Photo: Brooke Cagle
Chemical pesticides are widely used in modern agriculture and provide many benefits but also have negative effects. Studies have for example linked agricultural chemicals to surface water pollution and to negative impacts on bird populations in agricultural landscapes, survival and growth of bee colonies, biodiversity, and ecosystems. Despite this, the ecotoxic impacts of pesticides are often not considered in environmental assessments of food products.
A study from 2017 by researchers from Chalmers University of Technology in Sweden and SP Technical Research Institute of Sweden assessed and compared the potential freshwater ecotoxicity impact due to pesticide use in the primary production of six food products. The food products included in the study were chicken fillet, minced pork, minced beef, milk, pea soup, and wheat bread. Primary production refers to the cultivation of the crops on which the assessed food products are based, whether directly or as animal feed. To produce milk for example, dairy cows in Västra Götaland typically eat a mix of grass and clover, oats, barley and soybeans. All food products are produced in Västra Götaland, Sweden, but the soybeans that are used to produce chicken fillet, minced pork, minced beef and milk, are grown in Brazil. The fraction of pesticides that was emitted from the field and reached freshwater, for example due to wind drift, was assessed and used to calculate the potential freshwater ecotoxicity impact. The results were expressed as ecotoxicity impact per kg food product.
The animal-based food products were found to have considerably larger ecotoxicity impacts than the plant-based food products. In relation to pea soup, which has the smallest ecotoxicity impact per kg, bread, milk, minced beef, chicken fillet and minced pork have 2, 3, 50, 138 and 168 times larger impact potentials, respectively. The reason is that animal-based food production systems are less efficient at converting inputs (feed crops) to outputs (meat, milk, or eggs), due to losses of energy and nutrients associated with an additional trophic level in the food chain. Although only two plant-based food products were considered here (bread and pea soup), the finding that plant-based food products have lower ecotoxicity impacts than animal-based food products is likely to be generalizable across a wider range of plant-based food products based on cereals and/or legumes. Thus, diet-related ecotoxicity impacts could be reduced by substituting animal-based food products with plant-based food products, that is, by eating more vegetarian/vegan food and less meat. However, vegetarian diets may contain more “exotic” fruits and vegetables that may be associated with high ecotoxicity impacts.
Notably, chicken fillet and minced pork were found to have larger ecotoxicity impacts than minced beef and milk. This result stands in sharp contrast to typical carbon footprint and land-use results for meat products, which attribute larger impacts to beef than to chicken and pork, due to lower feed conversion ratios and reproduction rates in beef production system and due to methane emissions from enteric fermentation. This finding is explained by different feed rations of pigs, cattle, and poultry, and the associated use of pesticides in the production of feed crops. Both beef and dairy cattle feed on considerable amounts of grass/clover, with small impact potentials. In contrast, chickens and pigs feed on considerable amounts of soymeal from soybeans, with large impact potentials since Brazilian soybean production is very pesticide intensive. It was found that by substituting soybeans with locally sourced feed crops, the impact potentials of minced pork and chicken fillet can be reduced by ca. 70 and 90%, respectively.
Cropping systems in Brazil are characterized by large-scale intensively managed mono-cropping systems in a tropical climate and widespread use of genetically engineered crops. The pressure from pests and diseases is also large in Brazil since natural ecosystems in tropical climates naturally harbor a wide range of insects and fungi that can potentially harm crops and since mono-cropping systems favor the development of pests and diseases, due to lack of natural predators and since insects and fungal diseases can easily spread over large areas. In contrast, cropping systems in Sweden are less intensive, more diversified, and typically integrated in mixed landscapes with forests, permanent pastures, and arable lands with a mix between crop and grass production. Such cropping systems, in combination with a temperate climate, explains the lesser pressure from pests and diseases in Sweden. The pesticide legislation is also stricter in Sweden.
The method used to assess the ecotoxicity impacts due to pesticide use was life cycle assessment. First, a detailed and site-specific inventory of pesticide use in the primary production of the food products was made. Then, pesticide emissions were calculated using the model PestLCI v. 2.0.5. Last, the ecotoxicity impacts due to emissions to freshwater were calculated using the model USEtox v. 2.01. Residues of pesticides in the food products themselves were not considered. For more information about the assessment method and the models used, please see the published article.