Center for Clean Air Research

Project Title: Simulated Roadway Exposure Atmospheres for Laboratory Animal and Human Studies

Investigators: Jacob D. McDonald (Project PI), Joe L. Mauderly, Melanie Doyle-Eisele, Tim Larson

Institution: Lovelace Respiratory Research Institute, Albuquerque, NM

Objectives

This Project will develop inhalation exposure atmospheres for animal and human laboratory studies, with the primary objective of simulating environments containing key components of roadway emissions and the products of environmental factors that transform them. The exposures will help determine air contaminants that cause or potentiate the toxicity of roadway emissions or confound interpretations based on roadway proximity alone. Our hypotheses are that combined gasoline and diesel motor vehicle emissions toxicity decreases when transformed in the atmosphere. We further hypothesize that background air and nonexhaust roadway emissions (road surface dust, tire and brake wear material, inorganic ions, metals, and ozone) do not contribute significantly to roadway associated cardiovascular morbidity, nor do they potentiate the morbidity associated with roadway emissions. The animal and human toxicology projects will utilize the experimental exposure atmospheres generated in this project to determine the relative potency of different simulated roadway environments, and thus test hypotheses regarding causal components and combinations. The results of the animal studies will be used to select atmospheres for confirmatory human inhalation studies.

Approach

We will develop novel inhalation exposure atmospheres that simulate near roadway and downwind motor vehicle emissions after physical and chemical transformation in the air. Physical aging will be used to convert ultrafine particles that are emitted from the tailpipe at 10-20 nm to agglomerated particles that are 100-150 nm. A third atmosphere will utilize an irradiation chamber to chemically transform motor vehicle emissions. Non-tailpipe roadway emissions will be simulated by a road dust atmosphere with and without motor vehicle emissions. Urban background will be created to include a mixture on non-motor vehicle exhaust that includes ozone, hydrocarbons, metals and inorganic ions (sulfate/nitrate). Urban background potency will be compared against and in combination with motor vehicle emissions. We will define the biological potency of each atmosphere based on lipid peroxidation in ApoE-/-mice (further described in Project 3).

Expected Results

We will elucidate the important characteristics that define toxicity resulting from roadway emissions and their interaction with background air. We expect that fresh whole exhaust containing ultrafine particles and vapor will confer the most potent atmosphere. These results will be confirmed in both rodent and human studies.

Supplemental Keywords: particulate matter, volatile organic compounds, carbon monoxide, ozone, chemical transformation, motor vehicle, road dust