title: Short term effect of air pollution, noise and heat waves on preterm births in Madrid (Spain).
abstract: BACKGROUND
  Preterm birth (PTB) refers to delivery before 37 weeks of gestation and represents the leading cause of early-life mortality and morbidity in developed countries. PTB can lead to serious infant health outcomes. The etiology of PTB remains uncertain, but epidemiologic studies have consistently shown elevated risks with different environmental variables as traffic-related air pollution (TRAP). The aim of the study was to evaluate with time series methodology the short-term effect of air pollutants, noise levels and ambient temperature on the number of births and preterm births occurred in Madrid City during the 2001-2009 period.
  
  
  METHODS
  A time-series analysis was performed to assess the short term impact of daily mean concentrations (µg/m(3)) of PM2.5 and PM10, O3 and NO2. Measurements of Acoustic Pollution in dB(A) analyzed were: Leqd, equivalent diurnal noise level and Leqn, equivalent nocturnal noise level. Maximum and Minimum daily temperature (°C), mean Humidity in the air (%) and Atmospheric Pressure (HPa), were included too. Linear trends, seasonality, as well as the autoregressive nature of the series itself were controlled. We added as covariate the day of the week too. Autoregressive over-dispersed Poisson regression models were performed and the environmental variables were included with short-term lags (from 0 to 7 days) in reference to the date of birth. Firstly, simple models for the total number of births and preterm births were done separately. In a second stage, a model for total births adjusted for preterm births was performed.
  
  
  RESULTS
  A total of 298,705 births were analyzed. The results of the final models were expressed in relative risks (RRs) for interquartile increase. We observed evidence of a short term effect at Lag 0, for the following environmental variables analyzed, PM2.5 (RR: 1.020; 95% CI:(1.008 1.032)) and O3 (RR: 1.012; 95% CI:(1.002 1.022)) concentrations and Leqd (RR: 1.139; 95% CI:( (1.124 1.154)) for the total number of births, and besides these, heat temperatures at Lag 1 (RR: 1.055; 95% CI:( (1.018 1.092)) on preterm births in Madrid City during the studied period. In the model adjusted for preterm births, similar RR was obtained for the same environmental variables.
  
  
  CONCLUSIONS
  Especially PM2.5, diurnal noise levels and O3 have a short-term impact on total births and heat temperatures on preterm births in Madrid City during the studied period. Our results suggest that, given the widespread exposure of the population to the environmental factors analyzed and the possible effects on long-term health associated to low birth weight. There is a clear need to minimize this exposure through the decrease of air pollution and noise levels and through the behavior modification of the mothers.
authors.affiliation: National School of Public Health, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Virginia
authors.initials: V
authors.lastname: Arroyo
authors.affiliation: National School of Public Health, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Julio
authors.initials: J
authors.lastname: Díaz
authors.affiliation: National School of Public Health, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Ortiz
authors.affiliation: National School of Public Health, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Rocío
authors.initials: R
authors.lastname: Carmona
authors.affiliation: Research Group on Statistics, Econometrics and Health (GRECS), University of Girona, Girona, CIBER of Epidemiology and Public Health (CIBERESP), Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Sáez
authors.affiliation: National School of Public Health, Instituto de Salud Carlos III, Madrid, Spain. Electronic address: clinares@isciii.es.
authors.forename: Cristina
authors.initials: C
authors.lastname: Linares
mesh_terms: D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D002947:Cities; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D007259:Infrared Rays / Q000009:adverse effects*; D009622:Noise / Q000009:adverse effects*; D052638:Particulate Matter / Q000009:adverse effects* / Q000032:analysis; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology* / Q000209:etiology*; D013030:Spain; D014504:Urban Health
chemical_list: D052638:Particulate Matter