Emerging market currencies have slumped to 15-year lows as China’s equity rout and free-falling commodity prices reverberate throughout the -global economy.

Raw-material exporters Brazil, Russia and Colombia have suffered some of the heaviest sell-offs as the fall in the price of commodities such as oil, copper and iron ore continued unabated this week, with Brent crude falling to its lowest level since February. The turbulence is expected to increase once the US Federal Reserve chooses to finally lift interest rates from near-zero levels, a move that will probably have a chilling effect on developing markets.

James Lord, emerging market strategist at Morgan Stanley, said the Fed was an ever-present risk. “Any change in expectations about the first US rate hike driven by strong US economic data could add to the existing volatility.”