Serial measurements of exhaled nitric oxide at work and at home: a new tool for the diagnosis of occupational asthma.

Whereas serial measurements of lung function at work and at home are a well-known diagnostic tool for the diagnosis of occupational asthma (OA), little is known about the serial measurements of non-invasive parameters such as exhaled nitric oxide (eNO). A 51-year-old baker with variable shortness of breath without relation to work was examined for suspected OA. Skin prick test showed weak sensitizations to wheat and rye flour (without sensitizations to environmental allergens) that were corroborated by in vitro testing (CAP class 3). Baseline FEV1 of 58% predicted and a decrease of forced expiratory volume in 1 s (FEV1) after placebo (sugar powder) of 17% did not allow inhalational challenge testing. The patient performed daily measurements of FEV1 and eNO for about a month during a holiday at home and at work. Whereas symptoms and FEV1 did not show differences between holidays and work periods, eNO showed a clear increase from below 10 ppb to a maximum of 75 ppb. A diagnosis of baker's asthma was made, and the patient quit his job immediately after medical advice. A year afterwards, the patient was still taking asthma medication, but his symptoms had improved, FEV1 had increased to 73% predicted, and eNO was 25 ppb. We conclude that serial measurements of eNO at home and at work may be a useful tool for the diagnosis of OA.

Investigating the spill-over hypothesis: analysis of the association between local inflammatory markers in sputum and systemic inflammatory mediators in plasma.

Exposure to air pollutants represents a risk factor not only for respiratory diseases and lung cancer, but also for cardiometabolic diseases. It has been hypothesised that local inflammation in the lung and systemic subclinical inflammation are linked by impaired lung function and the spill-over of proinflammatory factors from the lung into the circulation which could act as intermediaries between environmental exposures and disease risk. We wanted to investigate whether local and systemic inflammatory markers are associated, which would support the spill-over hypothesis. Sputum and plasma samples were obtained from 257 women of the German SALIA cohort. We performed immunoassays to measure multiple biomarkers of airway inflammation in sputum as well as cytokines, chemokines and soluble adhesion molecules in plasma. Correlations were calculated and adjusted for potentially confounding variables. Even though several significant associations were detected between inflammatory mediators in sputum and plasma, correlation coefficients were rather low ranging from r≥-0.20 to r≤0.20. Comparatively stronger associations were observed between nitrite, eosinophil cationic protein, leukotrienes C/D/E4 and interleukin-8 in sputum. Notably, correlations were positive with all proinflammatory biomarkers and interleukin-1 receptor antagonist in plasma, whereas negative correlations were observed with the anti-inflammatory adipokine adiponectin. In conclusion, local inflammation in the lung and systemic subclinical inflammation appear mainly independently regulated in elderly women from the general population. Although we found multiple significant correlations between inflammatory biomarkers in sputum and plasma, our results do not provide clear support for the spill-over hypothesis.

Air pollution and subclinical airway inflammation in the SALIA cohort study.

BACKGROUND: The association between long-term exposure to air pollution and local inflammation in the lung has rarely been investigated in the general population of elderly subjects before. We investigated this association in a population-based cohort of elderly women from Germany. METHODS: In a follow-up examination of the SALIA cohort study in 2008/2009, 402 women aged 68 to 79 years from the Ruhr Area and Borken (Germany) were clinically examined. Inflammatory markers were determined in exhaled breath condensate (EBC) and in induced sputum (IS). We used traffic indicators and measured air pollutants at single monitoring stations in the study area to assess individual traffic exposure and long-term air pollution background exposure. Additionally long-term residential exposure to air pollution was estimated using land-use regression (LUR) models. We applied multiple logistic and linear regression analyses adjusted for age, indoor mould, smoking, passive smoking and socio-economic status and additionally conducted sensitivity analyses. RESULTS: Inflammatory markers showed a high variability between the individuals and were higher with higher exposure to air pollution. NO derivatives, leukotriene (LT) B4 and tumour necrosis factor-α (TNF-α) showed the strongest associations. An increase of 9.42 µg/m3 (interquartile range) in LUR modelled NO2 was associated with measureable LTB4 level (level with values above the detection limit) in EBC (odds ratio: 1.38, 95% CI: 1.02 -1.86) as well as with LTB4 in IS (%-change: 19%, 95% CI: 7% - 32%). The results remained consistent after exclusion of subpopulations with risk factors for inflammation (smoking, respiratory diseases, mould infestation) and after extension of models with additional adjustment for season of examination, mass of IS and urban/rural living as sensitivity analyses. CONCLUSIONS: In this analysis of the SALIA study we found that long-term exposure to air pollutants from traffic and industrial sources was associated with an increase of several inflammatory markers in EBC and in IS. We conclude that long-term exposure to air pollution might lead to changes in the inflammatory marker profile in the lower airways in an elderly female population.

