BayCEER Workshop 2022

Adsorption and Desorption of Persistent Organic Pollutants to and from Micro- and Nanoplastics (MNPs): Implications for human exposure to MNPs.

O 2.2 in Morning Session

13.10.2022, 11:45-12:00, H 36

Owing to the ubiquity of micro- and nanoplastics (MNPs), human exposure has become inevitable. While the evidence for direct adverse effects of MNPs on humans is scarce, MNPs can adsorb toxic pollutants like polycyclic aromatic hydrocarbons (PAHs) and subsequently release them under favorable conditions e.g. the human gastrointestinal (GI) tract.

To address the carrier behavior of MNPs, we investigated their sorption of PAHs using a novel third-phase partitioning (TPP) method. In brief, PAHs were incubated in water containing MNP particles and a polydimethylsiloxane-coated stir-bar until equilibrium is reached. The MNP-water adsorption coefficient for the target PAH is subsequently calculated. Benzo[a]pyrene (B[a]P) was selected as a lead substance along with dibenzo[a,l]pyrene (DB[a,l]P) and anthracene (Ant). The sorption of B[a]P to 20 MNPs was analyzed. To simulate human exposure to pollutants-contaminated MNPs, we investigated the GI bioaccessibility of MNP-sorbed PAHs using a sequential in-vitro digestive model.

Using the TPP method, we could demonstrate strong adsorption of B[a]P to MNPs which differed by over two-orders of magnitude, clustering according to polymer types. When comparing PAHs, their sorption to selected MNPs increased by over five-orders magnitude according to their hydrophobicity: Ant<B[a]P<DB[a,l]P. Regarding desorption, B[a]P’s bioaccessibility increased along the GI tract. The desorption of B[a]P from PA-6 was substantial and particle-size dependent. Under the current exposure scenario, the calculated contribution of MNPs to the total PAHs intake by humans is very small (< 0.1%). The novel TPP-method can become universally applicable for fast and reliable evaluation of contaminants adsorption to micro- and nanoparticles including MNPs. Our work provides realistic estimates of the risk posed by microplastics as PAH carriers under the current exposure level but also supports a possible grouping of MNPs according to their potential risks.

Keywords: Microplastics, Nanoplastics, Adsorption, Desorption, Polycyclic aromatic hydrocarbons.

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