Effect of nitrogen dioxide and sulfur dioxide on viability and morphology of oak pollen.
BACKGROUND
Nitrogen dioxide (NO2) and sulfur dioxide (SO2) generated by excessive coal combustion and motor vehicle emissions are major air pollutants in the large cities of China. The objective of our study was to determine the effects of the exposure of oak pollens (Quercusmongolica) to several concentrations of NO2 or SO2.


METHODS
Pollen grains were exposed to 0.5 ppm to 5.0 ppm NO2 or SO2 for 4 hours and assessed for morphological damage by field emission scanning electron microscopy and for viability using the trypan blue stain. Morphological changes in pollen grains were also examined after contact with acid solutions at pH 4.0 to pH 7.0.


RESULTS
Exposure to NO2 or SO2 significantly damaged pollen grains at all concentrations investigated, compared to exposure to air; with exposure to concentrations of 0.5 ppm to 2 ppm resulting in fissures or complete breaks in the exine and a concentration of 5 ppm resulting in complete breakdown and release of pollen cytoplasmic granules. Significantly greater amounts of pollen grain were damaged after exposure to SO2 (15.5-20.4%) than after exposure to NO2 (7.1-14.7%). Similarly, exposure to NO2 or SO2 significantly decreased the viability of pollen grains, compared with exposure to air; with SO2 being slightly more detrimental than NO2. Exposure to acid solutions also induced pollen damage, which appeared to be pH-dependent (from 24.6% at pH 6.0 to 55.8% at pH 4.0; compared to 3.8% at pH 7.0).


CONCLUSIONS
Short-term exposure of oak pollen to high concentrations of SO2 or NO2 significantly increases their fragility and disruption, leading to subsequent release of pollen cytoplasmic granules into the atmosphere. These results suggest that heightened air pollution during the oak pollen season may possibly increase the incidence of allergic airway disease in sensitized individuals by facilitating the bioavailability of airborne pollen allergens.
Department of Allergy, Beijing TongRen Hospital, Beijing, China.|Department of Allergy, Capital Medical University, Beijing, China.|Beijing Key Laboratory of Nasal Diseases, Beijing Institute of Otolaryngology, Beijing, China.
Yuhui
Y
Ouyang
Department of Biochemistry, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan.
Zhaojun
Z
Xu
Beijing Key Laboratory of Nasal Diseases, Beijing Institute of Otolaryngology, Beijing, China.
Erzhong
E
Fan
Beijing Key Laboratory of Nasal Diseases, Beijing Institute of Otolaryngology, Beijing, China.
Ying
Y
Li
Department of Allergy, Beijing TongRen Hospital, Beijing, China.|Department of Allergy, Capital Medical University, Beijing, China.|Beijing Key Laboratory of Nasal Diseases, Beijing Institute of Otolaryngology, Beijing, China.
Luo
L
Zhang
D000393:Air Pollutants / Q000633:toxicity*; D000485:Allergens / Q000187:drug effects* / Q000502:physiology; D002470:Cell Survival; D002681:China; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000502:physiology; D009585:Nitrogen Dioxide / Q000633:toxicity*; D011058:Pollen / Q000033:anatomy & histology / Q000187:drug effects* / Q000502:physiology; D029963:Quercus / Q000033:anatomy & histology / Q000187:drug effects* / Q000502:physiology; D013458:Sulfur Dioxide / Q000633:toxicity*
D000393:Air Pollutants; D000485:Allergens; D013458:Sulfur Dioxide; D009585:Nitrogen Dioxide
NO2; SO2; air pollutants; morphological damage; nitrogen dioxide; oak pollen; sulfur dioxide