Flossing your way to cancer

Toxins are everywhere these days. In your water, in your food, in your beauty products, in mostly everything you consume or surround yourself with. Most importantly, toxins are in the headlines. The media has done a great job sensationalizing many toxicology papers and creating eye-catching headlines, like mine, that are not necessarily correct.

Earlier this year, USA Today released an article titled “Oral-B Glide floss tied to potentially toxic PFAS chemicals, study suggests” and Medical News Today released a similar piece titled “Flossing could increase exposure to toxic chemicals”. These were all based on a recent article published using self-reported data from the Child Health and Development Studies in Oakland, CA. Due to the media sensationalizing this study, it is important to break down the headlines and understand what was actually said and done.

Figure 1. Structure of PFOA: a non-polymer PFAS

Figure 2. Structure of PFOS: a non-polymer PFAS

Figure 3. Structure of PFTE: a polymer PFAS. n signifies that this basic chemical unit is repeated multiple times to form a polymer.

The toxins of focus in the article, as the USA Today headline states, are PFAS. PFAS, short for per- and polyfluoroalkyl substances, are man-made chemicals that have been used in industry and consumer products for nearly 70 years. PFAS are fluorosurfactants which are a group of chemicals whose properties originate from a substitution of hydrogen with fluorine along the carbon backbone. PFAS include chemicals like PFOA, PFOS, and GenX and can be found in non-stick cookware, water-repellent materials, some cosmetics, food packaging, and products that resist grease, water, and oil. PFAS encompass many substances and the EPA has a list that includes over 5000 PFAS substances. The PFAS substances can be divided into two major families: polymer and non-polymer. Polymers and non-polymers are differentiated from each other by size, with polymers being a chemical made of many repeating units of non-polymers. The non-polymer PFAS include PFOA and PFOS and are the most commonly detected in the environment. The polymer PFAS are larger molecules than the non-polymer substances and include PFTE.

In the study described, they measured a total of 11 non-polymer PFAS (including PFOA and PFOS) in blood samples in 178 middle-aged women and collected data on behaviors that they believed would influence PFAS exposure. These behaviors included using things like non-stick cookware, microwave popcorn, glide floss (Oral-B), coated cardboard containers, seafood, and stain-resistant carpet and furniture. This is the first paper to consider dental floss as an exposure to PFAS. To narrow down the brand and type of floss, the researchers did something interesting. They analyzed 18 different floss types for the presence of fluorine and used it to evaluate the plausibility of PFAS exposure from dental floss. They found Oral-B Glide dental floss and two other dental floss products to have detectable levels of fluorine.

Fluorine is a chemical that is represented by the letter F on the periodic table of elements. We commonly know it as fluoride, which is made when you combine fluorine and a metal, like sodium. Fluoride can be a common component in many of our dental products, although Oral-B’s website does not specify whether their Glide floss contains any. They do have an instructional page that takes you through the different types of dental floss, where you can see a very familiar looking word: polytetrafluoroethylene (PTFE). PTFE is the most commonly used chemical for Teflon coating and is in the polymer family of PFAS which is not the same class as PFOA and PFOS (these are non-polymers).

The article does take notice of the report that Oral-B Glide is manufactured from PTFE; however, it is confusing why they chose to evaluate PFAS non-polymer exposure when the Oral-B Glide Floss is made with PTFE which is a PFAS polymer. It is particularly perplexing since the studies that describe the toxicity of PTFE are few in number, in comparison to PFOA, and the results do not present substantial conclusions. This is when a little chemistry knowledge is needed. PFOA is commonly used in the synthesis of PTFE and is an established dangerous chemical. Additionally, PTFE may also contain PFCA (another type of PFAS). The studies done to assess the presence of these PFAS in PTFE were done with non-stick pans while applying high levels of heat to see if PFOA and PFCA gases were released. It seems a stretch to imagine that dental floss would undergo enough heat to release these more dangerous toxins and thus contribute to the circulating levels of non-polymer PFAS. However, it is possible that PFTE, when metabolized by the body, breaks down into these more toxic metabolites.

It is mentioned in the discussion of the article that “PFASs are detected in PTFE-based dental floss…” and cites two papers. One of the papers clearly shows that PFOA was detected in both dental floss and dental tape. However, the concentration is minute in comparison to PFTE cookware, PFTE film/sealant tape, and popcorn bags. There is one main thing to keep in mind from this seemingly damning paper. It is unclear from their methods how they measured the PFOA in the dental floss/tape, but it is clear that it was not under circumstances that would mimic human use. The researchers for this paper note that since “…PFTE does not dissolve…” you have to measure PFOA presence by extracting from a ground or powdered material.

All in all, it is important for studies to assess the potential sources of exposure and hold industry accountable. However, it is important when evaluating new sources of exposure to be sure that the exposure in question could be significantly contributing to your toxins of interest. For the case of Oral-B Glide, it is possible that the PTFE used in this dental floss is contributing to elevated levels of PFAS in people’s bloodstream. Nevertheless, we currently do not have the research to support this connection, and so it is important to be mindful with our results and not let the media sensationalize them.

Peer edited by: Isabel Newsome and Nicholas Martinez.

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Watch what you drink! Or, can you?

