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
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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.

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    Studies of gases, acids and particles 68 clear response to O; alone have not shown a greater response when O3 was combined with NO,, SO, or CO. Most studies have been carried out in non-asthmatic subjects. There were no significant differences in the response to NO, (500 ppb, 940 g/m) plus SO, in normal and asthmatic subjects when studied in the same way by Linn et al.,!4 although the asthmatic subjects were exposed to a lower SO, concentration (300 ppb, 858 g/m) than the normal subjects (500 ppb, 1430 ug/m?). 6.20 The studies of mixtures of gases, acid aerosols and particles are generally similar in design to the studies of gases outlined above. They have included various combinations of gases plus acid aerosols (H,SO4, HNO3), sulphates, peroxyacetyl nitrate (PAN) and particles (plastic dust + vanadium coating, activated carbon). Details of individual studies are given in Annex 6C. 6.21 In the studies that included O3 this invariably had the dominant effect. There has usually been little response to co-pollutants such as H,SO, when these were given alone. Therefore any interaction would be seen as a greater response to the combination of O3 and the co-pollutant as compared with the response to O3 alone. In most studies the response to O3 was not increased significantly when it was given with co-pollutants, which included PAN and NO,,?2 HNO3,23 H,SO,,24 and H,SO,, NO, or SO>.?> In the study by Stacy ef al. the response to O3 plus H,SO, and O3; plus NH4HSO, was slightly greater than the response to O3 alone but the difference was not statistically significant.?° A small fall in FEV, was seen following a combination of O3 (370 ppb, 740 ug/m3), SO, (370 ppb, 1058 ug/m4) and H,SO, (100 ug/m?) in a study by Kleinman et al.?° but the component gases were not studied separately so whether an interaction occurred is uncertain although the magnitude of response is similar to that expected from O3 alone. A study by Koenig et al.,27 in adolescents with asthma, did not demonstrate any significant changes in lung function after exposure to oxidant gases (O3 plus NO,) with or without either H,SO, or HNO3. The authors suggest?’ that the 90 minute exposure period used in this study was too long and refer to an earlier study® from their laboratory in which effects of acid aerosols had been detected after a 45 minute exposure but not after one lasting 90 minutes. 6.22 A recent study by Linn er al.?? is of particular interest since it examined the repeatability of the demonstrated interaction between O3 and H,SO, within subjects. In the initial study 15 healthy and 30 asthmatic subjects inhaled O3 (120 ppb, 240ug/m°) or H,SO, (100 g/m?) or the combination for 6.5 hours a day on two successive days a week apart. Exposure to H,SO, alone had no effect, whilst O3 alone caused a small but significant reduction in lung function (mean fall in FEV, = 60 and 220 ml in normal and asthmatic subjects, respectively). The findings were greater on the first than on the second exposure day, though the difference was not statistically significant. FEV, fell more in asthmatic patients on all study days (due to exercise-induced bronchoconstriction); the FEV, decrement attributable to O did not differ significantly, however, between asthmatic and non-asthmatic subjects. When O3 was combined with H,SO, the decrement in lung function was increased and the difference from the O3-alone day was of borderline statistical significance in both groups (on average a fall in FEV, of 100 ml could be attributable to O3 and a fall of 189 ml to O3; + H,SO,). The authors then restudied I] subjects (10 asthma, | healthy) with a greater than average response to O3 + H,SO,4 compared to O; alone. On repeat testing the response to the combination of pollutants continued to be greater than the response to O, alone. The effects appeared to be additive rather than synergistic. — 6.23 The response to SO, was not changed when it was inhaled with inert or vanadium-coated plastic dust (aerodynamic diameter 2.2-15 tm) though only 27% by weight of the particles had diameters less than 8.9 um?° or activated carbon (mass median diameter 1.5 um)?! (see Annex 6D). There was no significant difference in the response of healthy subjects to NO, (510 ppb, 959 ug/m3) plus SO, (500 ppb, 1430 g/m) plus sodium chloride and zinc ammonium sulphate aerosols (332 and 25.8 ug/m3, respectively) for 2.25 hours compared to exposure to sodium chloride aerosol alone.+? 6.24 Bronchial biopsy and bronchoalveolar lavage were carried out by Aris ef al.?3 in