Cancer Risk: Are Pesticides the New Smoking?

What Are Pesticides, and Why Are They Used?

Pesticides are chemicals used in agriculture to control or destroy harmful organisms, such as insects, weeds, and fungi. They are widely used to prevent plant diseases and improve agricultural yields. However, they must be used carefully because they may adversely affect human health and the environment.

Pesticides have transformed modern agriculture, improving production efficiency and playing an important role in food security for a rapidly growing global population. From a public health perspective, however, pesticide exposure is associated with many harmful effects, including neurological disorders such as Parkinson’s disease, weakening of the immune system, and increased cancer risk.

Pesticide exposure has been associated with colorectal cancer, lung cancer, leukemia (in both children and adults), lymphoma, and pancreatic cancer. However, these studies have generally focused on individuals known to have been exposed to particular pesticides or on specific cancer types, providing a limited perspective.

RELATED TOPIC: Certain Pesticides Found to Be Linked to Pancreatic Cancer Risk

There has not yet been a comprehensive assessment of how pesticide use affects cancer risk across a broader population.

On 25 July 2024, Frontiers in Cancer Control and Society published a population-level study aiming to fill this gap. It examined cancer risks in the US population using a model of pesticide use adjusted for various factors. The aim was to identify regional differences and contribute to policies protecting public health.

Calculating Cancer Risk

The researchers developed a model using several data sources to estimate the additional cancer risk resulting from agricultural pesticide use. The main data included:

• US Geological Survey pesticide use data from 2019, covering 69 agricultural pesticides across 3143 counties.
• Cancer incidence (frequency) data per 100,000 people for various cancers, including bladder, colorectal, leukemia, lung, non-Hodgkin lymphoma, and pancreatic cancers, collected by the National Institutes of Health and Centers for Disease Control and Prevention between 2015-2019.
• Covariates such as smoking prevalence, the Social Vulnerability Index, agricultural land use, and the total US population in 2019.

Pesticide use profiles were developed through latent class analysis, a statistical method for identifying homogeneous subgroups within a heterogeneous population. A general linear model then estimated how these pesticide use patterns and covariates affected cancer incidence.

The model calculated the estimated annual increase in cancer cases attributable to differences in agricultural pesticide use, highlighting counties with the highest and lowest “additional” cancer risk associated with pesticide exposure.

The Most Affected Region: The Midwest

Although this model does not prove causality or assess individual risks, it demonstrates population-level associations between pesticide use patterns and cancer incidence.

The US Midwest, known for corn production, emerged as the region most affected by pesticide use. Compared with the lowest-risk counties, the Midwest saw a total of 154,541 additional cancer cases annually across all cancer types. The annual increases in colorectal and pancreatic cancers were reported as 20,927 and 3835 cases, respectively. Similar trends were observed for leukemia and non-Hodgkin lymphoma.

Pesticides and Smoking

Using the same model, the researchers also estimated the additional cancer risk associated with smoking. In many cases, pesticides posed a higher cancer risk than smoking according to the model.

The clearest difference was seen for non-Hodgkin lymphoma, with pesticides associated with 154.1% more cases than smoking. For all cancers, bladder cancer, and leukemia, the increases were 18.7%, 19.3%, and 21%, respectively.

This result emphasizes the importance of considering pesticide exposure alongside smoking when examining cancer risks.

Expanding the Scope of Research

Several limitations must also be noted. Data were missing for certain geographical areas, and the counties studied varied in size and population. The study also likely failed to account for seasonal and migrant workers with high pesticide exposure. In addition, its data were not independently validated and could not be used to assess individual risks.

The effects of pesticides on human health are a broad and critical research area, usually focusing on a limited number of pesticides or specific cancers. This study stands out for its broader, more comprehensive approach, seeking to highlight regional inequalities and identify less-studied pesticides that could become future research priorities.

Given the major public health implications, the authors encourage sharing these findings with the most vulnerable communities and raising awareness.

Are Pesticides Themselves the Real Culprit, or the Amount Used?

The harmful effects of pesticides generally depend on the amount of exposure. In other words, the real issue is not the pesticide itself but how and how much it is used. Used at high doses or without control, pesticides can seriously harm human health and the environment. Correct application methods and appropriate doses can minimize harm. Improper or excessive use, however, can increase health risks such as cancer. The amount and method of application are therefore critical to safe use.

Is Pesticide-Free Farming Possible?

Yes, pesticide-free farming is possible, but it requires more planning and knowledge than conventional farming. Alternative approaches such as organic farming, biological control, and integrated pest management aim to minimize pesticide use. They include strategies such as natural predators, beneficial insects, and crop rotation. However, pesticide-free farming may require more labor and expense and may not always be as productive as conventional methods. It nevertheless offers environmental and human health advantages.

Can We Feed the World Without Pesticides?

Feeding the world without pesticides may be possible, but it presents a major challenge. In conventional farming, pesticides are widely used to improve crop yields and control pests. Eliminating them entirely could cause crop losses and increase production costs, affecting the food supply.

However, sustainable farming methods such as organic farming, biological control, and integrated pest management (IPM) can maintain food production while reducing pesticide use. By protecting natural ecosystems, they offer more environmentally friendly and sustainable long-term solutions. Advanced technologies, precision farming, and genetic improvement methods can also increase agricultural productivity and reduce reliance on pesticides.

The worldwide feasibility of pesticide-free farming nevertheless depends on many factors, including climate, soil structure, and production scale. Efficient implementation requires extensive education, investment in technology, and policy changes. Thus, although a pesticide-free world is technically possible, how to manage this transition globally remains an important question.