title: Air pollution exposure during critical time periods in gestation and alterations in cord blood lymphocyte distribution: a cohort of livebirths.
abstract: BACKGROUND
  Toxic exposures have been shown to influence maturation of the immune system during gestation. This study investigates the association between cord blood lymphocyte proportions and maternal exposure to air pollution during each gestational month.
  
  
  METHODS
  Cord blood was analyzed using a FACSort flow cytometer to determine proportions of T lymphocytes (CD3+ cells and their subsets, CD4+ and CD8+), B lymphocytes (CD19+) and natural killer (NK) cells. Ambient air concentrations of 12 polycyclic aromatic hydrocarbons (PAH) and particulate matter < 2.5 micrometer in diameter (PM2.5) were measured using fixed site monitors. Arithmetic means of these pollutants, calculated for each gestational month, were used as exposure metrics. Data on covariates were obtained from medical records and questionnaires. Multivariable linear regression models were fitted to estimate associations between monthly PAH or PM2.5 and cord blood lymphocytes, adjusting for year of birth and district of residence and, in further models, gestational season and number of prior live births.
  
  
  RESULTS
  The adjusted models show significant associations between PAHs or PM2.5 during early gestation and increases in CD3+ and CD4+ lymphocytes percentages and decreases in CD19+ and NK cell percentages in cord blood. In contrast, exposures during late gestation were associated with decreases in CD3+ and CD4+ fractions and increases in CD19+ and NK cell fractions. There was no significant association between alterations in lymphocyte distribution and air pollution exposure during the mid gestation.
  
  
  CONCLUSIONS
  PAHs and PM2.5 in ambient air may influence fetal immune development via shifts in cord blood lymphocytes distributions. Associations appear to differ by exposure in early versus late gestation.
authors.affiliation: Department of Public Health Sciences, University of California, Davis, USA.
authors.forename: Caroline E W
authors.initials: CE
authors.lastname: Herr
authors.forename: Miroslav
authors.initials: M
authors.lastname: Dostal
authors.forename: Rakesh
authors.initials: R
authors.lastname: Ghosh
authors.forename: Paul
authors.initials: P
authors.lastname: Ashwood
authors.forename: Michael
authors.initials: M
authors.lastname: Lipsett
authors.forename: Kent E
authors.initials: KE
authors.lastname: Pinkerton
authors.forename: Radim
authors.initials: R
authors.lastname: Sram
authors.forename: Irva
authors.initials: I
authors.lastname: Hertz-Picciotto
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D005312:Fetal Blood / Q000166:cytology* / Q000276:immunology; D005333:Fetus / Q000276:immunology*; D005434:Flow Cytometry; D005865:Gestational Age; D006801:Humans; D016131:Lymphocyte Subsets / Q000166:cytology / Q000276:immunology; D008214:Lymphocytes / Q000166:cytology* / Q000276:immunology*; D018811:Maternal Exposure; D011247:Pregnancy
chemical_list: D000393:Air Pollutants