US dermatologists are expressing increased concern over what they see as foot dragging by the Food and Drug Administration on approving new chemicals for sunscreens.

During a congressional committee meeting in November of last year, Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, called the delays "an intractable problem."

More recently, however, an FDA spokesperson told US news media, the agency has "prioritized reviewing the safety and effectiveness of additional sunscreen ingredients."

US manufacturers of sunscreens can use only the 17 chemicals approved by the FDA, including just three that screen UVA rays, considered to play a role in causing skin cancers.

This compares with 27 available to manufacturers in the EU, including seven - such as ecamsule, Mexoryl and Tinosorb - expressly designed to filter UVA radiation.

In 2006, the FDA approved a petition by France's L'Oreal to use a form of Mexoryl in the US, but not for widespread use.

The main UVA blockers currently being used in the US are avobenzone and oxybenzone. The latter is said to degrade in sunlight or cause allergic reactions, while both have been linked in some cases to hormonal disruptions.