS yet.

OBJECTIVE

We conducted this study to investigate the global DNA methylation and hydroxymethylation status in lesional and perilesional HS skin compared to healthy controls.

METHODS

Immunohistochemical analysis was performed for 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) in 30 lesional and 30 corresponding healthy-appearing perilesional HS tissue samples. We included 30 healthy subjects as an interindividual control group.

RESULTS

5-hmC levels were significantly lower in healthy-appearing perilesional (p < 0.0001) and lesional HS skin (p < 0.0001) when compared to healthy controls. There was no significant difference between lesional HS skin and perilesional HS skin regarding 5-hmC levels (p = 0.6654). In contrast to 5-hmC, 5-mC staining showed no significant changes between the 3 groups. Univariate analysis revealed no significant association between patients' characteristics, disease severity, and the levels of 5-mC and 5-hmC.

CONCLUSION

Our findings indicate that imbalances in DNA hydroxymethylation may play a role in the pathogenesis of HS rather than DNA methylation. Further studies are warranted to investigate the significance of DNA hydroxymethylation and the regulating enzymes in HS in order to advance our knowledge of the inflammatory network in this disease.

Noninvasive Diagnosis of High-Grade Urothelial Carcinoma in Urine by Raman Spectral Imaging

The current gold standard for the diagnosis of bladder cancer is cystoscopy, which is invasive and painful for patients. Therefore, noninvasive urine cytology is usually used in the clinic as an adjunct to cystoscopy; however, it suffers from low sensitivity. Here, a novel noninvasive, label-free approach with high sensitivity for use with urine is presented. Coherent anti-Stokes Raman scattering imaging of urine sediments was used in the first step for fast preselection of urothelial cells, where high-grade urothelial cancer cells are characterized by a large nucleus-to-cytoplasm ratio. In the second step, Raman spectral imaging of urothelial cells was performed. A supervised classifier was implemented to automatically differentiate normal and cancerous urothelial cells with 100% accuracy. In addition, the Raman spectra not only indicated the morphological changes that are identified by cytology with hematoxylin and eosin staining but also provided molecular resolution through the use of specific marker bands. The respective Raman marker bands directly show a decrease in the level of glycogen and an increase in the levels of fatty acids in cancer cells as compared to controls. These results pave the way for "spectral" cytology of urine using Raman microspectroscopy.

Expression of PIWIL3 in primary and metastatic melanoma

PURPOSE

The PIWI-interacting RNA machinery in malignant melanoma (MM) has not been sufficiently studied. We aimed to investigate the PIWIL3 expression profiles in primary melanomas and metastases of MM including a correlation with clinical data.

METHODS

We studied 161 primary melanomas, 45 lymph node metastases, and 16 distant metastases of 183 patients with MM. We used immunohistochemistry to assess PIWIL3 protein expression in situ. The relationship between the immunoreactivity of PIWIL3 and clinical data was statistically evaluated.

RESULTS

We observed a significantly (P = 0.000059) higher median immunoreactivity score in primary melanomas (4.9; range, 0.1-6), lymph node metastases (5.1; range, 3.3-6), and distant metastases (5.6; range, 4.5-6). PIWIL3 was expressed significantly higher (P = 0.0002) in primary nodular melanomas and acral melanomas (5.2; range, 3.4-6) when compared to other melanoma subtypes (4.7; range, 0.1-6). On univariate analysis, a significant positive correlation was observed between primary melanoma PIWIL3 expression and tumor thickness (r = 0.2; P = 0.014). On univariate and multivariate analysis, PIWIL3 did not prove to be an independent predictor for melanoma relapse or death.

CONCLUSIONS

Our data indicate that PIWIL3 protein expression is elevated in more aggressive primary MM and metastatic disease. As also observed in other malignancies, PIWIL3 seems to play a role in MM progression.

