Wood Robin, Morrow Carl, Ginsberg Samuel, Piccoli Elizabeth, Kalil Darryl, Sassi Angelina, Walensky Rochelle P, Andrews Jason R
Desmond Tutu HIV Centre, Institute of Infectious Diseases and Molecular Medicine, and Department of Medicine, University of Cape Town Faculty of Health Sciences, Cape Town, South Africa.
Department of Electrical Engineering, Faculty of Engineering & the Built Environment, University of Cape Town, Cape Town, South Africa.
PLoS One. 2014 Sep 2;9(9):e106622. doi: 10.1371/journal.pone.0106622. eCollection 2014.
Tuberculosis is endemic in Cape Town, South Africa where a majority of the population become tuberculosis infected before adulthood. While social contact patterns impacting tuberculosis and other respiratory disease spread have been studied, the environmental determinants driving airborne transmission have not been quantified.
Indoor carbon dioxide levels above outdoor levels reflect the balance of exhaled breath by room occupants and ventilation. We developed a portable monitor to continuously sample carbon dioxide levels, which were combined with social contact diary records to estimate daily rebreathed litres. A pilot study established the practicality of monitor use up to 48-hours. We then estimated the daily volumes of air rebreathed by adolescents living in a crowded township.
One hundred eight daily records were obtained from 63 adolescents aged between 12- and 20-years. Forty-five lived in wooden shacks and 18 in brick-built homes with a median household of 4 members (range 2-9). Mean daily volume of rebreathed air was 120.6 (standard error: 8.0) litres/day, with location contributions from household (48%), school (44%), visited households (4%), transport (0.5%) and other locations (3.4%). Independent predictors of daily rebreathed volumes included household type (p = 0.002), number of household occupants (p = 0.021), number of sleeping space occupants (p = 0.022) and winter season (p<0.001).
We demonstrated the practical measurement of carbon dioxide levels to which individuals are exposed in a sequence of non-steady state indoor environments. A novel metric of rebreathed air volume reflects social and environmental factors associated with airborne infection and can identify locations with high transmission potential.
结核病在南非开普敦呈地方性流行，当地大多数人口在成年前就感染了结核病。虽然已经研究了影响结核病和其他呼吸道疾病传播的社会接触模式，但驱动空气传播的环境决定因素尚未得到量化。
室内二氧化碳水平高于室外水平反映了室内居住者呼出的气息与通风之间的平衡。我们开发了一种便携式监测仪，用于连续采集二氧化碳水平，并将其与社会接触日记记录相结合，以估计每日再呼吸的空气量。一项试点研究确定了使用该监测仪长达48小时的实用性。然后，我们估计了生活在拥挤城镇的青少年每日再呼吸的空气量。
从63名年龄在12至20岁之间的青少年那里获得了108份每日记录。其中45人居住在木屋中，18人居住在砖砌房屋中，家庭中位数为4人（范围为2至9人）。每日再呼吸空气的平均量为120.6（标准误差：8.0）升/天，其中家庭（48%）、学校（44%）、走访家庭（4%）、交通（0.5%）和其他场所（3.4%）对再呼吸空气量有贡献。每日再呼吸空气量的独立预测因素包括家庭类型（p = 0.002）、家庭居住人数（p = 0.021）、睡眠空间居住人数（p = 0.022）和冬季（p<0.001）。
我们展示了在一系列非稳态室内环境中对个体暴露的二氧化碳水平进行实际测量。一种新的再呼吸空气量指标反映了与空气传播感染相关的社会和环境因素，并可识别具有高传播潜力的场所。
