Pesticides

Study Questions:

<Define what a pesticide is and what organisms that are affected.
< Explain 5 positive ways pesticides have been used?
< Explain 5 negative impacts of pesticides. Explain what the pesticide treadmill is? genetic resistance?
<How do neurotoxins work specifically?
<What are some specific cancers assoicated with pesticide use? do such examples exist for Hungary? explain.
< Explain how the impact is felt and give an example of pesticide effect on the a. immunosystem b. behavior c. reproduction d. special risks for children
< Describe the 4 different types of pesticides.. how they differ and how they work.
< For EACH of the alternative methods explain the technique and give an example Refer to the in-class presenters examples if possible.
< Explain if sustainable or organic agriculture can work? describe the potential problems and explain if these concerns are valid.

Exposure: Why do we need to study pesticides? From the reports below, we know we are being exposed to pesticides through the food we eat and the water we drink:

The question of pesticides of significance in Hungary as it is worldwide:
Hungary is one of the big agricultural players in the new Member States, with a strong export economy. Whilst most of its 958,000 farmers are smallscale, 8,000 large enterprises dominate farming. Chemicals are used on the larger farms, and less than one percent (47,000 hectares) of the total acreage is organically farmed.The country also ranks as a pesticide producer on a global scale.

Close by:The safe disposal of obsolete pesticides is highlighted as a priority – approximately 20,000 tonnes in the Ukraine alone, resulting in severe water pollution problems. CEE NGOs are questioning whether there is a link between high child mortality rates, newborn abnormalities and chemical usage. NGOs were urged to question states and challenge them to provide useful information, and urge ministries to act.

While in the USA: From EPA: "Twenty- two pesticides have been detected in U.S. wells, and up to 80 are estimated to have the potential for movement to groundwater under favorable conditions. One area with conditions highly conducive to leaching is Long Island, New York, where soils are sandy, the water table is shallow, and agriculture is intensive. A total of l3 pesticides have been detected at least once in Long Island groundwater, and 8 of these have been found multiple times through continued monitoring. In upstate New York, sampling for pesticides has been limited to measurement of aldicarb in wells near treated fields. Low concentrations of aldicarb have been detected in 30 percent of the 76 wells sampled. Twenty-two other states, including Maine, Maryland, and New Jersey, also have reported some pesticide contamination of groundwater."

As with privitazation of water, the use of pesticides has both positive and negative sides to it:

Health effects:

How toxic are these pesticides?

• USA: Based on extrapolation of hospital surveys, an estimated 20,000 people receive emergency care annually for actual or suspected pesticide poisoning, and approximately 10% are admitted to the hospital. Each year, 20-40 people die of acute pesticide poisoning in the United States.Still unknown, however, is the number of affected workers in the United States who never see a doctor and who therefore go undiagnosed and unreported.
• Some argue that relative to the percent affected by cigarette smoke or fatty diets, that risk is very low at least with respect to carcinogenic effects.Other scientists however are concerned about non-carcinogenic effects - teratogenic/developmental, neurotoxicity and others whose impact has been less studied.
• World Health Organization, which considers acute pesticide poisoning a major health problem globally. estimates that between 1 and 5 million cases of acute pesticide poisoning occur annually, largely in underdeveloped nations where pesticide education, monitoring, and safety equipment is either limited or unavailable and where use of extremely toxic agrichemicals is more extensive.

Ways toxins affect the body:

Neurotoxicity Most episodes of acute occupational poisoning are due to organophosphate and carbamate insecticide exposure.

• Poisoning is manifest as cholinesterase inhibition in the blood and nervous system. This action, which prevents degradation of acetylcholine at the neuronal synapse, results in overactivity of cholinergic neurons.

Significant reductions in plasma cholinesterase are associated with a number of acute and subacute neurotoxic effects: muscle tremors, twitching and weakness, anorexia, nausea, vomiting, bronchospasm, excessive pupil contraction, blurred vision, headache, cognitive impairment, seizure, and coma.

In english, what this means: messages move from nerve to nerve through the body.. from the hand or heart to the brain and back again. When a nerve is excited it releases a chemical called a neurotransmitter from the end of the nerve which moves to the start of the next nerve to excite and so on. Specific pesticides prevent the neurotransmitter from being broken down after it has excited the nerve.. thus it keeps on reexciting the nerve and the nerve can't relax. If the nerve is one responsible for exciting the heart, it can't relax and eventually collapses.

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Cancers: The cumulative effects of widespread chronic low-level exposure to pesticides is only partially is understood. However, evidence suggests a strong correlation between pesticide exposure and the development of cancer in humans

.Of the 80,000 pesticides and other chemicals in use today, 10 percent are recognized as carcinogens. Cancer-related deaths in the United States increased from 331,000 in 1970 to 521,000 in 1992, with as estimated 30,000 deaths attributed to chemical exposure.

