James D. Fenters

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.

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 subchronic exposure to a mixture of O3, SO2, and (NH4)2SO4 on host defenses of mice

Mice exposed 5 h/d, 5 d/wk up to 103 d, to 0.2 mg O3/m3 or to a mixture of O3, 13.2 mg SO2/m3, and 1.04 mg (NH4)2SO4 aerosol/m3 showed significantly greater susceptibility to group C streptococcal aerosol infection relative to filtered air controls. Pulmonary bactericidal activity by alveolar macrophages was significantly enhanced in the lungs of mice exposed to the mixture relative to those inhaling filtered air or O3 alone. The total number and distribution of the free cells lavaged from the lungs, as well as cellular ATP levels, did not change due to the pollutant exposures. In vitro cytostasis in tumor target cells cocultured with peritoneal macrophages from the exposed mice was significantly enhanced in the O3-exposed and in the mixture-exposed treatment groups relative to controls and also in the mixture-exposed relative to the O3-exposed group when a target-to-effector-cell ratio of 1:10 was used; no such effects were observed when this ratio was 1:20. Splenic T-lymphocyte function, as measured by blastogenesis to mitogens and alloantigens, was affected by exposure to O3 and/or the mixture, although the patterns of effects were qualitatively different. Splenic B-cell function and macrophage antigen processing, as measured by the generation of antibody plaque-forming cells, was unaffected by exposure.

Evaluation of host resistance and immune function in cadmium-exposed mice☆

Adult female B6C3F1 mice received distilled water only or water containing 10, 50, or 250 ppm of cadmium chloride (CdCl2) for 90 days. Body weights were measured weekly. On selected days during exposure and on Day 91, Cd tissue concentrations were measured along with changes in primary antibody responses. On Day 91 mice also received a primary challenge with various infectious agents. T- and B-cell mitogenesis, natural killer (NK) cell function, delayed type hypersensitivity (DTH) as well as macrophage bactericidal activity, and phagocytosis were measured. There was no change in body weight gain, organ weights, or in humoral immunity during treatment even though cadmium had accumulated in significant quantities in the tissues. Compared with controls, exposure to cadmium had no statistically significant effect on mortality and mean survival time following primary or secondary challenge with any of the infectious agents. However, there was a dose-related, increased susceptibility to Herpes simplex type 2 virus. T- and B-lymphocyte proliferation was significantly reduced, and macrophage phagocytosis was significantly increased following cadmium exposure. NK cell activity was augmented, but not significantly. Macrophage bactericidal activity and DTH were not significantly altered.

Chronic Exposure to Nitrogen Dioxide

Squirrel monkeys continuously exposed to 1 ppm of nitrogen dioxide (NO2) for 493 days were challenged five times with monkey-adapted influenza A/PR/8/34 virus. All monkeys exposed to NO2 produced serum neutralization antibody within 21 days after virus infection, whereas only one control monkey exposed to filtered air showed comparable response. The differences observed in hemagglutination-inhibition antibody titers, body temperatures, respiratory functions, body weights, and hematological values between the experimental and control monkeys were not significant. Histopathologic examination of lung tissues indicated slight emphysema and thickened bronchial and bronchiolar epithelium only in monkeys exposed to NO2 and challenged with the influenza virus. Transmission election microscopic examination did not disclose any ultrastructural changes that could be attributed to the experimental exposures.

Cytotoxic effects of sulfuric acid mist, carbon particulates, and their mixtures on hamster tracheal epithelium

Abstract Hamster tracheal tissue was used to study the effects of H 2 SO 4 mist, carbon particles, and mixtures of the two on cilia beating frequency and morphological alterations of respiratory epithelium. Hamsters were exposed for 3 hr to 1.1 mg/m 3 H 2 SO 4 (mean size, 0.12 μm) and 1.5 mg/m 3 carbon (mean size, 0.3 μm) particle aerosols alone or in combination. Trachea of animals exposed in vivo to the mixture and held in vivo showed cytotoxic effects in the epithelium that were greater than those produced by either the acid mist or carbon alone. In tracheas of hamsters exposed in vivo and maintained in vitro the damage produced by acid mist—carbon mixture did not differ significantly from that produced by acid mist per se but was greater than that observed after exposure to carbon. Organ cultures of tracheal rings exposed for 3 hr to a 1:10 6 dilution of concentrated H 2 SO 4 and 100 μg/ml carbon produced epithelial damage in vitro similar to that seen in in vivo exposures. The extent of recovery over a period of 72 hr was also studied following different combinations of in vivo and in vitro exposure and/or maintenance.

