The Eiffel Tower disappeared behind a brown smog on Wednesday as Paris and much of northern France suffered a spike in pollution.
周三，埃菲尔铁塔消失在一片棕色雾霾之中，因为整个巴黎还有北欧的大部分地区的污染飙升。

“The pollution levels are consistent. If we don’t go over the alert level, we won’t be far away,” said Airparif, the body responsible for monitoring air quality in the greater Paris region.
“污染值始终如一。如果我们不超过警戒线，就不会太糟，”法国大巴黎地区空气质量监测网协会说道。

In Paris, authorities measure the concentration of particulates with a diameter of less than 10 microns – so-called PM10 – in the air to determine pollution levels.
在巴黎，官方测量了空气中微小颗粒的浓度，直径小于10微米的颗粒——所谓的PM10——决定了空气中的污染指数。

These particulates are created by vehicles, heating and heavy industry, and include the most dangerous particles that measure less than 2.5 microns in diameter, which can penetrate deep into the lungs and the blood system and can cause cancer.
机动车辆、暖气和重工业产生了这些空气中的微小颗粒，并且包括最危险的直径小于2.5微米的颗粒，它们会渗入肺部和血液系统引起癌症。

The safe limit for PM10 is set at 80 microgrammes per cubic metre (mcg/m3).
PM10的安全上限是80微克每立方米。

Since Wednesday morning, authorities have put in place certain emergency measures, such as limiting cars to 20kph (12mph) on motorways in the Paris area.
自从周三早晨开始，官方就已经落实了一些紧急措施，比如限制巴黎地区公路上汽车20公里/时.

Authorities have the power to put into place emergency measures such as allowing only one in two cars to enter the French capital and making public transport free.
官方有权将紧急措施付诸实践，比如只允许一半车辆开进法国首都，还有坐公交免费。。

This was last implemented on 17 March last year during a particularly bad spike in the pollution levels.
去年污染指数尤其飙升的时候，于3月17日他们执行了这些措施。

According to a 2011 World Health Organisation report, the planet’s most polluted city was Ahvaz in Iran with an average of 372 mcg/m3.
据世界卫生组织2011的报告，世界上污染最严重的城市是伊朗的阿瓦士，平均372微克每立方米。

Beijing had an average of 121 mcg/m3, while Paris was measured at 38 mcg/m3.
北京的平均值是121微克每立方米，而巴黎是38微克每立方米。

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