Microplastics in bivalves (oysters, mussels, Manila clams)
Bivalves filter seawater to feed and are eaten whole, including the gut, so they have long been considered one route by which marine microplastics enter the diet. On the other hand, a 2023 review of more than 750 papers found that the number per individual is low worldwide, under 10, and pointed out that many studies have flaws in their methods.
Amounts found in studies
| Study | What was tested | Size range and method | Results |
|---|---|---|---|
| Van Cauwenberghe & Janssen (2014) | Farmed mussels and Pacific oysters (Belgium and elsewhere) | — (confirmed in the abstract) | At the point of eating, 0.36 particles per g in mussels and 0.47 in oysters (wet weight). Estimated at up to 11,000 particles a year for people in Europe who eat a lot of shellfish |
| Yamamoto et al. (2021) | Manila clams, hard clams, freshwater clams (shijimi) and oysters bought at a fresh fish shop in Okayama City | — (confirmed in the abstract) | About 3 particles per individual, across the four types combined |
| Catarino et al. (2018) | Wild mussels from Scotland | Visual inspection, Nile Red staining, FTIR | 3.0 particles per g. Visual identification of fibers alone was correct only 48–50% of the time, so visual counting alone overcounts by about 2 times |
| Danopoulos et al. (2020) | Review of 50 studies, meta-analysis of 19 studies | Varies by study | Mollusks: 0–10.5 particles per g. Up to about 55,000 particles a year from seafood. 26% of the studies had a “high risk of bias” |
Results can differ by orders of magnitude depending on the smallest particle size counted and whether particles are counted or weighed. Numbers from different studies cannot be compared directly (→ Why numbers differ).
Good to know
- Shumway et al. (2023) examined more than 750 papers and scored the methods of 84 experimental studies from 0 to 2 points; the average was 0.9. They said “many papers have too many flaws” and concluded that microplastics in bivalves are extremely low worldwide, under 10 per individual (funded by sources including the U.S. NOAA Marine Debris Program).
- The European Food Safety Authority (EFSA, 2016) estimated that even eating a portion of mussels (225 g) at the level of the most contaminated report would add only about 7 μg of microplastics, with only a small added load of chemicals they contain (under 2% for bisphenol A).
- One study found that fibers falling onto the plate from indoor dust during a meal far outnumber those that come in from mussels (→ Dust during meals).
Data from Japan
There is a study (2021) of shellfish from a fresh fish shop in Okayama City. We found no study of bivalves in Japan that identified the material by spectroscopy and reported results per g.
Types of plastic found
Related explainers
Sources
- Van Cauwenberghe L, Janssen CR. Environ Pollut 2014;193:65-70 (PMID 25005888)
- Yamamoto K, et al. Acta Med Okayama 2021;75(3):381-384 (PMID 34176943)
- Catarino AI, et al. Environ Pollut 2018;237:675-684 (PMID 29604577)
- Danopoulos E, et al. Environ Health Perspect 2020;128:126002 (PMID 33355482)
- Shumway SE, et al. Rev Fish Sci Aquac 2023
- EFSA CONTAM Panel. EFSA J 2016;14(6):4501
Last checked 2026-10-01. “Confirmed in the abstract” means we report only what the paper's abstract says. This page is a translation of our Japanese page; if they differ, the Japanese page is the reference.