In June 2014, I wrote a blog post about microplastics in the oceanic environment. These are plastic debris smaller than 5 mm in diameter, and there’s a lot of it in the ocean. Now comes a report that we may be ingesting microplastics through sea salt. [Yang et al., 2015. Microplastic Pollution in Table Salts from China. Environ. Sci. Technol. 49(22):13622–13627. DOI: 10.1021/acs.est.5b03163]

The researchers collected 15 brands of salt from Chinese supermarkets. There are four sources of the salt we consume: (1) seawater; (2) saline lake water; (3) saline groundwater; and (4) mined rock salt. [In the Chinese market, saline groundwater and rock salt are not distinguished on the package labels.] The researchers found microplastics in all 3 types of salt, but the most were found in sea salts (550 – 681 particles per kilogram of salt). Fragments and particles were the most common types (compared to pellets and sheets), and polyethylene terephthalate (PET) was the most common type of plastic. PET is commonly used in clothing fibers (polyester) and liquid and food containers, among other things.

Using the World Health Organization’s recommended limit of 5 grams of salt annually, and assuming an individual consumes only sea salt, he or she will ingest about 1,000 microplastic particles each year; this doesn’t include microplastics from other sources, such as seafood. Is this a problem? Nobody really knows yet, but microplastics are known to adsorb contaminants, and thus might be a vector for some toxic chemicals.