Antioxidant vitamins and prevention of lung disease

Dietary and pharmacological intervention to mitigate the cardiopulmonary effects of air pollution toxicity

BACKGROUND

Exposure to air pollution contributes importantly to excess morbidity and mortality. And while regulatory actions under the "Clean Air Act" have saved millions of lives by improving air quality, there are still millions of people in the U.S. who live in areas where particulate air pollution (PM) levels exceed the U.S. Environmental Protection Agency's National Ambient Air Quality Standards. Therefore, apart from such localities working to attain such standards the protection of the health of public and in particular those at high risk might benefit from interventional strategies that would ameliorate air pollution's adverse health effects. Because inflammation and oxidative stress appear to mediate the health effects of air pollution, one interventional approach to consider is the use of dietary supplementation or medication with anti-inflammatory or antioxidant properties to block the biological responses that initiate the pathophysiological process that culminates in adverse health effects.

SCOPE OF REVIEW

This article reviews the capability of dietary supplementation, such as antioxidant vitamins, polyunsaturated fatty acids, and medications as a strategy to mitigate air pollution-induced subclinical cardiopulmonary effects.

MAJOR CONCLUSIONS

Antioxidant vitamins C and E protect the lungs against short-term ozone and PM exposure. Polyunsaturated fatty acids, such as fish oil and olive oil appear to offer protection against short-term air pollution-induced adverse cardiovascular responses.

GENERAL SIGNIFICANCE

Taking dietary supplements or medications with antioxidant or anti-inflammatory properties has the potential to provide at least partial protection against air pollution-induced adverse health effects in those individuals who are known to be most susceptible, namely those with pre-existing respiratory and cardiovascular diseases. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

Dual role of vitamin C utilization in NO2-induced oxidative stress in lung tissues of mice

Earlier studies with in vitro models have revealed that application of vitamin C can act as a primary NO(2) absorption substrate to contribute to NO(2)-induced cellular injury. In the present study, we showed that the pharmacological application of vitamin C had dual role in lungs of mice exposed to NO(2), with an exacerbated oxidative stress occurring at low concentrations, as indicated by excessive reactive oxygen species production and lipid peroxidation. However, at high concentrations, vitamin C functioned as an antioxidant removing reactive oxygen species and maintaining a reducing status in cells, alleviating NO(2)-induced oxidative toxicity.

The Epithelial Cell in Lung Health and Emphysema Pathogenesis

Cigarette smoking is the primary cause of the irreversible lung disease emphysema. Historically, inflammatory cells such as macrophages and neutrophils have been studied for their role in emphysema pathology. However, recent studies indicate that the lung epithelium is an active participant in emphysema pathogenesis and plays a critical role in the lung's response to cigarette smoke. Tobacco smoke increases protease production and alters cytokine expression in isolated epithelial cells, suggesting that these cells respond potently even in the absence of a complete inflammatory program. Tobacco smoke also acts as an immunosuppressant, reducing the defense function of airway epithelial cells and enhancing colonization of the lower airways. Thus, the paradigm that emphysema is strictly an inflammatory-cell based disease is shifting to consider the involvement of resident epithelial cells. Here we review the role of epithelial cells in lung development and emphysema. To better understand tobacco-epithelial interactions we performed microarray analyses of RNA from human airway epithelial cells exposed to smoke extract for 24 hours. These studies identified differential regulation of 425 genes involved in diverse biological processes, such as apoptosis, immune function, cell cycle, signal transduction, proliferation, and antioxidants. Some of these genes, including VEGF, glutathione peroxidase, IL-13 receptor, and cytochrome P450, have been previously reported to be altered in the lungs of smokers. Others, such as pirin, cathepsin L, STAT1, and BMP2, are shown here for the first time to have a potential role in smoke-associated injury. These data broaden our understanding of the importance of epithelial cells in lung health and cigarette smoke-induced emphysema.

