by Ben Best
Radiation from cell phones or power lines, mercury in fish, pollutants in the air, possible pollutants in tapwater, and trans fatty acids in foods are only a few of the many environmental agents which could be hazardous to health. Some health hazards are considerable, some hazards are tolerable in small doses, and some hazards are too negligible to merit serious attention. Table salt (sodium chloride) is an essential nutrient, but is toxic in excessive amounts.
Insofar as I have a somewhat obsessive concern with my personal health, I need to be careful to monitor my own psychological bias and strive to be honest about the evidence. I believed the hysteria about the Y2K problem, and although I readily admitted I was wrong, I undermined my credibility with myself and with others. I was seen by some as a psychological terrorist, despite the fact that I was completely sincere. I do know that there are persons who are drawn to spreading fear, uncertainty, and doubt (either consciously or unconsciously) as a means of attracting attention. The issue of pesticides and the value of spending extra money on organic foods has driven me to considerable soul-searching over what to believe and who to believe. Governments are ostensibly protecting the public against pesticide toxicity, but would be held responsible for any toxicity and thus have political motives to be dismissive of concerns about government-approved pesticides. Both environmentalists and food producers can justly be accused of being either anti-capitalists incapable of reasonable cost/benefit analysis, or pro-capitalists who have financial vested interests. Journalists often use alarmism and sensationalism to attract attention to their writings.
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Humans introduce pesticides in the environment to combat organisms regarded as pests, which includes rodents, insects, weeds, molds, bacteria, and fungi. It is a challenge to eradicate these pests while not causing harm to humans, pets, or beneficial organisms. The ideal pesticide will eliminate pests, but will break-down before having toxic effects on non-pest organisms. Protecting food during shipment and avoiding harm to agricultural workers can therefore be a challenging problem. Washing pesticides from the surface of foods is of little benefit when pesticides have been absorbed from the soil into the interior of the plants.
Dusting crops with elemental sulfur was reportedly used in ancient Mesopotamia for pest control. By the 15th century lead, arsenic, and mercury were being used on crops to kill pests. Arsenic-based pesticides predominated until the 1950s when DDT use became widespread. As a result of Rachel Carson&$39;s best-selling alarming/alarmist book SILENT SPRING, which primarily publicized the toxic effects of DDT on birds, DDT use came to be mostly banned workwide (although arguments still persist that DDT would be of great benefit in malaria control). The DDT family of organochlorides has been replaced by organophosphates, carbamates, and pyrethrins.
In the context of chemistry, the word "organic" means carbon-containing molecules, in contrast to the term "organic food", which means foods grown without the use of pesticides. Although herbicides used in growing food (such as paraquat and atrazine) can be toxic, I will mostly limit my discussion to insecticides, all of which are neurotoxic.
Organochlorides are simply organic (carbon-containing) compounds that contain the element chlorine. The organochloride molecule sucralose is deemed safe enough to be used as an artificial sweetener. Many pesticides, including DDT, chlordane, and dieldrin, are organochloride compounds. As insecticides, organochlorides open sodium ion channels resulting in continual firing of neurons that cause spasm and death. DDT is reputedly carcinogenic, and the DDT metabolite DDE (chloroethylene) blocks (male) androgenic hormones [ENVIRONMENTAL HEALTH PERSPECIVES; Danzo,BJ; 105(3):294-301 (1997)]. Because DDE is lipophilic, it accumulates in fat, and can be several times more highly concentrated in the breast milk of a mother than in her blood [PEDIATRICS; Weiss,B; 113(4):1030-1036 (2004)]. The persistence of organochlorides in the environment, in combination with their toxicity has led to their use being banned in most countries.
Organophosphates are esters of phosphoric acid. Organophosphates are used as plasticizers and solvents as well as for insecticides. Parathion, malathion, and chloropyrifos are examples of organophosphate insecticides. Organophosphate insecticides bind irreversibly to the enzyme acetylcholinesterase, which normally breaks-down the neurotransmitter acetylcholine. The accumulation of acetylcholine in synapses has a neurotoxic effect in insects as well as in vertebrates. Organophosphates generally break-down reasonably quickly in the environment, while persisting long enough on crops to eradicate insect pests.
Carbamates are organic compounds derived from carbamic acid [NH2COOH]. Carbamate pesticides include carbofuran, carbaryl, and ethienocarb. Like organophosphates, carbamates inactivate acetylcholinesterase, but they do so reversibly rather than irreversibly, and are thus less toxic than organophosphates. Like organophosphates, carbamates are readily degraded, and thus do not persist so long in the environment.
Pyrethrin insecticides are derived from the seed cases of chrysanthemums. Like the organochlorides, pyrethrins are neurotoxic to insects by opening sodium channels and thereby causing fatal spasms. But pyrethrins do not persist in the environment because they are broken-down by exposure to oxygen and light. Moreover, pyrethrins are readily hydrolyzed by stomach acids in mammals.
