Particulate Matter

Over the past decade, time-series studies conducted in many cities have contributed information about the association between daily changes in concentrations of airborne particulate matter (PM) and daily morbidity and mortality. In 2002, however, investigators at Johns Hopkins University and at Health Canada identified issues in the statistical model used in the majority of time-series studies. This HEI Special Report details attempts to address several questions raised by these discoveries.

Dr. Susanne Hering of Aerosol Dynamics Inc and her colleagues set out to design and validate a personal monitoring sampler for particles smaller than 2.5 µm (PM_2.5) that is suitable for subsequent chemical speciation work. The sampler intended to meet the measurement needs for PM_2.5 mass concentration and several of its major constituents including elemental carbon, organic carbon, sulfates, and nitrates.

Dr. Nadziejko and her colleagues at the New York University School of Medicine evaluated the effects of exposing healthy rats to concentrated ambient particles (CAPs) and changes in blood coagulation parameters. The investigators measured platelet number, blood cells counts, and levels of fibrinogen, thrombin-antithrombin complex, tissue plasminogen activator, plasminogen activator inhibitor, and factor VII of rats that were exposed to concentrated New York City particles and filtered air for 6 hours. Blood samples were obtained before and after exposure using an indwelling catheter.

This report describes two studies that measured emissions in roadway tunnels. Dr. Alan Gertler and colleagues at the Desert Research Institute studied particulate matter emissions in the Tuscarora Mountain Tunnel located on the Pennsylvania Turnpike. Dr Daniel Grosjean and colleague at DGA, Inc studied carbonyl emissions in the Tuscarora Mountain Tunnel and in the Caldecott Tunnel in California. The unique environment in tunnel studies allows the investigators to measure emission rates averaged over many vehicles, to determine the physical and chemical character of emissions under ambient conditions, and in some instances to compare current emissions with past emissions at the same location. Both groups of investigators also measured emissions at times when the proportions of gasoline engine vehicles and diesel engine vehicles differed, allowing them to estimate the differences between emissions from the two sources.

Dr. Lester Kobzik and colleagues at the Harvard School of Public Health used a mouse model of asthma to evaluate how inhaling pollutants affects the airways. The mice were sensitized to the allergen ovalbumin, which induces a lung condition in the mice similar to that found in people with asthma. The investigators hypothesized that exposure to concentrated ambient particles (CAPs) plus ozone would cause a synergistic (or greater-than-additive) response in the mice.

Dr Günter Oberdörster and colleagues at the University of Rochester School of Medicine and Dentistry hypothesized that inhaled ultrafine particles induce an inflammatory response in the airways of mice and rats and that animals with preexisting airway inflammatory conditions may be particularly vulnerable. The investigators focused on inhaled carbon and platinum particles because these elements are constituents of particles found in urban atmospheres.

Dr. Gerde and colleagues at the Lovelace Respiratory Research Institute examined the effects of organic compounds in diesel exhaust such as genotoxic polynuclear aromatic compounds (PAHs). The investigators removed most of the organic compounds from diesel exhaust particles and bound radioactive Benzo[a]pyrene (BaP), a type of PAH is known to cause cancer in laboratory animals, to them. They exposed the lower respiratory tract of three dogs to the particles and measured the levels of particle-bound BaP and free BaP released from particles in the peripheral region of the lungs.