Over 80% of sunscreen performed below their labelled efficacy (2020)

This is a topic where the details matter a lot. A sunscreen which is labeled SPF 50 but performs at SPF 45 is such a minimal difference that it would be impossible to notice in the real world. The variance of your application technique and applied thickness would actually matter more. There is also a lot of testing variability, so if a sunscreen rated to block 98% of certain rays only gets 97% in the test that would be acceptable in the real world, but it would get counted for this clickbait headline.

If a sunscreen comes with a high SPF rating and performs close enough in random testing (which is hard to replicate) then I wouldn’t have any concerns in the real world.

The body of the article has some more details about how the number of majorly deficient brands was much smaller, but that makes for less clickbaity headlines:

> The measured sunscreen efficacy of 4 models were below SPF15, of which 2 were sunscreen products with very high protection i.e. labelled with SPF50+

Knowing which 2 brands were labeled SPF 50 but performed below 15 would have been helpful, but the article is not helpful.

Have you tried living in Australia? I would like SPF 100 sunscreen pronto, please and thank you

SPF is a Sun Protection Factor, meaning it multiplies the time it takes for your skin to burn. For example, if very light skin normally burns in about 10 minutes, SPF 20 stretches that to ~200 minutes, which is already over 3 hours. Since dermatologists recommend reapplying every 2 hours regardless, going beyond SPF 30–50 (which blocks ~97–98% of UVB) doesn’t add much practical benefit. Even for very fair skin, correct application and reapplication are far more important than chasing SPF 100.

This is related to an article from yesterday, https://news.ycombinator.com/item?id=45145624, about the Choice Australia investigation that found that some sunscreens (named in that article) provided around SPF 4 when it was labeled as SPF 50+. It is a big deal because many people (like the 34 year old woman in the article who had skin cancer removed from her face) use a specific brand for years, believing it to be as effective as the label proclaims.

Where I live in summer I regularly get days with UV index above 15.

If you burn in 15 minutes under UV index 6 on the worst days that I've seen you'd burn in 5 minutes. So a SPF of 60 is as useful here like an SPF of 20 is wherever you live.

No, it should be like car speedometers where even a slight misreading on the wrong side is regulated harshly. [1]

I don't care for "close enough" brinksmanship.

The same is true for speed limits but y'all aren't ready for that

[1] Might be rumor but I heard that car speedometers often read high because there's a big penalty if they read low by even 1 MPH

As someone who burns extremely easily, I'm confused how this happens. I can feel the difference immediately; as little as ten minutes in direct sunlight makes me tinged red; and if I don't cover every inch I can tell which parts I missed the next day. If it doesn't work why would you use it?!

I do have sympathy for those with dark(er, which is basically everyone) skin who may not be able to directly tell the efficacy.

My concern is that mineral sunscreens are difficult to apply and leave a film on the skin (which is the entire point, I guess?); i hate that feeling, so I use chemical sunscreens. I'd bet that some of them have very nasty long-term side effects. So in the end i almost always go with trying to cover my skin with clothes/shade/whatever if at all possible.

This kind of SPF fatalism doesn't really make sense to me. There's absolutely no reason to quantize sun damage into "below burn time" and "above burn time." Damage is dose-dependent. Even burns come in different classes at different exposure durations; and maybe you'd prefer to get, you know, 30 seconds unprotected equivalent of sun damage instead of 3 minutes equivalent, at the same re-application interval.

If someone can make a true SPF 200 economically, it's valid for consumers to prefer that to a true SPF 100 or true SPF 50.

It's not a rumour. They usually read somewhere between 5-10% over actual speed. Use a more accurate GPS speedometer on your phone to check that.

Yes, this is how consumer labeling works today. Net weights, cash register scales, gasoline pumps, etc. Errors are only allowed if they're in the customers' favor.

That said, sunscreen is hard to apply precisely. One interesting emerging option is personal "makeup mirrors" that use a UV camera.

I assume your numbers are just made up, but if 98% is SPF 50 (1/50 or 2% reaches the skin), 97% is SPF 30 (1/30 or 3% reaches the skin). Both seem pretty good, but that is still a fairly marked difference.