Oxidatively damaged guanosine in white blood cells and in urine of welders: associations with exposure to welding fumes and body iron stores

The International Agency for Research on Cancer considers the carcinogenicity of welding fume of priority for re-evaluation. Genotoxic effects in experimental animals are still inconclusive. Here, we investigated the association of personal exposure to metals in respirable welding fumes during a working shift with oxidatively damaged guanosine in DNA of white blood cells (WBC) and in postshift urine samples from 238 welders. Medians of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) were 2.35/10⁶ dGuo in DNA of WBC and 4.33 µg/g creatinine in urine. The median of 8-oxo-7,8-dihydroguanosine (8-oxoGuo) was 7.03 µg/g creatinine in urine. The extent of both urinary parameters was higher in welders applying techniques with high particle emission rates to stainless steel than in tungsten inert gas welders (8-oxodGuo: 9.96 vs. 4.49 µg/L, 8-oxoGuo: 15.7 vs. 7.7 µg/L), but this apparent difference diminished after creatinine adjustment. We applied random intercept models to estimate the influence of airborne and systemic exposure to metals on oxidatively damaged guanosine in WBC and urine together with covariates. We observed a highly significant nonlinear association of urinary 8-oxoGuo with serum ferritin (P < 0.0001) and higher 8-oxoGuo concentrations for respirable iron >1,000 µg/m³ compared to ≤57 µg/m³. Similar effects were found for manganese. Airborne chromium but not nickel was associated with all oxidatively modified guanosine measures, whereas urinary chromium as well as nickel showed associations with urinary modified guanosines. In summary, oxidatively damaged urinary guanosine was associated with airborne and systemic exposure to metals in welders and showed a strong relation to body iron stores.

Automated quantification of FISH signals in urinary cells enables the assessment of chromosomal aberration patterns characteristic for bladder cancer

Targeting the centromeres of chromosomes 3, 7, 17 (CEP3, 7, 17) and the 9p21-locus (LSI9p21) for diagnosing bladder cancer (BC) is time- and cost-intensive and requires a manual investigation of the sample by a well-trained investigator thus overall limiting its use in clinical diagnostics and large-scaled epidemiological studies. Here we introduce a new computer-assisted FISH spot analysis tool enabling an automated, objective and quantitative assessment of FISH patterns in the urinary sediment. Utilizing a controllable microscope workstation, the microscope software Scan^R was programmed to allow automatic batch-scanning of up to 32 samples and identifying quadruple FISH signals in DAPI-scanned nuclei of urinary sediments. The assay allowed a time- and cost-efficient, automated and objective assessment of CEP3, 7 and 17 FISH signals and facilitated the quantification of nuclei harboring specific FISH patterns in all cells of the urinary sediment. To explore the diagnostic capability of the developed tool, we analyzed the abundance of 51 different FISH patterns in a pilot set of urine specimens from 14 patients with BC and 21 population controls (PC). Herein, the results of the fully automated approach yielded a high degree of conformity when compared to those obtained by an expert-guided re-evaluation of archived scans. The best cancer-identifying pattern was characterized by a concurrent gain of CEP3, 7 and 17. Overall, our automated analysis refines current FISH protocols and encourages its use to establish reliable diagnostic cutoffs in future large-scale studies with well-characterized specimens-collectives.

Biomonitoring of exposure to N-methyl-2-pyrrolidone in workers of the automobile industry

N-methyl-2-pyrrolidone (NMP) is an important organic solvent for varnishes in industry. NMP has been previously shown to be a developmental toxicant in rodents. This study reports current exposures to NMP in the spraying department of an automobile plant using biological monitoring. Two specific metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methyl-succinimide (2-HMSI), were analyzed in 69 urine samples of 14 workers exposed to NMP and 9 nonexposed controls. Three different working tasks ('loading' and 'cleaning' of the sprayer system and 'wiping/packing' of the sprayed materials) and three sampling times (preshift, postshift, and preshift of the following day) were studied in exposed workers. Median exposures of 5-HNMP and 2-HMSI in postshift urine of exposed workers were 0.91 and 0.52mg g(-1) creatinine, respectively, whereas median levels in controls were below the limit of detection. Decreased levels of 5-HNMP were observed in preshift urine samples on the following day (0.39mg g(-1) creatinine) in exposed workers, while the concentration of 2-HMSI did not change (0.49mg g(-1) creatinine). Highest exposures occurred during sprayer cleaning with a maximum level of 8.31mg g(-1) creatinine of 5-HNMP in postshift urine. In contrast to 'wipers/packers', no decrease in 5-HNMP could be observed in preshift urine samples on day 2 of the 'loaders' and 'cleaners'. Overall, exposure in terms of 5-HNMP postshift and 2-HMSI preshift of the following day were well below the current biological limit values of the European Union (70 and 20mg g(-1) creatinine). Our results provide initial data on NMP exposure in the automobile industry and suggest that the analysis of 5-HNMP in preshift samples also provides essential information, particularly in situations involving direct handling of liquid NMP-containing formulations.

