(Beyond Pesticides, June 21st, 2012) A new study details the toxic effects of long-term exposure to commonly used agricultural pesticides. Results indicate an increased likelihood of moderate to severe blood toxicity and a reduced total number of bone marrow cells, which can lead to degenerative diseases like aplastic anemia. The study, entitled “Pesticide Induced Alterations in Marrow Physiology and Depletion of Stem and Stromal Progenitor Population: An Experimental Model to Study the Toxic Effects of Pesticide” is published in the online version of the Journal of Environmental Toxicology .
The experiment, led by researchers at the Calcutta School of Tropical Medicine’s Department of Biochemistry and Medical Biotechnology, exposed a group of mice to a mixture of organochlorine, organophosphate and pyrethriod pesticides, including a preponderance of the chemicals cypermethrin, and chloropyrofos. The exposed mice showed an overall reduction in the ability of their bodies to produce bone marrow cells. Bone marrow, the soft flexible tissue found in the interior of bones, is a storehouse for stem cells. While the exact mechanism is unknown to researchers, the study reveals that the microenvironment in which stem cells develop is somehow deranged by pesticides. This derangement prevents the maturation of stem cells into every type of blood cell, including red and white blood cells and blood platelets. A suppressed level of these blood cells can result in degenerative diseases such as aplastic anemia, which often requires a bone marrow transplant to successfully treat.
Sujata Law, Ph.D., co-author of the study, remarked, “In order to prevent degenerative diseases related to pesticide exposure, it is of prime importance that those handling pesticides take precautions like wearing protective clothing, including masks and gloves.”
Another recent study in India found high levels of the organochlorine pesticide endosulfan in the bone marrow of children with blood cancers. The study, published in the journal Indian Pediatrics, affirmed the fact that the pesticide has the potential to accumulate in bone marrow. All of the children who had high endosulfan levels in their bone marrow were from areas where exposure to the pesticide is common. Children with blood cancer had elevated levels of endosulfan in their bone marrow compared to those without the disease. Six out of 26 children with blood cancer tested positive for endosulfan in the bone marrow compared to one out of 26 children who did not have blood cancer.
Although this study was based in India, the chemicals chlorpyrifos, cypermethrin, and endosulfan are still used to varying degrees in the U.S. Cypermethrin applications in the U.S. are approximately 1.0 million pounds of the active ingredient per year. EPA has identified the pyrethriod cypermethrin as a possible human carcinogen and classifies formulated pesticides containing it as slightly or moderately toxic. Synthetic pyrethroids are suspected endocrine disruptors, have been linked to certain cancers, and are particularly dangerous to aquatic life even at low concentrations. Despite the fact that there are plenty of effective pest management methods that are not nearly as toxic, these insecticides are some of the most popular household pesticides, available in the form of powders and sprays to control ants, mosquitoes, fleas, flies, and cockroaches. As research unfurls, particularly on the long-term and combined effects that these insecticides have, the high-volume uses of pyrethroids are major cause for concern to human and environmental health.
Organophosphates like chlorpyrifos are extremely toxic to the nervous system. They are cholinesterase inhibitors and bind irreversibly to the active site of an enzyme essential for normal nerve impulses. In 2010, Beyond Pesticides and over 13,000 other organizations sent a letter to the EPA calling for a ban on chlorpyrifos and a phase out of other organophosphate (OP) pesticides. Chlorpyrifos was phased out for residential use under a 2000 agreement between EPA and Dow Agrosciences, but continues to expose farmworkers and consumers through its use in agriculture. EPA’s action in 2000 removed chlorpyrifos’ residential uses but retained all agricultural uses except tomatoes (allowable residues on apples and grapes were adjusted), golf courses, and “public health” mosquito spraying. The agency argued at the time of its decision that it had adequately mitigated risks through the removal of high exposure uses to children in the residential setting, but it ignored the special risks to farmworkers’ children, as well as the availability of alternative agricultural practices and products that made chlorpyrifos unnecessary and therefore its risks unreasonable. This recent study provides sobering evidence of the long-term dangers farmworkers’ children could face.
The best way for consumers to reduce the impact that these chemicals have on our health and the environment is to choose organic foods. Beyond Pesticides advocates for the national conversion to organic systems planning, which moves chemicals off the market quickly and replaces them with green management practices.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.