01
Sep
In Utero and Childhood Pesticide Exposure Increases Childhood Cancer Risk
(Beyond Pesticides, September 1, 2021) A study published in Environmental Pollution finds the risk of acute childhood leukemia (AL) increases with prenatal and newborn exposure to pesticides (i.e., insecticides and herbicides). The study results support the hypothesis that chronic environmental pesticide exposure increases childhood leukemia risk up to two times. Maternal exposure has a stronger association with leukemia than childhood exposure. Insecticides and herbicides are of particular significance in increasing leukemia risk, especially for acute lymphoblastic leukemia. Although medical advancements in disease survival are more prominent nowadays, childhood AL remains the secondary cause of child mortality following physical injury. Furthermore, childhood leukemia survivors can suffer from chronic or long-term health complications that may be life-threatening.
Although the etiology or cause of childhood AL involves the interaction of multiple components like lifestyle and genetics, emerging evidence indicates that environmental contaminants like pesticides (e.g., 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. Moreover, several studies demonstrate an association between environmental or occupational pesticide exposure and the risk of childhood cancer, specifically focusing on leukemia.
Acute leukemia is the most common type of childhood cancer, affecting one out of three individuals, ages 0 to 14 years. Although the disease is rare, incidents are steadily increasing among adolescents and have been over the last 30 years. Therefore, studies like these highlight the importance of understanding how pesticide use can increase the risk of latent diseases (e.g., cancers) among vulnerable populations, such as children/infants. The authors note, “…[T]he findings of the present meta-analysis provide some evidence that low-dose long-term exposure to pesticides, mainly during pregnancy, increases the risk of childhood AL, especially among infants, supporting the still harmful role of pesticides…Moreover, mechanistic studies are deemed necessary to shed light into potentially relevant molecular pathways that underlie these associations, if replicated in future research.”
Despite several scientific studies demonstrating an association between pesticide exposure and adverse health outcomes like acute childhood leukemia (AL), methodological evidence remains inconclusive. The researchers evaluate the currently available, peer-reviewed literature on the association between pesticide exposure and different types of childhood AL, including acute lymphoblastic (ALL), acute myeloid (AML), and infant leukemia. The literature review focuses on studies published until January 2021 with specific attention to methodology. Researchers categorize effects by pesticide type, exposure-outcome (e.g., leukemia type), window/timeframe of exposure, and exposed population in evaluating the vast array of current studies.
The study results identify 55 studies from over 30 countries pertaining to over 200 different pesticide exposures from over 160,000 participants. Regardless of pesticide type, leukemia type, exposure timeframe, and population group, methodological studies demonstrate pesticide exposure increases the risk of childhood leukemia, particularly for infants. Maternal exposure to pesticides during gestation results in a more elevated leukemia risk for children than childhood (postnatal) exposure. Whether pesticide exposure is occupational or mixed, parental exposure to pesticides has the highest association with AL risk, including paternal (father) exposure. Exposure during pregnancy results in a 1.5 times greater risk of developing AL, with a 2.5 times increase in risk for acute lymphoblastic leukemia. When assessing pesticide subtypes, maternal exposure to insecticides and herbicides augments AL risk by a ratio of 1.6 and 1.4, respectively. Infant leukemia incidents depend on maternal pesticide exposure during pregnancy, with a higher risk for acute lymphoblastic and the highest risk for infant acute myeloid leukemia.
Environmental contaminants like pesticides are ubiquitous in the environment, with 90 percent of Americans having at least one pesticide compound in their body. This bodily contamination has implications for human health, especially during vulnerable life stages like childhood, puberty, pregnancy, and old age. Pesticide exposure during pregnancy is of specific concern as health effects for all life stages can be long-lasting. A 2020 study finds the first few weeks of pregnancy are the most vulnerable periods during which prenatal pesticide exposure can increase the risk of the rare fetal disorder holoprosencephaly. This disorder prevents the embryonic forebrain from developing into two separate hemispheres. Moreover, women living near agricultural areas experience higher exposure rates that increase the risk of birthing a baby with abnormalities. Just as nutrients are transferable between mother and fetus, so are chemical contaminants. Studies find pesticide compounds present 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.
Many studies indicate prenatal and early-life exposure to environmental toxicants increase susceptibility to diseases. For decades, studies have long demonstrated that childhood and in utero exposure to the U.S. banned insecticide DDT increases 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 (e.g., 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. Recent research from the Silent Spring Institute links 28 different EPA registered pesticides with the development of mammary gland tumors in animal studies. Many of these said chemicals are endocrine disruptors, thus have implications for breast cancer risk. 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 risk, 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.
The scientific connection between pesticides and associated cancer risks is nothing new. Several studies link pesticide use and residues to various cancers, from more 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 link between agricultural practices and pesticide-related illnesses being robust, over 63 percent of commonly used lawn pesticides and 70 percent commonly used school pesticides have links to cancer. U.S. National Institutes of Health’s National Cancer Institute also finds many cancer-causing substances are endocrine disruptors. Globally, cancer is one of the leading causes of death, with over 8 million people succumbing to the disease every year. Notably, the International Agency for Cancer Research (IARC) predicts new cancer cases to rise 67.4% 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.
Although pesticides products are subject to an extensive toxicological assessment before registration, current regulatory guideline studies fail to assess genotoxicity and carcinogenicity in utero that induces infant leukemia incidents. Children are more susceptible to the toxic effect of pesticide exposure as their endocrine and metabolic systems cannot adequately detoxify and excrete chemical compounds. Moreover, pesticides can hinder childhood development making children more vulnerable to acute health effects like asthma/respiratory issues, gut dysbiosis, cardiovascular diseases, and other physical and mental birth abnormalities.
Cancer is a leading cause of death worldwide. Hence, studies concerning pesticides and cancer help future epidemiologic research understand the underlying mechanisms that cause the disease. There is a serious deficiency in understanding the etiology of pesticide-induced diseases, including predictable lag time between chemical exposure, health impacts, and epidemiologic data. Therefore, advocates maintain that lawmakers and regulators should take a more precautionary approach before introducing these chemicals into the environment. With far too many diseases in the U.S. associated with pesticide exposure, eliminating pesticide use is a critically important aspect of safeguarding public health and addressing cost burdens for local communities. Beyond Pesticides’ Pesticide-Induced Diseases Database (PIDD) is a vital resource for additional scientific literature that documents elevated cancer rates and other chronic diseases and illnesses among people exposed to pesticides. This database supports the clear need for strategic action to shift away from pesticide dependency. For more information on pesticide exposure’s multiple harms, see PIDD pages on leukemia and other cancers, birth/fetal defects, endocrine disruption, and other diseases.
One way to reduce human and environmental contamination from pesticides is buying, growing, and supporting organic land management. Organic agriculture has many health and environmental benefits, which curtail the need for chemical-intensive agricultural practices. Numerous studies find that levels of pesticide metabolites in urine drop greatly when switching to an all-organic diet. Furthermore, given the wide availability of non-pesticidal alternative strategies, families and agricultural industry workers alike can 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 Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Pollution
