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Organic pollutants: almost everything is now detected

R+D CSIC 30 years

Nowadays, environmental monitoring involves the analysis of any sample (water, food, soil...) and has moved from analysing a limited number of pollutants to "non-target" analysis, in which almost everything in the sample is detected without restrictions. And at previously impossible levels: contaminants can now be detected at concentrations of less than 1 part per billion.

Detail of sampling in a mass spectrometry equipment. Credit: CSICIn 1994, pesticides containing aldrin, chlordane, DDT, arsenic or strychnine and derivatives (most of them organochlorines) were banned for any use. In fact, in Spain, they had already been banned for agricultural use since 1991. There were evidences of their toxic effect on living organisms.

The ban covered the import, marketing or use of all pesticides containing organochlorine compounds, i.e. organic compounds containing chlorine...

At that time, even with the ban, these organochlorine pesticides were detected in the environment. Nowadays, they are still present, but in much lower concentrations, explains Josep Maria Bayona, research professor at the Instituto de Diagnóstico Ambiental y Estudios del Agua (IDAEA-CSIC). His laboratory is a reference in the detection of pesticides and organochlorine compounds.

His team has developed and fine-tuned methods for analysing compounds, methods that have been transferred to companies and laboratories. One example is the method for detecting tributyltin (TBT), an organic biocide found in antifouling paints on ships, which was progressively banned between 2001 and 2008.

Sensitivity of analytical equipment has increased a thousand-fold

Detection techniques have improved significantly. The sensitivity of the equipment has folded by 1000. "Before we could detect a pollutant at concentrations of 100 ppb (parts per billion) and now we can detect concentrations of less than 1 ppb.

Another improvement is that "now, in some cases, we can introduce a sample of less than 1 millilitre directly into the mass spectrometer and analyse it, without the need for preparation. That was impossible some years ago”.  Nevertheless, in most cases is still necessary to prepare samples by chromatography, a technique that separates the components of a mixture to facilitate their analysis. Still, the whole process has been streamlined in general. While two or three decades ago it was possible to analyse one or two samples a day, today it is possible to analyse 25 or 30 samples, explains Josep Maria Bayona.

Detection techniques have improved significantly. The sensitivity of the equipment has folded by 1000.

Non-target analysis

Another great qualitative leap is the number of compounds that can be detected in a single analysis: before, between 2000 and 3000 pesticides could be detected; now, almost everything. And what is this everything? There are currently some 70,000 organic cobmpounds on the market, Bayona points out, and a large number of them can be identified by mass spectrometer analysis. But even in cases where a compound cannot be identified, there is software that calculates the probability that it is one or another of the 70,000 marketed compounds. This is possible because there are large databases available of mass spectra.

Mass spectra, a kind of of  'fingerprint' of the molecules. The peaks and numbers indicate masses of the molecules analysed, allowing their identification. Credit: CSIC

"I remember," says Bayona, "that the collections of mass spectra (a kind of "fingerprint" of molecules) had between 20,000 and 30,000 items.  Now we have collections of 300,000 mass spectra, thanks to the fact that laboratories share their data". Even so, he adds, "even with the software to help, you need the analyst's judgement, who knows how to interpret the results".

Victor Matamoros, scientist at IDAEA-CSIC, agrees that the arrival of non-target analysis is the most substantial change in the field. His team studies changes in the metabolism and physiology of plants caused by pollutants. This type of research is possible thanks to non-target analyses and opens up a huge range of possibilities, says Victor Matamoros, "such as knowing which drugs are absorbed by the plants, their effects on the harvesting (pollutants can reduce productivity), on biodiversity, on the health of ecosystems and on human health.

"Twenty years ago we knew that there were emerging pollutants such as pharmaceuticals in wastewater, but we didn't know if they were accumulated by plants. This is what we study now"

"Twenty years ago we knew that there were emerging pollutants such as pharmaceuticals in wastewater, but we didn't know if they were incorporated and accumulated by plants. This is what we study now," Matamoros adds. His team has found that in laboratory conditions, such as greenhouse or hydroponic cultures, drugs like antibiotics or carbamezapine can be absorbed by plants. "But we have seen that this incorporation is much lower in real crop fields, because the soil and microorganisms constitute a barrier that reduces the incorporation of these substances into the plants".

One of the room-labs of the IDAEA-CSIC Mass Spectrometry Laboratory. Credit: CSIC

Although much progress has been made in knowledge about organic pollutants, scientists don’t know yet how the pollutants transform, how they degrade and where (in water, in the air, in organisms?), whether they break down into other more toxic molecules or not, their effects on living beings and ecosystems....

Toxicological studies are also being carried out on pig slurry in water and in sewage treatment plants. This is a growing concern. On the one hand, there is more water reuse. On the other hand, due to the energy crisis and the rising cost of fertilisers, organic fertilisers such as pig slurry are increasingly used. This makes it necessary to monitor them for the presence of contaminants and pharmaceuticals.

Mercè Fernandez / CSIC Communication