GenX protest in downtown Wilmington (StarNews)

Do you remember when Wilmington, NC made national news in 2017 for having serious chemical contamination in their drinking water? An investigation by the EPA had identified that a chemical-manufacturing plant Chemours (a spin-off of DuPont, one of the largest chemical-manufacturing companies in the world) had been dumping the chemical known as GenX into the Cape Fear River, which is a drinking water source for residents of Wilmington. The issue was that, at that time, there was only limited information on GenX, a relatively new man-made chemical. Despite the limited information, the State ordered Chemours to stop their dumping. Perhaps a previous lawsuit against DuPont regarding C8 helped facilitate the State’s decision? Even so, there is still an ongoing effort to investigate and prevent GenX contamination in the area. The good news is that on February 14, 2019, the EPA announced a nationwide action plan for PFAS (per- and polyfluoroalkyl substances), in which GenX is included.

PFAS are a group of man-made chemicals, manufactured and used widely since the 1940s. They are often used in food packaging to make things grease and stain resistant (Teflon is also a type of PFAS!) but are also found in firefighting foams and have industrial applications. The drinking water contamination reported in Wilmington is an example of high-level exposures to such PFAS, and similarly, there could be other communities that are exposed to drinking water contamination from industrial facilities or places that use firefighting foams. Elevated PFAS exposure is concerning since these substances accumulate in our bodies, and an increasing number of studies link high-level exposures to adverse health outcomes.

Chemical structure of PFAS: commonly used (PFOA & PFOS) and emerging (GenX)
Source: EPA PFAS infographics

Amongst PFAS, the two of the most commonly used chemicals were PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid).
An increasing number of studies observed PFOA and PFOS accumulate in the human body and linked them to adverse health outcomes related to infant birth weights, immune system, cancer, and thyroid function. Due to the increasing health concerns, US manufacturers voluntarily phased out the two PFAS chemicals between 2000 and 2002, replacing them with new PFAS such as GenX. However, there is limited information about the potential adverse health effects in humans for the emerging PFAS, and we can still be exposed to PFOA and PFOS on multiple occasions. You could be unknowingly exposed to high levels of emerging PFAS, as in the case of drinking water contamination in Wilmington. Maybe you still use some consumer products that were manufactured before the phase-out of PFOA and PFOS. Even if you managed to get rid of all those products at home, PFOA and PFOS may be present in our surrounding environment since they do not break down easily. Or, consumer products manufactured internationally may contain PFOA and PFOS, if these substances are not regulated as in the US. So you can see here how difficult it would be for an individual to avoid high levels of exposures to chemicals that are known to be harmful to human health, and a combined effort at a population level is needed, like the PFAS action plan released by the EPA.

Current guidelines on PFAS by State
(Bloomberg Environment)

The PFAS action plan consists of regulatory actions to restrict on the known “bad actor” compounds, along with short- and long-term plans to better understand the exposure levels and potential health outcomes associated with PFAS, including the emerging compounds. Since PFOS and PFOA are the most commonly used types of PFAS with evidence of harmful human health effects, they are a high priority in administering regulations. Currently, PFAS are not regulated and there is only a non-enforceable and non-regulatory advisory level called “health advisory level”. The health advisory level, established in 2016 for PFAS, state that if both PFOA and PFOS are found in drinking water, the combined concentrations of PFOA and PFOS at 70 parts per trillion is the margin of protection for all Americans throughout their life. To enforce mandatory and nationwide regulations, the EPA is planning to include PFOA and PFOS in multiple laws and regulations.

There is no doubt that the comprehensive action plan for PFAS laid out by the EPA will help communities that are already affected by PFAS contamination, and advance the current state of knowledge. However, there is one more issue that requires careful attention – a concept called “regrettable substitution”. Under the current system, implementing regulations on a substance with known adverse human health effect could unintentionally bring about the same problem again with a substituting substance: manufacturers often replace a substance under regulation with a substituting substance that has similar chemical properties as the substance under regulation but has not been identified as a “bad actor”. Commonly, there is just not enough evidence on the substituting substance for it to be labeled as a “bad actor”: the chemical could be completely new to the market or just been used rarely that it was not sufficient to trigger noticeable adverse health outcome in humans. The absence of evidence is not evidence of absence! A classic example is the phase-out of bisphenol A (BPA) and replacement with bisphenol S (BPS). Mounting evidence in potential health outcomes associated with BPA led to voluntary phase-out of BPA by manufacturers and replacement with various substitutes including BPS. However, the toxicity and potential human health effects of these substituting chemicals were unknown at the time of substitution. Shortly after BPS became widely used as the substituting chemical for BPA, studies observed that the substituting chemical BPS was as harmful as the substituted chemical BPA. The replacement of BPA with BPS is not the only example of such regrettable substitution; man-made chemicals such as diacetyl, organophosphate pesticides, and polybrominated flame retardants are also well-known examples. The case of PFOA substitution with GenX could also be viewed in this perspective. There is increasing animal studies that identified potential harmful effects of GenX, but limited studies on human health. Upon future studies, GenX could also end up being a regrettable substitution! Given the repeated history of regrettable substitution in the man-made chemicals, it is now a time to take a step back and revisit the effectiveness of the current framework and develop a more stable platform to aid the selection of safe alternatives.

Want to learn more about how different countries are trying to tackle regrettable substitution? Visit the EPA website and the European Chemicals Agency website

Want to learn more about PFAS and EPA’s action plan? Visit EPA website that includes information on the PFAS action plan, data, and state-specific resources!

Want to learn more about drinking water contamination by PFAS in the US? Visit a website with an interactive map, developed by SSEHRI, Northeastern University.

Peer edited by Brittany Shephard and Candice Crilly.

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