<International Circulation>: How well do the ambient monitors measure pollution as it affects people with respect to their sampling method， placement， etc? 

   《国际循环》：假若考虑到影响个人的检测方法、设置等方面，那污染监测器是如何检测污染？
 
    Prof. Baccarelli: The data tell us pretty well what the pollution on a particular day is like.  If the levels are high or low on a particular day the monitors are not able to discriminate pollution coming from different areas.  If you want to know on a neighborhood-by-neighborhood basis that is difficult with the monitors used.  This is not just because of the neighborhood but because pollution changes dramatically depending on factors like proximity to a street， the level of traffic on that street， the floor of the apartment， and many other variables that change the real exposure of individuals.  At the same time， to do a study like this it is very convenient because we don’t want to know if a certain person is more exposed than another person but across the city on a certain day.  This is why many air pollution monitors have been set up， because public health authorities want to know if there is a need to issue an alert for bad pollution.  

    Baccarelli教授: 这些数据很清晰地告诉我们某个特定天的污染状况。假若在某天染污水平升高或下降，监测器并不能鉴别来自不同区域的污染。如果你想知道邻近区域的污染基线水平，那仅凭这些监测器是很难获得的。这不仅仅是因为邻近区域，还因为类似于街道、街道上的交通水平、公寓的楼层及其它影响个体真实暴露的可变因素所造成的污染的急剧变化。同时，开展这种研究是非常方便的，因为我们并不需要知道是否某些人暴露更多污染，而是某天整个城市的污染状况。这就是为什么许多城市建立了空气污染监测，因为公共卫生当局想确定是否需要发布环境污染警报。