With attention increasing regarding the level of air pollution in different metropolitan and industrial areas worldwide, interest in expanding the monitoring networks by low-cost air quality sensors is also increasing. Although the role of these small and affordable sensors is rather supplementary, determination of the measurement uncertainty is one of the main questions of their applicability because there is no certificate for quality assurance of these non-reference technologies. This paper presents the results of almost one-year field testing measurements, when the data from different low-cost sensors (for SO2, NO2, O3, and CO: Cairclip, Envea, FR; for PM1, PM2.5, and PM10: PMS7003, Plantower, CHN, and OPC-N2, Alphasense, UK) were compared with co-located reference monitors used within the Czech national ambient air quality monitoring network. The results showed that in addition to the given reduced measurement accuracy of the sensors, the data quality depends on the early detection of defective units and changes caused by the effect of meteorological conditions (effect of air temperature and humidity on gas sensors and effect of air humidity with condensation conditions on particle counters), or by the interference of different pollutants (especially in gas sensors). Comparative measurement is necessary prior to each sensor’s field applications.
Use of small air quality sensors is very popular during last few years not only in research but also in public sector. From scientific point of view there are possibilities to cover larger area in air quality monitoring by adding small and easy affordable sensors into the reference measurement networks. Such an application of sensors can be very useful for identifying new hotspots or for development of finescale air quality modelling. Nevertheless, there are some limits for real-time outdoor monitoring that must be considered-higher detection limits and weak possibility to deal with non-standard conditions (low temperatures or high air humidity). Therefore, it is very important to be careful with data postprocessing and data interpretation to not get misleading air quality information. Despite a few independent studies and tests of different types of small sensors have been already done (by universities, companies and also by EU Reference Laboratories), the standardized procedure for testing and verifying the data quality has not yet been developed. Sharing the field-measurement experience with different sensors and the data correction methods is therefore crucial. Here we provide results from test measurement of set of electrochemical Cairclip sensors (Cairpol, FR) for SO2, NO2, O3/NO2 and CO during summer (in year 2015) and winter period (2017/2018). The best performance both in comparison between pairs and also between sensors and reference monitors (RM) was found out in combined O3/NO2 Cairclip sensor. Nevertheless, the association of sensor's measured data with sum of O3 and NO2 measured by RM was much better in summer (R2 = 0.88) than in winter period (R2 = 0.31). Based on the known effect of air temperature and humidity on sensors data quality, we further applied some corrections based on dew point deficit (Td deficit). In this way verified data showed significant improvement in relationship with RM data (R2 = 0.88 with improved slope in summer and R2 = 0.58 in winter). Although the quality of sensor's measurement can be influenced by many factors at once and further research is needed to resolve all uncertainties, the simple corrections based on the most critical meteorological factors can be very effective.
BackgroundTo confirm or refute the hypothesis that the morbidity of children (since birth to age 5) born and living in the heavily polluted (PM10, benzo[a]pyrene) eastern part of Ostrava, Czech Republic, was higher than the morbidity of children living in other parts of the city.MethodsTen pediatricians in 5 districts of Ostrava abstracted the medical records of 1878 children born in 2001–2004 to list all illnesses of each child in ICD-10 codes. The children were divided into four groups according to their residence at birth and thereafter. Most of the children in the eastern area were living in the city district Radvanice and Bartovice.ResultsWe report on the incidence of acute illnesses in 1535 children of Czech ethnicity in the first 5 years of life. The most frequent acute illnesses (over 45% of all diagnoses) were upper respiratory infections (URI: J00-J02, J06). In the first year of life, the incidence of URI in 183 children in the eastern area – 372 illnesses/100 children/year – was more than twice as high as in the other 3 areas with a total number of 1352 children. From birth to the age of 5 years, the incidences of pneumonia, tonsillitis, viral infections (ICD-10 code B34) and intestinal infectious diseases were also several times higher in children living in the eastern part of Ostrava. The lowest morbidity was found in children living in the less polluted western part of the city.ConclusionsThe children born and living in the eastern part of the city of Ostrava had from birth through 5 years significantly higher incidence rates of acute illnesses than children in other parts of Ostrava. They also had a higher prevalence of wheezing, atopic dermatitis and allergic rhinitis.
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