Determining the threshold effect of ozone on daily mortality: an analysis of ozone and mortality in Seoul, Korea, 1995-1999
| Autor: | Jongmin Lee, Sun-Young Kim, Kyu Jeong Ahn, Ho Kim, Yun Chul Hong |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Adult
Male Ozone Adolescent Poisson distribution Biochemistry symbols.namesake chemistry.chemical_compound Oxidants Photochemical Statistics Humans Poisson regression Mortality Child General Environmental Science Mathematics Aged Air Pollutants Korea Generalized additive model Linear model Infant Newborn Infant Middle Aged Models Theoretical Regression chemistry Relative risk Child Preschool symbols Female Threshold model Demography |
| Zdroj: | Environmental research. 94(2) |
| ISSN: | 0013-9351 |
| Popis: | Many studies have shown a positive association between ambient ozone levels and mortality. Typically, these findings are based on models that assume a linear relationship between log mortality and ozone level. In this study, we adapted generalized additive models in which ozone effects are presumed to occur in three different ways: as a simple linear term, as a cubic natural spline term, and as a combination of two linear terms (a threshold model). We applied these models to daily time-series data for Seoul, Korea for the years 1995-1999 and found that the threshold model always fits best among the three. A 2.6% (95% CI: 1.7-3.5) increase of estimated relative risk (RR) in the total mortality associated with a 21.5 ppb increase of daily 1-h maximum ozone lagged by 1 day was observed by linear Poisson's regression. However, a 3.4% (95% CI: 2.3-4.4) increase in the estimated RR was observed using the threshold model. Adjustments for other ambient pollutants caused little changes to these results; 2.4-2.5% in the linear models and 3.2-3.4% in the threshold models. In addition, the largest difference in the estimated RRs of the linear and threshold models was observed in the summer: 1.9% (95% CI: 0.5-3.3) by the linear model and 3.8% (95% CI: 2.0-5.7) by the threshold model. These findings indicate that the conventional time-series Poisson regression model, which dose not take threshold into consideration, could underestimate the true risk of the ozone effect on daily mortality. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect