A methodology to assess a mobile urban street cleaning activity

An experimental methodology to assess the human exposure of a street cleaning service, performed by a worker handling a leaf blower followed by a water-flushing sweeper, was developed. The sampling campaign was achieved by considering data from road dust, personal air sampling and portable particulate matter detector. The experimental design allowed to obtain qualitative and quantitative information on the chemical composition of road dust, the size and chemical composition of potentially inhalable particles suspended during the street cleaning activity, as well as the duration of the particles' suspension effect. The methodology employed showed: i) the compliance with the occupational exposure threshold values for the total inhalable dust and with the occupational exposure limit values according to national and international regulatory approaches for polycyclic aromatic hydrocarbons (PAH) and inorganic elements; ii) a good agreement of the metals concentrations from the road dust (i.e., calcium, magnesium, potassium, iron, aluminium and sodium) with those from the material collected by the personal air sampler, highlighting the negligible effect of the investigated sweeping activity compared to the material already present on the road; iii) a similar pattern of inorganic elements within the three different monitoring areas; iv) a “dust wave” effect detected by the particle counter lasting no more than 2 min. Thus, such information suggested that performing the urban sweeping activity in the early mornings, when there is a general low PM10-PM2.5 average concentration, low traffic intensity, and the almost absence of passers-by, lead to a low probability of citizens’ exposure.