Toxicity of Ambient Air PM10. A critical review of potentially causative PM properties and mechanisms associated with health effects

High-dose studies indicate that PM: induces oxidative pulmonary inflammation and cardio-respiratory malfunctioning, which could contribute to a disease exacerbation mechanism. PM surface reactivity seems more important than PM mass, thereby prudently suggesting an important role for the anthropogenic (carbonaceous) fine fraction. The limited number of low-dose PM inhalation studies supports this suggestion. Coarse PM may still be important in health effects related to upper airways (like worsening of asthma); however, a role for secondary components (sulfates, nitrates) or ultrafine PM at levels occurring in ambient air have not yet been established.

Evidence that (diesel) exhaust particles play a role in PM health effects is still marginal. Studies have indicated that mixtures of particles and gases like ozone may result in more toxicity than the components separately. Current dosimetry models predict that (older) people with cardio-respiratory diseases may receive increased PM doses upon exposure. Ambient PM toxicity studies have been intensified in recent years. The current limited data, however, have not yet resulted in sufficient evidence to be convincing in indicating: a specifically important and causal role for one form of PM fraction or composition and mechanisms explaining PM health effects in people considered to be at increased risk.