Wolfgang Koch

Chronic Inhalation Exposure of Wistar Rats and two Different Strains of Mice to Diesel Engine Exhaust, Carbon Black, and Titanium Dioxide

AbstractWistar rats were exposed for 2 yr to diesel engine exhaust, carbon black (Printex 90, Degussa, FR. G), and ultraline TiO2 (P25, Degussa, FRG) and were subsequently kept in clean air for 6 mo. Particle exposure concentration was increased during the course of the experiment for carbon black and TiO2 to reach particle lung loads similar to those found in the diesel soot-exposed rats. The average particle exposure concentrations for diesel soot, carbon black, and TiO2 were 7, 11.6, and 10 mg/m3, respectively. Lung tumor rates in these rats increased with increasing cumulative particle exposure (mg/m3 x h) independent of the type of particle employed. The exposure to 2.5 mg/m1 diesel soot also induced a significantly increased lung tumor rate, but 0.8 mg/m3 diesel soot did not. With this study, it could be demonstrated that the carbon core of diesel soot is mainly responsible for the occurrence of diesel engine exhaust-related lung tumors; the role of diesel soot-attached polycyclic aromatic hydrocarb...

DETERMINATION OF PLATINUM EMISSIONS FROM A THREE-WAY CATALYST- EQUIPPED GASOLINE ENGINE

Abstract Platinum emissions from two automotive monolithic catalysts have been determined under laboratory conditions on a computer controlled dynamometer. Three stationary speed simulations and the U.S.-75 cycle were applied. Particles were classified on a Berner Impactor and analysed by atomic absorption spectrometry using a signal addition technique. Condensates were also sampled to determine volatile compounds. For quality control, several matrix element studies were performed to demonstrate the accuracy of the analytical method. The emission concentrations, as determined in several test runs and repetitive sampling, range from 3 to 40 ng m −3 . In contrast to published data from pellet oxidation catalysts, the emission concentrations determined are lower by 2 orders of magnitude. A possible volatile or watersoluble platinum fraction is most probably negligible.

A smog chamber for studies of the photochemical degradation of chemicals in the presence of aerosols

Abstract A smog chamber, especially designed for the simulation of the tropospheric photochemical degradation of chemicals adsorbed on aerosol surfaces, is described. With optimum aerodynamic diameters of the aerosols (0.5 μm) and by special thermostatization of the chamber residence times of the aerosols up to 2 days in the dark and up to 1 day in the presence of simulated sun irradiation are achieved. Experiments on the degradation of simple alkanes (up to n-nonane) and aromatics in the absence and presence of aerosols (SiO2 and TiO2) are reported. Rate constants for the reactions of OH with n-alkanes from n-butane to n-tridecane are determined to be (k ± 2 σ)/10−12 cm3s−3 = 2.54 ± 0.04, 4.13 ± 0.05, 5.68 ± 0.04, 7.31 ± 0.08, 8.79 (reference value), 10.3 ± 0.2, 12.4 ± 0.2, 13.3 ± 0.2, 13.9 ± 0.2, 15.5 ± 0.2), respectively, at 300 K. These rate constant measurements and the observed concentrations of OH remain unaffected in the presence of SiO2 aerosol at mass concentrations of l mg m−3. In the presence of TiO2 at 2 mg m−3 mass concentration, the steady-state concentration of OH is enhanced by an order of magnitude. In addition, a heterogeneous photodegradation process of the hydrocarbons occurs on the surface of the TiO2 aerosol.

Validation of an environmental exposure unit for controlled human inhalation studies with grass pollen in patients with seasonal allergic rhinitis

Background There is an increasing need for allergen inhalation systems to perform basic clinical research and test anti‐allergic drugs under well‐controlled conditions. This requires stability of environmental conditions like temperature and humidity, as well as allergen concentration and reproducible induction of allergic symptoms.

Ultrafine particles at workplaces of a primary aluminium smelter

The number concentration and size distribution of ultrafine particles in a Søderberg and a prebake potroom of an aluminium primary smelter have been measured using a scanning mobility particle spectrometer. The particle morphology was studied by transmission electron microscopy (TEM). The study shows the existence of elevated number concentrations of ultrafine particles in both potrooms. The main source of these particles is likely to be the process of anode changing. The ultrafine particles were measured directly at the source but could also be identified as episodes of high number concentrations in the general background air. Unlike the larger particles belonging to the 50-100 nm mode, the nanoparticle mode could not be detected in the TEM indicating that they may not be stable under the applied sampling conditions and/or the high vacuum in the instrument.

Subchronic Inhalation Study of Toner in Rats

AbstractA subchronic inhalation study of a special test toner was conducted by exposure of groups of F-344 SPF (specific pathogen free) rats for 6 hlday, 5 dayslwk for 13 wk. The test material was a special 9000 type xerographic toner, enriched in respirable size particles compared to commercial toner, such that it was about 35% respirable according to the ACGIH criteria. The nominal aerosol exposure concentrations were 0, 7.0, 4.0, 76.0, and 64.0 mg/m3 Body weight, clinical chemistry values, food consumption, and organ weights were normal except for a 40% increase in lung weight for the highest exposure group. Histopathological examination of the lungs indicated an exposure-related accumulation of particle-laden alveolar macrophages. A very slight degree of septal thickening of the alveolar structure was noted in the highest exposure group. Clearance results for the test material and a superimposed spike of 59Fe2O3 were essentially unchanged at exposure concentrations of 0, 1, and 4 mg/m3. At 76 mg/m3, s...

