The relation between temperature, ozone, and mortality in nine French cities during the heat wave of 2003.
BACKGROUND
During August 2003, record high temperatures were observed across Europe, and France was the country most affected. During this period, elevated ozone concentrations were measured all over the country. Questions were raised concerning the contribution of O3 to the health impact of the summer 2003 heat wave.


METHODS
We used a time-series design to analyze short-term effects of temperature and O3 pollution on mortality. Counts of deaths were regressed on temperatures and O3 levels, controlling for possible confounders: long-term trends, season, influenza outbreaks, day of the week, and bank holiday effects. For comparison with previous results of the nine cities, we calculated pooled excess risk using a random effect approach and an empirical Bayes approach.


RESULTS
For the nine cities, the excess risk of death is significant (1.01% ; 95% confidence interval, 0.58-1.44) for an increase of 10 microg/m3 in O3 level. For the 3-17 August 2003 period, the excess risk of deaths linked to O3 and temperatures together ranged from 10.6% in Le Havre to 174.7% in Paris. When we compared the relative contributions of O3 and temperature to this joint excess risk, the contribution of O3 varied according to the city, ranging from 2.5% in Bordeaux to 85.3% in Toulouse.


CONCLUSIONS
We observed heterogeneity among the nine cities not only for the joint effect of O3 and temperatures, but also for the relative contribution of each factor. These results confirmed that in urban areas O3 levels have a non-negligible impact in terms of public health.
Filleul
Laurent
L
Institut de Veille Sanitaire, Bordeaux, France. laurent.filleul@sante.gouv.fr
Cassadou
Sylvie
S
Médina
Sylvia
S
Fabres
Pascal
P
Lefranc
Agnés
A
Eilstein
Daniel
D
Le Tertre
Alain
A
Pascal
Laurence
L
Chardon
Benoit
B
Blanchard
Myriam
M
Declercq
Christophe
C
Jusot
Jean-François
JF
Prouvost
Hélène
H
Ledrans
Martine
M
D002947:Cities; D004781:Environmental Exposure; D005060:Europe / Q000453:epidemiology; D005602:France / Q000453:epidemiology; D018882:Heat Stress Disorders / Q000453:epidemiology / Q000266:history / Q000401:mortality; D049674:History, 21st Century; D006801:Humans; D007259:Infrared Rays / Q000009:adverse effects*; D009026:Mortality / Q000639:trends*; D010126:Ozone / Q000633:toxicity*; D011634:Public Health / Q000706:statistics & numerical data*; D018570:Risk Assessment; D013997:Time Factors
D010126:Ozone