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Doctoral Degrees (Occupational and Environmental Health)

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    The association of ambient nitrogen dioxide and particulate matter exposure on infant lung function.Ukuzibandakanya kwe-ambient nitrogen dioxide kanye nezinhlayiya ezikubeka egcupheni ukusebenza kwephaphu losana.
    (2022) Muttoo, Sheena.; Jeena, Prakash Mohan.; Naidoo, Rajen Nithiseelan.
    ABSTRACT Background: Vulnerable groups such as infants are particularly susceptible to exposure to air pollutants, including nitrogen dioxide (NO2) and particulate matter with aerodynamic diameter less than 10 microns (PM10), as structural and developmental changes in respiratory physiology are still occurring in-utero and progressively during the first few years of life after birth. Important and sensitive markers of lung growth and development include tidal volume (TV), functional residual capacity (FRC), and lung clearance index (LCI). Objective: This study aimed to determine if short-term exposure windows to air pollutants nitrogen dioxide and particulate matter, induces an acute response in infant lung function (ILF) and if this response is age-sensitive, given the critical period of lung growth and development in the first two years of life. Methods: ILF measures were determined by tidal breathing and multiple breath washout assessments without sedation in infants aged six weeks (n= 70), six (n= 72), twelve (n= 61), and twenty-four months (n=69). In preliminary descriptive analysis (Manuscript I), several risk factors were considered in multivariate models including low birth weight (LBW) and maternal smoking. To assess short-term air pollutant impacts on infant lung function (Manuscript III), individual exposure to NO2 and PM10 (twoweek average preceding the test date) was determined by hybrid modelling combining land use regression and dispersion modelling. These were included in linear mixed models adjusting for the repeated measures design for the outcome measures and an age*exposure interaction was introduced to obtain effect estimates for each age group. Results: In multivariate analyses LBW was associated with a lower TV at 6 weeks (β: -5.99mL (95%CI: -9.59; -2.39)), 6 months (β: -15.02mL (95%CI: -22.48; -7.57)) and 12 months (β: -23,7mL (95%CI: - 35.55; -11.85)), compared to children with normal birthweight. This was similarly observed for LBW and minute ventilation at 6 weeks (β: -157.78mL/min (95%CI: -338.95; 23.38)), 6 months (-β: 325.57mL/min (95%CI: -619.06; -32.08)) and 12 months (β: -527,58mL/min (95%CI: -947,85; - 107,32)), though these observations were less evident at the 24-month age group. Air pollutant exposure-outcome associations assessed by linear mixed models showed reduced tidal volume per unit increase in PM10, as observed at 6 weeks (β: -0.4mL (95%CI: -0.9; 0.0), p=0.065), 6 months (β: -0.5mL (95%CI: -1.0; 0.0), p=0.046) and 12 months (β: -0.3mL (95%CI: -0.7; 0.0), p=0.045). PM10 was related to an increase in respiratory rate and minute ventilation, while a reduction was observed for FRC for the same age groups, though not statistically significant for these outcomes. Such associations were however less evident for exposure to NO2, with inconsistent changes observed across measurement parameters and age groups. 2 Conclusion: From descriptive analyses, low birth weight was the main predictor for low tidal volumes and minute ventilation at 6 weeks, while observed differences were smaller at 12 and 24 months. Exploration of exposure-outcome associations showed that short-term (two-week average) exposure to PM10 results in acute lung function impairments among infants from a low-socioeconomic setting, after adjustment for relevant covariates, while the association with NO2 is less convincing. Iqoqa Isendlalelo: Abantu abasengozini njengabantwana basengcupheni yokuziveza emoyeni ongalungile ofaka initrogen dioxide (NO2) kanye nezinto ezino-aerodynamic diameter engaphansi kuka 10 kumamicrons (PM10), njengoba uhlaka kanye nokukhula koshintsho kumgudu wokuphefumula uyaqhubeka nokwenzeka uphinde undlondlobale ngesikhathi seminyaka embalwa emva kokuzalwa. Okubalulekile nezinto ezibucayi ngokukhula kwephaphu kanye nentuthuko okufaka itidal volume (TV), ifunctional residual capacity (FRC) kanye ne-index yokukhuculula iphaphu. Inhloso Lesi sifundo sihlose ukuthola ukuthi ukuvela isikhathi esifushane emoyeni one-nitrogen dioxide kanye nezinto eziyinhlayiya, ezivamise ukuguqula okungekuhle ekusebenzeni kwephaphu losana nokuthola ukuthi lokhu kuguquka kuhambisana neminyaka ikakhulu njengoba isikhathi sokukhula kwephaphu kanye nokuthuthuka eminyakeni emibili yokuqala emva kokuzalwa kubucayi. Izindlela I-ILF yanquma ngesilinganiso somfutho wokuphefumula kanye nokuphefumula kaningi kokuhluleka kokuvivinywa ngaphandle kwesidambiso osaneni olunamaviki ayisithupha, izinyanga eziyisithupha, eziyishumi nambili kanye nezinyanga ezingamashumi amabili nane. Ukubala isikhathi esincane samandla okungcola komoya ngokwe-ILF, ukuzithola komuntu ngamunye nomoya omubi i-NO2 kanye ne-PM10 (amasonto amabili kulandela usuku lokuhlolwa) kwakhonjiswa imodeli eyingxubevange efaka ukwehla kokusetshenziswa komhlaba kanye nemodeli yokuhlakazeka. Konke lokhu kwafakwa esifanekisweni esixubile sokulinganisa isilinganiso soqopho lwemiphumela kanye nokuveza ukuba sesimweni sokuhlangana nomphakathi kwethulwa ukuthola umphumela wokuhlawumbisela ngokweminyaka iqoqo ngalinye. Imiphumela Isingcolisi moya somphumela wokuba sengcupheni kubala ukuhlangana ngokwesilinganiso esixubile esitshengise ukwehla kuTV ngokwama-unit sakhula kuPM10, njengoba kuhloliwe kumaviki ayisithupha (B-0.4ml (95%CI-0.9;0,0), izinyanga eziyisithupha (B:-0.5mL (95%CI:-1.0,00), p=0,046) kanye nezinyanga eziyishumi nambili (B:-0-0,3mL(95%CI:-0.7;0.0), p=0.045). I-PM10 yayihlobene nokwanda kwezinga lokuphefumula kanye namaminithi okuvulela umoya, ngesikhathi kunciphisa kwahlolwa ngokweFRC eqoqweni elineminyaka ofanayo, yize ungabalulekile ngokwemiphumela yezinombolo. Ukuhlangana okunje kwaba kuncane ekubeni sengozini ye-NO2, noshintsho olungamile ndawonye lwahlolwa ngokomgudu wezilinganiso kanye neminyaka yamaqoqo. Isiphetho Uhlolo lokuziveza lwemiphumela mayelana nokuhlangana kwatshengisa isikhathi esincane (amasonto amabili kuqagelwa) sokuziveza kwe-PM10 nemiphumela yokulimala kwephaphu phakathi kwabantwana basebancane abavela ezindaweni ezihluphekayo, emva kokulungisa ama-covariates, ngesikhathi ukuhlangana neNO2 kunganelisi kakhulu.