The correlation between soy and childhood cancer in Brazil – 11/01/2023 – Health

In a study published on Monday (10/30), in the scientific journal Pnas, from the National Academy of Sciences of the United States, researchers suggest a correlation between the use of pesticides in soybean cultivation and deaths from leukemia among children in Brazil.

In recent years, rural producers in the Cerrado and Amazon regions have begun to expand soybean cultivation, replacing livestock farming.

According to research, the pesticides used on these plantations – mainly glyphosate – end up contaminating rivers and reaching water reservoirs, which can contribute to the emergence of cancer and the subsequent death of children.

The team of researchers reports that, in the initial phase of the study, around half of the families living in the areas studied used artesian wells to obtain water. The rest relied on surface water, which can be subject to contamination. The researchers focused on cancer-associated deaths in children under ten years of age who live in rural areas.

The study is based on data from 2008 to 2019, when there was an increase in soybean cultivation in the Cerrado and Amazon ecosystems. The data analysis took into account two main factors: the proximity between the sick children’s places of residence and rivers, and the distance to hospitals that offer treatment against childhood cancer.

It was concluded that 123 children died from acute lymphoblastic leukemia (ALL) related to soybean production in the period evaluated. Around half of the deaths that occurred over the ten-year period may be associated with increased exposure to pesticides,

ALL is a disease that can be treated. The results of the study seem to confirm that the only patients who died after the expansion of soybean cultivation in these regions were those who lived more than 100 kilometers from a hospital offering specific treatment.

Increase in soybean production

In recent decades, livestock production in the Brazilian Amazon began to be replaced by soybeans due to high global demand, which placed Brazil as the world’s largest producer of the input.

“The expansion occurred quite quickly”, observes researcher Marin Skidmore, assistant professor in the Department of Agricultural and Consumer Economics at the University of Illinois, in the United States, who led the research. According to scientists, between 2000 and 2019, soy production in the Cerrado tripled, while in the Amazon the increase was 20 times.

According to data from the environmental NGO WWF, around 20% of global soybean production is used for human consumption, while 80% is intended for livestock feed and poultry farming, especially for the production of red meat, chicken, eggs and dairy products.

What the study does not reveal

The research, however, is accompanied by some caveats. First, the study does not provide a causal relationship between cancer deaths and pesticide exposure, only presenting an association between the two factors.

The researchers highlighted that the work was developed to eliminate other potential factors. For example, no connection was found between soy consumption and cancer.

Jörg Rahnenführer, director of the Department of Statistical Methods in Genetics and Chemometrics at the Technical University of Dortmund, who was not involved in the research, criticizes the authors for not having considered external factors in the necessary depth.

“Although the suggested connection appears plausible and possibly correct, there are many other possible explanations for the relationships observed in the data. The authors conducted some additional, thoughtful analyses, but several other factors, such as socioeconomic variables, were not considered.”

Rahnenführer says the authors’ conclusions are based on assumptions that water pollution from pesticides is to blame for cancer deaths. This would suggest that more reliable results could be obtained by directly measuring water pollution and potentially related cancer cases. On the other hand, he recognizes that this type of analysis would be “much more complex”.

“It’s hard to imagine causes other than pesticides”

Matthias Liess, director of the Department of Ecotoxicology at the Helmholtz Center for Environmental Research (UFZ) in Leipzig, who was also not involved in the research, assesses that, despite the reservations, the data is of good quality, and the conclusion is solid.

“It is plausible that the association between soybean cultivation or the use of pesticides with children’s illness is not only correlational, but that there is also a causal relationship,” he stated.

An indication of this is that researchers have found a higher incidence of cancer in areas located downstream of soybean plantations than upstream. Thus, the cases would in fact be linked to water pollution. “It is difficult to imagine other causes besides pesticides in this impactful environment”, reinforces the toxicologist.