that old devil sun

By Dave Trecker

We’re called the Sunshine State for a reason. We have, on average, 237 sunny days a year, 266 in Southwest Florida. The five sunniest cities are Bonita Springs, Ft. Myers Beach, Marco Island, Naples and Punta Gorda. That’s one of the reasons people move here. Why put up with the gloomy Northeast or the cloudy, cold Midwest if you can live in sunny Florida?

But there’s a downside. That bright, warming sun causes skin cancer. Solar ultraviolet radiation is responsible for 10,000 deaths a year in the United States, a number that has been increasing at an alarming rate.

How can that be, you ask? We have the best technology in the world. We have super computers that can solve any problem. We can guide missiles to a pinpoint target, develop life-saving vaccines, explore outer space. Surely, we can soak up UV rays.

And we can, of course. We have a whole bunch of sunscreens to do just that, products widely available at CVS and Walgreens. It’s not like we have to go unprotected. Pick up some sunblock and slather it on.

So what’s the problem?

The problem is medical studies show that many of the most widely used sun blocks are absorbed into the bloodstream. Without data to prove that no harm results, the FDA is poised to yank approval of these chemicals. Pull them off of the shelves. And no new products can be added to the mix without extensivetesting.

Just what are we talking about here?

Sunscreens work in several ways.

Inorganics like titanium dioxide and zinc oxide simply reflect the UV rays. They are not absorbed through the skin, a big plus. But they are paint pigments. They make you look like a kabuki warrior, a big minus for most.

Organic sunscreens function differently. They soak up the light energy and transfer it to thermal energy, blunting the threat of sunburn. Oxybenzone, octinoxate, avobenzone, homosalate and others operate this way. Because they are small molecules, they are easily formulated into oils and salves, but their small size eases absorption through the skin. One big plus, one big minus.

A recent article in Chemical & Engineering News frames the dilemma. Unlike most of the rest of the world, the United States treats sunscreens like over-the-counter medicines. Their approval requires testing to show they are GRAS, “generally regarded as safe.” Because of the risk of bodily absorption, the tests can take years and cost tens of millions of dollars – not much for an expensive drug, but a killer for a cheap sunblock.

Putting the final nail in the coffin, scientists recently published a study showing that commonly used organic UV filters often “turn up in the bloodstream at levels that trigger a toxicology study requirement.” That isn’t to say they’re dangerous. But they must be tested.

That applies to some 15 existing sun blocks and a backlog of six to seven new ones.

The situation is far different overseas. Most of the rest of the world treats sun blocks as cosmetics, comfortable that the small organics have been used for decades without serious problems.

So where do we go from here?

Help may be on the way. A triazole derivative discovered 20 years ago has been resurrected and exhaustively examined. Called bemotrizinol, it seems to meet all of the requirements. It’s a big molecule. It soaks up a wide band of UV light. It’s stable, easily formulated and clear when applied. Little, if any, passes into the bloodstream, and the toxicology looks great.

A company called DSM recently completed testing of bemotrizinol and plans to submit the data to the FDA bymid-2023. Rapid approval is expected.

What should we do in the meantime?

Experts say to plaster on the titanium dioxide or zinc oxide. Looking like a kabuki warrior isn’t such a bad thing.

About the Author

Dr. Trecker is a chemist and retired Pfizer executive living in Naples.