China’s plans to tackle pollution over the winter could be the “next big event to unsettle global commodity prices,” and plant closures may be compounded by restrictions on transport and construction, according to Morgan Stanley.

“These policies really are unprecedented,” analysts including Tom Price said in an emailed note dated Monday that lifted the bank’s forecasts for most metals. Investors will probably be cautious as they wait to see the scale and timing of the measures, which could include disruptions to ports, rail and road, as well as closing steel and aluminum plants in key hubs, according to the bank.

The supply of metals in the top producing nation has already been affected this year by the closure of unapproved or outdated plants, and as the government ratchets up its safety and environmental oversight. In advance of the production curbs over the most-polluting months of November to March, the nation’s biggest steel hub, Tangshan city, on Monday shuttered half its iron ore processing plants as an emergency measure to avoid dangerous pollution levels. The order comes ahead of a high-profile political gathering in nearby Beijing in October.

The policy risks include disruptions to steel demand as well as supply. On Tuesday, Zhengzhou, the capital of Henan province, said it’ll suspend construction of buildings, roads and water facilities during the winter to fight pollution. The city also confirmed it would follow government orders applying to 28 conurbations in northern China and cut steel capacity by half and aluminum and alumina capacity by around a third over the period.

Aluminum will average $2,094 a metric ton in the fourth quarter and $1,984 a ton next year, Morgan Stanley said, lifting its earlier forecasts by 9 percent and 5 percent respectively. The bank also raised its estimates for copper, nickel and zinc, and picked palladium as the most promising commodity for its demand prospects.

For raw materials like iron ore, “the market has not fully priced the negative impact” of China’s environmental restrictions,” Goldman Sachs Group Inc. said in a note from Monday. The steel-making raw material sank into a bear market last week and the rout has further to run as China’s anti-pollution campaign will hurt demand at a time when global mine supplies are poised to expand, the bank said.

Steel reinforcement bar futures in China have slipped from a four-year high earlier in the month as the market weighs the prospect of supply cuts against signs of slowing demand.