Per- and polyfluoroalkyl substances (PFAS) are synthetic chemical compounds used since the mid-20th century for their properties of resistance to heat, water, and grease. They are ubiquitous in the environment, persistent, and accumulate in living organisms. As a result, many hotspots have been identified where PFAS levels in drinking water, soil, or food exceed safety thresholds, thereby exposing local populations to increased health risks.

Absorption and Elimination

PFAS are almost completely absorbed by the intestine and bind to serum proteins, concentrating mainly in the liver and kidneys. However, their elimination is limited by significant reabsorption in the renal tubules and intestine, leading to a long half-life, particularly for perfluorooctane sulfonic acid (PFOS), which can last from 2.7 to 5.0 years.

Health Effects

PFAS are associated with various adverse health effects, such as hormonal and immunological disruptions, elevated cholesterol and liver enzymes, and an increased risk of certain cancers. Due to their persistence and bioaccumulation potential, international regulations, such as those established by the Stockholm Convention, aim to limit their use. Despite this, areas of high contamination persist, highlighting the need for effective mitigation strategies.

PFAS Elimination Strategies

Given the enterohepatic reabsorption of PFAS, their excretion is primarily limited to urine and feces. Anion exchange resins (AER), such as cholestyramine and colesevelam, have been explored as potential treatments to reduce PFAS levels in the blood. These resins form insoluble complexes with bile acids in the intestine, thereby increasing the fecal elimination of cholesterol and potentially PFAS.

Study on PFOS Reduction by Cholestyramine

A controlled clinical study, conducted to evaluate the effectiveness of cholestyramine (an AER) in reducing serum PFOS levels in heavily exposed adults, provided promising results.

Background and Methods

This randomized double-sequence study was conducted among citizens of a contaminated area in Denmark. Participants, with serum PFOS levels above 21 ng/mL, were treated with 4 g of cholestyramine three times a day for 12 weeks, alternating with observation periods without treatment. The primary objective was to measure the change in serum PFOS levels between treatment and observation periods.

Results

Of the 45 participants, the initial median PFOS concentration was 191 ng/mL. During the treatment period, an average reduction of 115 ng/mL (60%) in PFOS levels was observed, compared to only 4.3 ng/mL during the observation period. Levels of other PFAS, such as PFHxS, PFOA, PFNA, and PFDA, also significantly decreased. No serious adverse effects were reported, although some participants experienced mild gastrointestinal symptoms.

A Promising Conclusion

The study demonstrated that cholestyramine can significantly reduce serum PFOS concentrations in highly exposed individuals. These results suggest that AER could be a viable therapeutic option to accelerate PFAS elimination in people exposed to high levels of these contaminants.

Further studies, with larger samples and longer follow-up periods, will be necessary to confirm these results and optimize treatment protocols. These efforts are essential to reduce health risks associated with PFAS and protect communities living in contaminated areas.

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