Assessment of micronuclei in lymphocytes from workers exposed to vapours and aerosols of bitumen

We investigated the micronucleus frequencies in peripheral blood lymphocytes of 225 mastic asphalt workers (age 17-62 years) and 69 non-bitumen-exposed road construction workers (age 18-64 years) in Germany before and after the working shift. Median shift exposure to vapours and aerosols of bitumen of exposed workers was 3.0 mg/m³. Micronuclei (MN) were determined with a standard method using cytochalasin B. Median MN frequency was 6.0 (interquartile range (IQR) 4.0-8.5) MN/1,000 binucleated lymphocytes (MN/1,000 BNC) in exposed workers and 6.0 (IQR 4.0-8.3) MN/1,000 BNC in non-exposed workers before shift. After shift, we observed 6.5 (IQR 4.4-9.3) MN/1,000 BNC in exposed workers and 6.5 (IQR 4.0-9.0) MN/1,000 BNC in non-exposed workers. Regression models were applied with the log-transformed MN frequency as the dependent variable in order to estimate the effects of exposure to vapours and aerosols of bitumen and of potential confounders. Age was the strongest predictor of MN formation in both exposed workers and referents. Our data suggest that MN formation was not associated with concentration of vapours and aerosols of bitumen during shift at the individual level. Although similar MN frequencies were observed in both groups, the modelling of factors potentially influencing MN frequency revealed a weak group difference in the post-shift model. We conclude that this small difference cannot be judged to be a relevant mutagenic effect of exposure to vapours and aerosols of bitumen, also with regard to the lack of adjustment for multiple testing and the lack of a group effect in the original data.

Detection of DNA strand breaks by comet assay in sputum leucocytes of bitumen-exposed workers: A pilot study

DNA strand breaks were determined in leucocytes of induced sputum (IS) and compared with DNA strand breaks in blood lymphocytes from 42 bitumen-exposed workers pre and post shift. Comet assay results were expressed in arbitrary units based on visual scoring (sputum leucocytes) and Olive tail moment (OTM, blood lymphocytes). DNA damage in IS leucocytes was overall high but did not change during shift. Level of DNA strand breaks in IS samples correlated with total cell count and neutrophil content (Spearman rank correlation coefficient rs = 0.47, p = 0.001, rs= 0.48, p = 0.001, respectively) and with IL-8 concentration before and after shift (rs = 0.31, P = 0.048, and rs = 0.43, P = 0.005). DNA damage in IS was not associated with DNA strand breaks in blood lymphocytes (rs = —0.04, p = 0.802 before shift, rs = 0.27, p = 0.088 after shift). A higher level of DNA strand breaks was measured in blood lymphocytes before shift (median OTM 1.7 before and 1.3 after shift, p = 0.023). A strong correlation was found between the number of neutrophils and IL-8 concentration in IS before and after shift (rs = 0.77 and rs= 0.75, p < 0.001). This study showed an association between genotoxic and inflammatory effects in the lower airways and compared simultaneously DNA strand breaks in IS and blood of bitumen-exposed workers.