Oxygen therapy at low flow causes oxidative stress in chronic obstructive pulmonary disease: Prevention by N-acetyl cysteine

Exposure to high oxygen concentration produces toxicity by free radical release. We aimed to study: whether stable chronic obstructive pulmonary disease (COPD) patients present an unbalance in the blood redox status; the effect of oxygen administration on blood redox balance; the efficacy of N-acetyl-cysteine (NAC) treatment against the oxidative stress-induced by oxygen administration and whether it is dose-related. To this, 45 stable state III COPD patients were recruited and reduced glutathione (GSH) and oxidised glutathione (GSSG) in erythrocytes and thiol proteins (P-SH) and carbonyl proteins (PC) in both erythrocytes and plasma were evaluated. All COPD patients underwent 2 l/m oxygen for 18 h and NAC at 1200 or 1800 mg/day or placebo for 48 h starting with oxygen administration. Blood samples were collected at basal conditions, after 8 and 18 h of oxygen administration and 24 h after oxygen withdrawal.

RESULTS

COPD patients present an unstable redox equilibrium mainly due to plasma sulphydryl protein depletion. Oxygen administration oxidize erythrocyte GSH, decrease P-SH and increase PC levels in both plasma and erythrocytes. NAC administration counteract the oxidative stress and at the highest dose completely prevent protein oxidation. In conclusion, stable state III COPD patients present an unstable redox balance; long term low flow oxygen administration induces systemic oxidative stress, which is prevented by NAC treatment.

Vitamin C controls the cystic fibrosis transmembrane conductance regulator chloride channel

Vitamin C (l-ascorbate) is present in the respiratory lining fluid of human lungs, and local deficits occur during oxidative stress. Here we report a unique function of vitamin C on the cystic fibrosis (CF) transmembrane conductance regulator (CFTR), a cAMP-dependent Cl channel that regulates epithelial surface fluid secretion. Vitamin C (100 microM) induced the openings of CFTR Cl channels by increasing its average open probability from 0 to 0.21 +/- 0.08, without a detectable increase in intracellular cAMP levels. Exposure of the apical airway surface to vitamin C stimulated the transepithelial Cl secretion to 68% of forskolin-stimulated currents. The average half-maximal stimulatory constant was 36.5 +/- 2.9 microM, which corresponds to physiological concentrations. When vitamin C was instilled into the nasal epithelium of human subjects, it effectively activated Cl transport in vivo. In CF epithelia, previous treatment of the underlying trafficking defect with trimethylamine oxide or expression of WT CFTR restored the activation of Cl transport by vitamin C. Sodium dependency and phloretin sensitivity, as well as the expression of transcripts for sodium-dependent vitamin C transporter (SVCT)-1 and SVCT2, support a model in which an apical vitamin C transporter is central for relaying the effect of vitamin C to CFTR. We conclude that cellular vitamin C is a biological regulator of CFTR-mediated Cl secretion in epithelia. The pool of vitamin C in the respiratory tract represents a potential nutraceutical and pharmaceutical target for the complementary treatment of sticky airway secretions by enhancing epithelial fluid secretion.

Elevated urinary 8-hydroxydeoxyguanosine, a biomarker of oxidative stress, and lack of association with antioxidant vitamins in chronic obstructive pulmonary disease

OBJECTIVE

The purpose of this study was to investigate whether patients with COPD are under oxidative stress and to elucidate the relationship between the level of oxidative stress and antioxidant vitamins.

METHODOLOGY

Nineteen male patients with COPD and 13 age- matched male control subjects were studied. Urinary 8-hydroxydeoxyguanosine (8-OHdG) concentrations were determined using an enzyme-linked immunosorbent assay kit and corrected for creatinine concentrations. Serum levels of vitamin C, alpha-tocopherol, and beta-carotene were determined by high performance liquid chromatography.

RESULTS

The median (interquartile range) 8-OHdG excretion was 8.1 ng/mg (5.3-10.9 ng/mg) in control subjects and 12.2 ng/mg (9.8-15.5 ng/mg) in COPD patients (P < 0.01). Urinary 8-OHdG levels were significantly elevated in ex-smokers in the COPD group compared with ex-smokers in the control group. Urinary 8-OHdG level was negatively correlated with FVC (r = -0.42, P = 0.016), FEV1 (r = -0.49, P = 0.0048), and oxygen tension in arterial blood (r = -0.41, P = 0.0005). No significant differences in antioxidant levels were demonstrated between the two groups. There were no significant correlations between urinary 8-OHdG excretion and the serum concentrations of antioxidant vitamins.

CONCLUSION

The burden of oxidative stress was observed to increase in COPD patients as judged by urinary 8-OHdG. A depletion of antioxidant vitamins in serum was not essential for this phenomenon. Elevated urinary 8-OHdG level may not be attributable to smoking status or to antioxidant vitamins in COPD.

