Objectives and expexted achievements

There is increasing concern about the possible adverse effects of ambient particulate matter (PM) on human health and the specific role of traffic exhaust emissions like diesel exhaust (DE). Over the past forty years, the atmospheric concentrations of traditional pollutants, such as black smoke and sulphur dioxide, have declined significantly as the result of clean air legislation. Recent epidemiology data show adverse health effects at lower PM concentrations than had been previously observed and even at concentrations below national ambient air quality standards and health-based guidelines. The specific role of traffic is largely unknown. However, the volume of road traffic has increased substantially, and despite improvements in engine technology the amount of emissions from automobile engines has also increased significantly, especially the amount of particulates released from diesel power engines. This change in the pattern of pollution has been paralleled by a progressive increase in the proportion of children and adults suffering with asthma and other allergic diseases. Evidence from Japan suggests that individuals living close to major highways are more likely to develop allergies, while in vitro studies have shown an adjuvant effect of diesel particulates on the development of specific IgE directed against airborne allergens. Epidemiological studies have also demonstrated a clear association between cardiovascular morbidity, decreased lung function, increased emergency room admissions and airborne concentrations of PM. Human exposure chamber studies have shown that short-term exposure to diesel exhaust has an acute inflammatory effect on normal human airways, with marked neutrophilia, activation of mast cells and the production of cytokines and chemokines relevant to neutrophil accumulation and activation.

Uncertainties about health effect-relevant PM characteristics and components and their respective sources seriously complicate the process of PM health risk assessment and standard setting as well as the application of cost-effective emission and risk control measures. Whether ambient PM with different compositions and contributions of sources will have different biological activity and toxicity remains to be determined: this is of substantial importance, both from the scientific and regulatory point of view.

Despite these uncertainties, recent regulatory decisions have resulted in new and tighter air quality standards (USA) and limit values (EU) for ambient air PM, forcing larger PM emission reductions than formerly anticipated. In addition, the EU air quality objectives for PM10 are stricter than in the USA air quality standards, resulting in the increased need in the EU for PM emission reductions. For ambient PM it is estimated that emissions in cities will need to be reduced to ~ 50% of the present values. The new PM standards will be revised in 2002 (USA) and 2003 (EU) following a critical review of data from new studies on exposure, air quality, emission and source apportionment and PM toxicity and health effects. In particular, in 2003 the EU will also consider whether the PM Daughter Directive should be adjusted or extended e.g. to control for the fine fraction of PM10 (i.e. PM2.5) or to relate to a source related PM fraction like traffic and motor vehicle exhaust emissions.

OVERALL OBJECTIVES

The overall objectives of the proposed research project are:

• To assess the inflammatory and toxicological potential of ambient suspended particles (collected at places across Europe with contrasts in traffic intensity) in comparison with diesel and gasoline engine particles.
To relate this to the previously demonstrated effects of exhaust on human airways.

• To relate this to epidemiological findings of adverse health effects of ambient particles.

• To overall assess toxicity in-vitro and in-vivo in animals and humans, as well as health effects in epidemiological studies in relation to the physico-chemical characteristics of PM.