Assessment of DNA Damage in WBCs of Workers Occupationally Exposed to Fumes and Aerosols of Bitumen

We conducted a cross-shift study with 66 bitumen-exposed mastic asphalt workers and 49 construction workers without exposure to bitumen. Exposure was assessed using personal monitoring of airborne bitumen exposure, urinary 1-hydroxypyrene (1-OHP), and the sum of 1-, 2 + 9-,3-,4-hydroxyphenanthrene (OHPH). Genotoxic effects in WBC were determined with nonspecific DNA adduct levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and the formation of DNA strand breaks and alkali-labile sites. Concentration of fumes and aerosols of bitumen correlated significantly with the concentrations of 1-OHP and OHPH after shift (r(s) = 0.27; P = 0.03 and r(s) = 0.55; P < 0.0001, respectively). Bitumen-exposed workers had more DNA strand breaks than the reference group (P < 0.0001) at both time points and a significant correlation with 1-OHP and OHPH in the postshift urines (r(s) = 0.32; P = 0.001 and r(s) = 0.27; P = 0.004, respectively). Paradoxically, we measured higher levels of DNA strand breaks, although not significant, in both study groups before shift. 8-OxodGuo adduct levels did not correlate with DNA strand breaks. Further, 8-oxodGuo levels were associated neither with personal exposure to bitumen nor with urinary metabolite concentrations. Significantly more DNA adducts were observed after shift not only in bitumen-exposed workers but also in the reference group. Only low-exposed workers had significantly elevated 8-oxodGuo adduct levels before as well as after shift (P = 0.0002 and P = 0.02, respectively). Our results show that exposure to fumes and aerosols of bitumen may contribute to an increased DNA damage assessed with strand breaks.

The use of biomarkers of exposure of N,N-dimethylformamide in health risk assessment and occupational hygiene in the polyacrylic fibre industry

BACKGROUND

N,N-dimethylformamide (DMF) was recently prioritised for field studies by the National Toxicology Program based on the potency of its reproductive toxic effects.

AIMS

To measure accurately exposure to DMF in occupational settings.

METHODS

In 35 healthy workers employed in the polyacrylic fibre industry, N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) in urine, and N-methylcarbamoylated haemoglobin (NMHb) in blood were measured. Workplace documentation and questionnaire information were used to categorise workers in groups exposed to low, medium, and high concentrations of DMF.

RESULTS

All three biomarkers can be used to identify occupational exposure to DMF. However, only the analysis of NMHb could accurately distinguish between workers exposed to different concentrations of DMF. The median concentrations were determined to be 55.1, 122.8, and 152.6 nmol/g globin in workers exposed to low, medium, and high concentrations of DMF, respectively. It was possible by the use of NMHb to identify all working tasks with increased exposure to DMF. While fibre crimpers were found to be least exposed to DMF, persons washing, dyeing, or towing the fibres were found to be highly exposed to DMF. In addition, NMHb measurements were capable of uncovering working tasks, which previously were not associated with increased exposure to DMF; for example, the person preparing the fibre forming solution.

CONCLUSIONS

Measurement of NMHb in blood is recommended rather than measurement of NMF and AMCC in urine to accurately assess exposure to DMF in health risk assessment. However, NMF and AMCC are useful biomarkers for occupational hygiene intervention. Further investigations regarding toxicity of DMF should focus on highly exposed persons in the polyacrylic fibre industry. Additional measurements in occupational settings other than the polyacrylic fibre industry are also recommended, since the population at risk and the production volume of DMF are high.

DNA strand breaks in the lymphocytes of workers exposed to diisocyanates: indications of individual differences in susceptibility after low-dose and short-term exposure