Effects of glutathione S-transferase M1, maternal smoking during pregnancy, and environmental tobacco smoke on asthma and wheezing in children

The rise in childhood asthma prevalence suggests a role for environmental factors in the etiology of this evolving epidemic; however, genetics also influence the occurrence of asthma. Glutathione S-transferase (GST) M1 may play a role in asthma and wheezing occurrence among those exposed to tobacco smoke, as it functions in pathways involved in asthma pathogenesis such as xenobiotic metabolism and antioxidant defenses. Effects of GSTM1 genotype, maternal smoking during pregnancy, and childhood environmental tobacco smoke (ETS) exposure on asthma and wheezing were investigated in 2,950 children enrolled in 4th, 7th, and 10th grade classrooms in 12 Southern California communities. The effects of in utero exposure to maternal smoking on asthma and wheezing occurrence were largely restricted to children with GSTM1 null genotype. Among GSTM1 null children, in utero exposure was associated with increased prevalence of early onset asthma (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.0-2.5), asthma with current symptoms (OR 1.7, 95% CI 1.1-2.8), persistent asthma (OR 1.6, 95% CI 1.1-2.4), lifetime history of wheezing (OR 1.8, 95% CI 1.3-2.5), wheezing with exercise (OR 2.1, 95% CI 1.3-3.3), wheezing requiring medication (OR 2.2, 95% CI 1.4-3.4), and emergency room visits in the past year (OR 3.7, 95% CI 1.9-7.3). Among children with GSTM1 (+) genotype, in utero exposure was not associated with asthma or wheezing. Our findings indicate that there are important long-term effects of in utero exposure in a genetically susceptible group of children.

Effect of antioxidant supplementation on ozone-induced lung injury in human subjects

To determine whether antioxidants can influence human susceptibility to ozone (O(3))-induced changes in lung function and airway inflammation, we placed 31 healthy nonsmoking adults (18 to 35 yr old) on a diet low in ascorbate for 3 wk. At 1 wk, subjects were exposed to filtered air for 2 h while exercising (20 L/min/m(2)), and then underwent bronchoalveolar lavage (BAL) and were randomly assigned to receive either a placebo or 250 mg of vitamin C, 50 IU of alpha-tocopherol, and 12 oz of vegetable cocktail daily for 2 wk. Subjects were then exposed to 0.4 ppm O(3) for 2 h and underwent a second BAL. On the day of the O(3) exposure, supplemented subjects were found to have significantly increased levels of plasma ascorbate, tocopherols, and carotenoids as compared with those of the placebo group. Pulmonary function testing showed that O(3)-induced reductions in FEV(1) and FVC were 30% and 24% smaller, respectively, in the supplemented cohort. In contrast, the inflammatory response to O(3) inhalation, as represented by the percent neutrophils and the concentration of interleukin-6 recovered in the BAL fluid at 1 h after O(3) exposure was not different for the two groups. These data suggest that dietary antioxidants protect against O(3)-induced pulmonary function decrements in humans.

Immunological dysregulation of lung cells in response to vitamin E deficiency

Vitamin E supplementation exhibits anti-inflammatory properties. In the lung, the beneficial effects of vitamin E supplementation on inflammation and infections are well documented, but potential consequences of alimentary vitamin E deficiency to the immunological status of lung cells are not known. It is unclear if temporary vitamin E deficiency exhibits deleterious consequences or can be compensated for by other cellular antioxidants. To address this question, the alimentary vitamin E supply to rats was modified. We then investigated the effects on major histocompatibility molecule (MHC) class II, cell adhesion molecules, interleukin (IL)10, tumor necrosis factor (TNF)alpha in various lung cells. The constitutive expression of MHC class II, intercellular adhesion molecule (ICAM)-1, L-selectin, alpha5-integrin, and CD 166, was demonstrated by flow cytometry on type II pneumocytes, alveolar macrophages, and on co-isolated lymphocytes. Vitamin E depletion increased ICAM-1 and CD166 on type II cells and macrophages, whereas the expression of L-selectin increased only on macrophages. Furthermore, the vitamin E depletion increased the cellular content and secretion of IL10 in type II cells, but decreased the content and secretion of TNFalpha. Vitamin E depletion decreased the cellular vitamin E content, but did not change the activity of antioxidant enzymes (catalase, superoxide dismutase) and the glutathion (GSH)/oxidized glutathion (GSSG) ratio in alveolar type II cells. The shift of protein kinase C (PKC) from the cytosol to membranes indicates that a PKC-dependent signaling pathway may be involved in the change of the immunological status of type II cells. All these effects were reversed by vitamin E repletion. In summary, these results are clearly compatible with the view that a temporary vitamin E deficiency induces a reversible immunological dysregulation in alveolar type II cells and lung macrophages. This deficiency might predispose the lung to develop acute or chronic inflammation.

