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Chronic Disease and the Environment
Limitations and Inappropriate Uses of AQS Data with the BRFSS
Although the AQS data can be used with BRFSS data to compare measures of
environmental risk factors and chronic disease, important restrictions
affect how the data should be used and interpreted. These restrictions
include, but are not limited to, the following:
- Analysis levels and temporality. Because the environmental data from the AQS used in this project were collected during the data years 2001–2006 and reported at the metropolitan area-level, they should only be used in conjunction with 2001–2006 BRFSS data
provided via the Chronic Disease and the Environment project. These data
have been re-weighted for metropolitan area-level analysis.
- Exposure assessment. The AQI only approximates the level of pollution
in a metropolitan area. Because it does not measure the extent to which
people are exposed to these pollutants, AQI values can not be used to
identify exposures and risks for specific individuals. Individuals within
a metropolitan area may have substantially higher or lower pollution
exposures due to a number of factors, including variations in individual
activity patterns and physical location within a metropolitan area. The
AQI values for a metropolitan area should not be linked to an individual
respondent from the BRFSS.
- Comprehensiveness. The AQS is not an indicator of overall air quality.
The criteria pollutants included in the AQS are only a subset of the 188
pollutants listed in the Clean Air Act. In addition, for certain
chemicals, ingestion or dermal exposure, as well as indoor sources of
inhalation exposure, may contribute substantially to the total exposures
of concern. The AQS assessment does not address these other means of
exposure.
- Quality. Because air pollution measured in the vicinity of a
particular source may not be representative of the prevailing air quality
of a county or urban area, AQS data may not accurately reflect the air
quality of an entire metropolitan area, particularly in geographically
large metropolitan areas with few AQS monitors. Also, the BRFSS can only
provide annual measures for health risks, necessitating the use of annual
summary statistics for air quality measures.
- Summary measures. A metropolitan area’s daily AQI value is based on
the highest pollutant-specific AQI value for that day. It thus provides
information about the predominant pollutant on a given day and some
information about the levels of the other pollutants (i.e., they each had
an individual AQI less than the daily AQI). However, the AQI does not
fully characterize the contributions of the other criteria pollutants to
air quality or take into account possible adverse effects associated with
combinations of pollutants.
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