Recently, the Wall Street Journal (WSJ) published a piece in their Numbers column titled: “Sunscreen Chemicals Accumulate in Body at High Levels.”
In it, the WSJ stated that the chemicals were above “the Food and Drug Adminsitration’s safety threshold.”
Unfortunately, that statement, is just a bit misleading.
Let me explain:
The FDA set a screening level of 0.5ng/mL in their proposed rule on sunscreen chemicals was using a the Threshold of Toxicological Concern approach, or TTC. TTC is what we call a screening value — if the exposure (or blood level) is below the TTC or screening value, then no further toxicological testing is required. However, if the exposure (or blood level) is greater than the TTC, then toxicological testing is warranted.
So, the WSJ calling the screening level used by FDA a “safety threshold” is misleading. When the FDA talks about the TTC, or screening level, in their proposed rule they spell out exactly what they mean:
The threshold value of 0.5 ng/mL is based on the assessment that the level would approximate the highest plasma level below which the carcinogenic risk of any unknown compound would be less than 1 in 100,000 after a single dose.US FDA Proposed Rule on Sunscreen Products for Over-the-Counter Human Use
To their credit, the WSJ does later clarify that chemicals above the screening threshold will need to be analyzed further. However, they then compare 4ng/mL THC (the chemical in marijuana that gets people high) to a blood alcohol concentration of 0.04%.
This argument is spurious at best as it completely ignores the fact that different chemicals act differently in the body at different concentrations due to differences in what proteins/receptors they bind to — said another way: comparing chemical X to chemical Y based on concentration is apples to BMWs comparisons — we don’t compare chemicals based on weight — we do it based on the number of molecules, which isn’t the same due to chemicals having different weights; furthermore, we have to actually take biochemistry and pharmacology into account as well — it’s actually far more complicated than a simple THC to beers comparison.
FDA Never Said “Safety Threshold”
Strikingly, the US FDA never uses the term “safety threshold” in their proposed rule. Why?
Because the screening level is not actually a safety threshold. It’s a regulatory screening level. FDA is not saying that chemicals with blood levels greater than 0.5ng/mL are unsafe.
What FDA is clearly saying is that any chemicals with blood levels below 0.5ng/mL are not going to pose a human health risk — so there is no reason to require further toxicological testing.
We need additional studies to assess the safety of the various sunscreen chemicals — I think we can all agree there. However, FDA believes it is currently premature to say any of these chemicals are actually toxic.
And, like the FDA, I strongly encourage everyone to use some type of sunscreen.
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