汽车尾气向来不受欢迎，但它究竟有何害处？最近一项研究发现，机动车所排放的气体会恶化患有哮喘病儿童的病情，并且引起其他呼吸道和心脏疾病。

     Exhaust from cars and trucks exacerbates asthma in children and may cause new cases as well as other respiratory illnesses and heart problems resulting in deaths, an independent institute that focuses on vehicle-related air pollution has concluded.

    The report, which was issued last week by the nonprofit Health Effects Institute, analyzed 700 peer-reviewed studies conducted around the world on varying aspects of motor vehicle emissions and health. It found “evidence of a causal relationship,” but not proof of one, between pollution from vehicles and impaired lung function and accelerated hardening of arteries.

    It said there was “strong evidence” that exposure to traffic helped cause variations in heart rate and other heart ailments that result in deaths. The study also found that the biggest effects occurred among people who lived within 300 to 500 meters of highways and major roads.

    “Like the issue of second-hand smoke, it’s very difficult to understand the exact mechanisms that make it bad -- but it’s easy to understand that it is in fact bad,” said Rich Kassel, an expert on diesel engines at the Natural Resources Defense Council, an environmental group.