Response of spontaneously hypertensive rats to inhalation of fine and ultrafine particles from traffic: experimental controlled study.
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.
Kooter
Ingeborg M
IM
Centre for Environmental Health Research, National Institute for Public Health and the Environment, Bilthoven, The Netherlands. ingeborg.kooter@rivm.nl
Boere
A John F
AJ
Fokkens
Paul H B
PH
Leseman
Daan L A C
DL
Dormans
Jan A M A
JA
Cassee
Flemming R
FR