Influence of welding fume on systemic iron status.

Iron is the major metal found in welding fumes, and although it is an essential trace element, its overload causes toxicity due to Fenton reactions. To avoid oxidative damage, excess iron is bound to ferritin, and as a result, serum ferritin (SF) is a recognized biomarker for iron stores, with high concentrations linked to inflammation and potentially also cancer. However, little is known about iron overload in welders. Within this study, we assessed the iron status and quantitative associations between airborne iron, body iron stores, and iron homeostasis in 192 welders not wearing dust masks. Welders were equipped with personal samplers in order to determine the levels of respirable iron in the breathing zone during a working shift. SF, prohepcidin and other markers of iron status were determined in blood samples collected after shift. The impact of iron exposure and other factors on SF and prohepcidin were estimated using multiple regression models. Our results indicate that respirable iron is a significant predictor of SF and prohepcidin. Concentrations of SF varied according to the welding technique and respiratory protection used, with a median of 103 µg l(-1) in tungsten inert gas welders, 125 µg l(-1) in those wearing air-purifying respirators, and 161 µg l(-1) in other welders. Compared to welders with low iron stores (SF < 25 µg l(-1)), those with excess body iron (SF ≥ 400 µg l(-1)) worked under a higher median concentration of airborne iron (60 µg m(-3) versus 148 µg m(-3)). Even though air concentrations of respirable iron and manganese were highly correlated, and low iron stores have been reported to increase manganese uptake in the gastrointestinal tract, no correlation was seen between SF and manganese in blood. In conclusion, monitoring SF may be a reasonable method for health surveillance of welders. Respiratory protection with air-purifying respirators can decrease iron exposure and avoid chronically higher SF in welders working with high-emission technologies.

Occupational non-immediate type allergic asthma due to ammonium persulfate.

While numerous cases of immediate-type occupational asthma due to persulfates with positive skin prick test reactions to ammonium persulfate are well documented, few non-immediate type reactions have been described in the literature. We report the case of an atopic worker who developed work-related asthmatic symptoms shortly after he began his job in persulfate production. The diagnosis of asthma was corroborated by methacholine testing. The patient showed a positive patch test reaction to ammonium persulfate, while skin prick test was negative. He presented an isolated late symptomatic airway obstruction after a cumulative dose of 0.6 mg ammonium persulfate administered by a dosimeter method. An immunologic mechanism was demonstrated by a significant increase in exhaled nitric oxide and the number of eosinophils in induced sputum. These findings suggest that isolated late bronchial reactions to persulfates are mediated by eosinophilic inflammatory responses.

Occupational IgE-mediated softwood allergy: characterization of the causative allergen.

Allergic reactions to wood dust allergens are rare, and only few in vitro diagnostic tools and information about relevant allergens are available. To differentiate between protein-based allergy and probably clinically silent glycogenic sensitization, it is helpful to characterize the relevant protein allergens and specify IgE binding. The current case report deals with the occupational softwood allergy of a carpenter exposed to different wood dusts. Skin tests and IgE tests against wood were performed with specifically tailored ImmunoCAPs and cross-reactive carbohydrate determinants. Potential allergens were identified by IgE blots and tandem mass spectrometry. The clinical relevance was verified by challenge tests. Specific IgE to softwood (spruce, pine and larch wood), beech wood, natural rubber latex (NRL) and horseradish peroxidase (HRP) were detected. Allergens in spruce wood, the dominant allergen source, were identified as peroxidases. Softwood were the strongest inhibitors. HRP reduced IgE binding to softwood to <50%, indicating predominantly proteinogenic epitopes, whereas IgE binding to NRL and beech wood was reduced to >50% by HRP, indicating predominantly glycogenic IgE epitopes. Skin and challenge tests underlined that softwoods were the source of sensitization. For the polysensitized patient, a clinically relevant softwood allergy was diagnosed, not only by challenge tests but also with specifically tailored in vitro tools.