Immunologic response in vaccinated mice during long-term exposure to nitrogen dioxide

Abstract Swiss albino mice were continuously exposed to either 2 ppm NO2, 0.5 ppm NO2 with daily 1-hour peaks of 2 ppm NO2, 5 days a week, or to filtered air. After a 12-week exposure the mice were vaccinated with A2/Taiwan influenza virus vaccine and the exposures to the various environmental conditions continued for an additional 28 weeks. At 2 weeks after vaccination, the serum neutralizing (SN) antibody titers and SN seroconversion rates were depressed to a various extent in mice exposed to NO2. At 4 weeks after the vaccination and later, the SN antibody titers did not differ significantly among the various groups. Nonvaccinated mice exposed to NO2 for 12 weeks showed a marked decrease in concentrations (mg/ml) of serum IgA, and an increase in serum IgM, IgG1 and IgG2 immunoglobulins. When concentrations of immunoglobulins were adjusted for age of mice after vaccination, a significant elevation was observed in serum IgM, IgG1 and IgG2 of mice exposed to NO2 as compared to controls. During the 2-week period immediately following the vaccination, exposure to NO2 appeared to be the predominant factor influencing the percentage concentration of the four serum immunoglobulins.

The effect of dimethylnitrosamine on host resistance and immunity

Adult female B6C3F1 mice were injected ip with 0.2 ml phosphate-buffered saline (PBS) only or PBS containing 1.5, 3, or 5 mg dimethylnitrosamine (DMN)/kg body wt daily for 14 days. On Day 16, mice were evaluated for changes in immune status as measured by the antibody response to sheep red blood cells (SRBCs), blastogenesis to T- and B-cell mitogens, natural killer (NK) cell function, delayed hypersensitivity, and alveolar macrophage (AM) bactericidal activity; and for changes in host resistance following challenge with various microorganisms or tumor cells. DMN-exposed animals exhibited reduced humoral antibody responses, T-cell mitogenesis, and AM bactericidal activity. B-cell mitogenesis, NK cell activity, and delayed hypersensitivity were increased. Resistance to challenge with Listeria monocytogenes, Trichinella spiralis, or Herpes simplex types 1 or 2 virus (HSV-1, HSV-2) was not significantly impaired, while that to Streptococcus zooepidemicus and influenza virus was significantly reduced. Resistance to B16-F10 tumor challenge was enhanced following DMN exposure. The data show that DMN treatment altered humoral immunity and antibody-mediated host defense mechanisms. Increased NK cell activity may account for the increased resistance to challenge with Herpes virus and B16-F10 tumor cells.

Health effects of long-term inhalation of sulfuric acid mist-carbon particle mixtures.

The effects of exposures of mice 3 hr/day, 5 days/week for up to 20 weeks to 1.4 mg/m/sup 3/ sulfuric acid mist and 1.5 mg/m/sup 3/ carbon particle mixtures as well as 1.5 mg/m/sup 3/ carbon only were investigated. The immunologic state of the animals was examined directly by the primary response of spleen cells after specific antigen stimulation, and indirectly by infectivity studies. A quantitative measure of the effects on the immune system without the antigenic stimulation was obtained by determination of serum immunoglobulin concentrations. Significant alterations of immunoglobulin titer, depression of primary antibody response in spleen cell antigenic stimulation, and decreased resistance to respiratory infection as measured by mortality, survival time, and pulmonary consolidation after 20 weeks of exposure to acid mist and carbon particle mixtures were noted. In addition, bactericidal capacity of lungs was reduced in mice exposed to either sulfuric acid and carbon mixtures or to carbon alone, and subtle morphological changes in the respiratory tract were detected by scanning electron microscopy. Thus the alterations of the defense system suggest that prolonged exposure to low concentrations of sulfuric acid and carbon particle mixtures reduces the ability of mice to resist the secondary stress of respiratory infection.

Effect of exposure to nitrogen dioxide on t and b cells in mouse spleens

Effects of exposure to nitrogen dioxide (NO2) on thymus-derived (T) and bursa-derived (B) cells were studied in albino mice. The mice were exposed continuously 24 hday to 940 μgm3 NO2 and to 188 μgm3 NO2 with daily 3-h peaks 5 daysweek of either 470, 940 or 1880 μgm3 NO2. After 1, 3, 6, 9 and 12 months of exposure, single-cell suspensions were prepared from spleen and incubated with phytohemagglutinin (PHA) or bacterial lipopolysaccharide (LPS). The PHA and LPS responses from mice exposed to NO2 were generally depressed when compared with those in mice exposed for the same time periods to filtered air.