Dr. George Jakab and associates the Johns Hopkins University School of Public Health examined the effects of inhaled formaldehyde, an airway irritant that is part of motor vehicle emissions, on alveolar macrophages. The investigators exposed mice to varying levels of formaldehyde alone or to formaldehyde mixed with carbon black particles. Carbon black particles were chosen because of their similarity to combustion derived particles. Different alveolar macrophage functions were evaluated using two assays. First, the investigators measured the ability of alveolar macrophages to kill the bacteria staphylococcus aureus. Second, the investigators measured the ingesting, or phagocytic, capacity of the macrophages. Chemical analyses of the interactions between formaldehyde and carbon black particles also were conducted to determine the amount of formaldehyde potentially available for interacting with lung cells.