Air pollution and student health

The role of air pollution in asthma

Laboratory studies have clearly shown that inhalation of SO2 by asthmatics can cause a significant degree of wheezing at concentrations considerably lower than those which affect non-asthmatics. Concentrations as low as 0.2 p.p.m. have a significant effect, especially in subjects who are mouth breathing or undergoing heavy exercise. The effects of SO2 appear to be short-lived and not increased by more prolonged exposure (10 min versus 1 hr). WHO air quality guidelines on levels of SO2 have been based to a large extent on these studies and are set at or just below the reported threshold for effects on at risk groups. Thus the 1 hr recommended maximum is 0.16 p.p.m. (350 micrograms/m3). These guidelines have been exceeded in the U.K. on many occasions in the recent past [2] suggesting that asthmatics are at risk in high pollution areas from SO2 induced exacerbations of their asthma. This is particularly true considering that virtually all the laboratory studies have been performed on mild asthmatics. The effects on moderate and severe asthmatics, or those with marked lability of their asthma, could conceivably be seen at much lower concentrations of SO2. Similarly O3 can cause impairment in lung function at concentrations frequently detected in ambient air in the U.K. in both asthmatics and non-asthmatics with no evidence of an increased effect on asthmatics. This appears to be a restrictive rather than an obstructive defect. Ozone can also cause an increase in airways responsiveness to both non-specific bronchoconstrictors such as histamine and specific allergen. Both these effects are likely to be due to the pro-inflammatory effects of ozone and as such could be implicated both in exacerbating asthma through increased airway responsiveness and causing asthma through triggering an inflammatory reaction in the airways. No study has addressed the important question as to whether the incidence of bronchial hyperresponsiveness is increased in areas of high ozone pollution. The results with NO2 in the laboratory are equivocal. On balance the evidence suggests that any effect on asthmatics is likely to be small. Similarly while inhalation studies with acid aerosols have demonstrated some impairment in lung function in asthmatics the changes have been small and of brief duration. Laboratory studies while raising the level of suspicion and allowing dose response curves to be calculated cannot accurately mimic the effects of real air pollution with its combination of interacting circumstances and effects of prolonged exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

Respiratory health and PM10 pollution. A daily time series analysis

This study evaluated changes in respiratory health associated with daily changes in fine particulate pollution (PM10). Participants included a relatively healthy school-based sample of fourth and fifth grade elementary students, and a sample of patients with asthma 8 to 72 yr of age. Elevated PM10 pollution levels of 150 micrograms/m3 were associated with an approximately 3 to 6% decline in lung function as measured by peak expiratory flow (PEF). Current day and daily lagged associations between PM10 levels and PEF were observed. Elevated levels of PM10 pollution also were associated with increases in reported symptoms of respiratory disease and use of asthma medication. Associations between compromised respiratory health and elevated PM10 pollution were observed even when PM10 levels were well below the 24-h national ambient air quality standard of 150 micrograms/m3. Associations between elevated PM10 levels, reductions in PEF, and increases in symptoms of respiratory disease and asthma medication use remained statistically significant even when the only pollution episode that exceeded the standard was excluded. Concurrent measurements indicated that little or no strong particle acidity was present.

Respiratory hospital admissions associated with PM10 pollution in Utah, Salt Lake, and Cache Valleys

This study assessed the association between respiratory hospital admissions and PM10 pollution in Utah, Salt Lake, and Cache valleys during April 1985 through March 1989. Utah and Salt Lake valleys had high levels of PM10 pollution that violated both the annual and 24-h standards issued by the Environmental Protection Agency (EPA). Much lower PM10 levels occurred in the Cache Valley. Utah Valley experienced the intermittent operation of its primary source of PM10 pollution: an integrated steel mill. Bronchitis and asthma admissions for preschool-age children were approximately twice as frequent in Utah Valley when the steel mill was operating versus when it was not. Similar differences were not observed in Salt Lake or Cache valleys. Even though Cache Valley had higher smoking rates and lower temperatures in winter than did Utah Valley, per capita bronchitis and asthma admissions for all ages were approximately twice as high in Utah Valley. During the period when the steel mill was closed, differences in per capita admissions between Utah and Cache valleys narrowed considerably. Regression analysis also demonstrated a statistical association between respiratory hospital admissions and PM10 pollution. The results suggest that PM10 pollution plays a role in the incidence and severity of respiratory disease.

Respiratory disease associated with community air pollution and a steel mill, Utah Valley

This study assessed the association between hospital admissions and fine particulate pollution (PM10) in Utah Valley during the period April 1985-February 1988. This time period included the closure and reopening of the local steel mill, the primary source of PM10. An association between elevated PM10 levels and hospital admissions for pneumonia, pleurisy, bronchitis, and asthma was observed. During months when 24-hour PM10 levels exceeded 150 micrograms/m3, average admissions for children nearly tripled; in adults, the increase in admissions was 44 per cent. During months with mean PM10 levels greater than or equal to 50 micrograms/m3 average admissions for children and adults increased by 89 and 47 per cent, respectively. During the winter months when the steel mill was open, PM10 levels were nearly double the levels experienced during the winter months when the mill was closed. This occurred even though relatively stagnant air was experienced during the winter the mill was closed. Children's admissions were two to three times higher during the winters when the mill was open compared to when it was closed. Regression analysis also revealed that PM10 levels were strongly correlated with hospital admissions. They were more strongly correlated with children's admissions than with adult admissions and were more strongly correlated with admissions for bronchitis and asthma than with admissions for pneumonia and pleurisy.