Diisocyanates are chemically reactive and induce asthma, but data on genotoxic effects of diisocyanates in humans are limited. The investigation presented here used short term diisocyanate chamber exposure to study DNA strand breaks in lymphocytes of 10 healthy individuals and of 42 workers, with airway symptoms, who had previously been exposed to diisocyanates. The alkaline version of the Comet assay was used to analyse DNA strand breaks in lymphocytes. In addition, blood samples of 10 further control individuals without any exposure to diisocyanates were studied. Substances studied were 4,4'-methylenediphenyldiisocyanate (MDI, n=25), 2,4-toluenediisocynate and 2,6-toluenediisocyanate (TDI, n=5), and 1,6-hexamethylenediisocyanate (HDI, n=12), at concentrations between 5 and 30 ppb for 2 h. Lymphocytes isolated from the subjects before exposure and 30 min and 19 h after were used to evaluate DNA damage. No significant changes in DNA strand-break frequencies were measured, as Olive tail moment (OTM), either between groups or before and after diisocyanate exposure. OTM was similar in subjects with an asthmatic reaction (MDI, n=5; TDI, n=1; HDI, n=1) and in subjects without such a reaction. However, a small and susceptible group (about 10% of the individuals studied) could be identified with higher frequencies of DNA strand breaks in lymphocytes after chamber exposure. The occurrence of DNA damage in this group may be based on indirect mechanisms such as oxidative stress or apoptosis.

Analysis of metabolites of N,N-dimethylformamide in urine samples

AIM

To assess the suitability of different methods for biological monitoring of internal dose to N,N-dimethylformamide (DMF) in occupational settings.

METHODS

The determination of urinary metabolites of DMF, N-hydroxymethyl- N-methylformamide (HMMF), N-methylformamide (NMF) and N-acetyl- S-(N-methylcarbamoyl) cysteine (AMCC) was carried out by four selected analytical procedures. Two methods solely measured total NMF (HMMF and NMF). The other two methods measured both total NMF and AMCC in one analytical run. All four methods were tested on 34 urine samples from workers exposed to DMF.

RESULTS

Comparison of the four methods for determination of total NMF in urine showed that results were similar for three methods, while the remaining one provided NMF levels significantly lower (by 22%) than the other methods. Thus, all but one of the tested methods for the determination of total NMF can be considered to be suitable for biological monitoring of internal dose to DMF. The two tested methods for the determination of AMCC afforded results that showed high correlation but differed significantly (by 10%).

CONCLUSION

The choice of the biomonitoring method depends mainly on the purpose for which the measurement is conducted. For evaluation of acute exposures or to assess safety measures in the working area, an updated version of the traditional method of Kimmerle and Eben (1975a, b) for the determination of total NMF in urine is sufficient. For risk assessment after exposure to DMF, the determination of AMCC should be carried out, since AMCC, but not total NMF, is supposed to be related to the toxicity of DMF. However, there is still a need to develop an easier, more sensitive and more selective method for the determination of AMCC in urine until AMCC can be considered for regulatory purposes in occupational settings.

Trends in the musk xylene concentrations in plasma samples from the general population from 1992/1993 to 1998 and the relevance of dermal uptake

OBJECTIVES

Musk xylene (MX), an environmentally important nitromusk compound, is used in different fragrances and soaps as substitute for natural musk. MX is known to occur in breast milk and plasma samples from the general population. Biological monitoring was carried out to study the change in MX concentrations in plasma from the general population over a period of about 6 years.

METHODS

Forty-one human plasma samples from the general population were collected and analyzed in 1998. The MX concentrations in plasma were compared with those in samples collected from the general population in 1992/1993. In order to study possible routes of exposure, we also analyzed perfumes (n = 8), various body-care products (n = 17), and detergents (n = 5) in the households from the persons who were exposed in 1998. The body-care products or the detergents were used every day or at least 3 -4 times per week.

RESULTS AND DISCUSSION

A remarkable decrease in MX levels was found on comparing the values from 1992,1993 and 1998. In 1998 12% (five out of 41) of the samples analyzed yielded positive results for MX (median: <0.1 microg/l, range: <0.1-0.29 microg/l), while in 1993 MX was found in 92% (66 out of 72) of the samples (median: 0.24 microg/l, range: <0.1- 1.12 microg/l). The observed decrease is explained by the discontinued use of MX in detergents in Germany since 1993. As a consequence, no MX could be found in the investigated detergents in the present study. However, MX could be analyzed in at least one perfume and/or perfumed bodycare product of the exposed individuals. The concentrations were in the range between 8.8 and 28.8 mg/kg in the investigated products. Because other confounding factors, e.g. diet and occupational exposure, could be excluded, the results point to the possibility that MX can be taken up through the skin. However, the small number of investigated persons limits this assumption.

