Long-range transport: gone with the wind

Pesticide Atlas 2022

Pesticides rarely stay in the place where they have been applied. Wind can move dust, particles, and droplets to residential areas close to agricultural land – or carry it to places many kilometres away. Approval processes are largely ignoring this problem.

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Air quality under threat: A cocktail of five to 34 pesticides was found at 75 percent of all monitoring stations.

When pesticides are applied with spray nozzles, droplets or mist can be blown by the wind onto neighboring land. This phenomenon is called pesticide drift. Incorrectly adjusted and inappropriate nozzles or excessive speed of the spray vehicle intensify the effect. Active ingredients may also travel much longer distances, from a few hundred metres to over 1,000 kilometres. This is called “long-range transport”. Active ingredients can rise into the air; because of ground warming, evaporation or adhering to tiny dust particles being blown up by the wind from uppermost soil layers. In this case, air currents distribute small suspended particles – so-called aerosols – in all directions. Cooling and rain cause them to sink back to the ground. They can end up almost everywhere: in nature reserves, in city parks and in human lungs.

The possibility of long-distance transport of pesticides has long been known. As early as 1999, a study collection drew attention to the fact that 30 pesticides were found throughout Europe, in some cases at measuring points far away from where they were applied. For a study published in 2020, two German NGOs (Bündnis für eine enkeltaugliche Landwirtschaft and Umweltinstitut München) examined pesticide contamination of air. At 163 sites throughout Germany – including protected areas, cities and organic fields – traces of 138 pesticides were detected.

30 percent of the substances found are not or no longer permitted in Germany, for example DDT, a long-lived organic compound that is difficult to degrade and prohibited in most western countries since decades. Cocktails of 5 up to 34 pesticides and their degradants were found at three quarters of the sites. Glyphosate, the most widely used herbicide in the world, was detected at all sites that were equipped with technical filters. This is significant because it disproves the assumption that glyphosate does not spread through the air – glyphosate and all its salts are considered non-volatile, which is why the European Food Safety Authority (EFSA) has so far ruled out the possibility of long-range glyphosate transport.

Another 2020 study examined airborne pesticide concentrations at 50 sites across France over a 12-months period. Glyphosate was detected at 80 percent of the sites investigated. This is further evidence for large distance transport of glyphosate through the air. The fact that longrange transport and drift occur worldwide is demonstrated by other recent studies. To assess possible contamination of non-target areas in South Tyrol, 71 grass samples of public playgrounds and schoolyards located next to intensively managed apple and wine orchards were examined. At least one pesticide and sometimes even pesticide cocktails were detected in 96 percent of the samples. The majority of the detected pesticides are classified as endocrine disruptors, which can affect the health of humans and animals, even in miniscule amounts. Another example from the USA shows air pollution probably caused by pesticide drift. According to a 2021 study, more than one million acres of soybeans and at least 160,000 acres of a conservation area were affected by exposure to the herbicide dicamba from adjacent agricultural fields.

Residue data were analyzed from grass samples by an international research group. They found endocrine active substances – some of them are suspected human carcinogens.

For years, civil society organizations in South Africa and other countries have been advocating for mandatory buffer zones as a risk mitigation measure. A new measure was also imposed in France to protect residential areas from drift of hazardous pesticides – farmers must respect now a buffer zone of 20 metres.

A national air monitoring program of pesticides exists only in Sweden. And in approval processes for pesticides and active ingredients, little attention is paid to the phenomenon. The risk of a possible long-range transport is only estimated theoretically. A verification of the contamination in practice, however, does not take place.

The estimated amount of pesticides that people can consume on a daily basis without any immediate risk to health is only based on digestive tract absorption and only for a single active ingredient at a time. In contrast, pesticide exposure through drift and long range transport takes place primarily through the respiratory tract – and the long term effects of pesticide cocktails entering the human body through the lungs are still largely unknown.

Organic farms that forgo pesticides are under threat from volatile substances – wind carries them onto organic fields and this can threaten their business.