Component-resolved immunologic modifications, efficacy, and tolerance of latex sublingual immunotherapy in children.

BACKGROUND: As the frequency of natural rubber latex (NRL) allergy has increased, attempts have been made to diminish exposure in high-risk patients. Despite some good results, complete NRL avoidance was not possible, so latex immunotherapy was developed. OBJECTIVE: To examine variations in immunologic parameters, clinical efficacy, and safety of NRL sublingual immunotherapy (SLIT). METHODS: This prospective, observational, open, case-control study included 23 patients (18 patients receiving NRL SLIT and 5 controls). Skin prick, conjunctival provocation, and in-use tests with NRL, specific IgE and specific IgG4 to NRL, specific IgE to recombinant NRL allergens, and basophil activation test (BAT) with whole latex, natural, and recombinant allergens were performed before immunotherapy (T0) and at 6 (T1) and 12 months (T2) of treatment. RESULTS: Patients were sensitized to Hev b 5, Hev b 6.01, and Hev b 6.02 proteins, optimal for SLIT. Changes in specific IgE were not significant. Increases in specific IgG4 between T1 and T2 were larger in the active group. BAT determinations showed significant decreases in recombinant Hev b 6.01 and natural Hev b 6.02 in the active group at T1 but not at T2. Both groups had new sensitizations at T1 but not at T2. The active group had significant increases in the response threshold in the in vivo tests at T1 and T2. Adverse effects were limited to local reactions. CONCLUSION: NRL SLIT is effective and safe in children with latex allergy. Our results suggest that specific IgE determinations and BAT measurements to natural and recombinant latex allergens may allow obtaining an allergen-based diagnosis to help determine specific immunotherapy.

Assessment of airborne exposure to endotoxin and pyrogenic active dust using electrostatic dustfall collectors (EDCs).

Passive airborne dust sampling using electrostatic dustfall collectors (EDCs) is one possibility especially for long sampling periods. In this study, EDCs were deposited in living rooms of private households and in social rooms of composting plants. The aim of the study was to determine whether endotoxin and pyrogenic activity are measurable using EDCs. In all extracts, endotoxin (via Limulus amebocyte lysate [LAL] assay) and pyrogenic activity (interleukin [IL]-1ß release via whole blood assay) were detectable. In addition, the monocyte chemotactic protein (MCP-1; CCL-2) as a secondary proinflammatory marker was measured with whole blood assay. Endotoxin activity and proinflammatory/pyrogenic activity of EDC extracts from social rooms in composting plants were higher compared to extracts obtained from EDCs in private household rooms. A significant correlation between LAL assay and whole blood assay was detectable. In conclusion, EDC sampling is an applicable method to evaluate settled dust from airborne bioaerosols displaying a longer period of exposure. The extraction of EDC without Tween enables one to measure endotoxin as well as proinflammatory/pyrogenic activity using the same sample for parallel detection and more reliable characterization of the airborne bioaerosol contamination.

Impact of interleukin-13 and -18 promoter polymorphisms in health care workers with natural rubber latex allergy.

