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Dispersion of pesticides in soils, aquifers, surface waters and oceans. Research on 'Nature'

The long journey of pesticides - from soils to groundwater, surface waters and oceans - is the subject of a research by the University of Sydney (Maggi et al., 2023) published on Nature, 'Agricultural pesticide land budget and river discharge to oceans'. (1)

Toxic chemical substances dangerous for human and animal health, as well as environmental pollutants already recorded in two thirds of the earth's surface, (2) deserve the attention hitherto silenced by LOBBY pervasive of Big Ag, including through scientific fraud. (3)

1) Pesticides in agriculture, what fate?

agriculture it is the anthropic activity with the greatest impact on the environment. In fact, cultivated land occupies about 48 million km2 of the earth's surface, ie 50% of habitable land. And these lands - connected to natural ecosystems through watersheds - are sprayed every year with about 3 million tons of pesticides. Pesticides can thus reach deep underground aquifers and surface watercourses. Until we reach the seas and oceans.

The final destination of pesticide active substances (Pesticide Active Substances, PAS) and their persistence in ecosystems have however been largely neglected. Unlike nitrogen fertilizers, whose elements nitrogen (N) and potassium (P) are transported to the sea through rivers with variable incidence in range of 32-45% (N) and 10-20% (P) with respect to the substances used. However, the path and fate of 3 million toxic chemicals released into the environment each year deserve less attention.

2) Pesticides, dispersion in ecosystems

Researchers focused the study on the 92 most used pesticides in agriculture worldwide. 55 herbicides, 17 insecticides, 16 fungicides and 4 multipurpose PAS. Noting how:

  • 82% of the substances degrade in the soil, (with evaporation in the atmosphere),
  • 10% percolates through the soils,
  • 7,2% remain below the root area of ​​plants.

Travel' of these substances was followed through 144 of the most important water basins on the planet, in an overall journey of about 13 km in length. The choice of basins considered both their passage through agricultural areas and their outlet to the seas or oceans.

3) River pollution

Through the drainage, pesticides reach rivers with a concentration ranging between 10 and 100 kg of PAS per km of river each year. Of these, only 1,1% is degraded along watercourses while the rest flows into the seas and oceans. The mix of poisons in salt water is mainly composed of herbicides (52,6%), followed by multipurpose PAS (35,6%), fungicides (11,2%) and insecticides (0,6%).

The residues di pesticides in the seas they have minimal concentrations (about 0,1%) but the risks of toxicity are of concern, according to the researchers, due to the marked vulnerability of fish, other animals and aquatic plants.

The most polluted rivers are those closest to agricultural areas where extensive use of pesticides is made:

  • United States (Mississippi and Sacramento), Argentina (Parana), India (Ganges), Western China (Yangtze, Pearl and Yellow River) and Southeast Asia (Irrawaddy and Yellow River) East Asia (Irrawaddy and lower Mekong),
  • in Europe the most polluted watercourses are the Po and the Danube, while Africa and Oceania are the continents that bring the least polluting pesticides to rivers, with the exception of Niger and Congo.

4) Groundwater and oceans

The share of pesticides remaining in soil and surface water poses a danger to non-target organisms and environmental pollution. (4) Furthermore, there is a lack of data on the damage that individual active ingredients can cause to different ecosystems, since the available studies concern classes of aggregated pesticides.

The aquifers are subject to long-term contamination, as evidenced by the presence in European groundwater of contaminants whose use has been banned for years. (5) Also in the root zone, herbicides prevail (72,5%, glyphosate in the lead), followed by multipurpose PAS (16,6%), fungicides (9,9%) and insecticides (1,1%).

The oceans are in turn polluted by mix of pesticides mainly from herbicides (62,9%), multipurpose PAS (26,8%), fungicides 9,7% and insecticides (0,7%). The most detected active ingredients, respectively, are glyphosate, metam potassium, chlorothalonil and chlorpyrifos.

5) Underestimated data

The data collected and processed, the researchers point out, are in themselves worrying and yet underestimated for several reasons:

  • the concentrations of PAS measured at numerous abstraction points in the watersheds of the United States and the European Union exceed the regulatory limits one or more times in the course of a year,
  • the comparison between the calculation models and the surveys carried out in rivers show the underestimation of PAS concentrations in other continents and countries (e.g. Argentina, Brazil, China, Egypt, India and Pakistan),
  • the study in question did not consider bioaccumulation. Indeed, at each successive level of the food chain, pesticide concentrations can be amplified, up to 1000-fold or more in aquatic species. With consequences also for human health, the final link in the food chain for some species, (6)
  • data on the ability of active substances (PAS) to degrade into a cascade of 'daughter' substances which can present levels of toxicity comparable to those of the 'mother' substance, sometimes more persistent, are scarce. As well as on the toxicity of other components of pesticide formulas, in addition to the active substances. (7)

6) Provisional conclusions

The so-called 'conventional agriculture', even if 'painted green' with appellations such as 'sustainable' or 'integrated', releases millions of tons of toxic chemicals into the environment which – as this study demonstrates – persist in ecosystems. In addition to being deposited in the organs and tissues of humans, as well as already demonstrated in numerous other scientific studies. (8)

One more element of attention, not considered in the study in question, is the pollution from microplastics and nanoplastics caused by plastic polymers which have been used for over 40 years to encapsulate pesticides. (9)

The large agricultural confederations meanwhile in the European Union, hand in hand with the pesticide and seed monopolists, they persist in boycotting the proposed SUR regulation (Sustainable Use and Reduction of pesticides).

Dario Dongo and Alessandra Mei

On the cover, elaboration on High pesticide concentrations continue to enter Great Barrier Reef. University of Queensland (Australia). 15.10.19


(1) F.Maggi et al. (2023). Agricultural pesticide land budget and river discharge to oceans. Nature. 12.7.23. DOI:

(2) Marta Strinati. Pesticides, two thirds of the planet at risk of environmental pollution. GIFT (Great Italian Food Trade).

(3) Dario Dongo. How the agrochemical industry hides the toxicity of pesticides. New studies. GIFT (Great Italian Food Trade).

(4) Dario Dongo, Ylenia Patti Giammello. Water pollution. Antibiotics, drugs, pesticides in the new EU monitoring plan. GIFT (Great Italian Food Trade).

(5) Dario Dongo. ISPRA, 2020 report on pesticides in water. GIFT (Great Italian Food Trade).

(6) Marta Strinati. Pesticide cocktails cause toxicity, even at the doses allowed in the EU. New study. GIFT (Great Italian Food Trade).

(7) Dario Dongo, Alessandra Mei. EFSA glosses over the safety risks of glyphosate. 'Stop Glyphosate'!. GIFT (Great Italian Food Trade).

(8) Marta Strinati. Glyphosate in the urine of 99,8% of French people. GIFT (Great Italian Food Trade).

(9) Marta Strinati. Microplastics in pesticides, the CIEL report. GIFT (Great Italian Food Trade).

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Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.

Alessandra Mei
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Graduated in Law from the University of Bologna, she attended the Master in Food Law at the same University. You participate in the WIISE srl benefit team by dedicating yourself to European and international research and innovation projects.

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