Mice were studied over seven weeks, with half exposed to smoke from four cigarettes a day for six days a week while the other half smoke free.

• 研究人员对老鼠进行了超过七周的实验，其中一半的老鼠一周六天每天暴露在4支卷烟的烟雾中，而另一半则完全处在无烟环境中。