I'm sorry, but the truth here is that DuPont knew for decades and hid those results from the public. https://www.bloomberg.com/news/articles/2016-07-06/dupont-lo...
Other compounds, like water vapor or methane, trap more heat than CO2. But they leave the atmosphere much more quickly: water rains out after a week or two, and methane breaks down in about a decade. But CO2 persists for many decades, perhaps even longer depending on the state of the biosphere.
So despite that fact that CO2 is harmless to human health at atmospheric concentrations, and actually beneficial to plants and some animals, the systemic harm due to its longevity can be huge.
I know Brita filters don't remove fluoride normally, but these compounds sound organic, which activated carbon usually does remove. Any idea whether standard filters remove this?
https://www.epa.gov/ground-water-and-drinking-water/drinking...
---------------- Can PFOA and/or PFOS be boiled out of my water?
No; PFOA and PFOS cannot be removed by heating or boiling water. However, there are steps you and your drinking water system can take to limit your exposure.In some cases, drinking water systems may be able to reduce concentrations of perfluoroalkyl substances, including PFOA and PFOS, by closing contaminated wells or changing rates of blending of water sources. Alternatively, public water systems can treat source water with activated carbon or high pressure membrane systems (e.g., reverse osmosis) to remove PFOA and PFOS from drinking water. These treatment systems are used by some public water systems today, but should be carefully designed and maintained to ensure that they are effective for treating PFOA and PFOS. In some communities, entities have provided bottled water to consumers while steps to reduce or remove PFOS or PFOA from drinking water or to establish a new water supply are completed.
Home drinking water treatment units are typically certified by independent third party organizations against ANSI (American National Standards Institute) standards to verify their contaminant removal claims. Some home filters remove impurities using activated carbon and reverse osmosis, which are the same technologies utilized by public water supply systems to remove PFOA and PFOS. However, there currently are no ANSI protocols for testing home treatment systems to verify that these devices effectively remove PFOA and PFOS or how frequently the filters should be changed in order to maintain removal efficiency. NSF International is currently developing such protocols.
The issue with chemicals like these and treatment is that without extensive testing there isn't much information about breakthrough rate and contact time and the relationship, so repeated testing is really the only way to know when you need to change media.
Manufacture cartridge change recommendations generally are pegged to chlorine removal only, so a filter may deplete it's PFOA removal potential in a 1/10 the recommended change interval.
> part from the commonly studied perfluoroocta noic acid (PFOA or C8) and perfluorooctane sulfonate (PFOS), eight additiona l PFASs were evaluated: perfl uorobutanoic acid (C4), perfluoro- pentanoic acid (C5), perfluorohexanoic acid (C6), perfluoroheptanoic acid (C7), perfluorononanoic acid (C9), perfluorodecanoic acid (C10), perfluorobutane sulfonate (PFBS), and perfluorohexane sulfonate (PFHS).
> Regardless of the test ed (S-)PAC, C4 removal was negligible, while PFOS removal was essentially complete. PFAS removal increased with increasing perfluorinated carbon chain length, and for a given perfluorinated carbon chain length, sulfonates were more adsorbable than carboxylat es.
tl;dr: long-chain PFAS are removed, while short-chain PFAS are hardly removed at all
[0] http://www.waterrf.org/ExecutiveSummaryLibrary/4344_ProjectS...
such as Teflon?
Can you provide some evidence for that claim? I know that perfluoro compounds degrade very slowly and accumulate in fatty tissue, but I haven't seen a supported claim about harmful effects. From the misleading links in the article, I suspect more than a few people confuse PFAS and PCBs.
Here's a study of thyroid hormone effects in rat cells:
Effects of perfluoroalkyl acids on the function of the thyroid hormone and the aryl hydrocarbon receptor
https://www.researchgate.net/profile/Manhai_Long/publication...
Why are these compounds hazardous?
- Harmful biological effects in the human body, like hormone-mimic activity.
- Low molecular polarity leads to bio-magnification in fats and oils up through the food chain, and persistence in human fat.
- The high strength of the carbon-fluorine bonds greatly reduces the rate at which typical environmental degradation mechanisms (hydrolysis, photolysis, atmospheric oxidation, enzymatic breakdown in cells...) act on these compounds, compared to their hydrocarbon counterparts.
Why are these compounds used?
The same properties that make them hazards once dispersed -- strong carbon-fluorine bonds that resist breakdown, low polarity -- make them desirable in applications where people want water-repellant surfaces or materials that resist high temperatures and/or chemical attack.
Why weren't the risks better known before?
It's a lot easier to test for acute hazards than for chronic ones. By acute toxicity metrics, like feeding a bunch of rats these compounds until the dose is high enough to kill half, these materials are generally less toxic than substances like potassium fluoride. It turns out that for low level chronic exposure, perfluorinated compounds are more hazardous than simple ionic fluorides due to persistence and accumulation.
The link between stability and persistence makes up a recurring theme in environmental toxicology: materials with lower acute hazards are often worse hazards in the long term. The very lack of reactivity that makes molecules less acutely hazardous in case of e.g. a fire or a worker accidentally splashing some on skin makes them more likely to be long term problems, because the same basic properties impair how quickly environmental sinks can break them down. Pure methanol ignites more easily than diesel fuel and has worse acute toxicity risks if a worker gets drenched in a spill. But diesel contamination from a leaking storage tank is more persistent.