Which countries or oceans show the highest microplastic loads in commercial sea salts in peer‑reviewed surveys?

1. Sea salt beats lake and rock salt in global surveys, repeatedly

Multiple global and regional peer‑reviewed studies report a consistent trend: sea salts contain more microplastics than lake salts, which in turn contain more than rock or well salts, a pattern attributed to broader marine plastic pollution and direct seawater origins of sea salt ^{[1] [7] [6]}. A large multi‑country survey that analyzed 39 salt brands from 21 countries found microplastic contamination highest in sea salts (0–1,674 particles/kg in that study), with lake and rock salts showing lower maxima ^{[1] [6]}.

2. Specific country‑level hotspots reported in peer‑reviewed work

Individual peer‑reviewed papers identify notably high loads in some countries: an Indonesian sea‑salt sample was singled out as having the highest quantities in a global survey reported in Environmental Science & Technology and summarized by Greenpeace and National Geographic ^{[8] [2]}. Regional studies show elevated counts from parts of the Mediterranean and Italian salterns (reported means up to ~1,653 ± 29 microplastics/kg in an Italian study) and from Bangladesh (mean ~472 MPs/kg across sampled commercial brands), indicating that heavily used coastlines and estuaries can produce high local salt contamination ^{[3] [4]}.

3. Oceans are implicated indirectly — coastal context matters more than “ocean of origin”

Studies frame sea salt as an indicator of local seawater microplastic pollution rather than a faithful map of entire ocean basins; correlations have been reported between unrefined sea‑salt microplastic levels and documented river/plastic emission sources near harvest sites ^{[6] [1]}. Because salt is usually harvested locally (solar evaporation ponds, salterns or coastal seawater), contamination reflects local coastal and estuarine conditions rather than a clean signal for a whole ocean such as the Indian or Atlantic ^{[6] [7]}.

4. Methodology drives reported extremes — caution in ranking countries or oceans

Reported concentrations differ by orders of magnitude across studies because of variable sample sizes, particle size cutoffs (e.g., >149 μm versus sub‑micron detection), digestion and filtration methods, and whether spectroscopy confirmed polymer identity; interstudy methodological discrepancies are highlighted explicitly by reviewers, limiting direct comparisons and definitive geographic rankings ^{[9] [5] [10]}. For example, European salts yielded medians around several hundred items per kg with ranges 74–1155 items/kg using 5‑µm filters, while other single‑site studies report thousands per kg — methodological choices explain much of that spread ^{[5] [3]}.

5. Balanced take: clear patterns, but no single global leaderboard

The peer‑reviewed evidence converges on a few reliable points: commercial sea salts are more contaminated with microplastics than lake or rock salts; coastal regions with heavy plastic leakage (documented in some Indonesian, Mediterranean/Italian and Bangladeshi samples) produce some of the highest measured loads; and variability between studies prevents declaring a definitive, method‑robust ranking of countries or entire oceans ^{[1] [2] [3] [4] [5]}. Where data are lacking, sources do not allow asserting that other countries or ocean basins are cleaner or dirtier — more standardized, geographically representative sampling and comparable lab methods are needed to produce an authoritative global map ^{[6] [5]}.