How Digestive Processes Can Affect the Bioavailability of PCBs Associated with Microplastics: A Modeling Study...

Area of Science:

• Environmental Chemistry
• Toxicology
• Gastroenterology

Background:

• The transfer of chemicals adsorbed onto microplastics within the human gastrointestinal tract is not well understood.
• Hydrophobic organic chemicals, such as polychlorinated biphenyls (PCBs), can adsorb to microplastics and pose health risks.
• The influence of digestive processes on the release and bioavailability of these chemicals from microplastics requires investigation.

Purpose of the Study:

• To investigate how digestive processes affect the kinetics of chemical exchange on microplastics.
• To quantify the impact of digestion on chemical concentrations and bioavailability in the human upper intestinal tract.
• To develop a model that incorporates digestion to predict chemical transfer from microplastics.

Main Methods:

• Utilized an in vitro gut fluid digestive model simulating the human upper intestinal tract.
• Measured chemical exchange kinetics of 10 PCBs on microplastics under varying digestive enzyme activities, using olive oil as a food proxy.
• Determined micelle-water and oil-water partition coefficients for PCBs to assess sorption contributions.

Main Results:

• A novel biphasic, reversible chemical exchange model incorporating digestion accurately fitted empirical data.
• Digestive processes increased microplastic chemical concentrations by 10-20 times compared to a non-digestion scenario.
• Higher enzyme activity led to increased chemical release from digested food, resulting in higher microplastic chemical concentrations.

Conclusions:

• Digestive processes substantially alter chemical transfer kinetics on microplastics, reducing overall chemical bioavailability in the gastrointestinal tract.
• The developed modeling tool and understanding of reduced bioavailability mechanisms have broad relevance for risk assessment.
• These findings necessitate the consideration of digestive processes in human health risk assessments of microplastics and in understanding aquatic food web biomagnification.