Effects of ozone on the defense to a respiratory Listeria monocytogenes infection in the rat. Suppression of macrophage function and cellular immunity and aggravation of histopathology in lung and liver during infection

We have investigated the effect of exposure to ozone on defense mechanisms to a respiratory infection with Listeria monocytogenes in the rat. For this purpose rats were continuously exposed to O3 concentrations ranging from 0.25 to 2.0 mg/m3 for a period of 1 week. In this model defense to a respiratory infection with Listeria depends on acquired specific cellular immune responses, as well as on natural nonspecific defense mechanisms. The results confirm earlier findings that show that ozone exposure can suppress the capacity of macrophages to ingest and kill Listeria. Moreover, the results show that ozone can also have a suppressive effect on the development of cellular immune responses to a respiratory Listeria infection, i.e., on T/B ratios in lung draining lymph nodes, delayed-type hypersensitivity responses to Listeria antigen, and lymphoproliferative responses in spleen and lung draining lymph nodes to Listeria antigen. The effects on the specific immune responses are especially overt if exposure to the oxidant gas occurs during an ongoing primary infection. The pathological lesions induced by a pulmonary Listeria monocytogenes infection were characterized by multifocal infiltrates of histiocytic and lymphoid cells. The foci sometimes had a granulomatous appearance. Moreover, the cellularity of the interstitial tissues was increased. In the lung many diffuse alveolar macrophages could be seen in the alveoli. Ozone exposure greatly increased the severity of the lung lesions and also of liver lesions resulting from the pulmonary infection. A prominent finding was the formation of granulomas in ozone-exposed and Listeria-infected rats. This increased severity of the lesions after ozone exposure and subsequent infection with Listeria was presumably not a result of additive ozone and Listeria-induced lesions, but rather an effect of ozone-induced impaired clearance of the bacteria, caused by depressed macrophage activity and cellular immunity. T-cell-dependent immune responses form an important component of defense to respiratory infections with bacteria and viruses, and possibly also to neoplasms. Since our study unequivocally shows an effect on T-cell-dependent immunity, ozone exposure has to be judged potentially hazardous with respect to such challenges of the lung.

Sequential health effect study in relation to air pollution in Bombay, India

A health study done for 4 years in 4129 subjects from 3 urban (high, medium and low according to SO2 levels) and a rural community showed a higher morbidity with raised levels. Initially in the respective 4 areas standardised prevalences (in percent) were: for dyspnoea 7.3, 6, 3.2 and 5.5; for chronic cough 5.1, 2.7, 1.7 and 3.3; for intermittent cough 15.6, 5.8, 0.4 and 3.7 and frequent colds 18.0, 20.8, 12.1 and 11 percent. The diagnosis of chronic bronchitis was done in 4.5, 4.5, 2.3 and 5.0 percent and cardiac disorders 6.8, 4.3, 8.2 and 2.7 percent in respective 4 areas. After 3 years, 55-60% of urban and 44% of rural subjects were reassessed. Several minor symptoms, besides above ones were related closely to the urban air pollutant profile. Increased greenery protected only at lower levels of pollution. Initial lung functions were best in "urban low" area but in all urban areas, yearly declines were larger than in rural subjects. A cross sectional study for effect of slums in 4 areas on 22272 subjects revealed generally higher morbidity in slum residents, particularly in "urban medium" area for frequent colds, cough and dyspnoea. Daily health diaries maintained in 2232 subjects revealed high morbidity in 2 more polluted areas; monthly trends correlated to SO2 and S.P.M. and daily fluctuations with SO2 revealed a threshold between 50 to 100 micrograms/CM/day. There were greater mortality (S.M.R.) in cardiorespiratory and malignant diseases related to pollution. The major factors affecting morbidity were pollution, nutrition, occupation, smoking and age.

The role of air pollution and other factors in local variations in general mortality and cancer mortality

Age-adjusted indices of female cancer mortality and total male mortality in 31 California countries were correlated with air pollution data and with geographic and socioeconomic data from the 1970 United States Census and elsewhere. Air quality was the worst in those countries where socioeconomic status was highest. Cancer mortality showed positive correlations with air pollution levels. Overall male mortality was lower in the affluent but polluted coastal counties. However, when partial correlation coefficients were calculated, controlling for the confounding variables, both overall male mortality and female cancer mortality showed positive correlations with air pollution indices. Stepwise regression analysis produced similar results.

Respiratory damage caused by long-term inhalation of high concentration of sulphur-dioxide in dogs

It has been tried in this study to produce chronic obstructive bronchitis in dogs by exposing them to high concentrations of SO2. The study was extended to 175 days and during that period the animals were exposed to 300-500 ppm SO2 for a total of 435 h. None of the three dogs developed serious respiratory damage. Most of the symptoms were transitory. Histological examinations showed increased number of goblet cells in trachea, main- and lobar bronchi and a slight alteration of the bronchial glands.