<International Circulation>: Different occupations like truck drivers and office workers generally have the same levels of blood pressure， is this true?

   《国际循环》：不同的职业，比如卡车司机和办公室工作人员，他们的血压水平相当，这如何解释？
 
    Prof. Baccarelli:  Yes， being a truck driver didn’t matter when we looked at subgroup risk of air pollution related blood pressure elevations.  Most likely， not even being exposed to traffic matters since the general level of pollution comes from multiple sources.  Being exposed to pollution directly from trucks did not seem to matter.  

    Baccarelli教授: 是的，当我们研究空气污染亚组风险与血压升高的相关性时，卡车司机这一职业并无任何意义。大多数情况，与暴露于交通问题不相关，因为染污水平通常来源于多个因素。直接暴露于卡车污染似乎并未造成任何影响。
 
    <International Circulation>: Although this is a small study the trend seems to be that on days air pollution is bad everyone’s blood pressure is going up a little bit.  Although prolonged exposure to pollution sources like vehicle exhaust doesn’t correlate with high blood pressure.  Why is that?

   《国际循环》：虽然这只是个小研究，结果似乎表明，在空气污染的天气中，每个人的血压都会轻微增高，而长期暴露在汽车尾气等污染源与血压增高并不相关，这如何解释？
 
    Prof. Baccarelli: It could be that the air pollution causes just a transient effect or that the truck drivers are just different from the perspective of their body constitution.  They might be generally healthier than the office workers we looked at.  This is an issue our study was not able to address.  These questions are really issues that should be addressed in a study much larger than ours.  Our study looked at groups based on occupation so we did not control for other physical profiles and health status.  We did try to adjust for things like smoking or alcohol consumption and found that truck drivers did consume both of these things more than office workers.   We adjusted for variables like body mass index (BMI)， which an important indication of body fitness.  We did find differences between the various occupations but what was more interesting was the differences within groups.  Office workers for instance had exposure to pollution levels from 30-260 micrograms/km whereas truck drivers had exposure to levels from 60-250， so there is a lot of overlap between the two groups.  There is an average difference but the difference within each group is much larger.  It is possible that in a larger study there would be more statistical power and greater capability to find the effect on the larger range of variation， which is the variation with the group rather than the smaller difference in variation between groups.  I wouldn’t say being exposed to traffic directly causes harm but needs a larger study for the specific risk to be identified. 

    Baccarelli教授: 空气污染只会造成一个短期效果，卡车司机也仅仅是身体构造的不同。他们可能比办公室工作人员更健康。我们的研究并不能解释这个问题。事实上，我们的研究并不能解决这些需要阐明的问题。我们是基于职业进行分组，因此并不能控制体型和健康状况。我们试曾对吸烟或饮酒进行较正，发现卡车司机对烟酒的消费远高于办公室工作人员。我们对身体质量指数（BMI，身体健康的重要指征）进行较正，找到了各种职业间的差异，但更有趣的是组内差异。例如，办公室工作人员暴露的污染水平为30-260微克/公里，而卡车司机则为60-250微克/公里，因此，两组间存在大量重叠。虽然有平均差异，但各组内的差异非常大。因此，更大型的研究将有更多的统计能力和在较大变异范围内找到影响因素的能力，而不是小群体之间微小差异。我并不认为，直接暴露于交通污染会有害，但仍需要更大型的研究来确定这特殊风险。