D P WORLD LONDON GATEWAY, a container terminal on the Thames estuary, is Britain’s fastest-growing port. The borough of Thurrock, where the port is situated, has the country’s third-worst levels of air pollution, in part because of fumes spewed out by ships in the port. Upriver, in London, the International Maritime Organisation (IMO), the United Nations agency for shipping, began a meeting on October 22nd aimed at taking action against air pollution. But new rules to make ships cleaner will impose crippling costs on the industry while worsening global warming.

The IMO will cut emissions of sulphur either by reducing its content in marine fuel from 3.5% to 0.5% from 2020 or by requiring ships to remove it from exhaust fumes. Sulphur from ships causes acid rain and air pollution, which contributes to between 212,000 and 595,000 premature deaths a year and 14m cases of childhood asthma, according to research published in Nature Communications in February.

Shipowners can meet the rules by installing “scrubbers”, but these are expensive. Only around 2,000 of 90,000 commercial vessels on the world’s seas will have them by the deadline. And dealing with sulphur has other ill-effects, points out Paddy Rodgers of Euronav, an oil-tanker firm. The most popular system washes sulphur out of engine fumes with seawater, which is then chucked overboard. The wastewater kills marine wildlife and causes cancer in humans, according to some research.

Most shipowners will switch to pricier low-sulphur fuels. But if all ships did so in 2020, demand for them would double (see chart) and the industry’s fuel bill would rise by $60bn, roughly the entire sum spent in 2016, say analysts at Wood Mackenzie, a research firm. It would also have a dramatic impact on aviation and road transport. Ships run on a heavy residue that remains after petrol, diesel and other lighter hydrocarbons are extracted from crude oil in refining. Competition for lighter fuel that clean ships require could raise the price of diesel for lorries by 50% and for jet fuel by 30-40% in 2020, reckons Philip Verleger, an energy economist. The resulting spike in global transport costs, he says, would hit world trade and wipe a staggering 3% off America’s GDP and 1.5% off the whole world’s in 2020.