The effect of exposure to sulphuric acid on the early asthmatic response to inhaled grass pollen allergen

Abstract

Particulate sulphates, including sulphuric acid (H 2 SO 4 ), are important components of the ambient aerosol in some areas and are regarded as air pollutants with potentially important human health effects. Challenge studies suggest little or no effect of H 2 SO 4 exposure on lung function in asthmatic adults, although some epidemiological studies demonstrate an effect of acid species on symptoms in subjects with asthma. To date, the effect of H 2 SO 4 on allergen responsiveness has not been studied.The effect of exposure to particulate H 2 SO 4 on the early asthmatic response to grass pollen allergen has been investigated in 13 adults with mild asthma. After establishment of the provocative dose of allergen producing a 15% fall in forced expiratory volume in one second (FEV1) (PD15) for each subject, they were exposed to air, 100 mg?m -3 or 1,000 g?m -3 H 2 SO 4 for 1 h, double-blind in random order ¢2 weeks apart, through a head dome delivery system 14 h after each exposure subject underwent a fixed-dose allergen challenge (PD15).Ten subjects completed the study. The mean early asthmatic responses (maximum percentage change in FEV1 during the first 2 h after challenge) following air, 100 mg?m -3 H 2 SO 4 , and 1,000 mg?m -3 H 2 SO 4 , were -14.1%, -16.7%, and -18.4%, respectively. The difference between 1,000 mg?m -3 H 2 SO 4 and air was significant (mean difference: -4.3%, 95% confidence interval (CI: -1.2--7.4%, p=0.013). The difference between air and 100 mg?m -3 H 2 SO 4 approached significance (mean difference: -2.6%, 95% CI: 0.0--5.3%, p=0.051).These results suggest that, at least at high mass concentration, sulphuric acid can potentiate the early asthmatic response of mild asthmatic subjects to grass pollen allergen, although the effect is limited.

Do group responses mask the effects of air pollutants on potentially sensitive individuals in controlled human exposure studies?

“…Of the seven studies that evaluated participants with asthma, only Bylin et al (1988) did not provide information regarding medication status. Of the six studies with information regarding medication status, only the two studies by Tunnicliffe et al (1994Tunnicliffe et al ( , 2001 included participants who required regular use of inhaled corticosteroids. All of the studies that evaluated SO 2 indicated that study participants refrained from using medication for at least 12 h prior to exposure; the other studies that evaluated individuals with asthma did not provide information regarding withholding medication.…”

“…In the study by Tunnicliffe et al (2001), we identified one study participant as potentially sensitive to H 2 SO 4 , based on the magnitude of their response at both 100 and 1000 lg/m 3 H 2 SO 4 (Fig. 4).…”

“…a Notes: BSA -body surface area; FEV 1 -forced expiratory volume in 1 s; ppb -parts per billion; sRAW -specific airway resistance; V E -minute ventilation. aTunnicliffe et al (2001) evaluated H 2 SO 4 ; all other studies evaluated SO 2 .…”

The upper airway response to pollen is enhanced by exposure to combustion particulates: a pilot human experimental challenge study.

“…In general, these studies have found an enhanced allergic response of asthmatics to allergen after exposure to ozone, nitrogen dioxide, and a combination of nitrogen dioxide and sulfur dioxide (Jorres et al 1996;Rusznak et al 1996;Strand et al 1998;Tunnicliffe et al 2001). Tunnicliffe and colleagues (2001) studied the effect of a 1-hr exposure to nitrogen dioxide (100 or 400 ppb) on airway responses to inhaled allergen in eight asthmatic subjects.…”

“…In a recent study on 10 atopic asthmatic adults, particulate sulfuric acid exposure potentiated early asthmatic response to grass pollen allergen (Tunnicliffe et al 2001). Subjects were exposed to sulfuric acid particulates at concentrations of 0.1 and 1.0 mg/m 3 for 1 hr.…”