A method for measuring deposited particles in the lung was investigated, and particle masses deposited in the lungs of rats and guinea pigs from inhaled diesel exhaust were determined. The lung tissues were dissolved with ethanol solution of potassium hydroxide, and the absorbance of solution was measured to determine the deposited particle mass. Determination of elemental carbon required the removal of organic matters from the filtrate of completely digested lung-tissue solution, followed by heat treatment in an inert gas. A high pressure liquid chromatography was applied for quantifying polynuclear aromatic hydrocarbons. The detection limit of particle concentration in the solution was 25 μg/ml. The mass of particles and elemental carbon deposited in the lungs increased with the particle concentration and the inhalation period. Approximately 28 mg and 16 mg of particles were deposited in the lungs of rats at the diesel exhaust particle concentrations of 3.7 mg/m3 and 2.3 mg/m3 for 30 months, and about 64 mg of particles was deposited in the lungs of guinea pigs exposed to the concentration of 2.9 mg/m3 for 24 months. The apparent deposition fraction of diesel particles for each experimental group was in the range between 8 % to 20 % for rats and 10 % to 45 % for guinea pigs. The concentrations of PAHs in the lungs were found to be very low compared to the estimated mass of inhaled PAHs.
In semiconductor manufacturing processes, product transport between cleanrooms has recently become inevitable with an increase of process steps to make devices with finer dimensions and a higher integrity. This work aims at developing a particle collection device for a clean elevator. We first characterized particles generated from actuating parts of transport equipment such as roller conveyors. We measured generation rate and charge distribution of particles released from the equipment. These measurements showed that the generated particles consist of fairly large number of submicrometer particles with more than 90 % of charged fraction. Based on this finding, we designed a particle collection device composed of parallel plate electrodes and dielectric fibers, and evaluated experimentally. It found that the performance of the device can be estimated by the conventional filtration theory.
With increasing integration of semiconductor devices, organic contaminants adhering to silicon wafer surfaces have become a serious problem because they strongly affect production yield and device performance. The cleanroom construction materials and polymers are the major source of organic contaminants in cleanroom. Therefore, outgassing test for cleanroom construction materials and polymers is just as important as the evaluation of organic contaminants in cleanroom air, because it will help us identify the organic contaminant sources and mechanisms of organic contamination. At present, outgassing test method for organic compounds with high boiling-points is to be established because polar organic compounds with high boiling-points tend to adhere to silicon wafer surfaces more strongly than the other organic compounds. We employed five outgassing test methods for cleanroom construction materials and polymers, which can be used for mini-environment and wafer carrier boxes, and studied the relationships between the outgassing condition and the outgassing test results. We found that there is a linearity between the logarithm of outgassing amount and the reciprocal of temperature, 1/T. The outgassing amount at an arbitrary temperature can be evaluated with a few data of other temperature by using the linearity.