BEIJING/SHANGHAI (REUTERS) - China will ban the imports of 16 more scrap metal and chemical waste products from the end of this year, the environment ministry said on Thursday (April 19).

The 16 banned products include steel smelting slag containing more than 25 per cent of the metal manganese, and ethylene polymer waste, the Ministry of Ecology and Environment said in a document published on its website.

The ministry also listed another 16 items that will be banned by the end of 2019, including timber waste and scrap metals such as stainless steel, tungsten and magnesium.

China told the World Trade Organisation last year (2017) that it would stop accepting imports of 24 types of foreign waste by the end of the year, and that it would phase out shipments of other waste products, including those readily available from domestic sources, by the end of 2019.

China's crackdown on imported waste, which was as much as 47 million tonnes in 2015, is part of its "war on pollution", and was meant to help upgrade the country's economy and move it up the global supply chain.

The ban has already caused massive pile-ups of trash overseas, but ministry spokesman Liu Youbin said at a press briefing on Thursday that it was a "key move to ensure environmental safety and protect public health".

"For the next step, the ecology and environment ministry together with other departments will conscientiously enforce and strictly forbid foreign garbage from crossing the border," said Mr Liu.

Even before the ban came into effect, the government cancelled the waste import permits of 960 companies in 2017, and shut down another 8,800 firms accused of violating restrictions on imported scrap paper and plastic.

The environment ministry said last year's total waste imports fell 12 per cent as a result, but it did not give an absolute number.

The newly formed Ministry of Ecology and Environment said at its inaugural meeting last month (March) that it would step up the fight against foreign waste, saying it was "a symbolic measure for the creation of an ecological civilisation in China".

Uncovering violations has been a major challenge, however, with smuggling still rife. Customs authorities are also having to step up their detection capabilities in order to identify which shipments violate China's scrap quality standards.

China's customs department seized 110,000 tonnes of smuggled waste in the first quarter of this year, it said this month.