Baseline repeated measures from controlled human exposure studies: associations between ambient air pollution exposure and the systemic inflammatory biomarkers IL-6 and fibrinogen.
BACKGROUND
Systemic inflammation may be one of the mechanisms mediating the association between ambient air pollution and cardiovascular morbidity and mortality. Interleukin-6 (IL-6) and fibrinogen are biomarkers of systemic inflammation that are independent risk factors for cardio-vascular disease.


OBJECTIVE
We investigated the association between ambient air pollution and systemic inflammation using baseline measurements of IL-6 and fibrinogen from controlled human exposure studies.


METHODS
In this retrospective analysis we used repeated-measures data in 45 nonsmoking subjects. Hourly and daily moving averages were calculated for ozone, nitrogen dioxide, sulfur dioxide, and particulate matter <or= 2.5 microm in aerodynamic diameter (PM2.5). Linear mixed-model regression determined the effects of the pollutants on systemic IL-6 and fibrinogen. Effect modification by season was considered.


RESULTS
We observed a positive association between IL-6 and O3 [0.31 SD per O3 interquartile range (IQR); 95% confidence interval (CI), 0.080.54] and between IL-6 and SO2 (0.25 SD per SO2 IQR; 95% CI, 0.060.43). We observed the strongest effects using 4-day moving averages. Responses to pollutants varied by season and tended to be higher in the summer, particularly for O3 and PM2.5. Fibrinogen was not associated with pollution.


CONCLUSIONS
This study demonstrates a significant association between ambient pollutant levels and baseline levels of systemic IL-6. These findings have potential implications for controlled human exposure studies. Future research should consider whether ambient pollution exposure before chamber exposure modifies IL-6 response.
Thompson
Aaron M S
AM
Gage Occupational and Environmental Health Unit, University of Toronto, Ontario, Canada.
Zanobetti
Antonella
A
Silverman
Frances
F
Schwartz
Joel
J
Coull
Brent
B
Urch
Bruce
B
Speck
Mary
M
Brook
Jeffrey R
JR
Manno
Michael
M
Gold
Diane R
DR
D000328:Adult; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D015415:Biomarkers / Q000097:blood; D004781:Environmental Exposure; D005260:Female; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D012621:Seasons; D055815:Young Adult
D015415:Biomarkers; C508600:IL6 protein, human; D018836:Inflammation Mediators; D015850:Interleukin-6; D005340:Fibrinogen