Exposure to Pesticides in the Womb Increases Risk Associated with Rare Eye Cancer Among Children

(Beyond PesticidesSeptember 29, 2022) A study published in the International Journal of Hygiene and Environmental Health finds an association between retinoblastoma risk and prenatal exposure to pesticides. Retinoblastoma is rare eye cancer, with over 200,000 cases in the US, most of which are children under the age of five. Despite occurring among offspring, this cancer is often not hereditary. Instead, a mutation in the RB1 gene during early development in the womb destabilizes and augments cell growth.

Although the etiology or cause of childhood eye cancer involves the interaction of multiple components like lifestyle and genetics, emerging evidence indicates that environmental contaminants like pesticides (eg, occupational exposures, air pollution, pesticides, solvents, diet, etc.) play a role in disease etiology. Pesticide contamination is widespread in all ecosystems, and chemical compounds can accumulate in human tissues resulting in chronic health effects. Children are particularly vulnerable to the impacts of pesticide exposure as their developing bodies cannot adequately combat exposure effects. Already, studies find low levels of pesticide exposure during pregnancy or childhood cause adverse health effects from metabolic disorders to mental and physical disabilities. While medical advancements in disease survival are more prominent nowadays, childhood cancer remains the leading cause of death from disease among children. Furthermore, childhood cancer survivors can suffer from chronic or long-term health complications that may be life-threatening. Therefore, it is essential to understand how pesticide accumulation and co-occurrence can increase the risk of latent diseases (eg, cancers) among vulnerable populations, such as children/infants.

The study coauthor Julia Heck, associate research professor of epidemiology at the University of California, Los Angeles (UCLA), notes, “Childhood cancer is one of the leading causes of death in children, but unlike adult cancers, there are not as many identified causes. Although retinoblastoma has high survival rates, children can suffer long-term effects from chemotherapy and radiation…, which is why it’s crucial to identify causes and prioritize prevention.”

The study evaluates the association between childhood eye cancer and exposure to pesticides during prenatal development via proximity to agrochemical pesticide applications. Researchers assess the risk for unilateral (one eye) and bilateral (both eyes) retinoblastoma among children aged five or younger using a population-based case-control study from the California Cancer Registry. Using addresses identified from the birth certificates of participants, the researchers applied Pesticide Use Reports and land use information in a geographic information system (GIS) to detect specific pesticides used within 4,000 meters of the residences. Prenatal exposure to acephate (an organophosphate insecticide) and bromacil (herbicide) has an association with increased unilateral retinoblastoma risk. However, in addition to acephate, pymetrozine (insecticide) and kresoxim-methyl (fungicide) have associations with both types of retinoblastomas.

There is a significant scientific connection between pesticides and cancer as several studies link pesticide use and residues to various cancers, from prevalent forms like breast cancer to rare forms like kidney cancer nephroblastoma (Wilms’tumor). Sixty-six percent of all cancers have links to environmental factors, especially in occupations of high chemical use. In addition to the robust links between agricultural practices and pesticide-related illnesses, over 65 percent of commonly used lawn pesticides and 70 percent of commonly used school pesticides have links to cancer. Although general pesticide exposure can increase susceptibility to cancer, prenatal and early-life exposure to environmental toxicants can increase cancer risk.

Many studies indicate prenatal and early-life exposure to environmental toxicants increases disease susceptibility. For decades, studies have long demonstrated that childhood and in-utero exposure to the US-banned insecticide DDT increase the risk of developing breast cancer later in life. Moreover, a 2021 study finds previous maternal exposure to the chemical compound during pregnancy can increase the risk of breast cancer and cardiometabolic disorders (eg, heart disease, obesity, diabetes) up to three successive generations. However, studies find numerous current-use pesticides and chemical contaminants play a role in similar disease outcomes, including mammary tumor formation. Even household cleaners, many of which are pesticides, can increase nephroblastoma (kidney cancer) and brain tumor risk in children. Furthermore, long-term exposure to organophosphate (OP) pesticides increases adverse health and cancer risks, specifically among women. Since DDT and its metabolite DDE residues, current-use pesticides, and other chemical pollutants contaminate the environment, exposure to these chemical mixtures can synergize to increase toxicity and disease effects.