It is a matter of debate whether single nucleotide polymorphisms (SNP) in the promoter region of interleukin (IL)-13, an IgE regulator, and IL-18, an inducer of immune responses, modulating the respective protein expression, are accompanied by an increased risk of atopy, allergic asthma, and total IgE levels. The suspected associations were noted in health care workers (HCW) with and without latex allergy. IL-13 (-1055C>T) and three IL-18 (-656T>G, -607C>A, -137G>C) SNP were studied in 523 HCW with natural rubber latex (NRL) exposure and diagnosis in the late 1990s. Three hundred and thirty-four HCW displayed NRL sensitization and allergic symptoms, 93 with latex-allergic asthma, and 189 HCW with neither symptoms nor NRL sensitization. SNP analyses were performed by real-time polymerase chain reaction (PCR) using newly developed LightCycler assays. Analysis of IL-13 -1055C>T by analysis of variance (ANOVA) revealed significantly elevated total IgE levels in HCW carrying the CT or TT variant compared with the CC variant. None of the studied SNP showed an association with NRL-specific IgE. The IL-18 variants -656GG and -607CC displayed 99.5% linkage disequilibrium. Frequencies of alleles -656GG and -607CC were elevated in HCW with NRL asthma (48.4%) compared with HCW without symptoms (37.6%). In contrast, IL-18 -137G>C variants displayed an overall homogenous distribution. The association between the IL-13 -1055T allele and elevated total IgE levels confirms the role of a genetic background for total IgE regulation. The studied IL-18 SNP demonstrated no significant association with the clinical outcome, total IgE, or specific IgE in HCW with natural rubber latex allergy.

Modulation of oxidative DNA damage by repair enzymes XRCC1 and hOGG1.

The influence of DNA repair gene polymorphisms (XRCC1: Arg194Trp, Arg280His, Arg399Gln; APE1: Asp148Glu; hOGG1: Ser326Cys) on oxidative DNA damage is controversial and was investigated in 214 German workers with occupational exposure to vapors and aerosols of bitumen,compared to 87 German construction workers without exposure, who were part of the Human Bitumen Study. Genotypes were determined by real-time polymerase chain reaction (PCR), and actual smoking habits by a questionnaire and cotinine analysis. Oxidative DNA damage in white blood cells (WBC) collected pre- and postshift was measured as 8-oxodGuo adducts/10(6) dGuo by a hjigh-performance liquid chromatography electron capture detection (HPLC-ECD) method, followed by calculation of the difference between post- and preshift values (Δ8-oxodGuo/10(6) dGuo). The 214 bitumen exposed workers showed higher median Δ8-oxodGuo values than the 87 references. In the whole study group (n=301) there was a trend for increasing adduct values for XRCC1 Arg(GG)399Gln(AA) during a shift, especially in nonsmokers (n=108. Referents (n=87) displayed a similar trend for hOGG1 Ser(CC)326Cys(GG). In contrast, XRCC1 Arg(GG)280His(AA) showed a decrease of median Δ8-oxodGuo/10(6) dGuo values in workers with exposure to vapors and aerosols of bitumen (n=214), especially in smokers (n=145). XRCC1 Arg194Trp and APE1 Asp148Glu displayed no marked association with Δ8-oxodGuo levels. Data indicate that the combination of different variants in DNA damage repair enzymes may modulate the production of 8-oxoguanine adducts in WBC produced by xenobiotics during a shift.

Development and application of mold antigen-specific enzyme-linked immunosorbent assays (ELISA) to quantify airborne antigen exposure.

The aim of our study was to develop specific enzyme-linked immunosorbent assays (ELISAs) and apply these to assess mold antigen exposure in composting plants. Sandwich ELISAs based on polyclonal antibodies to Aspergillus fumigatus (Af), Penicillium chrysogenum (Pc), and Cladosporium herbarum (Ch) antigens were developed and validated. Reactivity to 18 different mold species was tested. To optimize extraction procedure, inhalable dust samples taken by a parallel sampler were extracted with or without homogenization. In 31 composting plants stationary pumps were installed at 4 sites to collect 124 inhalable dust samples. The newly developed ELISAs were used in addition to an anti ß-1,3-glucan ELISA to quantify mold antigens. The Cladosporium ELISA showed less than 0.04% reactivity to extracts from other fungal genera, while the Af ELISA demonstrated a reactivity of up to 3.6% and the Pc ELISA reacted up to 11% to other mold species. Extraction of parallel sampled filters gave higher antigen amounts with homogenization. The increase was highest for Pc-antigens, followed by Af-antigens, and lowest for Ch-antigens. Mean lower detection limits of homogenized inhalable dust samples were 5 ng/m(3) (Af), 0.6 ng/m(3) (Pc), 0.2 ng/m(3) (Ch), and 0.6 ng/m(3) (ß-1,3-glucan). The ELISAs were able to detect antigens in 43% (Af), 37% (Pc), 94% (Ch), or 100% (ß-1,3-glucan) of the 124 airborne dust samples. Inhalable dust, ß-1,3-glucan, and Af-, Pc-, and Ch-antigen concentrations were significantly correlated. The newly developed mold antigen ELISAs are thus able to measure airborne exposure levels in composting plants and differentiate between distinct fungi genera.