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The Mayo Clinic overview of organic foods provides a good introduction to the subject. In the United States, foods certified as being organic by the United States Department of Agriculture (USDA) carry a "USDA Organic seal. The USDA has a Pesticide Data Program (PDP) which periodically publishes information about pesticides in food. An American environmentalist organization known as the Environmental Working Group (EWG) publishes a pesticides shopping guide which classifies foods as being "dirty" with pesticides or "clean". Critics of the EWG claim that EWG is engaging in alarmism, and that although conventional food contains several times more detectable pesticides than organic foods, the amounts of pesticides in conventional foods are much too small to have a biological effect [JOURNAL OF TOXICOLOGY; Winter,CK; 589674 (2011)].
A review of the health effects on organic foods in the AMERICAN JOURNAL OF CLINICAL NUTRITION found no convincing evidence for benefits, while explicitly ignoring the issue of pesticides. The review concluded that although antioxidant content may be higher in organic foods, there is no proven associated health benefit [AMERICAN JOURNAL OF CLINICAL NUTRITION; Dangour,AD; 92(1):203-210 (2010)]. A similar conclusion was reached in a review of health benefits of organic foods in the ALTERNATE MEDICINE REVIEW, but the latter also noted that organically grown food only had one-tenth the level of pesticides (2.6% versus 26%) of non-organic foods — and that the reduced organic food pesticides were associated with reduced pesticides in the consumers of organic food [ALTERNATIVE MEDICINE REVIEW; Crinnion,WJ; 15(1):4-12 (2010)].
Dr. Bruce Ames has suggested that because plants produce thousands of natural pesticides, it follows that pesticides for agricultural use constitute a negligible risk to human health [FASEB JOURNAL; Ames,BN; 11(13):1041-1052 (1997)]. But if natural pesticides were adequate for protecting plants from pests, there would be no financial incentive to use artificial pesticides. By one estimate, every dollar spent on pesticides results in four dollars worth of saved crops. The long-term effects of low-dose artificial pesticides are mostly unknown, which causes me concern.
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Much of the concern about pesticide use has focused on children. A typical infant drinks about 16 times as much apple juice per body weight as an adult, and an estimated 50% of pesticide exposure occurs during the first five years of life [PEDIATRICS; Weiss,B; 113(4):1030-1036 (2004)].
Detoxification of organophosphate pesticides in the human body is dependent upon paraoxonase 1 (PON1) enzyme, which is very low in newborns compared to adults (one study showed PON1 activity increases 3.5 times between birth and age 7) — making children particularly susceptible to organophosphate pesticide toxicity [TOXICOLOGY AND APPLIED PHARMACOLOGY; Huen,K; 244(2):181-189 (2010)]. Polymorphisms in the PON1 gene result in a high variation in the ability of PON1 enzyme to detoxify organophosphate pesticide [Ibid.]. Five days of an organic diet has been shown to dramatically reduce organophosphate pesticides in children [ENVIRONMENTAL HEALTH PERSPECTIVES; Lu,C; 114(2):260-263 (2010)]. Children 6 to 11 years old have the highest concentration of organophospate metabolites in their urine of any age group — and elevated urine organophospate metabolites have been correlated with increased Attention Deficit/Hyperactivity Disorder (ADHD) [PEDIATRICS; Bouchard,MF; 125(6):e1270-e1277 (2010)]. Elevated organophospate metabolites in the urine are indicative of continuous exposure because they are normally eliminated in 3 to 6 days [Ibid.].
Reduced mental development of children has been correlated with organophosphate pesticide exposure [BASIC & CLINICAL PHARMACOLOGY & TOXICOLOGY; Eskenazi,B; 102(2):228-236 (2008)], as has reduced thyroid function [TOXICOLOGY AND APPLIED PHARMACOLOGY; Lacasana,M; 249(1):16-24 (2010)] and sperm quality in male agricultural workers [REPRODUCTIVE TOXICOLOGY; Perry,MJ; 31(1):75-79 (2011)]. Children with high exposure to chlorpyrifos have shown a dose-related reduction of the brain cerebral cortex thickness along with other brain volume reductions [PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (USA); Rauh,VA;109(20):7871-7876 (2012)]. Dioxin and the organochlorides polychlorinated biphenyls (PCBs) have been shown to interfere with thyroid function in infants [PEDIATRIC RESEARCH; Koopman-Essenbloom,C; 36(4):468-473 (1994)]. Thyroid function is particularly critical for brain development in children [NEW ENGLAND JOURNAL OF MEDICINE; Haddow,JE; 341(8):549-555 (1999) and ENVIRONMENTAL HEALTH PERSPECIVES; Zoeller,RT; 110(Suppl 3):355-361 (2002)].
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