The synergetic effect of ambient PM2.5 exposure and rhinovirus infection in airway dysfunction in asthma: a pilot observational study from the Central Valley of California.
BACKGROUND
Elevated levels of particulate matter PM2.5 and rhinovirus infection have been known to exacerbate asthma. However, the combined effect of rhinovirus infection and high PM2.5 has not been investigated.


OBJECTIVE
To investigate the effect of PM2.5 and concomitant rhinovirus infection on airway function in asthma in an area with high PM2.5 concentration.


METHODS
Asthmatics and their matched controls were monitored for lung function, exhaled nitric oxide (eNO) and respiratory symptoms on days with varying levels of PM2.5. As the study was a repeated measure design, repeated clinical findings, and laboratory data were used in the mixed model analysis.


RESULTS
Wheezing and dyspnea in asthmatics were worsened with increasing ambient PM2.5. Increasing PM2.5 decreased FEV1% predicted (-0.51, -0.79 to -0.23) and FEF25-75% predicted (-0.66, -1.07 to -0.24) in subjects with asthma (all P < .01). Rhino viral infection reduced FEF25-75% predicted in subjects with asthma (-11.7, -20 to -2.9). The reductions in FEV25-75 and FEV1 per 10 μg/m(3) increase in ambient PM2.5 were 6% and 5% respectively. A significant interaction was observed between presence of rhinovirus infection and elevated PM2.5 in asthmatics causing a 4-fold decrease in FEF25-75 (P = .01) and a 2-fold decrease in FEV1% predicted values (P = .01) compared with asthmatics with no rhino viral infection.


CONCLUSIONS
Increasing ambient PM2.5 and low temperature independently worsened airway function in asthma. The interaction between rhinovirus and PM2.5 significantly impairs airway function in asthma. A larger sample size study is suggested to investigate these observations.
1Department of Medicine, Pulmonary & Critical Care Division, UCSF Fresno, California, USA.
Joseph
J
Vempilly
Belayneh
B
Abejie
Vivian
V
Diep
Melissa
M
Gushiken
Mamta
M
Rawat
Tim R
TR
Tyner
D000328:Adult; D001249:Asthma / Q000209:etiology* / Q000503:physiopathology*; D002140:California; D016022:Case-Control Studies; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008450:Maximal Midexpiratory Flow Rate; D052638:Particulate Matter / Q000009:adverse effects*; D010850:Picornaviridae Infections / Q000150:complications*; D010865:Pilot Projects; D012229:Rhinovirus
D052638:Particulate Matter