Donald E. Gardner

Metal toxicity for rabbit alveolar macrophages in vitro

Abstract A model system in vitro has been employed to assess the relative cytotoxic properties of soluble salts of metals that occur as environmental contaminants. Rabbit alveolar macrophages obtained by lung lavage were exposed in tissue culture for 20 hours to chlorides of Cd2+, Ni2+, Mn2+, and Cr3+ and to ammonium vanadate (VO3−). All metals except Cd2+ produced significant decreases in numbers of cells at concentrations that affected cell viability. Cd2+ was unique in decreasing cell viability without causing cell lysis. In comparing the relative cytotoxicity of the various metals, the number of viable cells remaining after 20 hours was expressed as a percent of the total number of cells in control cultures at 20 hours. Thus, the net number of viable cells was decreased to 50% of control at concentrations of 0.1 m m Cd2+ and VO3− or 4–5 m m Ni2+, Mn2+, and Cr3+. The specific activity of acid phosphatase, a lysosomal indicator enzyme, was also decreased at similar concentrations. Using scanning electron microscopy it was possible to correlate surface alterations with exposure concentrations and cell viabilities so as to suggest a mode and sequence of cell injury which may ultimately lead to cell death.

Size Considerations for Establishing a Standard for Inhalable Particles

The U. S. Environmental Protection Agency (EPA) is required, under the amended Clean Air Act of 1977, to review the scientific basis for the total suspended par-ticulate (TSP) ambient air quality standard and determine whether a revised particulate standard can be promulgated by December, 1980. It is recommended that research to develop information for a size-specific standard should focus on inhalable particulate (IP) matter defined as airborne particles ≤15 jum aerodynamic equivalent diameter. This particle size range relates to that fraction of particulate matter which can primarily deposit in the conducting airways and the gas-exchange areas of the human respiratory system during mouth breathing. It is also recommended that a second particle size cut-point of ≤2.5 yum diameter be incorporated in the air sampling devices, based upon considerations of the chemical composition and the size distribution of airborne particles, and on the predominant penetration of particles ≤2.5 /im diameter into the gas-e...

Protein accumulation in lung lavage fluid following ozone exposure

Abstract Accumulation of protein in lung lavage fluid was used as an indicator of pulmonary damage following exposure of guinea pigs to O 3 . Exposure of animals to 510, 1000, or 1960 μg/m 3 (0.26, 0.51, or 1.0 ppm) of O 3 for 72 hr resulted in significantly elevated levels of lavage fluid protein when compared to that of air controls. This effect was not observed in animals exposed to 196 μg O 3 /m 3 (0.10 ppm). When exposure time was reduced to 3 hr, the O 3 -induced protein accumulation in lavage fluids was undetectable unless the time of lavage was delayed 10–15 hr following the exposure. Under these conditions, elevated protein content was seen in lung lavage fluids obtained from animals exposed to O 3 ranging from 510 to 1470 μg O 3 /m 3 (0.26-0.75 ppm) and a dose relationship between the amount of protein accumulation in the lung and the concentration of O 3 to which the animals were exposed was observed. Vitamin C deficiency did not enhance this O 3 -induced lesion in guinea pigs. The dose relationship has also been confirmed by polyacrylamide gel electrophoresis of the lavage fluids. Lung lavage fluid protein content in animals exposed to 353 μg O 3 /m 3 (0.18 ppm) for 8 hr/day for 5 or 10 consecutive days was not different from that of air controls.

Influence of cadmium, nickel, and chromium on primary immunity in mice☆

The effects of metals on the primary humoral immune system of mice were investigated using a hemolytic plaque technique to determine the number of specific antibody-producing spleen cells. Inhalation of NiCl/sub 2/ for 2 hr resulted in a significant negative linear dose response, the lowest effective concentration tested being 250 ..mu..g of Ni/m/sup 3/. Following a 2 hr aerosol exposure to NiCl/sub 2/, the lung cleared Ni on a first-order kinetics basis. A significant reduction in the number of plaques per 10/sup 6/ cells also was observed with exposure to 190 ..mu..g of Cd/m/sup 3/. Analyses of the data from intramuscularly exposed mice indicated that concentrations greater than or equal to 3.90 ..mu..g of Ni/g body weight (as NiSO/sub 4/) and greater than or equal to 9.25 ..mu..g of Ni/g body weight (as NiCl/sub 2/) resulted in significant immunosuppression. Intramuscular treatments with NiO, CdCl/sub 2/, and CrCl/sub 3/ had no effect at the concentrations tested.

Health effects of short-term inhalation of nitrogen dioxide and ozone mixtures

Abstract The effects of single and multiple daily 3-hour exposures to nitrogen dioxide (NO 2 ) and ozone (O 3 ) mixtures on the resistance to streptococcal pneumonia were investigated. The concentrations of NO 2 ranged from 1.5 to 5.0 ppm, and those of O 3 , from 0.05 to 0.5 ppm. The effect of a single exposure to the mixture was additive, whereby the excess mortality rates were equivalent to those induced by the inhalation of each individual pollutant. The ability to clear inhaled bacteria from the lungs was diminished in mice exposed to the NO 2 O 3 mixtures for 3 hours. This impairment was manifested by the increased frequency of isolation of Streptococcus from the lungs for up to 6 days after the respiratory challenge. Excess mortalities observed after 20 daily 3-hour exposures suggested that a synergistic effect might be present upon repeated inhalation of pollutant mixtures, that made them more effective in reducing resistance to respiratory infection. The results emphasize the need for the establishment of primary air quality standards for short-term NO 2 exposures.