N-methylcarbamoylated valine of hemoglobin in humans after exposure to N,N-dimethylformamide: evidence for the formation of methyl isocyanate?

N,N-Dimethylformamide (DMF) is reported to cause testicular germ-cell tumors in exposed workers. The reports, however, are not in line with results obtained in animal and in vitro experiments, where DMF was shown not to be mutagenic and also not to be carcinogenic. Considerable interest raised on the formation of a reactive intermediate, presumably methyl isocyanate (MIC), during metabolism of DMF in humans over the last years. We report the formation of N-methylcarbamoylated valine of hemoglobin (Hb) in blood samples from workers exposed to DMF in the polyacrylic fiber industry. N-Methylcarbamoylated Hb was formed by the reaction of MIC with Hb. For this purpose, Hb adducts were monitored by means of a modified Edman degradation involving the release of the N-terminal valine adduct in form of 3-methyl-5-isopropylhydantoin (MIH). For internal standardization of the method, 3-ethyl-5-isopropylhydantoin (EIH) was used. Separation and analysis of MIH and EIH were carried out by gas chromatography and mass spectrometry with electron impact ionization (GC/EI-MS). Hb adducts in form of MIH were quantified in blood samples from exposed persons in concentrations between 26.1 and 412.0 nmol of MIH/g of globin. The observed adducts were proven to be identical to those derived from the in situ reaction between Hb and MIC. Taken together with the fact that only N-methylcarbamoylated Hb can undergo ring closure to the corresponding hydantoin, the reaction is indirect evidence for the occurrence of MIC in vivo. The formation of MIC directly in the cell and its possible distribution through the human body may lead to critical effects after exposure to DMF. Adducts were determined not to be totally specific for exposure to DMF since an identical adduct was also found in blood samples from the general population. However, concentrations were lower by a factor of about 100. The sources for background adducts are currently unknown.

Biological monitoring of workers exposed to N,N-dimethylformamide in the synthetic fibre industry

OBJECTIVES

Monitoring of workplace air and biological monitoring of 23 workers exposed to N,N-dimethylformamide (DMF) in the polyacrylic fibre industry was carried out on 4 consecutive days. The main focus of the investigation was to study the relationship between external and internal exposure, the suitability of the metabolites of DMF for biological monitoring and their toxicokinetic behaviour in humans.

METHODS

Air samples were collected using personal air samplers. The limit of detection (LOD) for DMF using an analytical method recommended by the Deutsche Forschungsgemeinschaft (DFG) was 0.1 ppm. The urinary metabolites, N-hydroxymethyl-N-methylformamide (HMMF), N-methylformamide (NMF), and N-acetyl-S-(N-methylcarbamoyl)-cysteine (AMCC), were determined in one analytical run by gas chromatography with thermionic sensitive detection (GC/TSD). The total sum of HMMF and NMF was determined in the form of NMF. The LOD was 1.0 mg/l for NMF and 0.5 mg/l for AMCC.

RESULTS AND CONCLUSIONS

The external exposure to DMF vapour varied greatly depending on the workplace (median 1.74 ppm, range < 0.1-159.77 ppm). Urinary NMF concentrations were highest in post-shift samples. They also covered a wide range (< 1.0-108.7 mg/l). This variation was probably the result of different concentrations of DMF in the air at different workplaces, dermal absorption and differences in the protective measures implemented by each individual (gloves, gas masks etc.). The urinary NMF concentrations had decreased almost to zero by the beginning of the next shift. The median half-time for NMF was determined to be 5.1 h. The concentrations of AMCC in urine were determined to be in the range from < 0.5 to 204.9 mg/l. Unlike the concentrations of NMF, the AMCC concentrations did not decrease during the intervals between the shifts. For the exposure situation investigated in our study, a steady state was found between the external exposure to DMF and the levels of AMCC excreted in urine about 2 days after the beginning of exposure. AMCC is therefore excreted more slowly than NMF. The half-time for AMCC is more than 16 h. Linear regression analysis for external exposure and urinary excretion of metabolites was carried out for a sub-group of 12 workers. External exposure to 10 ppm DMF in air (the current German MAK value) corresponds to an average NMF concentration of about 27.9 mg/l in post-shift urine from the same day and an average AMCC concentration of 69.2 mg/l in pre-shift urine from the following day. NMF in urine samples therefore represents an index of daily exposure to DMF, while AMCC represents an index of the average exposure over the preceding working days. AMCC is considered to be better suited for biomonitoring purposes because (1) it has a longer half-time than NMF and (2) its formation in humans is more closely related to DMF toxicity.