• Farmers are prone to certain cancers, including stomach, prostate, and brain cancer, non-Hodgkin's lymphoma, and leukemia. The National Cancer Institute (NCI) has linked the common weed killer 2,4-D to non-Hodgkin's lymphoma in several studies.
• Another NCI study found a link between breast cancer in women and elevated levels of DDE, a metabolite of the pesticide DDT, in their fat tissue.Women with the highest levels of exposure to DDT had four times the breast cancer risk of women with the least exposure. The link is not proven yet- though it has gotten a lot of press.
• Research also indicates that youngsters in homes where household and garden pesticides are used are seven times as likely to develop childhood leukemia. There still are unexplained clusters of cancer among farm-workers' offspring.

A recent study of pesticides and childhood brain cancers has revealed a strong relationship between brain cancers and compounds used to kill fleas and ticks. The specific chemicals associated with children's brain cancers were pyrethrins and pyrethroids (which are synthetic pyrethrins, suchas permethrin, tetramethrin, allethrin, resmethrin, and envalerate), and chlorpyrifos (trade name: Dursban).

I looked up studies completed in Hungary.. the first one in Medline I came upon - indicated the correlation between gastric cancer and pesticides in a farming community.

Pesticide use related to cancer incidence as studied in a rural district of Hungary.
Paldy A, Puskas N, Farkas I.
National Institute of Hygiene, Budapest, Hungary.
General mortality analysis showed an increasing tendency of circulatory diseases in two villages examined. Respiratory diseases and suicide were more frequent in the village with greater pesticide use (village I). The relative risk (RR) of gastric cancer for men is significantly higher in village I (high rate of pesticide use) than in the county as a whole (RR, 1.65; 95% confidence interval (CI), 0.96-2.83) and also in relation to the national data (RR, 3.20; 95% CI, 1.91-5.36). Since the nitrate concentration in the drinking water, the drug consumption, smoking and eating habits are similar in the two villages, and since alcohol consumption is higher in village II (moderate rate of pesticide use), it seems that nitrosable pesticides may play a role in the etiology of stomach cancer. This is supported by the fact that a higher number of gastric cancer cases was found where larger quantities of nitrosable pesticides had been used.

Exposure to pesticides, whether in laboratory experiments, animal studies, or epidemiologic studies in humans, clearly shows a significant effect on the immune system, such as T- and B-cell function, macrophage phagoeytosis, and host resistance

Pesticide use -especially in developing countries, where infections are a leading cause of death. could be extemely important if the immune system has been depressed by pesticides. In these cases the person would die from the infection, but in reality may have not died had they not been previously exposed to the pesticide. Thus it is difficult to estimate the true impact of pesticides.

• Russian investigators conducted research on people residing in the farming regions of central Moldova, in the former Soviet Union. From the 1960s to the 1980s, pesticide use in this region was nearly 20 times the world average. The agents used were primarily copper-containing fungicides, organophosphates, organochlorines, carbamates, and pyrethroids
• The investigators reported that 80% of children known to have been heavily exposed to such pesticides had significant deviations in more than five immunological parameters. T-cell ratios and cell counts were significantly altered and lymphocyte proliferative responses were suppressed, indicating losses in cell-mediated immunity." The report added that children in these areas were three times more likely to have infectious diseases of the gastrointestinal tract and two to five times more likely to have infectious diseases of the respiratory tract.
  
• Intuit children in the northern Hudson Bay area of Canada. Nursed on human milk laced with organochlorines, these children not only face a highly elevated risk of infection, but in some cases are so immunocompromised that they can't be vaccinated, because they don't produce any antibodies.

Reproduction:
A number of studies indicate (an recent example below) that field workers exposed to pesticides when spraying have reduced or mutated sperm.

In November 2002, Shanna Swan, a professor of family and community medicine at the university, announced findings suggesting that fertile men in more rural areas have lower sperm counts and less vigorous sperm than men in urban areas. Through her most recent study, published today in the online edition of the peer-reviewed journal Environmental Health Perspectives (EHP), Swan confirmed that men with lower sperm counts and quality had higher concentrations of alachlor, diazinon, and atrazine metabolites in their urine than men with higher-quality sperm.

Behavior:

As noted in the Hungarian study cited above, not only did the investigators find higher cancer rates, but also behavioral changes - increased sucides. Other studies indicate much the same...

•  A group of biologists and medical researchers at the University of Wisconsin in Madison, led by Warren P. Porter, has completed a 5-year experiment putting mixtures of low levels of these chemicals into the drinking water of male mice and carefully measuring the results. They reported recently that combinations of these chemicals -- at levels similar to those found in the groundwater of agricultural areas of the U.S. -- have measurable detrimental effects on the nervous, immune and endocrine (hormone) systems. Furthermore, they say their research has direct implications for humans.

