Use of TEOM monitors for continuous long-term sampling of ambient particles for analysis of constituents and biological effects

Abstract

Many countries have implemented exposure limits for the concentration of ambient particular matter and do therefore have to monitor their concentration. This could be performed with TEOM monitors (Tapered Element Oscillating Microbalancemonitors) that contain a filter on which particles are collected. These filters are regularly exchanged for new ones. The aim of this study was to test the feasibility of collecting used filters from monitors at different locations and establishing a method to extract particles and then study them with respect to their ability to generate oxidants, their endotoxin content, and ability to activate inflammatory cells. Filters from nine geographically spread locations in Sweden were collected during a 21-month period by local technicians who then sent them to the laboratory where they were extracted and analyzed. The procedure to let local technicians perform the filter exchange and send used TEOM filters to the laboratory worked well. A method was established in which pyrogen-free water was used to extract particles that then were aliquoted and stored for later analysis. Particulate matter (PM 10) from different locations showed both a considerable seasonal and spatial-dependent difference with respect to oxidative potential (oxidize glutathione), endotoxin content, and ability to activate blood monocytes to release interleukin-1β. This study shows that, instead of discarding TEOM filters, they can be collected and extracted so that particles that have been sampled in a standardized way could be analyzed with respect to variables that reflect their toxicity. This could be done at a low cost. In combination with information about the ambient particle concentration, such information could be helpful in the evaluation of differences in the risk of breathing air at various locations.

Monthly variation in masses, metals and endotoxin content as well as pro-inflammatory response of airborne particles collected by TEOM monitors

“…During the summer, the particle levels are relatively low, indicating the importance of analysing also what the particles carry on their surface. These results confirm the previous study (Nosratabadi et al 2019) and are realistic since at this time of the year, when it is warm and humid, conditions are particularly beneficial for bacterial growth (Fig. 1e).…”

“…The earlier study showed that the particle masses peaked in March/April while the oxidative capacity of the particles was at its highest early in the spring and the content of endotoxins and the pro-inflammatory response were highest in late summer. This indicates that the source and composition of the particles are different over the year and may pose different health risks (Nosratabadi et al 2019). In the present study, a more in-depth analysis of TEOM filters collected monthly in three cities in the southeast part of Sweden are presented.…”

“…The TEOM monitors and the collection of particles from the TEOM filter are described in detail in a previous study (Nosratabadi et al 2019). In short, TEOM monitors, which are used worldwide, measure the ambient concentration of particles (PM10 or PM2.5) in real time.…”

“…The two measuring locations in city 1 (Norrköping) showed the highest monthly averages that approached 40 μg/m 3 , while the monthly average in city 2 (Linköping) reached just over 30 μg/m 3 followed by city 3 (Kalmar) with about 25 μg/m 3 . High levels of airborne particles in the spring have for a long time been considered a problem in Nordic countries (Nosratabadi et al 2019). However, the timing of when the highest levels occur during the spring may vary slightly from year to year depending on the weather as can be seen in Fig.…”

“…This study is based on a previous study, where the possibility of using filters from existing TEOM stations for further characterisation of particle properties was explored (Nosratabadi et al 2019). The earlier study showed that the particle masses peaked in March/April while the oxidative capacity of the particles was at its highest early in the spring and the content of endotoxins and the pro-inflammatory response were highest in late summer.…”