Formation of cluster mode particles (1-3 nm) in preschools.

This study is the first study that reports the cluster particle (1-3 nm) formation (CPF) in two modern preschools located in Nur-Sultan city of Kazakhstan from October 28 to November 27, 2019. The average particle number concentration and mode diameter values during major CPF events in Preschool I and Preschool II were found to be 1.90 × 106 (SD 6.43 × 106) particles/cm3 and 1.60 (SD 0.85) nm, and 1.11 × 109 (SD 5.46 × 109) particles/cm3 and 2.16 (SD 1.47) nm, respectively. The ultraviolet PM concentration reached as high as 7 µg/m3 in one of the measurement days. The estimated emission rate in Preschool I for CPF events was 9.57 × 109 (SD 1.92 × 109) particles/min. For Preschool II, the emission rate was 7.25 × 109 (SD 12.4 × 109) particles/min. We identified primary cluster particles (CPs) emitted directly from the sources such as candle burning, and secondary CPs formed as a result of the oxidation of indoor VOCs or smoking VOCs. The secondary CPs are likely to be SOA. Indoor VOCs were mainly emitted during cleaning activities as well as during painting and gluing. Indoor VOCs are the controlling factors in the CPF events. Changes in the training and cleaning programs may result in significant reductions in the exposure of the children to CPs.

Exposure to fine, ultrafine particles and black carbon in two preschools in nur-sultan city of kazakhstan.

Children in preschools were studied as an exceptionally vulnerable group to lung diseases due to their immature immune system. Few data are available in the literature addressing the exposure of children in preschools to ultrafine (>10 nm) particles. Exposure of children to fine, ultrafine (10 nm-1 µm) particles and black carbon particles present inside and near two preschools in Nur-Sultan, Kazakhstan, during Fall 2019 was investigated. For Preschool I, the average daily (6 h) indoor (outdoor) PM1 , PM2.5 , and PM10 concentrations over three-week measurements were 15.0 (SD 12.5) µg/m3 , 34.6 (SD 35.1) µg/m3 , and 47.2 (SD 45.2) µg/m3 , respectively. Average indoor UFP concentrations (>10.0 nm) including candle burning events were 5.20 × 103 (SD 8.80 × 103 ) particles/cm3 , with the background UFP concentration to be 3.30 × 103 (SD 1.80 × 103 ) particles/cm3 . In Preschool II, the average UFP concentration (>30.0 nm) in the morning and afternoon was 3.94 × 103 (SD 5.34 × 102 ) and 3.36 × 103 (SD 1.90 × 103 ) particles/cm3 , respectively. Indoor black carbon (BC) concentrations were correlated with the outdoor smoking activity. The major sources of the indoor particles in the preschools were dust resuspension, candle burning, and infiltrated outdoor particles.