Workplace exposure to engineered nanoparticles.

Measurement strategies as well as results from measurements at workplaces are presented. Measurements were performed in research laboratories as well as by companies producing small amounts of nanostructured materials. The work was done in the frame of a BAuA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin) research project. Measurement results during manufacturing and processing of TiO(2), nanofibers as well as synthetic ceramic nanopowders and nanostructured materials used for the electrical industry are demonstrated. Measurements were conducted with a scanning mobility particle sizer (Grimm) and a concentration particle counter (TSI). Mean number concentrations of nanoparticles are presented. During determination of particle number concentrations, a distinction must be drawn between the particle number in the ambient air and the particle number resulting from work processes. Thus a special measurement strategy was developed including measurement of the ambient air and also analysis by electron microscopy to define the size of agglomerates as well as the data related to the chemical composition. To date, no significant increase of nanoparticle number has been found provided proper handling was guaranteed (e.g., closed systems, extractor hood). Nevertheless, a few particle agglomerates of the materials used during the work process, as shown by electron microscopy, were detected. Probably nanostructured materials can primarily be released during cleaning and maintenance operations as well as in the case of a failure of normal operation.

Dose-response relationships between occupational exposure to potash, diesel exhaust and nitrogen oxides and lung function: cross-sectional and longitudinal study in two salt mines.

OBJECTIVE: Several studies have shown that underground salt miners may have an increased incidence of chest symptoms and sometimes decreased lung function. Miners of two salt mines were investigated to evaluate relationships between the lung function and the workplace exposure. The effect of nitrogen monoxide (NO) and nitrogen dioxide (NO(2)) was investigated in view of the recent debate on European occupational exposure limits. METHODS: A total of 410/463 miners (mine A/mine B) were examined cross-sectional and 75/64% of the first cohort were examined after a 5-year period. Exposure was measured by personal sampling. Personal lifetime exposure doses of salt dust, diesel exhaust, NO(2) and NO were calculated for all miners. Dose-response relationships were calculated by multiple regression analysis. Each exposure component acted as an indicator for the complex exposure. RESULTS: Exposure response relationships were shown in the cross-sectional and longitudinal investigations in both mines. In the 5-year period, the adjusted (age, smoking, etc.) effect of the exposure indicators resulted in a mean decrease of FEV(1) between -18 ml/year (mine A) and -10 ml/year (mine B). The personal concentrations related to this effect were 12.6/7.1 mg/m(3) inhalable dust, 2.4/0.8 mg/m(3) respirable dust, 0.09/0.09 mg/m(3) diesel exhaust, 0.4/0.5 ppm NO(2) and 1.7/1.4 ppm NO (mine A/B). Exposure was related to symptoms of chronic bronchitis only in mine B. CONCLUSION: The effects found in both mines indicate that the mixed exposure can cause lung function disorders in salt miners exposed over a long time. Because of the high correlation of the concentrations it was not possible to determine the effects of a single exposure component separately or to recommend a specific occupational exposure limit. However, possible maximum effects associated with the mixed exposure can be evaluated in the ranges of concentrations of the individual substances in the mines.

Continuous dry dispersion of multi-walled carbon nanotubes to aerosols with high concentrations of individual fibers.

The assessment of the toxicity of airborne nanofibers is an important task. It relies on toxicological inhalation studies and validated exposure measurement techniques. Both require nanofiber-containing aerosols of known morphological composition and controlled fraction of individual fibers. Here, a dry powder dispersion method is presented that operates with mixtures of nanofibers and microscale beads. Aerosolization experiments of mixtures of multi-walled carbon nanotubes (MWCNTs) and glass beads that were continuously fed into a Venturi nozzle enabled high generation rates of aerosols composed of individual and agglomerate nanofiber structures. The aerosol process achieved good stability over more than 2 h with respect to concentration and aerodynamic size distribution. Its operation duration is limited only by the reservoir volume of the cyclone used to separate the beads from the aerosol. The aerosol concentration can be controlled by changing the mass ratio of MWCNTs and glass beads or by adapting the mass feed rate to the nozzle. For two agglomerated MWCNT materials, aerosol concentrations ranged from 1700 to 64,000 nano-objects per cm3. Comprehensive scanning electron microscope analysis of filter samples was performed to categorize and determine the morphological composition of the aerosol, its fiber content as well as fiber length and diameter distributions. High fractions of individual fibers of up to 34% were obtained, which shows the setup to be capable of dispersing also highly tangled MWCNT agglomerates effectively.

Immunological biomarkers in salt miners exposed to salt dust, diesel exhaust and nitrogen oxides.

OBJECTIVES: Air pollutants can affect lung function and also the immune system. In a study about lung function of salt miners in relation to the complex exposure in a salt mine, we also analysed selected immunological parameters and inflammation markers in the blood of miners. Effect of salt dust, diesel exhaust, nitrogen oxides (NOx) and smoking on the biomarkers was analysed. METHODS: Blood was drawn from 286 salt miners, and the soluble intercellular adhesion molecule-1 (s-ICAM), monocyte chemotactic protein (MCP-1) and clara cell protein (CC16) were analysed by an immunoassay, blood profile was done and lymphocyte subpopulations (CD3, CD3/CD4, CD3/CD8, CD19, NK-cells, CD3/HLA-DR) were determined by flow cytometry. Salt dust was measured by two-step gravimetry (personal sampling). Diesel exhaust was measured as elemental carbon concentration by coulometry. NOx were determined by an electrochemical cell method. Differences between non-smokers, former smokers and active smokers were analysed by analysis of variance. Linear regression analysis to describe exposure-response relationships was done with regard to confounding factors [smoking, inflammatory diseases, time of blood drawing, respiratory infection and body-mass index (BMI)]. RESULTS: Significant differences between non-smokers and active smokers were found for most of the leukocyte types (e.g. granulocytes P = 0.000, lymphocytes P = 0.002, T-cells P = 0.033) and for some soluble parameters (ICAM P = 0.000, IgM P = 0.007, IgE P = 0.035). Increasing numbers of total lymphocytes, T-cells and HLA-DR positive T-cells in relation to exposure were found by linear regression analysis (e.g. for inhalable dust:total lymphocytes P = 0.011, T-cells P = 0.061, HLA-DR positive T-cells P = 0.007). CONCLUSION. Comparison of immunological markers in non-smokers and active smokers confirms leukocytosis and inflammation following tobacco consumption. The combined exposure of salt dust, diesel exhaust and NOx seems to influence the immune system. Together, the results suggest that the analysis of leukocytes and their subsets can complete other investigations (lung function, questionnaire) to monitor exposure-response relationships in occupational studies investigating the effect of inhaled substances. Longitudinal studies will be necessary to determine the predictive value of the immunological changes.