Dietary antioxidants and ozone-induced bronchial hyperresponsiveness in adults with asthma

Ozone exposure aggravates asthma, as has been demonstrated in both controlled exposures and epidemiologic studies. In the current double-blind crossover study, the authors evaluated the effects of dietary antioxidants (i.e., 400 IU vitamin E/500 mg vitamin C) on ozone-induced bronchial hyperresponsiveness in adult subjects with asthma. Seventeen subjects were exposed to 0.12 ppm of ozone or to air for 45 min during intermittent moderate exercise. Bronchial hyperresponsiveness was assessed with 10-min sulfur dioxide (i.e., 0.10 ppm and 0.25 ppm) inhalation challenges. Subjects who were given dietary antioxidants responded less severely to sulfur dioxide challenge than subjects given a placebo (i.e., forced expiratory volume in the 1st sec: -1.2% vs. 4.4%, respectively; peak flow: +2.2% vs. -3.0%, respectively; and mid-forced expiratory flow: +2.0% vs. -4.3%, respectively). Effects were more pronounced when subjects were grouped by response to sulfur dioxide at the screening visit. The results suggest that dietary supplementation with vitamins E and C benefits asthmatic adults who are exposed to air pollutants.

Association of smoking with serum and dietary levels of antioxidants in adults: NHANES III, 1988-1994

OBJECTIVES

This study examined the association of smoking with serum levels and dietary intakes of antioxidants in a nationally representative sample.

METHODS

This study classified 7873 apparently healthy adults aged 17 to 50 years from National Health and Nutrition Examination Survey III (NHANES III) data as nonsmokers or as smokers if their serum cotinine levels were either lower than 14 ng/mL or 14 ng/mL or greater, respectively. SUDAAN software was used for the statistical analysis.

RESULTS

Smokers of both sexes had significantly (P < .001) lower serum levels of vitamin C, alpha-carotene, beta-carotene, beta-cryptoxanthin, and lutein/zeaxanthin. Reduction in the serum vitamin E, lycopene, and selenium levels in smokers was slight. Smokers also had significantly lower dietary intakes of vitamin C and beta-carotene. A significant (P < .001) inverse relation was found between serum vitamin C and beta-carotene levels and cotinine levels independent of diet effect, and a positive relation (P < .001) was found between serum levels and dietary intakes.

CONCLUSIONS

Antioxidants appear to have differing declines in serum levels as a result of reduced dietary intakes and the effects of smoking.

Differences and trends in antioxidant dietary intake in smokers and non-smokers, 1980-1992: the Minnesota Heart Survey

PURPOSE

Differences and secular trends in dietary antioxidant vitamin intake (vitamins E, C, and beta-carotene) in current non-smokers, light smokers, and heavy smokers were examined as part of the Minnesota Heart Survey.

METHODS

Three cross-sectional surveys were conducted in adults ages 25-74 years in 1980-82 (N = 1682), 1985-87 (N = 2326), and 1990-92 (N = 2487). Dietary information was obtained from a 24-hour dietary recall. Smoking was assessed through self-report. Intakes were adjusted for age, energy intake, body mass index, education level, and exercise level (vitamins E, C and beta-carotene).

RESULTS

Antioxidant vitamin intakes were significantly higher in non-smokers than in light (1-20 cig/day) and heavy smokers (>20 cig/day) when all three survey periods were combined. In men, mean vitamin E intake was 9.2 mg, 8.6 mg, and 7.8 mg for non-smokers, light smokers, and heavy smokers, respectively. Results were similar in men for beta-carotene (non-smokers 1408 microg, light smokers 1287 microg, and heavy smokers 1064 microg), and vitamin C (non-smokers 81 mg, light smokers 67 mg, and heavy smokers 56 mg). Women had results of similar magnitude and direction. From 1980-92, secular trends in men showed non-significant increases from 1980-82 to 1990-92 in beta-carotene (+6.1%), while decreases were observed in vitamins E (-1.1%) and C (-2.6%). In contrast, women had large decreases in all antioxidant vitamin intakes: vitamin E (-13%), vitamin C (-18.6%), and beta-carotene (-16.2%).

