Toxicity test shows traffic dust is most toxic.

Wessels, A, W Birmili, C Albrecht, B Hellack, E Jermann, G Wick, RM Harrison and RPF Schins. 2010. Oxidant generation and toxicity of size-fractionated ambient particles in human lung epithelial cells. Environmental Science and Technology http://dx.doi.org/10.1021/es9036226.

A simple chemical test that can measure the level of toxicity of dust particles shows that dust generated by road traffic can augment air pollution's already dangerous health effects, mainly heart disease, cancer and respiratory conditions such as asthma and allergies.

The research by German and British researchers predicts quite accurately a particle's potential toxicity. The tests could be used to pinpoit the areas with the most dangerous air pollution so efforts can be made to reduce exposures. Although we know that most types of air pollution are dangerous to human health, until now we have had no reliable screening test that identified particularly hazardous forms of air pollution.

Dust particles – called “particulate matter” (PM) – are a major source of urban pollution. PM is composed of natural and human-made particles of various sizes and compositions. Breathing them in can lead to health problems, such as allergies and asthma.

Scientists know that dust particles from different locations have varying toxicities. However, accurately testing the particles to compare their relative harm is exceedingly difficult.

To get around this difficulty, the researchers took a new approach and tested the oxidant-generating capacity of dust samples. The oxidation capability of chemicals, or how likely they are to modify the components of cells, is strongly associated with various adverse health effects, including cancer and premature aging. 

The researchers tested dust samples of various sizes from four different urban to rural locations in the United Kingdom. Health effects were identified by exposing cells and measuring a range of effects, such as enzyme actions, DNA damage and immune markers.

They found that the oxidant generating capability of the different samples, and thus their toxicity, depended on where the sample was collected but not the size of the particles. The particles with the highest toxicity came from urban areas with heavy traffic.

To test for oxidant generating capacity is relatively simple and requires no animal models. The samples are analyzed in a standard scientific instrument – an Electron Paramagnetic Resonance (EPR) – that gives a measure of the tendency to cause free radical formation.