Chamber studies

Formaldehyde causes eye, upper respiratory tract, and skin irritation and is a skin sensitizer. Although sensory irritation, eg, eye irritation, has been reported at concentrations as low as 0.1 ppm in uncontrolled studies, significant eye/nose/throat irritation does not generally occur until concentrations of 1 ppm, based on controlled human chamber studies. Odor detection has commonly been reported to occur in the range of 0.06—0.5 ppm (133—135). 

Models of chemical reactions of trace pollutants in groundwater must be based on experimental analysis of the kinetics of possible pollutant interactions with earth materials, much the same as smog chamber studies considered atmospheric photochemistry. Fundamental research could determine the surface chemistry of soil components and processes such as adsorption and desorption, pore diffusion, and biodegradation of contaminants. Hydrodynamic pollutant transport models should be upgraded to take into account chemical reactions at surfaces. 

Maximal levels for -coumaric and ferulic acids of 30.0 and 6.5 pmol/1 0 g of soil ha e been reported (158) and concentrations of 4 x 10 M and 3 x 10 M, respectively, for these two acids in other soils (161)Other gtudies indicate a similar concentration range of 2.3 x 10 to 10 M for -hydroxybenzoic, vanillic and j>-coumaric acids (169). These levels may be too low to have direct measurable allelopathic effects on plants in greenhouse or growth chamber studies (non-rhizosphere soils, low microbial population). However, in field rhizosphere soils (high microbial population) these levels could be sufficient to influence microbial growth... 

AES was developed in the late 1960s, and in this technique electrons are detected after emission from the sample as the result of a non-radiative decay of an excited atom in the surface region of the sample. The effect was first observed in bubble chamber studies by Pierre Auger (1925), a French physicist, who described the process involved. 

The recoil factors r define the probability of whether an attached radioactive atom desorbs from the particle surface in consequence of an alpha decay or not. Mercer and Strowe (1971) found a recoil factor = 0.81 in their chamber studies in contradiction to the value of ri 0.4 measured by Kolerski et al. (1973). No other results about the recoil factor are available in the literature. 

Winer, A.M., Damall, K.R., Atkinson, R. Pitts, Jr., J.N. (1979) Smog chamber study of the correlation of hydroxyl radical rate constants with ozone formation. Environ. Sci. Technol. 7, 622-626. 

Asthma rates in children in Southern California are high and oxidant pollution levels are likewise high. It is important to determine the relationship between the two. It is also important to determine whether there are chronic pulmonary effects produced by either these oxidants and/or particulate pollution. Since children spend more time outdoors than adults and since they exercise more while outdoors, the added assault from increased ventilation may be of importance. The studies feature a comprehensive exposure assessment that has led to a better understanding of the relationship between exposure and effects. It is also important to identify sub-populations of children and adults who are more susceptible to air pollution-related respiratory effects if they exist. Altered susceptibility could be based on genetic or non-genetic mechanisms (nutritional status for example). Both the epidemiologic and chamber studies provide opportunities to examine issues of hypersusceptibility and to determine the reasons for it if it exists. 

Figure 5.2 Literature data on fraction of drugs absorbed (in percent) after human nasal administration versus apparent permeability (Tapp) data from Ussing chamber studies on porcine nasal mucosa (Reprinted with permission from Elsevier B.V.).

The success of these computer simulations must be rated as quite good. Figure 2-8 compares concentration-time measurements from a smog-chamber study of NO,-propylene-air with computer-calculated results based on the same initial conditions. The time dependences and absolute concentrations agree fairly well, but not perfectly. Note that the... 

Table 2-6 is a list of some compounds that may be present in photochemical smog, but have not yet been reported. The presence of some of these compounds (such as PBzN and ketene) seems very probable, in diat they have been observed in smog-chamber studies, whereas others are... 

TABLE 3-5 Compounds Investigated in Smog-Chamber Studies, with References... 

