A large number of studies have been published over the last 15 years demonstrating negative impacts on respiratory and cardiac health in populations exposed to high concentrations of ambient particulate matter (PM).

Whilst the association between the ambient PM concentrations and impaired health has proven remarkably consistent across a large number of studies, the magnitude of the effect varies markedly between different locations. Hence, whilst generally exposure to PM is bad for your health, PM in certain locations appears particularly harmful. One argument that has been developed to explain this discrepancy is that whilst the use of ambient PM concentrations has proven useful in establishing causation with health effects, it is ultimately limited due to its insensitivity to the source and composition of the inhaled particles.

This is important as much of the mass of ambient particles consists of components with low or negligible toxicity, such as elemental carbon, whilst metals and poly aromatic hydrocarbons (PAHs), which contribute minimally to the mass, are known to be particularly toxic.

To address how differences in PM composition, related to source, influence the toxicity of ambient PM, DEFRA are currently sponsoring the Environmental Research Group at King’s College London to compare the composition and biological activity of PM₁₀ samples collected from roadside, urban background and rural sites in the SE of England.

To assess the toxicity of PM samples they will be incubated in models of human respiratory tract lining fluids, the first physical interface encounter by inhaled compounds, and their capacity to drive damaging biological oxidation quantified. This will provide a measure of their oxidative potential, which has been implemented in the capacity of inhaled PM to induce inflammation and tissue injury in the lung.

By comparing the results of these toxicological tests with PM composition, it is hoped the key toxic components of PM can be identified, which may provide better measures of the potential of PM to elicit health effects than mass alone.

Item date 06/05/2008