CONCLUSIONS

Light and heavy smokers had a significantly lower overall mean dietary antioxidant vitamin intake than non-smokers. Over the decade, antioxidant dietary intake remained relatively stable in men and decreased in women in Minneapolis-St. Paul, despite improvements in access to antioxidant rich fruits and vegetables.

Hypothesis for temporal displacement of metabolic and neuronal accommodation in smoking addiction

Using the overlapping criteria of (1) current smoking status and (2) homeostatic accommodation of smoking, the categories of nonsmoker, beginning smoker, smoker, and quitting smoker are structured into a cyclic representation of smoking addiction. This cyclic representation reveals that elimination of homeostatic accommodation of smoking is a critical success factor to the process of becoming a nonsmoker, while the act of stopping smoking is necessary yet insufficient to the success of that process. Homeostatic accommodation is described as having two components: metabolic and neuronal. A hypothesis for temporal displacement of metabolic and neuronal accommodation is presented to explain the behavior of "chippers" (occasional smokers) and adolescent smokers. Recommendations are made for research on the rates of development and dissipation of metabolic and neuronal accommodation of smoking, and for the development of a bimodal therapy that addresses both metabolic and neuronal accommodation and reduces relapse for quitting smokers.

Acute effects of ozone on pulmonary function of cyclists receiving antioxidant supplements

OBJECTIVES

To identify whether acute lung function effects of ozone can be modulated by antioxidant vitamin supplementation.

METHODS

Amateur cyclists (n = 26) were studied in the summer of 1994 in The Netherlands. Repeated lung function measurements were performed with a rolling seal spirometer after training sessions or competitive races on four to 14 occasions. The cyclists were assigned to two study groups. The supplementation group (n = 12) received antioxidant supplements (15 mg beta-carotene, 75 mg vitamin E, and 650 mg vitamin C) once a day for three months. The control group did not receive supplementation. For each subject, lung function after exercise was regressed on the previous eight hour mean ozone concentration. The individual regression coefficients were pooled for each study group and weighted with the inverse of the variance.

RESULTS

The eight hour mean ozone concentration was 101 micrograms/m3 (30 to 205 micrograms/m3). For the supplementation group, there was no effect of ozone on FVC, FEV1, peak expiratory flow (PEF), and maximal mid-expiratory flow (MMEF). For the control group the mean coefficients were negative, except for MMEF. The difference between the groups was 2.08 (95% confidence interval (95% CI) 1.31 to 2.85) ml/microgram/m3 for FVC, 1.66 (95% CI 0.62 to 2.70) for FEV1, 6.83 (95% CI 3.17 to 10.49) for PEF, and 0.42 (95% CI -1.38 to 2.22) for MMEF.

CONCLUSION

The results suggest that antioxidant vitamin supplementation protects against acute effects of ozone on lung function in heavily exercising amateur cyclists.

DNA damage in leukocytes and buccal and nasal epithelial cells of individuals exposed to air pollution in Mexico City

There is an increased interest in using biological markers to monitor individuals for possible exposure to environmental toxicants. Test systems which permit the sensitive detection of DNA damage and DNA repair are critically important in such studies. The single cell gel electrophoresis (SCG) assay is a rapid and a sensitive method for the evaluation of DNA damage at the single cell level, providing information on the occurrence of DNA single-strand breaks and alkali labile sites using alkaline conditions. In this study, the differences in the basal level of DNA damage between young adults from the south (exposed principally to high levels of ozone) and young adults from the north (exposed principally to hydrocarbons and particles) of Mexico City were investigated by the SCG assay using three different cell types (leukocytes and nasal and buccal epithelial cells). We found an increased DNA migration in blood leukocytes and nasal cells from individuals who live in the southern part of the city compared to those living in the northern part; however, no differences were observed for buccal epithelial cells. These results show the feasability of using the SCG assay to evaluate DNA damage in different tissues and its great potential for use in the monitoring of humans potentially exposed to genotoxic pollutants.

