Pesticides have become more harmful globally, study finds

The toxicity of pesticides increased worldwide between 2013 to 2019, with Brazil among the countries leading the way. The conclusion can be found in a study published this month in the journal Science and contradicts the goal of reducing pesticide risks by 2030, established at the 15th United Nations Conference on Biodiversity (COP15).

German scientists from the University of Kaiserslautern-Landau examined 625 pesticides across 201 nations. They used the total applied toxicity (TAT) indicator, which considers the volume used and the toxicity level of each substance.

Six out of eight species groups are most vulnerable to increasing levels of toxicity – terrestrial arthropods (such as insects, arachnids, and centipedes), whose toxicity has surged by 6.4 percent per year; soil organisms (4.6%), fish (4.4%), aquatic invertebrates (2.9%), pollinators (2.3%), and terrestrial plants (1.9%).

Global TAT sank only for aquatic plants (−1.7%) and terrestrial vertebrates (−0.5% per year). Humans are part of the latter.

“The increasing global TAT trends pose a challenge to achieving the UN pesticide risk reduction target and demonstrate the presence of threats to biodiversity globally,” the study reads.

Brazil in the spotlight

Brazil appears as one of the main actors in this scenario. The study identifies the country as having one of the highest levels of toxicity per agricultural area on the planet – alongside China, Argentina, the US, and Ukraine.

Furthermore, Brazil, China, the US, and India together account for 53 to 68 percent of the total applied toxicity worldwide.

Brazil’s relevance is directly linked to the weight of its agribusiness, especially extensive crops. Even though traditional cereals and fruits occupy large areas, the toxicity associated with crops such as soybeans, cotton, and corn has a significantly greater impact if one bears in mind their cultivated area.

Types of pesticides

One of the most relevant findings of the study indicates that the problem is highly concentrated – on average, only 20 pesticides per country account for more than 90 percent of the total applied toxicity.

The study points out that different chemical classes dominate the impacts. Classes of insecticides – such as pyrethroids and organophosphates – contributed over 80 percent of the TAT of aquatic invertebrates, fish, and terrestrial arthropods. Neonicotinoids, organophosphates, and lactones accounted for more than 80 percent of the TAT of pollinators.

Organophosphates, along with other classes of insecticides, contributed most to the TATs of terrestrial vertebrates. Acetamide and bipyridyl herbicides contributed more than 80 percent to the TAT of aquatic plants, while a broader mix of herbicides (including acetamide, sulfonylurea, and others) determined the TAT of terrestrial plants. High-volume herbicides such as acetochlor, paraquat, and glyphosate belong to these classes and have been associated with environmental and human health risks.

Conazole and benzimidazole fungicides, along with neonicotinoid insecticides applied to seed coatings, contributed mainly to the TAT of soil organisms.

Distant global target

The study also assessed the progress of 65 nations. The diagnosis is that, without structural changes, only one country will achieve the UN target of reducing pesticide toxicity by 50 percent by 2030 – Chile.

According to the researchers, China, Japan, and Venezuela are on track to achieve the target and show downward trends across all indicators. However, they need to speed up changes in pesticide use.

Thailand, Denmark, Ecuador, and Guatemala are moving away from the target, with at least one indicator doubling in the last 15 years. They need to reverse the rapid increase trends and return to their previous trajectory.

All other countries in the study, including Brazil, need to bring pesticide risks back to levels seen more than 15 years ago. This means reversing decades-old patterns of use in both volume and toxicity of mixtures.

The scientists point to three main ways to curb the escalating risks – replacing highly toxic pesticides, expanding organic farming, and adopting non-chemical alternatives. Biological control technologies, agricultural diversification, and more precise management are named as strategies capable of cutting down impacts without hurting productivity.