Pesticides and immune system — a clear link
Автор: Сидоренко Малина
Рубрика: 3. Медико-биологические дисциплины
Дата публикации: 28.04.2014
Статья просмотрена: 12 раз
Сидоренко М. Pesticides and immune system — a clear link [Текст] // Медицина и здравоохранение: материалы II Междунар. науч. конф. (г. Уфа, май 2014 г.). — Уфа: Лето, 2014. С. 14-15.
Pesticides are widely used substances for preventing, destroying, repelling of pests such as insects, weeds, roundworms, birds, mammals, microbes. Pesticides are divided into four main groups: herbicides; fungicides; insecticides and bactericides. They can also be classified as inorganic, synthetic, or biologicals (biopesticides). Pesticides work by interfering with an essential biological mechanism in the pests, but because all living organisms share many biological mechanisms, pesticides are never specific to just one species.  They may also harm people who are exposed to pesticides through occupational or home use, through eating foods or liquids containing pesticide residue, or through inhaling or contacting pesticide-contaminated air. 
The amount of pesticides used each year is enormous. Health concerns about pesticides have tended to focus on their potential to act as acute poisons or their ability to cause cancer. But pesticides may pose other important risks as well. 
In lab tests where high doses of pesticides were given, researchers have observed some significant health effects.  Genetic damage, reproductive problems, and possible links to cancer are just some of the risks associated with pesticides.  Central nervous, endocrine and immune systems talk to each other all the time by many different chemical mechanisms and support individual level functions of reproduction, growth and behaviors.  Studies show that pesticides can function as nerve poisons and as pseudo hormones, modify hormone levels, and/or impact immune system function. Therefore, the hypothesis is that if one of these is impacted then because of the interconnection in the communications among them, it is likely that all other systems will be affected.  Recently, evidence has accumulated that many commonly used pesticides can suppress the normal response of the human immune system to invading viruses, bacteria, parasites, and tumors.  Laboratory studies show that a variety of organochlorine, organophosphate, carbamate, and metal-based pesticides (such as those based on arsenic, copper, or mercury) can suppress the immune system of mammals.  The changes in the immune system include reduction of the effectiveness of NK cells to attack and kill tumor cells, migration of cells to sites of inflammation—a process known as chemotaxis—is also inhibited, other immune functions associated with tumor-fighting processes and auto-immunity may be disrupted (chlordane). Inhibition of cell signaling of T helper lymphocytes and modifying antibody production, macrophage function, cell death and cellular immune responses are also observed (permethrin) 
Working in conjunction with the Center for Disease Control, Rolf Halden, a researcher at Arizona State University’s Biodesign Institute and collaborators set out to investigate whether in utero exposure to chlordane or permethrin is associated with changes in cytokine levels at birth.  Cytokines are signaling proteins that play a critical role in the immune system, particularly during the processes of inflammation and infection.  Halden and his colleagues measured serum levels of nine cytokines in newborns, comparing these with recorded birth weight, length, head circumference and gestational age.  They also measured umbilical cord serum from 300 newborns at the Johns Hopkins Hospital, analyzing these for permethrin, chlordane and PBUT—a chemical often used in commercial preparations of permethrin, to enhance the chemical’s insecticidal properties.  Results of the study showed a clear correlation between higher chlordane concentrations and lower levels of a particular cytokine, labeled IL-12.  This cytokine is linked with an inflammatory immune response and its reduced levels suggest impairment of this response.  The team concludes that such changes in IL-12 could be associated with a decreased ability in newborns to resist infection or combat tumor formation.  Permethrin levels in serum were also associated with cytokine alterations, though in this case, levels of the cytokine IL-10 decreased in response to the pesticide.  IL-10 is an anti-inflammatory cytokine, so its reduction may be associated with increased inflammation as well as an increase in allergic reactions, which are typically moderated by IL-10.  Decreased levels of this cytokine may trigger diseases associated with increased inflammation, including various allergies and asthma. The results of the study were significant and represent the first compelling association between chlordane and permethrin exposure and levels of inflammatory cytokines in the fetus. 
