Emergency hospital admissions for cardiovascular diseases and ambient levels of carbon monoxide: results for 126 United States urban counties, 1999-2005.
BACKGROUND
Evidence on risk of cardiovascular disease (CVD) hospitalization associated with short-term exposure to outdoor carbon monoxide (CO), an air pollutant primarily generated by traffic, is inconsistent across studies. Uncertainties remain on the degree to which associations are attributable to other traffic pollutants and whether effects persist at low levels.


RESULTS
We conducted a multisite time-series study to estimate risk of CVD hospitalization associated with short-term CO exposure in 126 US urban counties during 1999-2005 for >9.3 million Medicare enrollees aged > or =65 years. We considered models with adjustment by other traffic-related pollutants: NO2, fine particulate matter (with aerodynamic diameter < or =2.5 microm), and elemental carbon. We found a positive and statistically significant association between same-day CO and increased risk of hospitalization for multiple CVD outcomes (ischemic heart disease, heart rhythm disturbances, heart failure, cerebrovascular disease, total CVD). The association remained positive and statistically significant but was attenuated with copollutant adjustment, especially NO2. A 1-ppm increase in same-day daily 1-hour maximum CO was associated with a 0.96% (95% posterior interval, 0.79%, 1.12%) increase in risk of CVD admissions. With same-day NO(2) adjustment, this estimate was 0.55% (0.36%, 0.74%). The risk persisted at low CO levels <1 ppm.


CONCLUSIONS
We found evidence of an association between short-term exposure to ambient CO and risk of CVD hospitalizations, even at levels well below current US health-based regulatory standards. This evidence indicates that exposure to current CO levels may still pose a public health threat, particularly for persons with CVD.
Bell
Michelle L
ML
School of Forestry and Environmental Studies, Yale University, Kroon Hall, 195 Prospect St, New Haven, CT 06511, USA. michelle.bell@yale.edu
Peng
Roger D
RD
Dominici
Francesca
F
Samet
Jonathan M
JM
D000368:Aged; D000393:Air Pollutants / Q000009:adverse effects*; D001334:Automobile Driving / Q000706:statistics & numerical data; D002248:Carbon Monoxide / Q000009:adverse effects*; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000706:statistics & numerical data; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D006278:Medicare / Q000706:statistics & numerical data; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014505:Urban Population / Q000706:statistics & numerical data*
D000393:Air Pollutants; D002248:Carbon Monoxide