Simultaneous determination of two human urinary metabolites of N,N-dimethylformamide using gas chromatography-thermionic sensitive detection with mass spectrometric confirmation

Two human urinary metabolites of the industrial solvent N,N-dimethylformamide (DMF), N-hydroxymethyl-N-methylformamide (HMMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), were assayed using a new analytical method (gas chromatography and thermionic sensitive detection). Clean-up of urine samples includes a liquid-liquid extraction step followed by a solid-phase extraction step to separate HMMF and AMCC from other urine components. During clean-up, AMCC is converted into ethyl-N-methylcarbamate (EMC), and during gas chromatography, HMMF is degraded in the injector to N-methylformamide (NMF). All the validation data necessary for a quantitative procedure are given. The method was applied to urine samples from workers exposed to DMF and from the general population. The results were confirmed by mass spectrometric determination. For this purpose a further liquid-liquid extraction step was introduced in the clean-up procedure. Background levels of AMCC in the general population were identified.

Determination of N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) in the general population using gas chromatography-mass spectrometry

Carbamoylation of glutathione, peptides and DNA is thought to be one of the most important reactions occurring in an organism after exposure to nitrosoureas, methylformamides or isocyanates. The carcinogenic effects of carbamoylation are not yet fully clarified. Although carbamoylation is known to occur after occupational exposure, it has never been reported in the general population. To clarify the situation, we investigated the levels of N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) in urine samples from persons without occupational exposure using a sensitive and specific method (gas chromatography-mass spectrometry, GC-MS). AMCC is the degradation product of N-methylcarbamoylated glutathione. The clean-up procedure of urine samples includes two liquid-liquid extraction steps and solid phase extraction using a cation-exchange resin to separate AMCC from other urinary components. N,N-Dimethylpropionic acid amide (DMPA) is used as internal standard. During the preparation of the samples, AMCC is converted to ethyl-N-methylcarbamate (EMC) in the presence of anhydrous potassium carbonate (K2CO3) and ethanol. The reliability and accuracy of this method have been proven in detail. The relative standard deviation for the within-series imprecision for three different concentrations was determined to be between 10.9% and 14.3%, while the relative standard deviation for the between-day imprecision was between 11.3% and 14.8%. The mean recovery for AMCC was determined to be between 79.2% and 85.6%. The limit of detection for the simultaneous measurement of two fragment masses was 30 micrograms L-1. Using this GC-MS method, we analysed urine samples from 42 individuals of the general population in order to determine their urinary excretion of AMCC. It was identified in 40 samples. The mean concentration was 40 micrograms L-1. AMCC can be formed in two ways. The first possibility is the dietary intake of isothiocyanates, especially methyl isothiocyanate, which is a component of wine and cruciferous vegetables (such as cabbage, turnips and cress). During the metabolism of isothiocyanates in humans, the sulfur is partly exchanged for oxygen resulting in the formation of the corresponding isocyanate derivatives. The other possibility is the physiological formation of AMCC. In humans, this may occur via a two step process: carbamoylation and methylation, or vice versa. However, as AMCC was identified in about 95% of urine samples, and the standard deviation for the level of AMCC excreted was low, physiological formation seems to be the more probable pathway.