Symptoms, spirometry, and serum antibody concentrations among compost workers exposed to organic dust.

Work-related symptoms and diseases of 190 currently exposed compost workers, 59 former compost workers, and 38 nonexposed control subjects were investigated in a cross-sectional study. Using a standardized questionnaire, participants were asked for work-related symptoms, exposures to bioaerosols, atopic diseases, and smoking habits. The subjects underwent a physical examination and a lung function test. In addition, total immunoglobulin (Ig) E, IgE specific to environmental allergens and moulds, and IgG specific to molds and actinomycetes were quantified. Compared to controls, compost workers suffered more often from cough and irritation of the eyes in terms of mucosal membrane irritation (MMI). Former compost workers reported similar work-related complaints, but most MMI symptoms had improved after termination of bioaerosol exposure. In contrast, cough and dyspnea persisted, indicating a chronic process. Lung function parameters of compost workers were within the reference ranges. Nevertheless, forced vital capacity (FVC) was significantly lower than for controls. Specific IgE to environmental allergens and molds was positive in 25.3% and 7.4%, respectively, of currently exposed compost workers. There were no marked differences in IgE and IgG concentrations among the three groups. Compost workers suffered with a higher frequency from cough and MMI symptoms. The findings that MMI symptoms improved in former compost workers after leaving the job confirmed the association with bioaerosol exposure. Further, the reduced FVC may be produced by this exposure. There was no higher frequency of mold sensitization in the group of compost workers compared to controls, which may be an indication of a healthy worker survivor effect.

Pre- and postshift levels of inflammatory biomarkers and DNA damage in non-bitumen-exposed construction workers-subpopulation of the German Human Bitumen Study.

Circadian variations in immune defense and tissue repair may interfere with shift effects of occupational exposure when investigating biomarkers in cross-shift studies. This investigation compared biomarkers of inflammation and DNA damage in 59 nonsmoking and 59 smoking male construction workers pre- (6-10 a.m.) versus postshift (4-7 p.m.). Cellular compositions were analyzed in blood, induced sputum (IS), and nasal lavage fluid (NALF) and soluble inflammatory biomarkers were analyzed in IS and NALF. DNA damage was measured as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) adducts and DNA strand breaks (alkaline Comet assay) in white blood cells (WBC). Apoptosis was quantified as percent apoptotic cells by annexin V and 7-amino-actinomycin staining in blood lymphocytes using flow cytometry. In nonsmokers higher preshift than postshift levels of interleukin-8 (IL-8) in IS and more DNA strand breaks were detected. However, more DNA adducts were found postshift. Among smokers, the cellular composition of IS and NALF differed between pre- and postshift samples, in particular more neutrophils pre- than postshift. In contrast, more cells in early apoptosis were observed post shift in both smokers and nonsmokers. These results indicate a potential influence of circadian rhythms on several biomarkers used in epidemiological studies. Data suggest interference with shift-work effects of occupational exposure in cross-shift studies and also the need to consider smoking as a modifying variable.

Impact of different welding techniques on biological effect markers in exhaled breath condensate of 58 mild steel welders.

Total mass and composition of welding fumes are predominantly dependent on the welding technique and welding wire applied. The objective of this study was to investigate the impact of welding techniques on biological effect markers in exhaled breath condensate (EBC) of 58 healthy welders. The welding techniques applied were gas metal arc welding with solid wire (GMAW) (n=29) or flux cored wire (FCAW) (n=29). Welding fume particles were collected with personal samplers in the breathing zone inside the helmets. Levels of leukotriene B(4) (LTB(4)), prostaglandin E(2) (PGE(2)), and 8-isoprostane (8-iso-PGF(2α)) were measured with immunoassay kits and the EBC pH was measured after deaeration. Significantly higher 8-iso-PGF(2α) concentrations and a less acid pH were detected in EBC of welders using the FCAW than in EBC of welders using the GMAW technique. The lowest LTB(4) concentrations were measured in nonsmoking welders applying a solid wire. No significant influences were found in EBC concentrations of PGE(2) based upon smoking status or type of welding technique. This study suggests an enhanced irritative effect in the lower airways of mild steel welders due to the application of FCAW compared to GMAW, most likely associated with a higher emission of welding fumes.

