Multiple Scientific Studies Link Pesticides to Cancer
By Brandon Turbeville
In my article, “Pesticide Content In Food Less Regulated By Codex Than Vitamins and Minerals,” I briefly discussed the connection between commonly used pesticides and neurological disorders such as Parkinson’s Disease.
In addition, I mentioned the rather contradictory position held regarding the use of such pesticides, which banned their commercial use in some aspects, but continues to tacitly allow their use in food production.
However, neurological diseases are not the only negative side effects presented by Persistent Organic Pollutants (POPs) or general pesticides. Indeed, pesticides have been linked to cancer as well.
For instance, a study published in Blood, the journal of the American Society of Hematology, found that exposure to certain pesticides doubled an individual’s risk of developing Monoclonal Gammopathy of Undetermined Significance (MGUS) compared to individuals in the general population. MGUS is a “pre-cancerous condition that can lead to multiple layer myeloma which is a painful cancer of the plasma cells the bone marrow.” When one is diagnosed with MGUS, the patient requires life-long monitoring because MGUS is a condition that virtually every multiple layer myeloma patient experiences prior to developing the myeloma.
In addition, in a study conducted as part of the Agricultural Health Study and published in the American Journal of Epidemiology, a potential link between pesticides and prostate cancer was reported. In particular, Methyl Bromide, a gas used to kill pests in the soil and fumigate grain bins and storage areas, was associated with increased risk of the disease by approximately two to four times as much as those who were not exposed to the pesticide. This is not surprising considering the fact that the National Institute for Occupational Safety and Health acknowledges Methyl Bromide as a potential occupational carcinogen.
A link between other pesticides such as chlorpyrifos, coumaphos, fonofos, phorate, permethrin, and butylate, was also established for men who had a family history of prostate cancer. One interesting note regarding this study is that the individuals examined by scientists were compared to the incidence rates of the two states in which the subjects lived. That is, they were compared to the average occurrence of prostate cancer for that area. However, since more in-depth analysis had not been conducted at the time, we have no way of knowing just how many cases of prostate cancer in the average occurrences were caused by pesticide exposure themselves. Such information would be extremely valuable due to the fact that the aforementioned cancer rates could have been caused by pesticide residues in food or proximity to these particular chemicals.
Children, of course, are at particular risk for the adverse effects of pesticides because of their developing biological systems. So it is not entirely surprising that a link between childhood cancers and pesticides has been discovered as well. Researchers from Georgetown University Lombardi Comprehensive Cancer Centre completed a study involving 41 pairs of children with Acute Lymphoblastic Leukemia (ALL) and their mothers who were tested and compared with 41 pairs of healthy children and their mothers. The study found that children with ALL, a cancer that commonly develops before seven years of age, had a higher ratio of household pesticides in their urine than the healthy children, indicating a possible link between the chemical and the cancer.
The link between pesticides and childhood brain cancers are slightly more established, however. In a study published in Environmental Health Perspectives in 2009, researchers confirmed a link between pesticide exposure and increase in astrocytomas (brain cancers). The study confirmed previous research that has suggested a link between industrial and household use of pesticides and herbicides with childhood brain cancer. Not only that, but there is the distinct potential that the parents use or exposure to pesticides may affect the child even before birth. As the study claims,
Parental exposures may act before the child’s conception, during gestation, or after birth to increase the risk of cancer. Before conception, exposures may cause mutations or epi-genetic alterations in gene expression, such as genomic imprinting or DNA methylation, in the sperm or egg. Exposure after conception (i.e. during the pregnancy or after birth) may cause somatic cell mutations or alterations in hormonal or immunological function that affect cancer risk.
Of course, this merely reaffirms the knowledge that humans have possessed for millennia, i.e. that what the parents ingest into their bodies can and probably will affect the child they produce. Pesticides are no different in this respect.
