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The U.S. Food and Drug Administration has issued a long awaited update to sunscreen rules aimed at strengthening regulations of over-the-counter sunscreens Thursday.

Two of the 16 currently used main chemical ingredients in over-the-counter sunscreen products are considered safe, the FDA says, as part of a proposal here aimed at improving the safety and quality of sunscreen products sold without prescription in the United States.

The agency named two ingredients — PABA and trolamine salicylate — as not permitted for use in non-prescription sunscreen products, adding that it is asking the industry for additional data on 12 other ingredients.

The health regulator said the proposed rule has been issued to establish conditions under which some sunscreen drug products can be sold without FDA-approved marketing applications.

The agency proposed that of the 16 currently used ingredients, only two — zinc oxide and titanium dioxide — are considered safe and effective based on available data.

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“This action is an important step in the FDA's effort to take into account modern science to assure the safety and effectiveness of sunscreens,” FDA Commissioner Scott Gottlieb, MD, said at a news briefing Thursday.

“The proposed rule that we issued today would update regulatory requirements for most sunscreen products in the United States, to better ensure consumers have access to safe and effective sun care options in line with the latest science,” Gottlieb added.

In November 2016, the FDA had issued guidelines detailing the data that makers of over-the-counter sunscreens need to produce to prove the ingredients in the products are safe and effective.

“Broad spectrum sunscreens with SPF values of at least 15 are critical to the arsenal of tools for preventing skin cancer and protecting the skin from damage caused by the sun’s rays, yet some of the essential requirements for these preventive tools haven’t been updated in decades,” FDA Commissioner Scott Gottlieb said.

Among other measures, the agency also plans to raise the maximum proposed sun protection factor or SPF value on sunscreen labels from SPF 50+ to SPF 60+.

SPF is a measure of the extent of protection a product offers against the ultraviolet radiation in sun rays, that is generally considered harmful.

SPF 15 blocks 93% percent of UVB rays, while SPF 30 and SPF 50 blocks block 97 and 98 percent of UVB rays, respectively, helping to prevent skin cancer. Therefore, the FDA is still encouraging sunscreen users to continue using skin protectants as the rulemaking process continues.

“It is important that, as this rulemaking effort moves forward and the FDA gathers additional scientific information, given the recognized public health benefits of sunscreen use, consumers continue to use sunscreen in conjunction with other sun-protection measures,” said Dr. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research in a statement.

Although sunscreen has been in existence since the 1940s it has only been regulated by the FDA since 1978. In May 2018, the Food & Drug Administration (FDA) released a new enforcement policy for over-the-counter sunscreen drug products marketed without an approved application, the first revision of policy since 2011.

Environmental Working Group (EWG), a nonprofit health and environmental advocacy group, called the proposal a “big step toward cleaning up a largely unregulated industry.”

“We expect many companies to quickly reformulate to avoid those ingredients that the FDA considers unsafe or for which there is not enough data to prove safety,” said Scott Faber of EWG on a press call after FDA’s announcement.

Dr. Shamard Charles of NBC News contributed to this report.