Health Effects of Airborne Particulate Matter and GassesEPA Grant Number: R829215
Title: Health Effects of Airborne Particulate Matter and Gasses
Investigators: Pinkerton, Kent E. , Aust, Ann , Buckpitt, Alan , Kennedy, Ian M. , Lighty, JoAnn S , Veranth, John
Current Investigators: Pinkerton, Kent E. , Aust, Ann , Kennedy, Ian M. , Leppert, Valerie , Veranth, John
Institution: University of California - Davis , University of Utah , Utah State University
Current Institution: University of California - Davis , University of California - Merced , University of Utah , Utah State University
EPA Project Officer: Hunt, Sherri
Project Period: October 1, 2001 through September 30, 2004 (Extended to September 30, 2005)
Project Amount: $833,481
RFA: Health Effects of Particulate Matter (2001) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Nanotechnology , Health Effects , Particulate Matter , Air
Description:The goal of this proposal is to examine the mechanisms of particulate toxicity in the lungs of neonatal rats following short (1-3 day) and long-term (28-day) exposure to iron/soot or coal flyash particles in the presence or absence of ozone. We will specifically examine effects that directly impact on epithelial cells of the neonatal airways, centriacinar regions, and alveoli. Since epithelial cells are the first cells in the respiratory tract to come into contact with inhaled particles, we hypothesize that damage to these cells can serve as a direct and highly sensitive measure of particle toxicity. We hypothesize that epithelial cells lining the transitional zone between the airways and gas exchange regions of the lungs (i.e., the central acinus) are particularly sensitive and play a key role in the initiation and progression of particle-induced pulmonary injury. We further hypothesize that epithelial-particle interactions initiate a cascade of events that underlie the adverse effects associated with inhaled particles. We hypothesize that particle toxicity (in the presence of a transition metal - iron) begins with the depletion of cellular glutathione levels in epithelial cells, thus accentuating cytotoxic events leading to cell death. In turn, cell death begins the process of cellular proliferation. Each of these events impact negatively on the ability of the lungs to translocate and clear particles, thus leading to further irritation and injury. We will test each of these hypotheses using novel approaches to examine epithelial cell structure and function throughout the airways and alveoli.
Approach:Exposure regimens under controlled conditions will be used to define the pattern of injury in the lungs of neonatal rats to iron/soot particles, coal flyash particles and ozone. Exposures will be to particles alone or in combination with ozone. Particle/ozone exposures will be for 3 days (6 hours/day). Particles will be generated using a diffusion flame system to combust fuels. Particle concentration will be carefully controlled to not exceed 250 mg/m3, while the concentration of ozone will be set at 0.20 ppm. This concentration of ozone exceeds the National Ambient Air Quality Standard (NAAQS), but is frequently encountered in many urban areas of the United States as well as around the world. Pulmonary response(s) to exposure will be evaluated immediately after or within 24 hours following the completion of each exposure protocol used.
To establish health effects of particle exposure in the respiratory system, neonatal rats will be examined during two different periods of postnatal development. These ages are 7 to 14 days postnatal age and 28 to 30 days postnatal age. These times have been selected to allow us to determine the effects of particle/oxidant gas exposure during two critical phases of lung development. The lungs of rats 4 to 14 days of age undergo dramatic growth with doubling of lung size every 4 to 6 days accompanied by high levels of cellular proliferation. By 21 to 28 days of age, the rat lungs have ceased to undergo a high level of cellular proliferation but continue to expand as the young animal continues to grow. Exposure to particles and/or gases during these critical windows of lung development may have immediate and lasting adverse effects on the respiratory system. Therefore, we will expose neonatal rats to iron/soot particles freshly generated in the laboratory (University of California, Davis) as well as to coal flyash particles (generated at the University of Utah). Coal flyash particles will be re-aerosolized in our laboratory (UC Davis) using a dry powder generator. The effects of a co-pollutant ozone will also be tested in conjunction with exposure to iron/soot and coal flyash particles. Four exposure scenarios will be tested: (1) filtered air alone (control), (2) iron/soot (freshly generated in a diffusion flame system), (3) iron/soot in combination with 0.20 ppm ozone and (4) 0.20 ppm ozone alone.
To define the potential mechanisms involved in the toxicity of particles in the respiratory tract, novel approaches and state-of-the-art techniques developed in our laboratories at UC Davis and Utah State University will be used. Injury patterns in the lungs of young rats will be evaluated by cellular changes in the airways and alveoli, through the application of morphometric measurements and markers of cellular proliferation, as well as measures of oxidative stress and alterations of bronchoalveolar lavage parameters (i.e., cell numbers, cell differential, protein levels). These studies will be instrumental to determine the actual degree of toxicity for iron and/or soot alone or in combination with simultaneous exposure to ozone. Concurrent studies will be done in a human epithelial cell culture system to define the mechanisms of iron/soot particle toxicity at the cellular level.
Neonatal exposure to iron/soot (or coal flyash) and ozone using an acute time frame (i.e., 3 days) from 4 to 7 days of age, as well as a subchronic time frame (i.e., 28 days) will allow us to examine animals at 28 to 30 days of age. Animals will be examined within 24 hours following exposure as well as at 28 to 30 days of age. These timepoints will allow us to determine immediate as well as persistent, lingering effects of particle/ozone exposure. Biological endpoints to be measured include cell viability, proliferation, oxidative stress (lipid peroxidation, protein oxidation, DNA damage, glutathione, glutathione-S-transferases, and cytochrome P450), and histopathology. The effects of co-exposure of particles with ozone will also be examined to determine the potential for inter-active effects in what should constitute a better simulation of "real-world" exposure conditions.
Studies in human epithelial cell culture systems will allow us to determine the potential effects of particles containing iron at the cellular and molecular level. The bioavailability of iron from iron-containing particles generated will be determined by in vitro iron mobilization using citrate and ferritin induction in human lung epithelial cells (A549). Molecular mechanisms of induction of proinflammatory mediators, such as interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-alpha) will also be explored.