Boleslaw Marczynski

Respiratory and other hazards of isocyanates.

Isocyanates are increasingly being used for manufacturing polyurethane foam, elastomers, adhesives, paints, coatings, insecticides, and many other products. At present, they are regarded as one of the main causes of occupational asthma. The large number of workers who are exposed to these chemicals have a concentration-dependent risk of developing chronic airway disorders, especially bronchial asthma. Different pathophysiologic mechanisms are involved. Immunoglobulin E (IgE)-mediated sensitization and irritative effects have been clearly demonstrated in both exposed subjects and animals. Presumably, neural inflammation due to neuropeptide release of capsaicin-sensitive afferent nerves is crucial. We collected data on 1780 isocyanate workers who had been examined by our groups. Of them 1095 (including subjects from outpatient departments) had work-related symptoms, predominantly of the respiratory tract. Specific IgE antibodies were found in 14% of the 1095 subjects. The methacholine challenge test was shown to be an inadequate predictor of the results of inhalative isocyanate provocation tests in workers and in asthmatic controls. Isocyanate (toluene diisocyanate TDI) air concentrations of 10 ppb (0.07 mg/m3) and 20 ppb (0.14 mg/m3), respectively, did not cause significant bronchial obstruction in the majority of previously unexposed asthmatics with bronchial hyperreactivity. IgG-mediated allergic alveolitis, a rare disease among isocyanate workers, was found in approximately 1 % of the symptomatic subjects. Experimental studies exhibit dose-dependent toxic effects and give evidence for tachykinin-mediated bronchial hyperreactivity after exposure to isocyanates. The clinical role of genotoxic effects of isocyanates and their by-products demonstrated here in vitro and in vivo has yet to be clarified.

Carcinogenic Risk of Toluene Diisocyanate and 4,4′-Methylenediphenyl Diisocyanate: Epidemiological and Experimental Evidence

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

Detection of 8-hydroxydeoxyguanosine, a marker of oxidative DNA damage, in white blood cells of workers occupationally exposed to styrene

Abstract Styrene-7,8-oxide (SO), the major in vivo metabolite of styrene, is a genotoxic compound and a potential carcinogenic hazard to occupationally exposed workers. The aim of the present work was to investigate the ability of styrene exposure to induce formation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) in white blood cells (WBC) of boatbuilders occupationally exposed to styrene. The study of these adducts was conducted to see if styrene exposure can cause oxidative damage of DNA. The 8-OHdG/105 dG ratio from 17 styrene-exposed workers showed significant increases (mean ± SD, 2.23 ± 0.54, median 2.35, P < 0.001) in comparison to the controls (1.52 ± 0.45, median 1.50). However, 11 out of 17 workers who were between the ages of 32 and 60 years and had been occupationally exposed to styrene for >10 years showed higher 8-OHdG/105 dG ratios (2.31 ± 0.62, median 2.37) in comparison to 6 workers with <6 years of occupational styrene-exposure (2.11 ± 0.36, median 2.05; P > 0.05, no significant difference between the two groups of workers). The studies presented here provide an indication that styrene exposure can result in oxidative DNA damage.

Increased Incidence of DNA Double-strand Breaks and Anti-ds DNA Antibodies in Blood of Workers Occupationally Exposed to Asbestos

Asbestos, proven to be carcinogenic in humans and animals, is reported to have no genotoxic effect. Asbestos workers have an increased risk of lung cancer, mesothelioma, and other tumours. Earlier findings showed that crocidolite can induce DNA strand breaks in cultured rat embryo cells as assessed by nick translation. We investigated DNA double-strand breaks in white blood cells (WBC) of ten workers occupationally exposed to asbestos. According to our results, obtained with neutral filter elution, individuals who had been exposed to asbestos fibres showed two to four times more DNA double-strand breaks (dsb) in white blood cells than ten non-exposed persons. The induced DNA fragments are of about 250 kb (compared to chromosomal DNA of Saccharomyces cerevisiae standard marker). Using additionally the chromosomal DNA protective method of agarose-plugs, DNA fragments in the range of 200 to 1000 kb have been found in the white blood cells of the same ten workers occupationally exposed to asbestos. In the white blood cells of non-exposed subjects no DNA fragments could be detected with this method. Compared to 51 non-exposed persons, elevated anti-ds DNA antibody concentrations were found in ten workers occupationally exposed to asbestos. The fact that workers occupationally exposed to asbestos have distinctly more double-strand breaks and anti-ds DNA antibodies could mean that an increased incidence of DNA-fragments may be an important indicator in the chronic effect of asbestos-associated carcinogenesis. Apparently, the chronic effects of asbestos observed here do not seem to be identical with that of previously reported acute in vitro effects.

