Exposure to indoor air pollution (IAP) from the burning of solid fuels for cooking, heating, and lighting accounts for a significant portion of the global burden of death and disease, and disproportionately affects women and children in developing regions. Clean cookstove campaigns recently received more attention and investment, but their successes might hinge on greater integration of the public health community with a variety of other disciplines. To help guide public health research in alleviating this important global environmental health burden, we synthesized previous research on IAP in developing countries, summarized successes and challenges of previous cookstove implementation programs, and provided key research and implementation needs from structured discussions at a recent symposium.
In this study, modifications were made to previously applied two-zone models to address important factors that can affect exposures during cleaning tasks. Specifically, we expand on previous applications of the two-zone model by (1) introducing the source in discrete elements (source-cells) as opposed to a complete instantaneous release, (2) placing source cells in both the inner (near person) and outer zones concurrently, (3) treating each source cell as an independent mixture of multiple constituents, and (4) tracking the time-varying liquid concentration and emission rate of each constituent in each source cell. Three experiments were performed in an environmentally controlled chamber with a thermal mannequin and a simplified pure chemical source to simulate emissions from a cleaning product. Gas phase concentration measurements were taken in the bulk air and in the breathing zone of the mannequin to evaluate the model. The mean ratio of the integrated concentration in the mannequin's breathing zone to the concentration in the outer zone was 4.3 (standard deviation, σ = 1.6). The mean ratio of measured concentration in the breathing zone to predicted concentrations in the inner zone was 0.81 (σ = 0.16). Intake fractions ranged from 1.9 × 10(-3) to 2.7 × 10(-3). Model results reasonably predict those of previous exposure monitoring studies and indicate the inadequacy of well-mixed single-zone model applications for some but not all cleaning events.
Thermogravimetry (TG) is an analytical technique that monitors the mass of a substance as it is subjected to a controlled temperature program. TG is the modern day frontier of the much older and well-established technique of gravimetry. Although many compositional analyses may be performed by conventional gravimetry, thermogravimetry offers a more rapid method because of the smaller sample size and faster heating rates. Thus, special instrumentation requirements are imposed on the more modern, rapid, and automated thermogravimetric method. Many commercial TG systems are available. The major difference in these are in the furnace (size, design, and positioning with respect to the furnace tube and sample specimen), degree of computerization, direction of purge gas flow (horizontal or vertical) with respect to the sample specimen, and microbalance type and sensitivity. Recent years have brought computerization of data handling as well as many of the hardware components of the technique. This paper will present and discuss the role of the basic components of a thermogravimetric apparatus in performing compositional analysis. Some of the aspects of computerization of the technique will be included.
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