The long journey of pesticides-from soils to groundwater, surface waters and oceans-is the subject of research by the University of Sydney (Maggi et al., 2023) published in Nature, ‘Agricultural pesticide land budgets and river discharge to oceans. (1)
Toxic chemicals dangerous to human and animal health, as well as environmental pollutants already surveyed in two-thirds of the Earth’s surface, (2) deserve the attention hitherto silenced by Big Ag‘s pervasive lobbying, including through scientific fraud. (3)
1) Pesticides in agriculture, what fate?
Agriculture is the anthropogenic activity with the greatest impact on the environment. In fact, cultivated land occupies about 48 million km2 of the earth’s surface, or 50 percent of the habitable land. And these lands-connected to natural ecosystems through watersheds-are sprayed with about 3 million tons of pesticides each year. Pesticides can thus reach groundwater, deep underground, and surface waterways. All the way to the seas and oceans.
However, the final destination ofPesticide ActiveSubstances ( PAS) and their persistence in ecosystems have been largely neglected. In contrast to nitrogen fertilizers, whose elements nitrogen (N) and potassium (P) are transported to the sea through rivers with incidence varying in the ranges of 32-45% (N) and 10-20% (P) with respect to the substances used. Therefore, not the path and fate of 3 million toxic chemicals released into the environment each year deserve less attention.
2) Pesticides, dispersion in ecosystems.
The researchers focused the study on the 92 most widely used pesticides in agriculture planetwide. 55 herbicides, 17 insecticides, 16 fungicides and 4 multipurpose PAS. Noting how:
- 82% of the substances are degraded in the soil, (with evaporation to the atmosphere),
- 10% percolates through soils,
- 7.2% remain below the root area of plants.
The ‘journey’ of these substances was followed through 144 of the most important watersheds on the planet, in a total journey of about 13 thousand kilometers in length. The choice of basins considered both their passage through agricultural areas and their outlet into the seas or oceans.
3) Pollution of rivers
Through drainage, pesticides reach rivers with concentrations ranging from 10 to 100 kg of PAS per km of river each year. Of these, only 1.1 percent are degraded along waterways while the rest flow into the seas and oceans. The mix of poisons in saltwater is predominantly composed of herbicides (52.6 percent), followed by all-purpose PAS (35.6 percent), fungicides (11.2 percent), and insecticides (0.6 percent).
Pesticide residues in the seas have minimal concentrations (about 0.1 percent) but toxicity risks are of concern because of the marked vulnerability of fish, other aquatic animals and plants, according to researchers.
The most polluted rivers are those closest to agricultural areas where pesticides are widely used:
- 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 waterways are the Po and the Danube, while Africa and Oceania are the continents that contribute the least pesticide pollutants to rivers, with the exception of Niger and Congo.
4) Aquifers and oceans.
The proportion of pesticides remaining in soil and surface water poses a hazard to non-target organisms and environmental pollution. (4) There is, however, a dearth of data on the damage that individual active ingredients can do to different ecosystems, since the available studies are on aggregate classes of pesticides.
Groundwater is subject to long-term contamination, as evidenced by the presence in European aquifers of contaminants whose use has been banned for years. (5) Herbicides also predominate in the root zone (72.5 percent, glyphosate in the lead), followed by all-purpose PAS (16.6 percent), fungicides (9.9 percent), and insecticides (1.1 percent).
Oceans are in turn polluted by pesticide mixes predominantly herbicides (62.9%), multi-use PAS (26.8%), fungicides 9.7% and insecticides (0.7%). The most commonly detected active ingredients are glyphosate, metam potassium, chlorothalonil, and chlorpyrifos, respectively.
5) Underestimated data
The data collected and processed, the researchers point out, are concerning in themselves and yet underestimated for several reasons:
- PAS concentrations measured at numerous sampling points in watersheds in the United States and the European Union exceed regulatory limits one or more times in a year,
- comparison of model calculations and surveys performed in rivers show the underestimation of PAS concentrations in other continents and countries (e.g., Argentina, Brazil, China, Egypt, India, and Pakistan),
- The study under review did not consider bioaccumulation. At each successive level of the food chain, pesticide concentrations can in fact amplify, up to 1,000 times or more in aquatic species. With consequences also for human health, the final link in the food chain for some species, (6)
- Data are scarce on the ability of active substances (PAS) to degrade into a cascade of ‘daughter’ substances that may exhibit toxicity levels comparable to those of the ‘parent’ substance, sometimes more persistent. As well as on the toxicity of other components of pesticide formulas, in addition to active substances. (7)
6) Interim Conclusions
So-called ‘conventional agriculture,’ when even ‘green-tinted’ with appellations such as ‘sustainable’ or ‘integrated,’ releases millions of tons of toxic chemicals into the environment that-as this study shows-persist in ecosystems. As well as deposited in the organs and tissues of humans, as well as already demonstrated in numerous other scientific studies. (8)
An additional element of concern, not considered in the study under review, is the microplastic and nanoplastic pollution caused by plastic polymers that have been used to encapsulate pesticides for more than 40 years. (9)
The big agricultural confederations in the European Union meanwhile, arm in arm with the pesticide and seed monopolists, insist on boycotting the proposedSustainable Use and Reduction of pesticides (SUR) regulation.
Dario Dongo and Alessandra Mei
On the cover, elaboration on High pesticide concentrations continue to enter Great Barrier Reef. https://tinyurl.com/ysuyszu6 University of Queensland (Australia). 15.10.19
Notes
(1) F. Maggi et al. (2023). Agricultural pesticide land budget and river discharge to oceans. Nature. 12.7.23. DOI: https://doi.org/10.1038/s41586-023-06296-x
(2) Marta Strinati. Pesticides, two-thirds of the planet at risk of environmental pollution. GIFT(Great Italian Food Trade). 26.9.22
(3) Dario Dongo. How the agrochemical industry hides the toxicity of pesticides. New studies. GIFT(Great Italian Food Trade). 13.6.23
(4) Dario Dongo, Ylenia Patti Giammello. Water pollution. Antibiotics, drugs, pesticides in new EU monitoring plan. GIFT(Great Italian Food Trade). 17.10.22
(5) Dario Dongo. ISPRA, 2020 report on pesticides in water. GIFT(Great Italian Food Trade). 24.12.20
(6) Marta Strinati. Pesticide cocktails cause toxicity, even at doses allowed in the EU. New study. GIFT(Great Italian Food Trade). 24.10.20
(7) Dario Dongo, Alessandra Mei. EFSA glosses over the safety risks of glyphosate. ‘Stop Glyphosate!. GIFT(Great Italian Food Trade). 22.7.23
(8) Marta Strinati. Glyphosate in the urine of 99.8% of French people. GIFT(Great Italian Food Trade). 15.1.22
(9) Marta Strinati. Microplastics in pesticides, the CIEL report. GIFT(Great Italian Food Trade). 20.7.22
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
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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