Drivers in the United States are benefiting from falling gas prices, but the current low oil prices are not good news for everyone.

U.S. petrochemical producers predominantly make chemicals from natural gas, while their competitors in Asia and Europe use petroleum-based raw materials.

In recent years, with shale drilling in the United States leading to an abundance of natural gas at low prices, U.S. producers have had a significant competitive advantage over producers in other regions. But as oil prices have come down over the past year that advantage has halved, according to Stephen Zinger, head of chemicals in the Americas for consulting firm Wood Mackenzie.

U.S. costs would match those of overseas producers if oil prices drop to $40 to $50 per barrel, Zinger told the American Chemical Society magazine Chemical & Engineering News. If the situation continued for several years it could change the investment outlook for some producers, he said.

At the moment, it's not clear how low oil prices will go. Global oil markets are currently being oversupplied as a result of the decision by the Organization of Petroleum Exporting Countries (OPEC) to sustain production levels.

Oil prices dropped to their lowest level in more than five years on Monday and Morgan Stanley said that prices could fall as low as $43 a barrel next year.

The investment bank predicted that Brent Crude would average $70 a barrel in 2015, down $28 from a previous forecast, before rising to $88 a barrel in 2016.