The U.S. Food and Drug Administration said on Tuesday it still could not approve two sunscreen ingredients for use in the United States despite years of review, citing a lack of data to support their safety and effectiveness.

The additives, ecamsule and enzacamene, are to protect the skin against cancer-causing ultra-violet (UV) rays. In January, the FDA reached a similar conclusion on six other ingredients that had been pending approval.

FDA staff have been reviewing sunscreen ingredients for more than a decade. That process was to be streamlined with passage of the Sunscreen Innovation Act in November 2014.

The agency's decision is a blow to manufacturers who want to expand over-the-counter sunscreen products for U.S. consumers.

"Americans are not going to have access to the innovative sunscreens that have been available, in some cases for decades, all over the world," said Michael Werner, a lawyer and policy adviser to the Public Access to SunScreens (PASS) Coalition.

Theresa Michele, head of nonprescription drug products at the FDA, wrote in a blog post that there was not enough data on the long-term effects of the ingredients and how much was absorbed into the skin, among other information.

Despite the effort to speed up the process, products must meet the agency's standards, Michele wrote.

L'Oreal applied for review of ecamsule in 2007 and Buchanan Ingersoll sought a review of enzacamene in 2002 on behalf of Merck & Co Inc, whose consumer business is now owned by Bayer AG.

European regulators have approved products for skin protection containing other UV filters that dermatologists and others in the industry have said offer better protection.

It could take years for companies to provide the FDA the kind of data it wants, Werner said.