Development of a sandwich ELISA to measure exposure to occupational cow hair allergens.

BACKGROUND: Cow hair and dander are important inducers of occupational allergies in cattle-exposed farmers. To estimate allergen exposure in farming environments, a sensitive enzyme immunoassay was developed to measure cow hair allergens. METHODS: A sandwich ELISA was developed using polyclonal rabbitantibodies against a mixture of hair extracts from different cattle breeds. To assess the specificity of the assay, extracts from other mammalian epithelia, mites, molds and grains were tested. To validate the new assay, cow hair allergens were measured in passive airborne dust samples from the stables and homes of farmers. Dust was collected with electrostatic dust fall collectors (EDCs). RESULTS: The sandwich ELISA was found to be very sensitive (detection limit: 0.1 ng/ml) and highly reproducible, demonstrating intra- and interassay coefficients of variation of 4 and 10%, respectively. The assay showed no reactivity with mites, molds and grains, but some cross-reactivity with other mammalian epithelia, with the strongest reaction with goat. Using EDCs for dust sampling, high concentrations of bovine allergens were measured in cow stables (4,760-559,400 µg/m²). In addition, bovine allergens were detected in all areas of cattle farmer dwellings. A large variation was found between individual samples (0.3-900 µg/m²) and significantly higher values were discovered in changing rooms. CONCLUSION: The ELISA developed for the detection of cow hair proteins is a useful tool for allergen quantification in occupational and home environments. Based on its low detection limit, this test is sensitive enough to detect allergens in passive airborne dust.

The Human Bitumen Study: executive summary.

Bitumen has attracted attention from the scientific community and regulating agencies. The debate on health effects of exposure to vapours and aerosols of bitumen during the hot application of bitumen ranges from respiratory and neurological effects to carcinogenicity. In 2000, the German Hazardous Substances Committee (AGS), in collaboration with the German Bitumen Forum, initiated the examination of a group of mastic asphalt workers and a same number of construction workers without exposure bitumen using a cross-shift design. The study was then extended to the Human Bitumen Study, and the recruitment was finished in 2008 after examination of 500 workers on 80 construction sites. Three hundred and twenty workers exposed to vapours and aerosols of bitumen at high processing temperatures and 118 workers at outdoor construction sites were included. In the Human Bitumen Study external exposure to vapours and aerosols of bitumen, internal exposure to PAH by analysing urinary 1-hydroxypyrene, the sum of hydroxyphenanthrenes and the sum of 1- and 2-hydroxynaphthalenes, irritative effects in the upper and lower airways and genotoxic effects in blood cells were investigated. The study turned out to be one of the largest investigations of workers exposed to vapours and aerosols of bitumen under current exposure conditions. The present paper summarizes its background and main topics.

Modulation of urinary polycyclic aromatic hydrocarbon metabolites by enzyme polymorphisms in workers of the German Human Bitumen Study.