This study is one of the first to examine the risk for childhood retinoblastoma with ambient exposure to specific pesticides during pregnancy. Just as nutrients are transferable between mother and fetus, so are chemical contaminants. Studies find pesticide compounds in the mother’s blood can transfer to the fetus via the umbilical cord. Therefore, pesticide exposure during pregnancy has implications for both mother and child’s health. Although there is a lack of understanding of childhood cancer risk from parental exposure to pesticides via residential areas adjacent to pesticide applications, the study demonstrates parents’ exposure to pesticides increases childhood cancer risk among offspring. Previous studies show women living near agricultural areas experience higher exposure rates that increase the risk of birthing a baby with abnormalities. Considering current and past-use pesticides and chemical contaminants play a role in multiple disease outcomes and the rate of chronic diseases like cancer continues to increase in the US, and additional studies find these diseases to be pesticide-induced, advocates urge the public to increase pressure on regulators and lawmakers to enact meaningful measures that eliminate pesticide use and the hazards.

Although the study authors say, “Identifying specific pesticides correlated with cancer is the first step toward banning or replacing them with less harmful options,” Beyond Pesticides advocates that studies like this help to eliminate reliance on pesticides with the adoption of organic practices rather than shift to another pesticide, creating a treadmill effect. Additionally, several pesticides can work together to increase the severity (synergize) of health complications associated with chemical exposure. Therefore, it is impractical to associate disease risks with the identification of a single chemical pesticide.

The study concludes, “Future studies are needed to also assess agriculturally common pesticide mixtures and mixture effects. The associations we observed between retinoblastoma and residential proximity to applications for specific pesticides have previously raised concern as to their carcinogenic potential contribution to the growing body of knowledge concerning prenatal pesticide exposure and rare childhood cancers of the nervous system. Strategies for reducing exposure in those living near agricultural fields should be considered as a protective health measure.”

Globally, cancer is one of the leading causes of death, with over eight million people succumbing to the disease every year. Notably, the International Agency for Cancer Research (IARC) predicts a 67.4 percent rise in new cancer cases by 2030. Therefore, it is essential to understand how external stimuli—like environmental pollution from pesticides—can drive cancer development to avoid exposure and lessen potential cancer risks. Moreover, pediatricians strongly agree that pregnant mothers and young children should avoid pesticide exposure during critical development periods. Advocates say this is good advice for the general population, since the effects of pesticide exposure span the entire population.

Fortunately, buying, growing, and supporting organic land management can reduce human and environmental contamination from pesticides. Organic agriculture has many health and environmental benefits, which curtail the need for chemical-intensive agricultural practices. Numerous studies find that pesticide metabolite levels in urine significantly decrease when switching to an all-organic diet. Moreover, there are widely available non-pesticidal alternative strategies that allow families and agricultural industry workers to apply these methods to promote a safe and healthy environment, especially among chemically vulnerable individuals. For more information on how organic is the right choice for both consumers and the farmworkers that grow our food, see the Beyond Pesticides webpage on the Health Benefits of Organic Agriculture.

Studies concerning pesticides and cancer help government officials and the public understand the underlying mechanisms that cause the disease. Beyond Pesticides tracks the most recent reports on pesticides through the Daily News Blog and Pesticide-Induced Diseases Database (PIDD). This database supports the need for strategic action to shift away from pesticide dependency. For more information on the adverse effects of pesticides on human health, see PIDD pages on cancer, including retinoblastoma, birth/fetal defects, and other diseases. Additionally, since pesticides can have multi-generation impacts on our health, you can learn more about the hazards posed to children’s health through Beyond Pesticide’s Pesticide and You Journal article, “Children and Pesticides Don’t Mix.”

All unattributed positions and opinions in this piece are those of Beyond Pesticides.

Source: UCLA, International Journal of Hygiene and Environmental Health

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