The investigation of potentially toxic elements (PTE) and particulates absorbed on particle filters exposed to vehicle emissions at road level

The main focus of this study is to determine the levels of potentially toxic elements (PTE) collected from cabin particle filters in and around Cork city. Cabin particle filters are used in motor vehicles to extract toxins from air coming through the ventilation system. A systematic study of pollutants captured over fixed mileages on cabin filters has not previously been reported in literature, despite being an obvious and widespread sample source to measure potential exposure in traffic streams. This study presents quantitative data for a range of analytes from filters harvested from vehicles at set mileages. Different open and closed vessel acid digestion methods were compared to determine which extraction method yields optimum recoveries for a known standard reference material (NIST 1648a Urban Particulate Matter). Analyte concentrations from filter samples were determined using inductively coupled plasma emission spectroscopy (ICP-OES). SEM analysis was used to provide imagery of the filter surface to determine the size of particulates being extracted by the filters. The extraction efficiencies of particle filters were analysed with respect to the following variables: filter manufacturer, car model, varying kilometerages and different filter types. Air purifiers were also placed in the car’s cabins to analyse the concentrations of analytes passing though the ventilation system into the cabin, with and without a particle filter in place. Cycling filters, worn by a cyclist for 500 km intervals, were also tested to analyse the difference between exposures in a vehicle compared to at the roadside. From SEM images obtained there appears to be degradation in the filter structure with use, this degradation affects the filters ability to retain particulates. This degradation has a direct impact on the retention of certain PTEs which are bound to course or fine particulates. It was found that for all analytes, the level of capture increases steadily between 0 and 15, 000 km, followed by a significant increase between 15,000 and 30,000. The capture rate levels off between 30,000 and 45,000 km. Cabin filters with an activated carbon layer (combination filters) demonstrate a significant increase in pollutant capture. The possible health implications of exposure to reported analytes captured on the filters is also discussed due to the prevalence of convertible cars in warmer climates. This study leads to a recommendation of the use of combination filters in all vehicles