Smoky signals

pollution alerts have become frequent in France. Paris authorities issued pollution alerts twice last month. The first was issued on August 13, when a northwesterly wind significantly reduced levels of oxygen. Authorities urged city residents to leave their cars at home and use public transport. Later, they lifted the alert as winds helped to disperse a concentration of ozone over the city that had led to the health warnings.

Then on August 17, officials issued new pollution alerts for Paris and Strasbourg. Public health officials said that the two cities registered pollution levels at