SPRINT has quantified the ‘cocktail’ of pesticides present in freshwater, air, soil, farm household dust and crops across Europe and in Argentina. Our results support the case that regulators should consider mixtures when assessing pesticide risk.
Scientists are increasingly worried about the complex mixtures of pesticides present in our environment.
In the EU, over 400 active ingredients for pesticides are currently approved for use (as listed on the EU pesticides database). Farmers often apply multiple products to their crops to protect them from pests and disease. The resulting residues can travel far and wide – for instance, in air and water, on food, or even on the soles of our shoes.
This creates mixtures of pesticide residues – many of which are considered hazardous to humans, wildlife, and ecosystems. These mixtures are not only found on farmland; they also permeate our everyday surroundings and the wider environment too.
Of concern, a growing body of evidence finds that pesticides can have unpredictable and stronger effects when they are combined in mixtures. To give just one example, a 2022 study from France found that a pesticide mixture found in farmland soil was highly toxic to springtails – important soil-dwelling insects. This was even though the individual substances in the mix were at levels that regulators consider ‘safe’.
SPRINT: counting pesticides for more effective regulations and policy
In the largest study of its kind, the SPRINT research project measured used pesticides in the environment. We did this across multiple locations in Europe and Argentina, and in multiple matrices, or ‘components’, such as soil, water and air.
Why did we do this? Several reasons, including:
- For a better picture of pesticides’ risks to human health and the environment. Healthwise, when deciding whether a pesticide is safe to be on the market, regulators will consider how much of the substance we will encounter through food and drink. But we may also ingest pesticides from our environment, which could amplify their risks – especially for farm workers and their rural neighbours.
- For a clearer picture of which combinations of pesticides occur, and where. Little is known about the health and ecological risks posed by pesticide mixtures that you’re likely to find in the environment. What we do know about the ‘cocktail effect’ is concerning, yet regulators only tend to assess risks of individual substances.
- To guide risk-reduction strategies. Policies that aim to reduce pesticides’ risks need a clear sense of what the initial risks actually are. SPRINT measured what is in the environment now, to help define targets to work towards.
Our findings...
Infographic displaying total numbers of pesticides found by SPRINT in indoor dust, air, crops, sediment, soil, and freshwater across all samples. It is important to note that the figures above indicate the total number of different pesticides found across all samples. For example, in indoor house dust, the number of individual pesticides found in a single home were between 25-121, with a median of 80 in conventional farms and 65 in organic farm households.
How many pesticides were found in indoor dust of farms?
Pesticide residues were studied in 65 conventional farms and 63 organic farms.
Our study of household dust from farmers' homes in 10 European countries in 2021 detected 197 pesticides in total. The number of pesticides in each home ranged between 25 and 121.
They were in much lower concentrations than on farmland. But their high number is explained by their slow degradation in the dark, dry conditions of most homes – where they can linger for years.
43% of the pesticides we found in the dust are linked to highly toxic effects, including cancer and disruption of the hormonal system in humans.
This work was recently written about by the Guardian, reiterating the importance of this research. When reading this article, please consider the clarifications made above.
>> Learn more about this study in our accessible research summary: Pesticide residues and human health hazards compared against EU classifications
Blog: Pesticide residues in indoor house dust: key recommendations for minimising exposure
Total number of different pesticides detected in samples of air, crops, sediment, soil, water and dust collected from 10 European countries. Source: Silva et al (2023)
How many pesticides were found in crops?
Our study of crops from 10 European sites in 2021 found a total of 78 pesticides.
A total of 76 were found on crops from conventional farms, and 25 on crops from organic farms.
Many of these compounds were already banned, such as the carcinogenic insecticide, dieldrin, which the EU prohibited 40 years earlier in the 1980s.
>> Learn more about this study in our accessible research summary: Pesticide residues and human health hazards compared against EU classifications
How many pesticides were found in freshwater?
Many freshwater bodies, such as ponds, lakes and streams, are already in a very poor state, and suffer biodiversity loss. Pesticide contamination is partly to blame for this.
