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Chronic Exposure to Ambient Levels of Urban Particles Affects Mouse Lung Development

¹ Experimental Air Pollution Laboratory, Department of Pathology, São Paulo University Medical School, São Paulo, Brazil; and ² Department of Pathology, College of Medicine, University of Vermont, Burlington, Vermont

Correspondence and requests for reprints should be addressed to Thais Mauad, M.D., Ph.D., Department of Pathology, Sao Paulo University Medical School, Av Dr Arnaldo, 455 room 1155, 01246-903 São Paulo SP, Brazil. E-mail: tmauad{at}usp.br

Rationale: Chronic exposure to air pollution has been associated with adverse effects on children's lung growth.

Objectives: We analyzed the effects of chronic exposure to urban levels of particulate matter (PM) on selected phases of mouse lung development.

Methods: The exposure occurred in two open-top chambers (filtered and nonfiltered) placed 20 m from a street with heavy traffic in São Paulo, 24 hours/day for 8 months. There was a significant reduction of the levels of PM_2.5 inside the filtered chamber (filtered = 2.9 ± 3.0 µg/m³, nonfiltered = 16.8 ± 8.3 µg/m³; P = 0.001). At this exposure site, vehicular sources are the major components of PM_2.5 (PM 2.5µm). Exposure of the parental generation in the two chambers occurred from the 10th to the 120th days of life. After mating and birth of offspring, a crossover of mothers and pups occurred within the chambers, resulting in four groups of pups: nonexposed, prenatal, postnatal, and pre+postnatal. Offspring were killed at the age of 15 (n = 42) and 90 (n = 35) days; lungs were analyzed by morphometry for surface to volume ratio (as an estimator of alveolization). Pressure–volume curves were performed in the older groups, using a 20-ml plethysmograph.

Measurements and Main Results: Mice exposed to PM_2.5 pre+postnatally presented a smaller surface to volume ratio when compared with nonexposed animals (P = 0.036). The pre+postnatal group presented reduced inspiratory and expiratory volumes at higher levels of transpulmonary pressure (P = 0.001). There were no differences among prenatal and postnatal exposure and nonexposed animals.

Conclusions: Our data provide anatomical and functional support to the concept that chronic exposure to urban PM affects lung growth.

Key Words: particulate matter • lung development • alveolization • pressure–volume curves • mouse

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Epidemiologic studies have shown adverse effects of traffic-related particulate matter on children's lung growth. What This Study Adds to the Field Mice exposed to traffic-related particulate matter in the pre- and postnatal period develop significant alterations of alveolar structure and lung elastic properties, reinforcing the hypothesis that traffic-related pollution adversely impacts lung growth.