Reacción a "High concentrations of nanoplastics found in Atlantic Ocean"

The article provides one of the first estimates, albeit preliminary, of the abundance of nanoplastics (<1 µm) in the Atlantic basin. Although the scientific community has been refining protocols for macro- and microplastics for almost a decade, the reliable detection of nanoplastics remains complex: few techniques avoid false positives in environmental matrices.

In this study, Atlantic Ocean waters were sampled at twelve stations at three depths and analysed using thermal desorption coupled with proton transfer mass spectrometry (TD-PTR-MS). To make it understandable, the sample is heated, the polymers are volatilised, they are loaded by proton transfer and the spectrometer measures the mass/charge ratio; this identifies and quantifies the polymers present.

The work is very well structured, has a broad sample design, contamination controls have been carried out, and it shows complete transparency about its limitations from the outset. These are:

1. Laboratory controls corrected, but not zero. Traces of plastic are found (0.90 ± 1.45 mg/m³), although they consider this to be controlled as the values are much lower than those in the samples.
2. Conservative concentrations, due to 1 µm filtering to remove dirt and real organic matter, as well as partial recovery (not all plastic can be recovered in the tests carried out), which leads us to believe that the actual estimates are probably higher.
3. Only one campaign has been carried out (in November 2020): all temporal variability remains to be explained.

With all this, the authors report averages of approximately 18 mg/m³ in the top 10 metres and about 5.5 mg/m³ near the bottom. These values, to be clear, are one or two orders of magnitude higher than most microplastic data in the open sea, but at the same time 10 times lower than the high values found on beaches (sometimes exceeding 100 mg/m³).

To understand whether these data are high or low, we need to take a look at history. It should be borne in mind that, since the mid-1950s, global plastic production has multiplied exponentially, and every decade millions of tonnes have been dumped into the ocean, where they have been subjected to ultraviolet radiation, waves and biofouling. This means that materials have been fragmenting into the nano range for decades, increasing the available concentration. Of this ‘soup’ that has been building up for 70 years, there has only been recent systematic monitoring of the macro and micro fractions, not of nanoplastics. The values for nanoplastics are completely unknown; it is only now that the scientific community is trying to understand how they are generated, and therefore, despite the gaps described, the study presented sets a quantitative precedent and will serve as a reference for future multi-temporal campaigns and complementary methods, which will correct or improve the results.