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We report exacerbation of symptoms and chemical intolerances in three of four self-described chemically sensitive women following relocation to a newly constructed office building. Levels of total volatile organic compounds (TVOCs) in this building prior to occupancy were approximately 200 μg/m3 (toluene equivalent units) with a myriad of individual components present. By day 50 after occupancy, the concentration of TVOCs in the building dropped to approximately 50 μg/m3. Nevertheless, three women reported significant worsening of their symptoms with spreading of their sensitivities to previously tolerated chemical exposures. One woman relocated to another building, while the other two managed their symptoms by reducing time spent in the building or by using a room air cleaner. By day 600 following occupancy, although TVOCs had increased significantly (perhaps due to cleaning agents), there were fewer individual VOCs present in the air, and some of the women were able to tolerate the air in the building. We conclude that complex mixtures of VOCs at very low levels tolerated by the majority of building occupants may pose problems for persons who report pre-existing chemical sensitivities. TVOC measurements may not correlate with symptoms in these individuals. Reasonable accommodations by an employer can reduce problem exposures, making it possible for some affected individuals to continue productive employment.

Examples are given of occupant activities and consumer and construction products inside residences that cause transient and persistent emissions of volatile organic compounds (VOC). Transient emissions arise from window cleaning, carpet laying, smoking, and automobile operations. Persistent VOC emitters include gasoline, mothballs and pressed-wood products containing urea-formaldehyde resins. Simple screening methods are given for making indoor measurements of VOC. Detailed laboratory and research house studies of formaldehyde emissions decay from pressed-wood building products are described. 14 refs., 4 figs., 3 tabs.

Cold-pressed pellets of unfired BeO, called Thermalox 995, have been fired at temperatures between 400° and 1900°C. The thermally stimulated exoelectron emission (TSEE), thermoluminescence (TL), and electron paramagnetism (EPR) have been measured and correlated with sintering and grain growth. Changes in TL and TSEE sensitivity are as much as five, and two and a half orders in magnitude, respectively. The changes in concentration of the paramagnetic trapping centers correlate fairly well with the changes in TL sensitivity showing that the two are intimately related. The TSEE data show a markedly different trend; the traps are of a different type from those producing TL and are not detected by EPR. The most satisfactory radiation dosimeters are obtained after firing at 1300°C when the mean grain size is about 7 μm. The commercially available ceramic disks of Thermalox 995, with grains about double this size, are close to being in an optimum condition for TL-TSEE dosimetry. Dosimeters with a mean g...

Oxygen, water vapor and/or carbon dioxide adsorbed on ceramic BeO before or after irradiation profoundly affect the thermally stimulated exoelectron emission (TSEE). In their presence the TSEE is dominated by a single peak at a surface temperature of ∼275°C. Removal of these adsorbates by outgassing during read-out causes the exoelectron emission to intensify with the TSEE curve becoming more complex. Apparently, sorption layers render inoperative certain traps effective for TSEE. Increased temperature during irradiation reduces the response (20% between 22° to 150°C). The influence of the gas surrounding the sample during irradiation was tested for the inert gases helium, nitrogen, neon, argon and krypton using 5.6 keV, 22 keV and 0.66 MeV photons. The enhancement in sensitivity for argon and krypton was much less than expected, which indicates that absorption of radiation in the volume of the solid is more important for excitation of the dosimeter than hitherto assumed.

High-area thorium oxide, outgassed at 200°C, is covered by surface hydroxyl groups and strongly bound water molecules. Gravimetric sorption studies show that onto this hydration layer, a monolayer of water can be physically adsorbed. This physisorbed water slowly becomes more firmly bound, apparently as water of hydration of the surface hydroxyl. For one type of thorium oxide, the conversion proceeds more rapidly at relative pressures above 0.5, and adsorption-desorption cycling to 1.0 p/p 0 profoundly changes the nature of the surface to permit a discrete second step in the adsorption isotherm. The second step appears to be associated with restructuring processes. Nuclear magnetic resonance (n.m.r.) data for surface water point not only to a sluggish approach to an equilibrium state but also to the development of special structure in the multilayer region.

The adsorption of water vapour and nitrogen has been measured on thorium oxide ground for 500 h. The thorium oxide appeared crystalline in character with nitrogen adsorption showing mesopores but not micropores. Stepped isotherms of water and hysteresis extending to low relative pressure were found after outgassing at 200 °C. However, after outgassing at 400°C, the step structure was lost together with a reduction in adsorptive capacity close to the step height. Of the two possible explanations for the step structure, restructuring at the water—oxide interface and intercalation, the latter is favoured. A pseudo-lamellar structure involving traces of worn porcelain separating thorium oxide crystals is suggested with entry of water molecules permitted at a critical threshold pressure.

In this paper we present a method for the measurement of alpha particle energy using polycarbonate materials as nuclear track detectors (NTDs). This method is based on the interaction of the radiation with the solid-state materials, using the relationship between the energy deposited in the material by the ionising particle and the track developed after an established chemical process. The determination of the geometrical parameters of the formed track, such as major axis, minor axis and overall track length, permit determination of the energy of the alpha particle. The track analysis is performed automatically using a digital image system, and the data are processed in a PC with commercial software. In this experiment 148Gd, 238U, 230Th, 239Pu and 244Cm alpha particle emitters were used. The values for alpha particle energy resolution, the linear response to energy, the confidence in the results and the automatisation of the procedure make this method a promising analysis system.

As part of a search for conducting refractory oxides which can be heated directly from room temperature to temperatures in excess of 2,000° C by induced radio-frequency currents without the need for pre-heating arrangements, a study has been made of the behaviour of hot-pressed thorium dioxide doped with various amounts of tantalum pentoxide. These systems possess no apparent advantages in oxidizing atmospheres, but do exhibit striking properties when prepared in reducing conditions and operated in a neutral atmosphere.