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L'Affaire Siloxane
- s0rce 4mo agoSiloxanes contaminate everything. We routinely see them on various surfaces when doing X-ray photoelectron spectroscopy.
- isoprophlex 4mo agoIndeed. "Grease peaks" we called them, they were always there in basically all NMR or MS spectra I took as an organic chemist. Like PFAS or microplastics, you just can't get rid of them.
- mrob 4mo agoYou can see this grease by the effect it has on water contact angle. If you have a smooth glass/metal/ceramic surface, cleaned by a highly effective method (e.g. an ultrasonic cleaner), water poured on it will slide off easily without forming beads ("water-break test"). But if you leave it out in ordinary air for some time, the water will form beads again even if you never touch it. Exact time varies depending on air quality, but probably within a few hours.
- s0rce 4mo agoThat's not always siloxanes, just atmospheric hydrocarbons.
- cubefox 4mo agoI bet some of these modern environmental contaminants is causing the increasing age cohort cancer rates.
- awakeasleep 4mo agoLook up the biocompatibility and safety profiles of siloxanes
- cubefox 4mo agoYeah probably one of the others.
- ericd 4mo agoApparently we also put polydimethylsiloxane in deep frying oil. Wonder what that does to our innards.
- RobotToaster 4mo ago> while a further 7,000 kilograms of treated urine were sitting in orbital storage tanks, waiting to be processed. Is that a record for the biggest piss bottle ever made?
- mannykannot 4mo agoA two meter cubed volume would be sufficient to hold that much. I would guess that cruise ships store more urine than that, though presumably not separated from everything else humans dump into toilets. With the qualification 'in orbit', I imagine it is.
- lugoues 4mo agoI thought they just dumped it overboard but maybe there are some ethical cruises... maybe.
- idlewords 4mo agoIt's fine to dump sewage overboard if you're far enough from shore. Cruise ships treat it to some extent, but ultimately it all becomes fish food.
- euroderf 4mo agoIn the same way that every breath you take contains at least one atom-or-molecule of Caesar's last breath, every sip you take contains at least one atom-or-molecule of every cruise ship waste jettison. (Assuming sufficient worldwide diffusion time.)
- mannykannot 4mo agoIt seems that in most ports they are required to hold and treat it (and, perhaps to a lesser extent, in inshore waters.) Fouling the places they take their customers to is ultimately bad for business.
- sprinkly-dust 4mo agoI hope to see these seemingly mundane unknown unknowns raised in space travel centered hard science fiction. I think The Martian and Seveneves almost captured these but not quite.
- tedd4u 4mo agoProject Hail Mary has a devilish contamination subplot.
- RobotToaster 4mo agoI'm sceptical of the claim that they couldn't eliminate the majority of them from stuff that's shipped up to the ISS. Even if it meant making special space certified hair conditioner.
- s0rce 4mo agoI don't see why not either, just get "organic"/plant or mineral based cosmetics, deodorants and hair products.
- Centigonal 4mo agoIt's really, really complicated. Even "organic" or "all natural" products often contain synthetic contaminants as a result of manufacturing, packaging, or shipping processes. Unless NASA were to set up separate factories and supply chains for manufacturing all known sources of siloxane contamination (either on their own or in partnership with manufacturers), it would be very difficult to actually get a siloxane-free product with any kind of certainty or consistency. An example with a different contaminant: We can't seem to keep carcinogenic plasticizers out of our RXBars and our baby formula[1]. Those products are already way more regulated than something like wet wipes, and the companies that make them have a strong interest in keeping them free of contamination. [1] https://www.plasticlist.org/ https://www.plasticlist.org/
- idlewords 4mo agoThere's a nice paper on this, ICES-2018-123 "Dimethylsilanediol (DMSD) Source Assessment and Mitigation on ISS: Estimated Contributions from Personal Hygiene Products Containing Volatile Methyl Siloxanes (VMS)". The upshot is more than half of the siloxane burden on ISS comes from God knows where (packaging, plastics, machinery, you name it). https://ttu-ir.tdl.org/items/ff1a240e-1fb1-4b04-acb2-42e9c45337c5 https://ttu-ir.tdl.org/items/ff1a240e-1fb1-4b04-acb2-42e9c45...
- LeifCarrotson 4mo agoFrom the paper: > The main sources of VMS were determined to be antiperspirants ... skin lotions ... wipes ... and hair conditioner. Several siloxanes-free options are available for [these products]. These products are now being assessed for crew member use in future increments. From the blog: > At present the agency is testing a new filtration system to put in front of the heat exchangers, to try to protect them, and continuing to try to cut down on siloxanes at the source level. There are probably people at NASA now whose entire career has been built on siloxane control. Why wasn't the result to simply ban siloxane-containing cosmetics and wipes? The cosmetics are up to the individual astronaut, which is a little crazy, but the wipes are provided by NASA, and they're still using siloxane-bearing wipes, which shortens the life of their water systems and costs crazy amounts of money.
