Plastic products advertised as biodegradable have recently emerged, but they sound almost too good to be true. Scientists have now found out that, at least for now, consumers have good reason to doubt these claims.

In a new study appearing in the ACS journal Environmental Science and Technology, plastics designed to degrade didn't break down any faster than their more conventional counterparts.

Susan Selke, Rafael Auras and colleagues note that to deal with our plastic waste problem, many countries and local governments have adopted laws, such as single-use bag bans, to deal with increasing amounts of trash. Most plastics end up in landfills, where they sit for decades or longer without breaking down.

More recently, some manufacturers now make plastics with additives that are supposed to make the products biodegradable. But the effectiveness of this approach has been unclear. Selke and Auras's team wanted to see if the additives were working under typical disposal conditions.

The researchers evaluated plastics containing five different compounds designed to encourage breakdown.

They found no evidence that the additives enhanced biodegradability in compost or under simulated landfill conditions, or when buried in soil for three years.

They say their findings have wide-ranging implications for consumers, the environment and the companies that make these products.