BC activity-concentration and contribution

For this study, 30 volunteers participated and around 70% of the subjects were sampled twice, registering a total of 12329- 5 min observations. Activities from the TAD were categorized in five groups including home, work, in-transit, other indoors and outdoors activities (Table VIII-1). Data showed a positive skewed distribution, however the data was discussed considering the GM data. Average individual exposure concentration was 1481 ng m^-3 values, and was similar to the BC concentration (1300 ng m^-3)obtained by (Delgado-Saborit, 2012) which sampling conditions were personal exposure measured to subjects who were student or office workers from the university of Birmingham UK .

196 The lowest average exposure (24 hours) for a subject was 302 ng m^-3. This subject spent most of the time at home and used the microwave to heat food, kept the windows closed and mainly worked on the computer. On the contrary, the highest average exposure concentration was (4110 ng m^-3) where the subject spent a lot of time outdoors and visited a pub and other indoor microenvironments. In general, across all subjects and microenvironments, the highest average BC concentration was obtained during commute (2753 ng m^-3) followed by other indoor and outdoor concentrations (1912 and 1928 ng m^-3 respectively). In light of the fact that the primary source of BC is combustion, our results are in agreement with previous findings that report higher concentration during transport commute (Apte et al., 2011, Dons et al., 2011, Dotse et al., 2012, Dons et al., 2012, Buonanno et al., 2013b). The lowest average concentrations were registered while subjects spent time at work (1292 ng m^-3) and home (1056 ng m^-3). Concentrations were close to the results obtained by (Dons et al., 2012) of 1077 and 1360 ng m^-3 for work and home respectively.

Table VIII-1 Summary of BC (ng m^-3) concentrations across various microenvironments (N= 5-min observation).

Microenvironment N Mean SD Min Max GM

Home 8242 1742 2113 32 34454 1056

Work 2677 1695 2125 136 47405 1290

Other indoor 552 6960 30941 136 359287 1912

In-transit 788 5652 9309 120 103960 2753

Outdoor 70 3152 4552 600 28048 1928

The commute concentrations were higher for volunteers using the bus (GM=7902 ng m^-3) (Table VIII-2) and the exposure concentrations for bus were similar to reported results in the literature - 6575 ng m^-3 (Dons et al., 2012), 3800 ng m^-3 (Buonanno et al.,

197 2013b) and 3500 ng m^-3 (Delgado-Saborit, 2012). Car concentrations (4129 ng m^-3) were higher than those reported for Lexington, KY (2200 ng m^-3) (Lee et al., 2010) and Birmingham UK (2800 ng m^-3) (Delgado-Saborit, 2012), but significantly lower than values obtained for India (42000 ng m^-3) (Apte et al., 2011), for Belgium 6432 ng m^-3 (Dons et al., 2012) and for Italy 6445 ng m^-3 (Buonanno et al., 2013b). On the other hand, train concentration were similar to the observed at the train station 2824 and 2838 ng m^-3 respectively, and values was similar to the reported by (Dons et al., 2012) for Belgium with 2394 ng m^-3. However, the BC concentrations in this study were lower than the reported by (Delgado-Saborit, 2012) of 5600 ng m^-3.

Observed concentrations can be influenced by the wind speed, traffic (Dons et al., 2013a, Gramsch et al., 2013), time of the journey (Dons et al., 2011, Lee et al., 2010, Li et al., 2015a), routes (Apte et al., 2011), and the air conditioning system among others. For instance, (Lee et al., 2010) reported that in-vehicle BC and PM2.5

concentrations were higher during the morning and in the working day.

Other indoor microenvironment concentrations were also high, primarily locations visited were GP visits, pubs, shopping centres, shops, and gym, reporting BC level of GM=6034, 6736, 4028, 3241 and 3276 ng m^-3 respectively. Shopping centre concentrations in this study were higher than the reported for Belgium with 2584 ng m^-3 (Dons et al., 2011).

Although the exposure time in some of the microenvironments such as the library, nursery, other indoors, and supermarket(s) was short, concentrations ranged between 1500 to 2500 ng m^-3. Considering for instance GP concentrations which were almost similar to the bus, it is important to confirm the high values by testing acute exposure

198 during the daily activities. Despite the low time spent at the petrol station, subjects were exposed to BC concentrations higher than 10000 ng m^-3 in a 15 min average time exposure. Sources of exposure were mainly the vehicular emissions from several vehicles. While subjects were at home, the exposure to BC (1056 ng m^-3)was lower and values were similar to the reported for Belgium (1223 ng m^-3) (Dons et al., 2011) and Birmingham, UK (950 ng m^-3) (Delgado-Saborit, 2012), but lower than concentrations reported for Ghana -14500 ng m^-3 (Van Vliet et al., 2013).

However, noticeably high BC concentrations were observed in kitchen microenvironment (2175 ng m^-3), which can be attributable to the location of the microenvironments (kitchen room was between the living room and the bathroom).

Previous kitchen measurements reported concentration of 1600 ng m^-3 (Delgado-Saborit, 2012).

Considering no only the location but also the activities developed higher exposure can be observed for subjects traveling by bus (8115 ng m^-3) more than just waiting at the bus stop (1499 ng m^-3). A lower concentration was observed for cycling (2187 ng m^-3) and walking (2236 ng m^-3), these obtained values were similar to the previous study developed in Birmingham, UK with 1300 and 3200 ng m^-3 respectively (Delgado-Saborit, 2012) and lower than the reported values for Belgium with 3175 and 3555 ng m^-3 respectively (Dons et al., 2012). And for Xuhui District, Shanghai which reported BC concentration of 6580 and 5590 ng m^-3 respectively (Li et al., 2015a). Subjects reported to be sitting outside such as in parks, garden, or in front of the house registered an average concentration of 3058 ng m^-3.

199 Table VIII-2 BC concentrations in ng m^-3 grouped by visited places (N=5-min).

Location N Mean SD Min Max GM

Home activities that provide higher concentration were; household activities like DIY, tidying, cleaning, dusting, vacuuming and other activities at home which involve movement (Table VIII-3). It is documented that kitchen activities such cooking, baking, and frying contribute to the high concentrations in this microenvironment (Custódio et al., 2014). Our results are in agreement since the obtained concentration for frying were 2748 ng m^-3, followed by cooking/baking 2053 ng m^-3.

High BC average concentrations can be observed while subjects socialize (6918 ng m

-3). The obtained values are higher than the report for previous studies 1525 ng m^-3