title: Response of spontaneously hypertensive rats to inhalation of fine and ultrafine particles from traffic: experimental controlled study.
abstract: BACKGROUND
  Many epidemiological studies have shown that mass concentrations of ambient particulate matter (PM) are associated with adverse health effects in the human population. Since PM is still a very crude measure, this experimental study has explored the role of two distinct size fractions: ultrafine (<0.15 microm) and fine (0.15- 2.5 microm) PM. In a series of 2-day inhalation studies, spontaneously hypersensitive (SH) rats were exposed to fine, concentrated, ambient PM (fCAP) at a city background location or a combination of ultrafine and fine (u+fCAP) PM at a location dominated by traffic. We examined the effect on inflammation and both pathological and haematological indicators as markers of pulmonary and cardiovascular injury. Exposure concentrations ranged from 399 microg/m3 to 3613 microg/m3 for fCAP and from 269 microg/m3 to 556 microg/m3 for u+fCAP.
  
  
  RESULTS
  Ammonium, nitrate, and sulphate ions accounted for 56 +/- 16% of the total fCAP mass concentrations, but only 17 +/- 6% of the u+fCAP mass concentrations. Unambiguous particle uptake in alveolar macrophages was only seen after u+fCAP exposures. Neither fCAP nor u+fCAP induced significant changes of cytotoxicity or inflammation in the lung. However, markers of oxidative stress (heme oxygenase-1 and malondialdehyde) were affected by both fCAP and u+fCAP exposure, although not always significantly. Additional analysis revealed heme oxygenase-1 (HO-1) levels that followed a nonmonotonic function with an optimum at around 600 microg/m3 for fCAP. As a systemic response, exposure to u+fCAP and fCAP resulted in significant decreases of the white blood cell concentrations.
  
  
  CONCLUSIONS
  Minor pulmonary and systemic effects are observed after both fine and ultrafine + fine PM exposure. These effects do not linearly correlate with the CAP mass. A greater component of traffic CAP and/or a larger proportion ultrafine PM does not strengthen the absolute effects.
authors.affiliation: Centre for Environmental Health Research, National Institute for Public Health and the Environment, Bilthoven, The Netherlands. ingeborg.kooter@rivm.nl
authors.forename: Ingeborg M
authors.initials: IM
authors.lastname: Kooter
authors.forename: A John F
authors.initials: AJ
authors.lastname: Boere
authors.forename: Paul H B
authors.initials: PH
authors.lastname: Fokkens
authors.forename: Daan L A C
authors.initials: DL
authors.lastname: Leseman
authors.forename: Jan A M A
authors.initials: JA
authors.lastname: Dormans
authors.forename: Flemming R
authors.initials: FR
authors.lastname: Cassee