Influence of Community Air Pollution on the Lungs of Mice. Part I: Hyperplasia and Hypertrophy of Type 2 Cells, and Increase in Alveolar Wall Area

Abstract

Colonies of 115 mice each were exposed for 43 days to the ambient outdoor atmosphere of Los Angeles (LA) and Santa Barbara (SB), cities that frequently and infrequently exceed air quality standards, respectively The air monitoring stations closest to the LA and SB vivarial sites provided data on nitrogen dioxide (NO₂), ozone (O₃, sulfur dioxide, carbon monoxide, hydrocarbons, and particulates. All Los Angeles air pollutants were higher than those in Santa Barbara. In particular, the 1-h average of O₃ exceeded the 1985 California state O₃ standard of 0.10 ppm on 21 of the 43 days, versus just 2 for Santa Barbara. The NO₂ mean for LA was 4 times higher than the SB mean, 0.10 versus 0.03 ppm, respectively Image analysis measurements of Type 2 cells and alveolar walls showed the following greater measurements for the LA animals: (a) numbers of Type 2 cells (p - .05); (b) mean area of Type 2 cells (p -.06); (c) alveolar wall area (p -.001); and (d) alveolar wall perimeter (p - .001). In addition, the ratio of the alveolar wall perimeter to the alveolar wall area was decreased for the LA animals (p <.02). No definitive conclusions can be made since the study is the first of its kind. The trends observed were expected in that Type 2 cell numbers and size, and also alveolar wall thickness, were increased relative to the SB animals. Cell and wall increases are well recognized as early responses to injury of both the human and animal lung.

An independent indoor test at a separate vivarial facility was carried out at the same time with measurements of O₃ and NO₂ only There were two groups in the testing, one exposed to room air (RA) and the other in the same room but within a chamber that excluded air pollutants (C). The restricted monitoring, and technical problems with monitoring, obviated comparisons of all four groups and independent conclusions as well. The lung data have been included for the suggestion that the effects of indoor air may be intermediate between those of the two outdoor environments.