CO	carbon monoxide
NO2	nitrogen dioxide
SO2	sulfur dioxide
O3	ozone
PM2.5	particles smaller than 2.5 μm
PM10	particles smaller than 10 μm
ER	excess rate
RR	relative risk
OR	odds ratio
β	regression coefficient
SE	standard error
CI	confidence interval
GLM	generalized linear model
GAM	generalized additive model
DLM	distributed lag model
ICD-9	International Classification of Disease, Revision 9
ICD-10	International Classification of Disease, Revision 10
ICPC-2	Code(s) International Classification of Primary Care, Second Edition
GDP	gross domestic product;