As discussed earlier, pesticides also pose a cancer risk for adults, particularly those who work with these chemicals. A study published in Occupational and Environmental Medicine in June 2007 found that agricultural workers who had the highest exposure to pesticides were 2 times more likely to develop brain cancer as those whose occupations did not bring them into contact with these chemicals. It was also found that those who used pesticides on their house plants were at an elevated risk for brain cancer. Recent research has also suggested that pesticides and industrial chemicals are linked to testicular cancer, genital abnormalities, low amounts and potency of semen, and other male reproductive conditions.
Indeed, the connection between these substances and cancer is widely known. As the researchers mention in the Environmental Health Perspectives study, the EPA itself classifies chlordane, heptachlor, tetrachlorvinphos, carbaryl, and propoxur as probable or likely carcinogens to humans and lindane, dichlorvos, phosmet, and permethrin as suggestive or possible carcinogens.
While it is not known exactly how these chemicals cause cancer, it is known that many pesticides exude hormone-mimicking, mutagenic, and/or immune-hampering qualities and these properties have been linked to cancer in their own right.
As I mentioned in my last article regarding this subject, neurological and developmental problems are also associated with pesticide exposure. This is not surprising considering the fact that many insecticides kill their targets by attacking their nervous systems.
As with other concerns, children are at highest risk, including those still in the womb.
Although more research has been conducted on the effects of some these chemicals on animals than humans, researchers suggest that these effects are quite similar. As a study published in the Canadian Medical Association Journal states,
Neuordevelopmental, hematological, immunologic, and reproductive effects have been found in animals at levels of exposure that overlap the range of exposures and body burdens found in humans. The health effects of POPs in humans is unclear, although available epidemiological evidence suggest they are similar to those in animals, affecting neurodevelopment, and thyroid, estrogen, and immune function. The developing brain and immune system may be most vulnerable.
While toxicity of pesticides in humans may not have been studied ad naseum, it is safe to say that it is, nevertheless, well established. In a more recent study published in Frontiers In Bioscience, it was stated more directly. The authors write,
Most pesticides are not highly selective, and are also toxic to nontarget species, including humans. A number of pesticides can cause neurotoxicity. Insecticides, which kill insects by targeting their nervous system, have neurotoxic effect in mammals as well. . . . . . Insecticides interfere with chemical neurotransmission or ion channels, and usually cause reversible neurotoxic effects, that could nevertheless be lethal. Some herbicides and fungicides have also been shown to possess neurotoxic properties. The effects of pesticides on the nervous system may be involved in their acute toxicity, as in case of most insecticides, or may contribute to chronic neurodegenerative disorders, most notably Parkinson’s disease.
In past research there have also been connections drawn between Persistant Organic Pollutants and diabetes. In a cohort study published in 2006, serum concentrations of POPs (Persistent Organic Pollutants) were examined in accordance with diabetes prevalence. What the scientists found was “striking dose-response relations between serum concentrations of six selected POPs and the prevalence of diabetes.”
Although, admittedly, there are several limitations to this particular study, clearly this is a subject that needs to be further investigated. Indeed, it would be wise, considering the growing corporate structure and mass-produced nature of the world’s agriculture, to fund and conduct a number of independent studies investigating the safety of pesticides used on food and the possible side effects of their use.
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 “Heavy Pesticide exposure linked to brain cancer.” Reuters. June 12, 2007.http://www.reuters.com/article/idUSTON27410120070612
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 Lee, Duk-Hee., Lee, In-Kyu. Song, Kyungeun. Steffes, Michael. Toscano, William. Baker, Beth A., Jacobs, David R. Jr., “A Strong Dose-Response Relation Between Serum Concentrations of Persistent Organic Pollutants and Diabetes.” Diabetes Care. Vol. 29. Number 7. July 2006. American Diabetes Association. http://care.diabetesjournals.org/content/29/7/1638.abstract Accessed May 24, 2010.
Read other articles by Brandon Turbeville here.
Wikimedia Image: Monsanto chemical farmer