China is paying a high price for pollution associated with shipping.

The thousands of ships that ply China’s waterways are delivering a toxic cocktail of pollution, with just one ship capable of emitting the same pollution as half a million trucks each day, the report by the Natural Resources Defense Council (NRDC) said.

Seven of the world’s 10 largest ports are in China, with more than a quarter of the planet’s maritime cargo passing through China, and the heavily populated coastal cities such as Guangzhou, Shanghai and Shenzhen are among the most polluted.

Globally, environmental regulations for ships are overseen by the International Maritime Organization (IMO). But while the IMO has cut pollution by implementing special emissions control zones in America and Europe, which use low-sulfur marine fuels as standard, Asia has been left untouched.