Aerosol concentration

Continuous readings unaffected by clouds, night b i directly relatable to fine aerosol concentration at a point semiportable used in a number of previous studies sensitive models available automated... 

Health effects attributed to sulfur oxides are likely due to exposure to sulfur dioxide, sulfate aerosols, and sulfur dioxide adsorbed onto particulate matter. Alone, sulfur dioxide will dissolve in the watery fluids of the upper respiratory system and be absorbed into the bloodstream. Sulfur dioxide reacts with other substances in the atmosphere to form sulfate aerosols. Since most sulfate aerosols are part of PMj 5, they may have an important role in the health impacts associated with fine particulates. However, sulfate aerosols can be transported long distances through the atmosphere before deposition actually occurs. Average sulfate aerosol concentrations are about 40% of average fine particulate levels in regions where fuels with high sulfur content are commonly used. Sulfur dioxide adsorbed on particles can be carried deep into the pulmonary system. Therefore, reducing concentrations of particulate matter may also reduce the health impacts of sulfur dioxide. Acid aerosols affect respiratory and sensory functions. 

Figure 7-2 shows the vertical profiles of temperature, dew point, light scattering (a measure of aerosol concentration) and the concentrations of O3 and SO2. Here we see that up to about 1.5 km, the temperature, dew point, light scattering... 

Examples of inferred enhancements of atmospheric primary aerosol concentration in the glacial atmosphere relative to the modem are factors of 4 to 7 for insoluble particles from continents, and 3 for seasalts (Alley et al, 1995), over Greenland. 

De Angelis, M., Barkov, N. I., and Petrov, V. N. (1987). Aerosol concentration over the last climatic cycle (160 kyr) from an Antarctic ice core. Nature 235,... 

Intermediate-duration inhalation exposures to aerosols of a few organophosphate ester hydraulic fluids (Durad MP280 and "triaryl phosphate ester") produced lethal neurotoxic effects in chickens and rabbits (MacEwen and Vemot 1983 Siegel 1965). Rats and hamsters appear to be less susceptible to the neurotoxic action of organophosphate esters tests of several organophosphate fluids produced no deaths in rats exposed to substantial aerosol concentrations. 

Testicular atrophy was observed upon gross necropsy after male rats were continuously exposed for 90 days to an aerosol concentration of 101 mg/m3 Durad MP280, but not in rats exposed to 10.3 mg/m3 (MacEwen and Vemot 1983). Testicular atrophy was not observed in male rats continuously exposed for 90 days to an aerosol concentration of 100 mg/m3 Fyrquel 220 (MacEwen and Vemot 1983). 

Male and female rats showed no treatment-related gross or histological reproductive tract alterations when exposed by inhalation 6 hours/day, 5 days/week for 3 weeks to a 990 mg/m3 aerosol of cyclotri-phosphazene (Kinkead et al. 1989a, 1990), or aerosol concentrations of Skydrol 500B-4 <300 mg/m3,... 

No data were located regarding toxic effects in humans following inhalation exposure to polyalphaolefin hydraulic fluids. Three of nine tested polyalphaolefin hydraulic fluids were lethal in rats at 4-hour aerosol concentrations ranging from <5,330 to <10,720 mg/m3. LC50 values for the three lethal fluids in females ranged from 1,390 to 1,670 mg/m3. Deaths were associated with respiratory irritation. The data are inadequate for acute inhalation MRL derivation. No intermediate or chronic inhalation MRLs for polyalphaolefin hydraulic fluids were derived due to the lack of data. 

Acute lethality studies in animals exposed by inhalation, ingestion, or dermal contact to several mineral oil hydraulic fluids indicate that mineral oil fluids are not potent toxicants. Mineral oil hydraulic fluids produced no deaths in rats after 4-hour exposures to aerosol concentrations of 110-210 mg/m3 or gavage administration of single doses <5,000 mg/kg (Kinkead et al. 1987a, 1988). Rabbits, likewise, did not die after single 24-hour exposures to occluded dermal doses of several mineral oil hydraulic fluids <2,000 mg/kg (Kinkead et al. 1985, 1987a, 1988). 

Theoretical calculations of unattached fractions of radon or thoron progeny involve four important parameters, namely, 1) the count median diameter of the aerosol, 2) the geometric standard deviation of the particle size distribution, 3) the aerosol concentration, and 4) the age of the air. All of these parameters have a significant effect on the theoretical calculation of the unattached fraction and should be reported with theoretical or experimental values of the unattached fraction. 

In addition to the quasi-steady state assumption, the other assumptions required to arrive at equation (1) are 1. the aerosol itself does not coagulate 2. there is a fully developed concentration gradient around each aerosol particle and 3. the concentration of unattached radon progeny atoms is much greater than the concentration of aerosol particles (in order that concentration gradients of radon progeny atoms may exist). This last assumption is usually not valid since the radon progeny concentration is usually much less than the aerosol concentration. 

Theoretical unattached fractions of RaA using average aerosol concentrations and count median diameters as found in track and trackless Canadian uranium mine are presented in Table III. The reported uranium mine aerosol properties are N 120,000 particles/cm3 and CMD = 0.069 ym for a trackless mine and N =... 

Although unattached fractions predicted using the kinetic and diffusion theory for high aerosol concentrations, such as mine atmospheres, are comparable, the same cannot be said for unattached fractions predicted at low aerosol concentrations, such as indoor air. For low aerosol concentrations, neither the kinetic nor the diffusion theory predicts unattached fractions close to those predicted by the hybrid theory. Exclusive use of either of these two theories results in large errors. 

Figure 1. Mean diurnal patterns for aerosol concentrations (—o—) and size (—+—) top, and Rn-222 concentrations (—o—) with PAEC (Working Level) (—H— ) bottom, for seven days in September 1985.

Aerosol concentrations, radon, and PAEC (in Working Levels) clearly peak in early hours after sunrise and at about the time of morning human use of the building which is coincident with the outdoor peak in radon and fine aerosols due to their overnight accumulation near ground level under local temperature inversions. ... 

T e daily average aerosol concentration is 4060 x 10 particles per m with a fluctuation of + 50 percent based on the standard deviation of the mean. The mean particle size likewise shows large variation with a mean of 0.04 + 0.01 ym. There was some evidence in the aerosol analyzer data for major and minor modes in the size distribution as found by George et al. (1980, 1984). The mean diameter of the particles remained constant as seen in the graph. Both Rn-222 and PAEC (WL) values followed similar diurnal patterns. It is reasonable to expect higher WL levels during the morning due both to increase in radon and aerosol concentrations. The mean diurnal PAEC is 0.006 WL for this seven-day period in September. 

Indoor small ion concentrations or both positive and negative ions averaged about 0.1 x 10 ions m, which was measurably 1 SS than outdoor concentrations given in the literature (0.5 x 10 m ). The relatively high aerosol concentrations were a contributing... 

The concentration of radon and its short-lived daughters were measured as well as the unattached fractions of the daughter products and the aerosol concentration. 

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