Some Japanese researchers reveal the effects on pesticide exposure to the levels of cytokines.  The effects of fenitrothion (MEP), an organophosphorus insecticide, and glyphosate (GLP), a phosphorous containing amino acid-type herbicide, on cytokines production by human peripheral blood mononuclear cells (PBMC) was studied.  The production of IFN-gamma and IL-2 was inhibited by MEP in a concentration-dependent manner, but GLP slightly inhibited their production.  The production of TNF-alpha and IL-1 beta was not affected by MEP and GLP at the concentrations which significantly inhibited the proliferative activity and T cell-derived cytokine production. MEP inhibited the production of T cell-derived cytokine (IFN-gamma and IL-2), which indicates that MEP might have the potential of immunosuppressive action. 
Another study shows that exposure to the organochlorines aldrin and dieldrin reduces mouse resistance to viral infection, while DDT decreases antibody production in mammal and bird species.  The organophosphate parathion delays antibody production and suppresses T-cell response in cell cultures, while chronic low-dose exposures of the commonly used organophosphate malathion can depress several different immune responses.  Many solvents, inert ingredients, and contaminants that are part of pesticide formulations can also suppress immune responses in laboratory tests.  Among Indian factory workers chronically exposed to several pesticides, blood lymphocyte levels one element of immune system health decreased by as much as two thirds from baseline levels and returned to normal only after pesticide exposure ceased.  For example, residents of agricultural districts in southern Russia where pesticide use was substantial had lower T-cell counts than control groups in the general population, and the former group also had higher rates of infectious diseases.  Immune suppression from pesticide exposure may also play a role in the development of some cancers.  As a group, farmers face higher risks than the general population for contracting Hodgkin's disease, melanoma, multiple myeloma, and leukemia all of which are cancers of the immune system. 
Another evident for the link between pesticide exposure and autoimmune diseases was revealed. Dr. Allen Broughton and Roberta Madison studied 21 patients at the Department of Health Science at California State University.  Each patient first had a flu-like illness followed by chronic health complaints including fatigue, malaise, headaches, loss of memory, difficulty with task, muscle and joint pain.  The study was not conducted immediately after the exposure, thereby it was measuring long term and not short term effects.  Although the results found no difference in total number of white blood cells and lymphocytes, it did find there was a large increase in what are called «autoantibodies» in the pesticide exposed patients (autoantibodies are malfunctioning antibodies that are attacking healthy tissue by mistake).  In fact, autoantibodies were found against five organ systems.  Out of eleven patients tested, nine had antimyelin autoantibodies directed against peripheral myelin. 
A study conducted by Dr. John Peters at the University of California, and reported in the Journal of the National Cancer Institute, found that children exposed to regular home pesticide applications had approximately 3 and one-half times greater risk of developing leukemia. If the children were exposed to outdoor pesticides as well they had nearly 6 times increased risk for leukemia. 
An interesting research shows that women who use insecticides are at elevated risk for autoimmune diseases such as rheumatoid arthritis and lupus.  The study, which looked at more than 75,000 women, shows that those who spray insecticides at least six times per year have almost two and a half times the risk of developing lupus and rheumatoid arthritis versus those who do not use insecticides.  The risk doubles if insecticides were used in the home for 20 years or more.  Since previous studies have linked a higher risk of lupus to farmers using pesticides, lead study author Christine G. Parks, PhD, an epidemiologist with the National Institute of Environmental Health Sciences in Research Triangle Park, NC, decided to investigate household insecticide use in the home and garden.  In the study, 178 of the women had rheumatoid arthritis, 27 had lupus, and 8 more women lived with both disorders. 
There are many researchers that are revealing the negative effect of pesticides on human health. May be it’s time to change the plant protection strategy and prevent such a challenge as autoimmune diseases instead of searching a cure for them while poisoning ourselves with pesticides.