Health effects of exposures to mixtures of air pollutants / Advisory Group on the Medical Aspect of Air Pollution Episodes.

  • Great Britain. Advisory Group on the Medical Aspects of Air Pollution Episodes
Date:
1995
Catalogue details

Licence: Open Government Licence

Credit: Health effects of exposures to mixtures of air pollutants / Advisory Group on the Medical Aspect of Air Pollution Episodes. Source: Wellcome Collection.

    61/140 (page 51)
    caused by the highest allergen challenge was significantly increased by O3, from 10% to 28%. In subjects with allergic rhinitis, only the reduction in FEV, was evaluated; this also increased significantly, from 1% to 8%. No significant effects of allergen challenge were found in the healthy subjects. Ozone was also found to significantly decrease the PC 3 )FEV, value for methacholine in the asthmatic subjects, but not in those with rhinitis. No significant correlations were found between the responses of subjects in terms of the O3-induced changes in responsiveness either to allergen or to methacholine, or the O3-induced changes in lung function. 5.47 This study 3° had an improved study design compared with that of Molfino et al. 35 with the O3 and control treatments randomised, a longer time period between treatments, and an increased number of subjects. It is also possible to compare the effects of allergen challenge following O3 not only with those following filtered air, but also with those on the third day, when only an allergen challenge was performed: the results were generally consistent. The lack of a correlation between O3-induced changes in lung function and allergen responsiveness is consistent with the assumption that the latter is more closely linked to inflammatory changes induced by O; and also with recent suggestions that these are not associated with lung function changes. 5.48 This study provides strong support for the assertion that O3 exposure can increase allergen responsiveness. However, the O3 concentration used was high, and has only ever been recorded in the UK in the exceptional summer of 1976. More studies are needed at realistic O3 concentrations. 5.49 The effect of O3 on response to allergen has also been examined with nasal antigen challenge. Twelve subjects with a history of seasonal allergic rhinitis were exposed while at rest to 500 ppb O; (1000 ug/m3) or filtered air for 4 hours. This was followed by nasal challenge with varying levels of either grass or ragweed antigen.3’ There were no significant effects of O3 pre-exposure on the severity of self-recorded symptoms of rhinorrhoea, sneeze or chest tightness in response to antigen challenge. However, this concentration of O3 was sufficient, in the absence of antigen challenge, to increase the severity of lower respiratory tract symptoms, and to cause an inflammatory response in the nose, with an increased numbers of eosinophils and neutrophils recovered in nasal lavage. Since the O3 concentrations in this study were well above those recorded in the UK, and are clearly sufficient to have a significant impact on the nose without antigen challenge, their relevance to the hypothesis that O,; may alter susceptibility to nasal challenge with aeroallergens at ambient UK levels is limited. This type of study needs to be repeated at lower concentrations of ozone. 5.50 A recent study?8 used a ‘split nose’ design to investigate the effects of O; exposure on subsequent inflammatory responses to allergen exposure, by applying allergen to one nostril, and saline to the other. The authors suggest that nasal responses to O3 can be used as a surrogate for its effects on bronchial mucosal inflammation in asthmatic subjects. The study involved exposure of 10 allergic asthmatic subjects, who were sensitive to house dust mite, to clean air or 400 ppb O3 (800 ug/m?) for 2 hours while at rest; exposures were separated by at least 4 weeks. Nasal lavage was performed before exposure, immediately after exposure, and then after subsequent nasal allergen/saline challenge. Allergen doses were increased in ten-fold steps until a standard level of symptom severity was reached; in 5 of the 10 subjects this required 1/10 of the dose after pre-exposure to O3 rather than clean air. There was evidence that O3 pre-exposure increased the influx of eosinophils and neutrophils resulting from allergen challenge, even though the allergen dose used was lower in half the subjects. Data from the control nostril indicated that O; alone also had inflammatory effects, with increased eosinophil and neutrophil influx being detected. 5.51 The effect of prior exposure to NO, on response to nasal allergen challenge has recently been reported.2? Exposure to allergen after either air or NO, (400 ppb, 752 ug/m3; for 6 hours) significantly increased mast cell tryptase in nasal lavage fluid from patients with a history of seasonal allergic rhinitis. However, a significant increase in eosinophil cationic protein in response to allergen was only observed when the prior 5]