Why are you confused? You can be (and are likely) doing deep, long term damage to your skin even if your skin doesn't have an immediate reaction to sun exposure (i.e sunburn). This is a key point that cancer council australia are constantly trying to drill into peoples heads.

> I'd bet that some of them have very nasty long-term side effects.

Why?

Jesus H Christ, UV index of 15? I thought the 12 we see in the middle of Texas summers was bad. I've burnt in 10 minutes through a windshield with that.

Mineral sunscreen works very intuitively, and feeling that grime makes sense. If you have dark skin, many if not most mineral sunscreens will be quite visible. You're trying to literally cover your skin with a screen and you should be able to feel it and probably see it. You can also wash it off quite easily (to the extent it's a problem at the beach).

Chemical sunscreen that avoids this is designed to sink into the skin like lotion. So there's something literally in your skin blocking uv or it won't work very well. I'd say this increases the odds of circulating something carcinogenic or otherwise toxic into your bloodstream.

Many people don't burn so quickly.

They could also have a lot of short exposures, like someone who is only outside for 5-10 minutes at a time but 2-3 times per hour every day, as was the case with one of my early jobs that involved walking between buildings a lot.

A common mistake to make is believing that if you're not burning, you're not accumulating damage.

5-10%, definitely not. Wrong tire size will do that though.

Have had a GPS speedo on the dash for a good dozen cars through the years and never seen more than a few mph off on a flat surface. That's something I actually noticed and looked for, for some reason. A few mph over speed is fairly common, but we're talking 1-2% at most. (confirmed with Tesla Model 3, Corolla, Fusion, Prius, Elantra, Mirage, etc etc).

The UV index in the southern hemisphere goes a lot higher than anything you experience up in the northern hemisphere. Do yourself a favour and go have look at the UV index on a hot summers day in Sydney in January.

Cars show higher speeds especially when the model has an option for larger tire diameters, but is equipped with smaller ones. There typically isn't a setting for tire diameter, so they compute speed using the larger diameter in all cases.

TIL that chemical sunscreen does go into the bloodstream: https://www.fda.gov/news-events/fda-brief/fda-brief-fda-anno...

For example today in sw Australia in late winter/spring it's a uv index of 5.

Summer time it sits at 13+ at noon on a clear day.

https://www.bom.gov.au/climate/maps/averages/uv-index/?perio...

Recently I went into the whole rabbit hole of sunscreens as I moved to Brazil from Switzerland, and now need to use it everyday (ok I know, theoretically also back home would be nice!). So I bought a mineral sunscreen. It feels "healthier" but also doesn't have that good lotion-like characteristic that you can just apply and forget. I really hope sunscreen companies are able to crack this one up.

Yeah that would be like 50% more sun getting to your skin

I know it sounds like a lot but in my experience the difference is mostly a fixed offset plus a tiny percentage due to tire pressure/size.

A fixed 2mph difference at 20mph is 10% so imho they're at least _technically correct_.

Chemical sunscreens:

Endocrine disruption: Oxybenzone (BP-3) and related benzophenone-type UV filters have demonstrated endocrine-disrupting properties in vitro and in animal studies, with some human data suggesting possible hormonal alterations and increased risk of uterine fibroids and endometriosis.[6-7] However, most human plasma concentrations are much lower than those producing effects in bioassays, and current evidence suggests low intrinsic biological activity and risk of toxicity for most organic UV filters except oxybenzone.[8-9]

Contamination: Benzene, toluene, and styrene have been found in a large proportion of sunscreen products, likely due to manufacturing processes rather than the UV filters themselves. Benzene contamination is a particular concern due to its established carcinogenicity.[1]

In the risk of not picking up your hyperbole, I did think the windshields block UV and thus you cannot get sunburned through them.

I think the real concern here isn't the slight variances, it's the outliers. Two products labeled SPF50+ testing under 15 isn't just a rounding issue, that's straight-up consumer deception

5% at 70 mph is 3.5 mph

10% at 30 mph is 3 mph

I saw this with various European cars.

My experience is that it seems to be a fixed percentage rather than a fixed amount i.e. the absolute difference increases with speed.

In new vehicles, yes.

The protection factor from that degrades over time / with exposure, too.