Rotterdam has completed the first phase of the world’s most sophisticated, fully automated, air-pollution-warning system, which will soon be nationwide. It consists of 31 electric “sniffers”.

Bombed to rubble in World War II, Rotterdam later became a marvel of economic growth. Holland’s second biggest city now boasts the world’s busiest port and a vast complex of petrochemical plants with blue-chip owners like Shell and British Petroleum. Unfortunately, the marvel also gushes appalling fumes — acrylates, hydrocarbons, paint…