Albumin and hemoglobin adducts of benzo[a]pyrene in humans--analytical methods, exposure assessment, and recommendations for future directions.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in our environment and can cause cancer. Exposure to PAHs can be assessed by protein adduct dosimetry using benzo[a]pyrene (B[a]P) as a model compound. We present an overview of analytical methods to detect B[a]P- derived protein adducts in humans, their uses in exposure assessment, and recommendations for future research. Two major methodologies, enzyme-linked immunosorbent assay (ELISA) and chemical-specific assays, could be traced in the literature but there remains limitations with both assays. ELISA is nonspecific due to cross-reactivity of the antibody with other PAHs and results are better interpreted in terms of PAH exposure. ELISA is unable to distinguish between exposed and nonexposed persons in the majority of studies. Adduct concentrations are higher by several orders of magnitude compared to those determined by chemical-specific methods. The latter methods mostly analyzed protein adducts derived by (+)-anti-B[a]P-diol epoxide. For this purpose, gas or liquid chromatography in combination with mass spectrometry or fluorescence detection were used. However, the prevalence of positive samples remained low when chemical- specific assays were used mainly due to the lack of sensitivity. Overall, data on B[a]P-derived protein adducts in humans remain inconclusive. Future research should focus on the development and standardization of a sensitive and specific method for B[a]P-derived protein adducts prior to its use in field studies. Finally, exposures of B[a]P at the workplace and via diet, a major route of exposure of the general population, can be studied. The results will contribute to the understanding of B[a]P-induced cancer and will allow for health preventive measures.

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 (rs = 0.27; P = 0.03 and rs = 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 (rs = 0.32; P = 0.001 and rs = 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. (Cancer Epidemiol Biomarkers Prev 2006;15(4):645–51)

DNA damage in human white blood cells after inhalative exposure to methylenediphenyl diisocyanate (MDI) — case report

A workplace-related inhalative exposure test in a challenge chamber was performed on an industrial worker in a methylenediphenyl diisocyanate (MDI) atmosphere from 5 to 20 ppb and the isolated white blood cell DNA was analysed by electrophoresis, anion-exchange chromatography and melting behaviour. The results of electrophoresis indicate that inhaled MDI induces double-strand breaks of DNA. Some of the DNA fragments were estimated to be in the region of 100-500 bp. Anion-exchange chromatography confirmed this finding. Following denaturation and rapid renaturation the results demonstrated that some DNA fragments are cross-linked by MDI. Comparing the melting curves before and after inhalative exposure in the challenge test chamber, genomic DNA revealed differences in the shape of the melting curve (hyperchromic effect). The results suggest that occupational MDI exposure could be associated with white blood cell DNA damage.

New Biomarkers of Occupational Exposure to Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) are metabolized in a complex manner. Although biological activity is associated with diol-epoxide formation, phenolic metabolites have predominantly been used in human biomonitoring. In this study monohydroxylated and new metabolites were characterized as biomarkers for occupational PAH exposure. In 97 male workers, personal exposure to 16 airborne PAH compounds was measured during shift. In postshift urine, 1-hydroxypyrene and 1,6- and 1,8-dihydroxypyrene (1-OHP, DiOHP) were determined as metabolites of pyrene (P), and the sum of 1-, 2-, 3-, 4-, and 9-hydroxyphenanthrenes (OHPHE), and PHE-dihydrodiols (PHED) as metabolites of phenanthrene (PHE). The referent group comprised 21 nonsmoking construction workers. Median (interquartile range) shift concentrations of airborne P and PHE were 1.46 (0.62–4.05 μg/m3) and 10.9 (3.69–23.77 μg/m3), respectively. The corresponding parameters were 3.86 (2.08–7.44) μg/g creatinine (crn) for 1-OHP, 0.66 (0.17–1.65) μg/g crn for DiOHP, 11.44 (5.21–34.76) μg/g crn for OHPHE, and 12.28 (3.3–97.76) μg/g crn for PHED in PAH-exposed workers. The median levels of 1-OHP and OHPHE were 0.09 (0.08–0.17 μg/m3) and 0.59 (0.45–1.39 μg/m3), respectively, in the referents. PHE correlated significantly with OHPHE and PHED, and P with 1-OHP but not with DiOHP. Under a doubling of PHE, OHPHE increased by a factor of 1.56 and PHED by 1.57. With a doubling of P, 1-OHP rose by 1.31 and DiOHP by 1.27. P is predominantly metabolized into 1-OHP, whereas PHE is metabolized equally into OHPHE and PHED. Thus metabolites of PHE were found as reliable biomarkers for PAH exposure.

INCREASED INCIDENCE OF DNA DOUBLE-STRAND BREAKS IN LUNG AND LIVER OF RATS AFTER EXPOSURE TO CROCIDOLITE ASBESTOS FIBERS

AbstractThe aim of this study was to find out whether UICC crocidolite asbestos fibers induce in vivo DNA double-strand breaks in the nuclei of cells in lung and liver of rats. The effect of crocidolite on chromosomal DNA of rats exposed to crocidolite fibers was analyzed by pulsed-field gel electrophoresis (PFGE) using the chromosomal DNA-protective agarose-plugs method and laser densitometric evaluation of stained DNA bands. The profiles of laser densitometric scanning showing PFGE separation of DNA for exposed rats are right-shifted in liver and lung compared with the controls of the same age. DNA from the liver of nonexposed rats showed one peak in the range of 250–850 kb. Compared to this finding, at 4, 13, and 16 mo after crocidolite instillation DNA of rats showed shorter DNA fragments in the range of 250–700 kb. This indicates a more intact DNA in controls. At 4, 13, and 16 mo after crocidolite instillation, we also found DNA fragments in exposed lungs in the region between 250 and 2200 kb produce...

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 (FEV1) 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 FEV1 and FVC was observed in the bitumen-exposed group independent of their smoking habits, whereas in the non-smoking reference group, the decline in FEV1 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.