Data concerning the influence of sequence variants of metabolizing enzymes on the effect modulation of current exposure to vapors and aerosols of bitumen in humans are limited. To assess the influence of 18 single-nucleotide polymorphisms (SNP) in genes coding for enzymes involved in polycyclic aromatic hydrocarbon (PAH) and amine metabolism regarding their impact on urinary markers 1-hydroxpyrene (1-OHP) and the sum of 1-, 2+9-, 3-, 4-hydroxyphenanthrene (OHPHE). Based on personal ambient monitoring data for bitumen emissions, 218 German workers exposed to vapors and aerosols of bitumen during a shift and 96 German roadside construction workers without exposure to bitumen but with similar working tasks were studied. SNP determination based on DNA aliquots isolated from blood samples by real-time PCR or direct sequencing. The impact of sequence variants on the urinary levels of 1-OHP and sum of OHPHE was estimated with mixed linear models, adjusted for age, creatinine, exposure, smoking, SNP, and time of measurement. In the mixed linear model, an increasing metabolite level of OHPHE was only slightly modulated by the CC variant of the cytochrome P450 SNP CYP1A1 3801T>C (rs4646903; P = 0.051). In contrast, GSTM1 carriers showed a significant (P= 0.046) and double-mutated variants of three NAT2-specific SNP (NAT2*341CC, P = 0.06; NAT2*481TT, P = 0.06; NAT2*803GG, P = 0.042) displayed a decreasing influence on OHPHE levels. None of the SNP studied showed a significant effect on 1-OHP. The modulating SNP effects on OHPHE in the adjusted model were less pronounced when compared with the effects observed in a recent study with 170 workers occupationally exposed to PAH in German industries. This may be due to the much lower PAH exposure in the Human Bitumen Study.

Irritative effects of vapours and aerosols of bitumen on the airways assessed by non-invasive methods.

Irritative effects caused by vapours and aerosols of bitumen were assessed by non-invasive methods including spirometry, nasal lavage fluid (NALF) and induced sputum (IS) in a cross-shift study comparing 320 bitumen-exposed workers with 118 road construction workers as the reference group. Lung function parameters, forced vital capacity (FVC) and forced expiratory volume in one second (FEV(1)) were within normal ranges in both the reference and the bitumen-exposed groups pre- and post-shift with marginally lower values in smokers of both groups. During the shift, a slight decline in FEV(1) and FVC was observed in the bitumen-exposed group independent of their smoking habits, whereas in the non-smoking reference group, the decline in FEV(1) was not observed. No significant differences between bitumen-exposed workers and the reference group and no significant shift effect were observed on the upper airways using NALF analysis. The IS concentrations of interleukin (IL)-8, total protein and matrix metalloproteinase-9 were significantly higher in bitumen-exposed workers than in the reference group. However, the concentration of these three biomarkers in the IS samples, which are indicators of inflammatory effects on the lower airways of bitumen-exposed workers, was already higher in exposed workers before shift and did not show an increase during the shift. Therefore, the key finding of this aspect of the Human Bitumen Study is the detection of potentially (sub-) chronic irritative inflammatory effects in the lower airways of bitumen-exposed workers.

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.

Urinary metabolites of polycyclic aromatic hydrocarbons in workers exposed to vapours and aerosols of bitumen.

Urinary hydroxylated metabolites of polycyclic aromatic hydrocarbons (PAH) were investigated as potential biomarkers of bitumen exposure in a cross-shift study in 317 exposed and 117 non-exposed workers. Personal measurements of the airborne concentration of vapours and aerosols of bitumen during a working shift were weakly associated with post-shift concentrations of 1-hydroxypyrene (1-OHP) and 1-, 2+9-, 3- and 4-hydroxyphenanthrenes (further referred to their sum as OHPHE), but not 1- and 2-hydroxynaphthalene (OHNA). Smoking showed a strong influence on the metabolite concentrations, in particular on OHNA. Pre-shift concentrations of 1-OHP and OHPHE did not differ between the study groups (P = 0.16 and P = 0.89, respectively). During shift, PAH metabolite concentrations increased in exposed workers and non-exposed smokers. Statistical modelling of post-shift concentrations revealed a small increase in 1-OHP by a factor of 1.02 per 1 mg/m(3) bitumen (P = 0.02) and 1.04 for OHPHE (P < 0.001). A group difference was observed that was diminished in non-smokers. Exposed non-smokers had a median post-shift 1-OHP concentration of 0.42 µg/l, and non-smoking referents 0.13 µg/l. Although post-shift concentrations of 1-OHP and OHPHE were slightly higher than those in the general population, they were much lower than in coke-oven workers. The small content of PAHs in vapours and aerosols of bitumen, the increasing use of additives to asphalt mixtures, the strong impact of smoking and their weak association with airborne bitumen limit the use of PAH metabolites as specific biomarkers of bitumen exposure.