Our 2021 study of freshwater bodies in 11 heavily farmed areas of Europe and Argentina detected 115 pesticides altogether.
Up to 37% of these are listed on PAN’s International List of Highly Hazardous Pesticides. And, in some locations, concentrations of certain pesticides exceeded regulatory limits under the EU’s Water Framework Directive. This means they posed risks to wildlife.
Another of our studies, across 10 European countries, detected 112 pesticides in water.
The deterioration of freshwater ecosystems is highly concerning. While they represent just 0.01% of water on Earth, they are home to around 10% of all recorded species.
>> Learn more about these studies in our accessible research summaries:
- Assessing pesticide residues occurrence and risks in water systems: a pan-European and Argentina perspective
- Pesticide residues and human health hazards compared against EU classifications
How many pesticides were found in sediment?
Sediment accumulates at the bottom of streams, rivers and other waterbodies and is critical to the health of freshwater ecosystems. It is known to trap pollutants, including pesticides, and could act as a ‘chemical timebomb’.
Our study tested sediment from 38 water bodies across 8 European countries.
We found 99 different pesticide residues in the sediment samples.
27 of these were not approved for agricultural use at the time of the study. They included DDE, a breakdown product from the long-banned and highly toxic pesticide DDT.
>> Learn more about this study in our accessible research summary: Pesticide residues in European sediments: concerning for aquatic environments?
How many pesticides were found in air?
Agricultural pesticides can become airborne through spray drift, vapor from contaminated soil or water, or in contaminated soil particles eroded by the wind.
In 2021-2022, we tested air weekly on farms in Portugal and the Netherlands.
We found 99 pesticides in total.
Nearly all of the 96 samples contained between 10 and 30 pesticides.
In another 2021 study, this time across 10 European countries, we found 76 different substances altogether.
Levels of each pesticide were low, but we don’t yet know if inhaling these substances over the long term carries health risks, or how their risk changes within pesticide mixtures.
>> Learn more about these studies in our accessible research summaries:
- Pesticides and their breakdown products in rural air
- Pesticide residues and human health hazards compared against EU classifications
How many pesticides were found in soil?
Healthy soils are crucial to food production. As such, several EU policies, such as the Zero Pollution Action Plan, call for the prevention and reduction of soil pollution, including by pesticides.
Our study of farmland soil across 10 European countries in 2021 detected 100 different pesticides altogether.
Most of the 201 soil samples (88%) contained more than one pesticide. One sample contained 21 different substances.
We found 151 different combinations of pesticides containing 2- 21 substances.
Obsolete organochlorine pesticides, such as DDT, were among the most common compounds in these soils.
>> Learn more about this study in our accessible research summary: Pesticide residues in organic and conventional agricultural soils across Europe: measured and predicted concentrations
Things to note
Our project helps show how many pesticides are ‘out there’. However, we need more research to understand what harms (if any) these pesticides can cause to our health and the environment – in these combinations, at these levels and over the long term.
In addition, an even bigger study – or different study locations – could lead to different figures. However, we have provided a good representation of agriculture in Europe – covering conventional and organic farms that produce a variety of crops.
Conclusions and policy recommendations
Evidence from SPRINT highlights the vast number of pesticides in the environment and that they occur in many combinations.
Our results support the idea that regulators should assess pesticides’ risks within a mixtures context. This is not only the case for new pesticides that are yet to be approved (pre-market authorisation). It should also apply to substances that are already in use (post-market authorisation).
Regulators already do some testing of mixtures - of active ingredients that occur in the same plant protection product. But we have shown which mixtures are likely to be found in the environment.
The findings also highlight the persistence of banned pesticides, such as DDT. This means that risk assessments of newer pesticides may need to consider interactions with older ones.
By understanding how these chemicals interact and persist in the environment, policymakers can take effective steps towards reducing pesticide exposure and protecting human health and biodiversity.
This article was written by Michelle Kilfoyle, Dr Charlotte Chivers, and our dissemination and exploitation committee, based on SPRINT research.
Infographic designed by Charlotte Chivers.
