It is not yet clear how exposure to low ambient concentrations of particulates might produce the health effects observed in epidemiological studies and whether certain attributes of particles may be more closely associated to these health effects. The characteristics of particles that are being investigated for their roles in causing health effects include metal content, particle size, and particles as carriers of other toxic compounds (such as gases or biological toxins from bacteria and pollens etc.). Transition metals (such as Fe, Cu, Co, Mn) have been hypothesised to be associated with health effects, because they can cause the.
