Perfluoroalkyl substances (PFASs) have been used in a variety of products for many decades. It is well worth repeating that one of the more dangerous variants of PFASs that was formerly found in Teflon until it was replaced by a similar substance which may also be toxic. But that’s not the only place it’s found.
This has been the case with a variety of other toxic chemicals in use today whose substitutes have been determined to be even more harmful than the original one. The real problem with PFASs is that they are now found in a good number of popular and commonly used products.
“Hundreds of environmental scientists have joined forces to begin a public campaign to urge countries around the world — including the United States — to limit their use of a class of chemicals known as poly- and perfluoroalkyl substances, or PFASs.”
“While one type of this chemical has been banned for years — studies had shown that the PFAS formerly found in Teflon products may have contributed to higher risks of cancer — scientists have reason to believe that the replacement PFASs could also be toxic.” 
“PFASs enable objects to be resistant to high temperatures, ultimately increasing durability and in some cases, preventing fires in wiring and gauges found in vehicles such as cars and planes. A few of the other items that contain these PFASs include pizza boxes, sleeping bags, electronics (like cell phones and hard disk drives), as well as backpacks, footwear and even hospital equipment (it can be found in stents, needles and pacemakers, along with hospital gowns and divider curtains). A complete list can be found here.”
Manmade and natural environments have seen a significant proliferation of toxic and carcinogenic chemicals.
There has been a literal onslaught of chemicals and toxins in various environments, both natural and manmade. The modern home is now the site of so many new building materials that their outgassing chemicals (such as VOCs) can trigger all sorts of upper respiratory ailments and allergic reactions.
Likewise, many office buildings and malls, factories, and warehouses also have their fair share of indoor pollutants and chemical contaminants. Some of these buildings are so contaminated that they have been designated as “sick buildings.”
The point of this digression from the PFAS issue is that when the human body is incessantly exposed to so many different chemicals, it will eventually reach a point of a maximum tolerable toxic load.
In Environmental Medicine, the total body burden is known as the aggregate amount of chemicals and toxicities which have accumulated at any given point in time. The body is always sloughing off these chemicals and toxins via the liver, the skin and the GI tract.
However, when the normal detoxification pathways become compromised, the unwanted chemicals accumulate faster than they are released.
PFAS: A Problem Due to Total Overuse
Because PFASs have become so pervasive in so many products and applications, they contribute considerably to the total body burden of those who are exposed to them. Whether they remain moderately toxic or cross the threshold of becoming carcinogenic has more to do with how an individual processes them.
“Research is needed to understand the potential for adverse health effects from exposure to the short-chain PFASs, especially regarding low-dose endocrine disruption and immunotoxicity,” wrote the authors Linda S. Birnbaum, from the National Institute of Environmental Health Sciences and National Toxicology Program and Philippe Grandjean, from the Harvard School of Public Health, in an article published in the recent edition of the journal Environmental Health Perspectives. 
The preceding excerpt provides a short explanation as to why PFAS-containing products ought to be avoided whenever possible. Especially when they are introduced in clothing and footwear, medical products and hospital equipment can they pose an inordinate risk.
For those who have medical conditions like Hyper-Toxicity Syndrome, MCS (Multiple chemical sensitivities) or EI Syndrome (Environmental illness syndrome), they ought to be particularly careful about their use and/or proximity to products that contain poly- and perfluoroalkyl substances.
 Yahoo Health