Musk xylene: analysis, occurrence, kinetics, and toxicology

1,3-Dimethyl-2,4,6-trinitro-5-tert.-butylbenzene (musk xylene, MX), a synthetic musk, is often used in fragrances and soaps to substitute the natural musk. MX belongs to the common group of nitromusk compounds. The main environmental intake of MX occurs after sewage introduction. The consumption of fish and drinking water as well as the use of body care and perfumed household products could lead to an ingestion of this substance in humans. Although the acute oral and dermal toxicity of MX is low, some hint for the carcinogenic potential of MX was found in one animal experiment. These findings and the high potential of MX as environmental contaminant, it is stable against biological and chemical degradation and it is highly lipophil, raised considerable attention in the field of environmental medicine. Biological monitoring and the toxicology of MX, which previously has been described to occur in human milk, human fat tissue, as well as human blood samples, are of central interest. The aim of this article is to summarize the data on the analysis, occurrence, kinetics, and toxicology of MX. As there is a lack of knowledge on human toxicity and human carcinogenicity of MX, a final evaluation of the toxicological data with regard to public health is still impossible. Nevertheless, in view of the published data about MX, there is no evidence for any substantial human risk at the moment.

N-methylcarbamoyl adducts at the N-terminal valine of globin in workers exposed to N,N-dimethylformamide

N,N-dimethylformamide (DMF) is a commonly used industrial solvent. The formation of some metabolites of DMF in humans occurs via N-methyl-carbamoylated species (e.g. N-methylcarbamoylated glutathione). The aim of our study was to investigate whether DMF leads to N-methylcarbamoylated adducts at the N-terminal valine of haemoglobin (Hb). Therefore, Hb adduct levels of ten DMF exposed workers and ten controls were analysed by a specific and sensitive detection method using capillary gas chromatography and a mass selective detector (GC/MS). Using this method we were able to show for the first time that Hb adducts are formed during the metabolism of DMF in humans. The general population, however, shows still unidentified background levels of this adduct which are on average lower by a factor of 50. The pathway for the formation of the investigated DMF-Hb adduct in workers exposed to DMF is still unknown. As identical adducts were also found after exposure to methylisocyanate (MIC), our work indicates the formation of MIC during the metabolism of DMF. The formation of Hb adducts with DMF and its relevance for occupational health is a subject of further research.

Gas chromatographic method using electron-capture detection for the determination of musk xylene in human blood samples. Biological monitoring of the general population

Musk xylene (2,4,6-trinitro-1,3-dimethyl-5-tert.-butylbenzene, MX), a synthetic musk often used in different fragrances and soaps to substitute the natural musk, is a potential contaminant of humans. In this publication, a specific and sensitive detection method for the determination of musk xylene in human blood samples is described. The clean-up of the blood samples includes an extraction step followed by a solid-phase adsorption to separate MX from other plasma components. Separation and detection was carried out by capillary gas chromatography and an electron capture detector (GC-ECD). The results were verified using qualitative capillary gas chromatography and a mass selective detector with electron impact ionisation (GC-EI-MS). epsilon-Hexachlorocyclohexane (epsilon-HCH) is used as internal standard. The reliability of the GC-ECD method has been proved. The relative standard deviations of the within-series imprecision were 12.7% for samples with a concentration of 0.5 microg/l and 2.1% for samples with a concentration of 5.0 microg/l, whereas the relative standard deviations for the between-day imprecision were 14.9% (0.5 microg/l samples) and 3.4% (5.0 microg/l samples). The losses during sample treatment were between 10.1% and 17.8%. No interfering peaks were observed. The absolute detection limit was 0.1 microg/l plasma. A total of 72 human blood samples were analysed to determine the MX concentrations within the general population. In 66 of the 72 human blood samples, the MX concentrations ranged from 0.10 to 1.12 microg/l plasma for the described method. In six samples no MX was detected. The median concentration was 0.24+/-0.23 microg MX/l plasma. The 95 percentile was 0.79 microg/l. No correlation could be found between MX concentrations and smoking habit, broca index, age, sex as well as fish consumption habits. Nevertheless, the results demonstrate the exposure of the general population to MX.