Depending on meteorologic conditions, aerosol formation in the atmosphere is better approximated, but never fully simulated, by smog-chamber studies under either static (batch-reactor) or dynamic (flow-reactor) conditions. 

Cyclic olefins and diolefins form aerosol even when present at very low concentrations, as confirmed by smog-chamber studies for cyclo-hexene and 1,6-heptadiene. ... 

Assuming that the rate of gas-to-particle conversion of any condensable species is greater than its rate of formation in the gas phase (which is the case for heten eneous nucleation predominant in the atmosphere, but may not be valid for homogeneous nucleation in clean-air smog-chamber studies) ... 

The diurnal patterns of ozone, nitric oxide, and nitrogen dioxide concentrations observed during photochemical oxidant episodes in California have been confirmed by smog-chamber studies. There may be, however, a decrease in reliability with decreasing concentration of values less than 0.1 ppm that were measured by the colorimetric method. The magnitude of these uncertainties among the various monitoring networks in the United States has still to be assessed. 

Kerr, H. D., T. J. Kulle, M. L. Mcllhany, and P. Swidersky. Effects of ozone on pulmonary function in normal subjects. An environmental-chamber study. Amer. Rev. Respir. Dis. 111 763-773, 1975. 

Smog-chamber studies are needed for validating both the detailed chemical models and the lumped models. Many of the past chamber studies have not used sufficiently well-defined initial conditions. Measurements of more products and of the reactive intermediates will provide more stringent tests for models. 

Laboratory (smog-chamber) studies of aerosol formation from aromatic hydrocarbons gas-phase reaction mechanism, physical processes controlling gas-to-aerosol conversion, kinetic data on aerosol formation... 

ControUed-environment chamber studies for humans, 390-93 for materials, 644-51 for plants, 462-70... 

Uhde E, Bednarek M, Fuhrmaim F, Salthammer T (2001) Phthalic esters in the indoor environment-test chamber studies on PVC-coated wallcoverings. Indoor Air 11 150-155... 

In a chamber study, a single exposure of six male volunteers for 8 hours did not cause irritation-related symptoms in the eyes or the respiratory tract at exposures up to 50mg/m NMP ... 

Kerr HD et al Effects of nitrogen dioxide on pulmonary function in human subjects An environmental chamber study. Environ Res 19 392-404, 1979... 

Eckert, D.J. and McLean, E.O. (1981) Basic cation saturation ratios as a basis for fertilizing and liming agronomic crops I. Growth chamber studies. Agronomy Journal 73, 795-799. 

In concentrations approximating present air quality standards (Table III), O3 or SO2 in combination with NO2 could measurably suppress CO2 uptake rates of sensitive plants if exposed under favorable growing conditions. In the controlled environmental chamber studies, 1-hr exposures to 10 pphm O3 (which is slightly above the primary and secondary standards — i.e., 8 pphm for 1 hr) for example, depressed alfalfa CO2 absorption rates by approximately four percent. Exposures to 15 pphm hr SO2 in combination with an equal amount of NO2 reduced uptake rates by 7 percent. Alfalfa, barley or oat canopies exposed to these pollutants singly required higher concentrations (i.e., 1- to 2-hr treatments with more than 20 pphm SO2 or 40 pphm NO2) to measurably reduce canopy uptake rates. 

Finally, chamber studies of the reactions of N02 and O, at various relative humidities from 8 to 70% were carried out by Mentel et al. (1996) and the con-... 

Spicer, C. W., Smog Chamber Studies of NOv Transformation Rate and Nitrate/Precursor Relationships, Enriron. Sci. Technol., 17, 112-120 (1983). 

Smog chamber studies have documented similar aerosol growth mechanisms. For example, in the photochemical oxidation of dimethyl sulfide, the formation and growth of particles in an initially particle-free system was observed. However, if seed particles with 34-nm mean size were present, an oscillation in the... 

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