Street Trees not only look great calm traffic but are also great for our health.
Exposure to airborne particulate pollution is associated with premature mortality and a range of inflammatory illnesses, linked to toxic components within the particulate matter (PM).
The effectiveness of trees in reducing urban PM concentrations has been intensely debated.
Modelling studies indicate PM reductions from as low as 1% to as high as ∼60% can be achieved from the planting of street trees on nature strips.
Particulate matter concentrations inside a row of roadside houses, in England, were measured after temporarily installing a kerbside line of young birch trees. Independently, the two approaches identify >50% reductions in measured PM levels inside those houses screened by the temporary tree line.
Electron microscopy analyses show that leaf-captured PM is concentrated in agglomerations around leaf hairs and within the leaf structure. Iron-rich, ultrafine, spherical particles, probably combustion-derived, form a particular hazard to health, especially where the is high concentrations of traffic.