Zhang Kai, Batterman Stuart A
Environmental Health Sciences, University of Michigan, Ann Arbor, MI 48109-2029, USA.
Sci Total Environ. 2009 Oct 15;407(21):5493-500. doi: 10.1016/j.scitotenv.2009.07.008. Epub 2009 Aug 15.
Traffic congestion increases air pollutant exposures of commuters and urban populations due to the increased time spent in traffic and the increased vehicular emissions that occur in congestion, especially "stop-and-go" traffic. Increased time in traffic also decreases time in other microenvironments, a trade-off that has not been considered in previous time activity pattern (TAP) analyses conducted for exposure assessment purposes. This research investigates changes in time allocations and exposures that result from traffic congestion. Time shifts were derived using data from the National Human Activity Pattern Survey (NHAPS), which was aggregated to nine microenvironments (six indoor locations, two outdoor locations and one transport location). After imputing missing values, handling outliers, and conducting other quality checks, these data were stratified by respondent age, employment status and period (weekday/weekend). Trade-offs or time-shift coefficients between time spent in vehicles and the eight other microenvironments were then estimated using robust regression. For children and retirees, congestion primarily reduced the time spent at home; for older children and working adults, congestion shifted the time spent at home as well as time in schools, public buildings, and other indoor environments. Changes in benzene and PM(2.5) exposure were estimated for the current average travel delay in the U.S. (9 min day(-1)) and other scenarios using the estimated time shifts coefficients, concentrations in key microenvironments derived from the literature, and a probabilistic analysis. Changes in exposures depended on the duration of the congestion and the pollutant. For example, a 30 min day(-1) travel delay was determined to account for 21+/-12% of current exposure to benzene and 14+/-8% of PM(2.5) exposure. The time allocation shifts and the dynamic approach to TAPs improve estimates of exposure impacts from congestion and other recurring events.
交通拥堵会增加通勤者和城市居民接触空气污染物的机会，这是因为在交通中花费的时间增加，以及拥堵时车辆排放增加，特别是在“走走停停”的交通状况下。在交通中花费时间的增加也减少了在其他微环境中的时间，这种权衡在以前为暴露评估目的进行的时间活动模式（TAP）分析中并未被考虑。本研究调查了交通拥堵导致的时间分配和暴露的变化。时间转移是使用来自国家人类活动模式调查（NHAPS）的数据得出的，该数据被汇总到九个微环境（六个室内地点、两个室外地点和一个交通地点）。在插补缺失值、处理异常值并进行其他质量检查后，这些数据按受访者年龄、就业状况和时间段（工作日/周末）进行分层。然后使用稳健回归估计在车辆中花费的时间与其他八个微环境之间的权衡或时间转移系数。对于儿童和退休人员，拥堵主要减少了在家中花费的时间；对于年龄较大的儿童和在职成年人，拥堵改变了在家中花费的时间以及在学校、公共建筑和其他室内环境中的时间。使用估计的时间转移系数、文献中得出的关键微环境中的浓度以及概率分析，估计了美国当前平均出行延误（9分钟/天）和其他情景下苯和PM(2.5)暴露的变化。暴露的变化取决于拥堵的持续时间和污染物。例如，确定每天30分钟的出行延误占当前苯暴露的21±12%，占PM(2.5)暴露的14±8%。时间分配的变化以及对TAPs的动态方法改进了对拥堵和其他经常性事件的暴露影响的估计。