- adolph 4mo agoAn interesting substory that is simultaneously reminiscent of the Fogbank story and how Hayek's "curious task" is much more broadly applicable: There is a good cautionary tale here from the Space Shuttle era. That vehicle had heat resistant tiles that had to be attached to the aluminum belly of the orbiter. A special cloth had been certified for wiping the aluminum clean before applying the primer that securely bonded the tiles to the metal. After years of uneventful use, tile engineers discovered that new replacement tiles were no longer curing properly. A careful investigation revealed that the supplier of that special cloth had changed the lubricant used in the machine that sews its hem. Minute amounts of the lubricant were being deposited on the stitching, and enough of that residue was getting on the aluminum skin to prevent the tile adhesive from curing properly.
- s0rce 4mo agoIn medical device manufacturing you have systems in place that your vendors have to disclose changes to their manufacturing process that hopefully can catch stuff like this before people die. I can see how minute stuff gets easily passed off as not an important change.
- duskwuff 4mo agoEspecially if the real change is a couple levels separated from the problem. For instance, I can imagine a situation where the manufacturer of that "special cloth" didn't even change anything themselves, but their lubricant supplier silently changed the formula of their sewing machine oil. (Or maybe even that one of the suppliers to the lubricant company changed something - it's turtles all the way down.)
- s0rce 4mo agoYes, you would also audit the quality system for your suppliers to confirm they are sufficiently controlling for upstream changes. In theory you can have all your ducks in a row.
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- shmeeed 4mo agoPart of my job is to keep siloxanes out of a complex, multi-step, multi-sub-contracted manufacturing process. A supplier change that should have been a simple affair has cost us several kilobucks in analyses in the past months. I hate the stuff.
- wingmanjd 4mo agoThis is the first time hearing the term "kilobucks". I love it (and am stealing it for future conversations).
- goodmythical 4mo agoI wish megabucks and gigabucks had the same ring...
- HPsquared 4mo agoMegabucks is a common word but not often used as a unit
- liotier 4mo agoIn French project management parlance, we use k€ all the time.
- msk-lywenn 4mo agoI guess the french equivalent of kilobucks would be briques (bricks)
- Ectiseethe 4mo agoHistorically, a "brique" used to be a million of anciens Francs (old Francs), then converted to 10 000 nouveaux Francs (new Francs) in 1960. Since the switch to euro, I think the most commonly accepted value of one "brique" is (unofficially) 10 000 €, but the uncertainty makes it basically useless.
- ggm 4mo agoI feel the microplastics contamination story which turns out to be measuring nitrile gloves used preparing samples is in this space. We can now measure things down to levels that may exceed our ability to exclude them as contaminants, routinely.
- mananaysiempre 4mo agoI’d say that has been true since we started using spectrometers (of all kinds). Those things are preposterously sensitive and pretty damn routine. Nowadays of course there are also other, more narrowly scoped detection methods as well, such as PCR.
- ggm 4mo agoPCR/amplification is black magic. I'm also amazed by "no the DNA will be too old" keeps turning out not to be entirely true: People getting out of jail from re-testing evidence 20+ years later, Hominid DNA statements being made from archaic bones.. Animal population studies used to be (in my understanding) largely observational. Now, people can do scat tests and identify individuals.
- golem14 4mo agoThere is an even more fantastic incident with Ritonavir (Norvir), where the manufacturer lost the ability to make a retroviral drug for an extended time. Something like that during a covid like moment would suck donkey rocks. https://pmc.ncbi.nlm.nih.gov/articles/PMC4479028/ https://pmc.ncbi.nlm.nih.gov/articles/PMC4479028/
- voidUpdate 4mo agoI am mildly concerned about the "normalised deviance" of the siloxanes in the water. It's probably an acceptable amount and it's probably fine, but "eh, its only a bit worse than expected, what's the worst that could happen" is what lost 2 space shuttles
- ben_w 4mo agoWhile this is all new to me, surprises like this are a big part of why I now think we should aim for the Moon first, and only consider Mars when the moon bases are nice and boring. If there was any "we don't even know if this is an emergency" surprise interaction along these lines, a 3-day emergency resupply mission (or evacuation) is much, much easier than a 6-9 month trip when the planets align.
- krunck 4mo agoNo mention was made of eliminating the siloxane use by astronauts: leave-in hair conditioner, deodorant, etc. I wonder if they track PFAS/PFOS contamination also?