Alveolar clearance and retention of inhaled insoluble particles in rats simulated by a model inferring macrophage particle load distributions

Abstract This paper presents the description of a revised, physiology-oriented compartmental kinetics (“POCK”) model of alveolar clearance and retention of biologically insoluble, respirable particles. By postulating a deposit-activated maximum macrophage recruitment rate leading to a quasi-steady state of the alveolar macrophage population on the alveolar epithelial surface, the model uses a theoretical derivation of an exposure-dependent distribution of particles in the alveolar macrophage population to determine the total load in mobile and immobilized macrophages. For this, the model assumes an invariant maximum volume capacity of the macrophages for particle uptake and a material-dependent critical load of the macrophages that causes total loss of their inherent mobility. Prior to a gradual onset of mobility decrease, there is a material-dependent range of low macrophage burdens without mobility impairment. Using independently determined physiological data for classical clearance rate coefficients, as well as for the lifetime of the alveolar macrophages and their particle turnover by phagocytosis, the model seems to be applicable to experimental results obtained for rats. A constant set of model parameters and a minimum of three material-dependent, physiologically meaningful model variables were sufficient to simulate the alveolar lung burden and available lymph node load data of 15 different subchronic or chronic exposures of Fischer 344 rats to diesel soot, carbon black or xerographic toner. For constant deposition rates, the model predicts the establishment of quasi-steady states for the total load of the alveolar macrophage pool. The final load would increase with increasing deposition rate and, particularly under overload conditions, i.e. at high deposition rates, the number of immobilized macrophages would grow significantly. According to the model, overload does not cause an excessive growth of the total burden of the macrophage pool, but leads to a tremendous increase of the particulate burden of the interstitial space. This compartmental burden is not available for macrophage-mediated classical clearance. Except for partial removal to the lymph nodes, the interstitial burden will persist even when exposures are discontinued and the alveolar macrophage population recovers to full mobility. Subchronic exposure studies seem to bear this out, but due to lack of experimental data for the burdens in most of the alveolar subcompartments of the model, the corresponding predictions cannot be validated at the present time.

Evaluation of the Respicon® as a personal inhalable sampler in industrial environments

The Respicon has been introduced as a sampler for health related measurements of airborne contaminants at workplaces. The instrument is aimed at simultaneous collection of three health related aerosol fractions: (a) the coarser inhalable fraction, defining the aerosol fraction that may enter the nose and mouth during breathing; (b) the intermediate thoracic fraction, defining the fraction that may penetrate beyond the larynx and so reach the lung; and (c) the finer respirable fraction, defining the fraction that may penetrate to gas exchange region of the lung. The instrument has a number of features attractive to occupational hygienists: in addition to providing the three aerosol fractions simultaneously, it is light and compact enough to be used as a personal sampler. yet can be a tripod mounted for area sampling, it can provide samples not only for gravimetric analysis but also microscopic and chemical analyses; and it is also available in a photometric direct-reading version. The instrument has previously been evaluated as an area sampler and, in this mode of operation, has shown reasonable accuracy in collecting respirable, thoracic and inhalable particles, the latter up to particle diameters of ca. 80 microm. Except for some scattered unpublished data there exist no systematic investigations in the Respicons performance when used as a personal sampler in the industrial environment. In this paper, we will report on a study of side by side comparison of the Respicon with the IOM inhalable sampler, regarded as a reference instrument for the inhalable fraction. The main study was performed at six different workplaces in a nickel refinery. Statistical analysis of the gravimetrically-determined concentration data reveals consistently lower aerosol exposure values for the Respicon as compared to the IOM sampler. The data for the nickel workplaces are compared with findings from other studies. The results are interpreted in the light of the overall results and the possibility of introducing a correction factor is discussed.

In-flight spraying in aircrafts: determination of the exposure scenario

Exposure measurements were carried out in parked aircrafts during and after application of a biocide aerosol spray (simulated in-flight spraying). The aerosol product SRA spray (Standard Reference Aerosol Spray) was used for spraying. Concentrations of the pyrethrins--the active ingredients--in the air of the passenger cabin (airborne particles, measured during spray application and 40 minutes afterwards) varied from 11 to 65 microg/m3; those of the synergist piperonyl butoxide were 200-485 microg/m3. The concentrations on surfaces of the cabin furniture differed widely. Low concentrations were determined on surfaces in vertical positions (median values: pyrethrins < or =2 ng/cm2; piperonyl butoxide < or =17 ng/cm2), while under seats, on seats and on headrests the concentrations were up to 55.5 ng/cm2 for pyrethrins and 1162.5 ng/cm2 for piperonyl butoxide (median values). The inhaled doses for sprayers (using 100 g of spray) and persons sitting in the passenger cabin were calculated to be 17 microg for pyrethrins and 200 microg for piperonyl butoxide (maximum values). Maximum total external body doses for the applicators during spraying were 830 microg for pyrethrins and 8840 microg for piperonyl butoxide. The potential dermal dose for persons sitting in the passenger cabin was about a factor of two lower.

A solution of the two-dimensional atmospheric diffusion equation with height-dependent diffusion coefficient including ground level absorption

Abstract An analytical solution of the two-dimensional atmospheric diffusion equation has been developed including the effects of ground level absorption. In the model the height dependence of the wind velocity and the vertical turbulent diffusion coefficient is approximated by power functions of z. The deposition correction to the ground level concentration is a universal function of vx v , where v is proportional to the deposition velocity, x is the distance from the source and v is a stability parameter.