Medium and long-term behavioral effects in mice of extended gestational exposure to ozone

CD-1 mice were continuously exposed to ozone (O3) from 6 days before the formation of breeding pairs to Day 17 of pregnancy. The concentrations used were 0, 0.2, 0.4, and 0.6 ppm; the lowest-observed-effect levels for eye irritation and respiratory function are in the range of 0.08-0.2 ppm for both humans and animals (47). Ozone failed to produce significant effects on either reproductive performance, postnatal somatic and neurobehavioral development (as assessed by a Fox test battery) or adult motor activity (including within-session habituation). In social interaction tests performed in the pre-juvenile period (23-25 days) and the juvenile period (43-45 days), social response endpoints were not modified in O3 mice, but exploration and self-grooming showed concentration dependent effects (decrease and increase, respectively). Performance at 84-98 days in an eight-arm radial maze with water reinforcement was initially impaired in O3 mice, but the results were not entirely consistent; e.g., the data failed to show a concentration dependence of the effects. Overall, the data confirm previous results of an experiment with more limited exposure [pregnancy Days 7-17 (6)] by showing that prenatal O3 exposure, even when extended to include a period before the start of pregnancy and the preimplantation phase, does not produce major or widespread somatic and neurobehavioral effects. Some of the results, however, point to subtle or borderline behavioral deficits which deserve to be considered both in further animal experiments and in the assessment of risk to developing humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ascorbic acid supplementation during the inhalation exposure of guinea-pigs to industrial dust on bronchoalveolar lavage and pulmonary enzymes

The aim of this study was to investigate the interaction between ascorbic acid (AA) and inhaled particles separated from the dumped waste of a nickel smelter and refinery. Tricoloured male guinea pigs were exposed in an inhalation chamber to 50 mg kg-1 of < 5 microns particles that mainly consisted of metal oxides. Exposure lasted for 4 weeks (5 days per week and 5 h per day). The drinking water of half of the exposed and half of the control groups was supplemented with 1 g l-1 AA. Each group received 0.4 mmol kg-1 AA in their food. Ascorbic acid supplementation increased the pulmonary AA concentration in both exposed and control groups to the same extent, but in bronchoalveolar lavage fluid the increase was higher in control than in exposed guinea pigs. The number of alveolar macrophages was increased by exposure and AA increased the number only in the exposed group; the acid phosphatase activity of the alveolar macrophages was increased only by AA, and more in the exposed than in the control group. Alkaline phosphatase activity in bronchoalveolar lavage fluid was the same in both supplemented groups, but it was enhanced in the exposed group with a low intake of AA. Effects on lactate dehydrogenase were not consistent. Neither exposure nor AA influenced significantly this enzyme in bronchoalveolar lavage fluid, but in the lung both AA and exposure caused an increase in the activity. The levels were similar in the AA-treated control and exposed guinea pigs.

Air pollution and asthma: molecular mechanisms

Air pollution, in particular that generated by road traffic, is a matter of rising public concern and has been implicated in the worsening of asthma. In this article, the evidence that air pollutants (particularly sulphur dioxide, ozone and nitrogen dioxide) can affect the airways of asthmatic patients is reviewed, and the possible molecular mechanisms that may link air pollution to increased inflammation in the airways are discussed. Airway epithelial cells may respond to oxidant pollutants by the activation of transcription factors, such as nuclear factor kappa B, resulting in increased transcription of genes for certain cytokines, such as interleukin 8 and inflammatory enzymes, such as inducible nitric oxide synthase and cyclo-oxygenase.

The toxicity of air pollution in experimental animals and humans: the role of oxidative stress

Nitrogen dioxide (NO2) and ozone (O3) occur throughout the world as the primary pollutants of urban air. NO2 and O3 oxidize cell membrane lipids and proteins. Inflammatory agents are elaborated from the lung either as a direct result of oxidation or as a consequence of leukocytes recruited into the lung by injury. My hypothesis is that NO2 and O3 initiate or exacerbate chronic lung disease through an inflammatory mechanism which can be reduced by supplementation with greater amounts than those required to alleviate vitamin deficiency symptoms of vitamins C (ascorbic acid) and E (alpha-tocopherol). Children, whose lungs are developing, are the most likely group to benefit from supplementation with vitamins C and E because the adverse effects of inflammation on the developing lung are likely to be greater and the time of exposure is longer than in adults. This hypothesis is in accord with current human and experimental animal data and the chemistry of O3 and NO2 toxicity, and is supported by recent ecological epidemiological studies of persons supplementing their intake of vitamins C and E.