Phase 2:

Collection and Testing

In the second phase, the national maps of the risks to health of PM will be used to select locations for particle collection and monitoring.  Maps will be developed that describe the comparative risks of PM across the country for total and cardiovascular mortality and for hospitalization for cardiac and respiratory diagnoses.  Guided by these maps, locations will be selected where the toxicity of PM is clearly distinct.  Dr. Breysse’s team will then travel to these locations and conduct in-depth monitoring using the protocol developed during the first phase and also collect sufficient PM mass for both detailed characterization and the bioassays.  The protocol will give consideration to potential seasonal variation in PM characteristics and toxicity.  The on-site monitoring will cover particle size and number, metals and metal oxides, polycyclic aromatic hydrocarbons (PAHs), sulfates and nitrates, and elemental and organic carbon (EC and OC). 

The collected particles will be tested in the in vitro and in vivo assay battery developed in the first phase.  While we recognize the inherent limitation posed by extrapolation of findings from these assays to human health, we are using the models and assays in a context set by an initial comparative ranking of the human health risks from the PM in the various locations.  The results from the Phase 2 laboratory assays will provide information on the comparative toxicity in well-characterized test systems, providing further insights into toxicity and mechanisms of action.  By using in vitro and in vivo models, we will be able to compare toxicity measures across the assay systems, recognizing that responses, even on a comparative basis, may not be the same in different assay systems.