Cytotoxic effects of vanadium on rabbit alveolar macrophages in vitro

Because of the suspected action of lung irritants on pulmonary defense mechanisms, studies were performed in vitro to assess the potential toxicity of vanadium oxides on rabbit alveolar macrophages. Alveolar macrophages obtained by lung lavage and maintained in supplemented Medium 199 were exposed to particulate forms of vanadium pentoxide (V2O5), vanadium trioxide (V2O3), or vanadium dioxide (VO2). Cell viability after a 20-hr exposure was reduced by 50% at approximately 13 μg V/ml as V2O5, 21 μg V/ml as V2O3, and 33 μg V/ml as VO2. Cytotoxicity was determined to be directly related to solubility in the order V2O5 > V2O3 > VO2. When V2O5 was dissolved in media prior to exposure of cells, only about 9 μg V/ml was required to reduce viability by 50% and to decrease total cell numbers by 70% in 20 hr as compared to control cultures. Dissolved V2O5 at 6 μg V/ml also reduced phagocytosis of polystyrene-latex spheres by about 50% as compared to controls after 20 hr. Exposure of cells or cell-free sonicates to dissolved V2O5 at concentrations as high as 50 μg V/ml produced only small changes in the specific activities of lysozyme or β-glucuronidase. However, acid phosphatase in the cell-free system was 70% inhibited by dissolved V2O5 at 1 μg V/ml. These findings suggest that exposure to vanadium oxides may alter alveolar macrophage integrity and function to the detriment of pulmonary defense.

Influence of exposure mode on the toxicity of NO2.

Pollutant gases are subject to a variety of physical and chemical interactions within the atmosphere due to cyclic production and various meteorological influences. In consequence there is generally a diurnal concentration profile for NO2 which consists of peaks of short duration and irregular occurrence superimposed on a low background. Since this variation could play an important role in the toxic effect of NO2, the influences of various exposure modes was studied. Continuous and intermittent exposure studies were used to determine the relationship between biological response and length of exposure to various concentrations of NO2. As the concentration decreased, the slope of the regression line decreased. After adjusting for total differences in the product concentration x time, the response for the two exposure modes was essentially the same. When a constant concentration x time level was employed, a short-term exposure to a high concentration produced a greater effect than exposure to a lower concentration administered over a longer period. Using these curves, the relationship between level of effect, concentration, and time can be determined. Results of these studies indicated that the frequency and amplitude of short-term peaks are of significance even though the exposure is interrupted with periods of zero concentration of NO2.

Cytotoxicity to alveolar macrophages of trace metals adsorbed on fly ash.

Fly ash fractionated into <2-, 2- to 5-, and 5- to 8-μm size ranges and coated on the surface with PbO, NiO, or MnO2 was used to examine the cytotoxic effects in vitro of particle concentration and size to alveolar macrophages (AM). For the various fly-ash samples, statistically significant decreases were demonstrated in viability, total protein, and lactate dehydrogenase activity with increasing concentration and decreasing particle size. The toxic effect was not due to solubilization of the test metals in the media since no toxicity could be demonstrated using particle-free leaches. The percentage of metal adsorbed on the fly ash varied within a narrow range and therefore at a given concentration the AM were exposed to fairly constant amounts of the test elements irrespective of particle size. Thus cytotoxicity is particle size as well as dose dependent and the greater toxicity of the smaller particles appears to be due to their larger surface area.

Effects of repeated exposures to peak concentrations of nitrogen dioxide and ozone on resistance to streptococcal pneumonia

Exposures to various mixtures of nitrogen dioxide (NO2) and ozone (O3) reduced the resistance of mice to streptococcal pneumonia as evidenced by increased mortality rates and shortened survival time. Daily 3-h exposures (5 d/wk) for 2--6 mo to an air pollutant mixture consisting of 940 microgram/m3 (0.5 ppm) NO2 and 196 microgram/m3 (0.1 ppm) O3 were most effective in reducing the resistance to infection. The decrease in resistance to the infection occurred sooner than the mice continued to be exposed to the air pollutants instead of clean air for 14 d after the respiratory challenge with Streptococcus pyogenes aerosol. After 3 mo of exposure to the pollutant mixture, there was some decrease in the ability of mice to clear inhalated streptococci from their lungs. At the same time the total cell count in the fluid lavaged from the lungs of mice was markedly reduced, as were the viability and phagocytic activity of the alveolar macrophages. Exposure to the pollutants combined with challenge with Streptococcus aerosol resulted in marked morphological changes in lung tissues as seen by scanning electron microscopy.

Role of time as a factor in the toxicity of chemical compounds in intermittent and continuous exposures. part II. effects of intermittent exposure

Because of fluctuations in levels of industrial air pollution linked to weather and other factors, a joint U.S.‐Soviet research team studied differences in the effect of time in exposures of air‐breathing animals to controlled varied concentrations of air pollutants. An experimental model environment was used to investigate the effects of nitrogen dioxide (NO2), sulfur dioxide (SO2), and benzene (C6H6) in the air environment of laboratory animals, with both continuous and intermittent exposures. For intermittent exposures the investigators used amounts of toxic gases whose cumulative total equaled the total in the continuous exposures, and intercalated the intermittent exposures with periods of nonpolluted air. To equal the cumulative total concentration of the single continuous exposures over an equal time period, the concentrations of toxic gases were necessarily greater in the intermittent exposures. Part I of this work deals with the effects of continuous exposure to C6 H6 on the central nervous syste...