  Dr. Porter and his colleagues point out that the nervous system, the immune system, and the endocrine (hormone) system are all closely related and in constant communication with each other. If any one of the three systems is damaged or degraded the other two may be adversely affected. The Wisconsin researchers therefore designed their experiments to examine the effects of agricultural chemicals on each of the three systems simultaneously. To assess immune system function, they measured the ability of mice to make antibodies in response to foreign proteins. To assess endocrine system function, they measured thyroid hormone levels in the blood. And to assess nervous system function they measured aggressive behavior in the presence of intruder mice introduced into the cages. They also looked for effects on growth by measuring total body weight and the weight of each animal's spleen.

  The experiments were replicated many times, to make sure the results were reproducible. They found effects on the endocrine system (thyroid hormone levels) and the immune system, and reduced body weight, from mixtures of low levels of aldicarb & nitrate, atrazine & nitrate, and atrazine, aldicarb & nitrate together. They observed increased aggression from exposure to atrazine & nitrate, and from atrazine, aldicarb & nitrate together.

   The Wisconsin research team wrote, "Of particular signficance in the collective work of Boyd and others,[3] Porter and others,[4] and our current study[2] is that THYROID HORMONE CONCENTRATION CHANGE was consistently a response due to mixtures, but NOT usually to individual chemicals."

  In the five-year experiment, thyroid hormone levels rose or fell depending upon the mixture of farm chemicals put into the drinking water. Dr. Porter and his colleagues present evidence from other studies showing that numerous farm chemicals can affect the thyroid hormone levels of wildlife and humans. PCBs and dioxins can have similar effects, they note.
  
  Proper levels of thyroid hormone are essential for brain development of humans prior to birth. Some, though not all, studies have shown that attention deficit and/or hyperactivity disorders in children are linked to changes in the levels of thyroid hormone in the blood. Children with multiple chemical sensitivity (MCS) have abnormal thyroid levels. Furthermore, irritability and aggressive behavior are linked to thyroid hormone levels.

  Interviewed recently by Keith Hamm of the SANTA BARBARA [CAL.] INDEPENDENT,[5] Dr. Porter explained, "Earlier work had shown that thyroid hormone typically changed when exposure to these pesticides occurred. Thyroid hormone not only affects and controls your metabolic rate, that is, how fast you burn food, it also controls your irritability level. For example, Type A personalities are more assertive, more aggressive, more hyper. These people tend to have higher levels of thyroid hormone. Type B personalities--people that are really laid back, really take things very easily--have lower levels of thyroid hormone. We expected that changes in thyroid [would] change irritability levels. This was a concern because there was information that kids are getting more hyper and [that their] learning abilities are going down," Dr. Porter said.

   A recent study of 4 and 5 year-old children in Mexico specifically noted a decrease in mental ability and an increase in aggressive behavior among children exposed to pesticides.[6] Elizabeth A. Guillette and colleagues studied two groups of Yaqui Indian children living in the Yaqui Valley in northern Sonora, Mexico. One group of children lives in the lowlands dominated by pesticide-intensive agriculture (45 or more sprayings each year) and the other group lives in the nearby upland foothills where their parents make a living by ranching without the use of pesticides. The pesticide-exposed children had far less physical endurance in a test to see how long they could keep jumping up and down; they had inferior hand-eye coordination; and they could not draw a simple stick figure of a human being, which the upland children could readily do.

  Special risks to children's health:

Worries over pesticides and their special risks to children are well-founded. Experimental tests in lab animals have found the young to be more vulnerable than adults to the toxic effects of many chemicals simply because their bodies still are developing.

• Children tend to retain a greater portion of a given dose of certain toxins than adults and are not as capable of detoxifying them in their bodies.
• They are at greater risk from neurotoxins since the nervous system in an infant or young child has not developed fully yet.
• There is a greater risk of developing cancer if exposure to carcinogens begins during infancy, rather than later in life. This is because youngsters are believed to be more susceptible to carcinogenesis since cells are dividing rapidly during childhood, and the cancer process occurs at the cellular level, through mutations.
• For this reason EPA now is dropping exposure limits to 1/10 of current adult doses on products which are most likely to be taken in or exposed to infants.

Types of Pesticides

1. Metal Pesticides:
I will spare you a detailed chemistry of the pesticides.However you need to understand that large differences exist.
The earliest of the pesticides were used by the Chinese over a thousand years ago. They included toxic metals ( mercury, cadmium, arsenic) still in use today worldwide.It is difficult to kill some of the fungi that attack plants, so in some cases these metal poisons still work the best. The problem is nothing breaks down a metal... once sprayed on the plant, they can remain in the soil or in orchard plants for decades or centuries. Till recently, coffee beans were sprayed with arsenic.

2. Organochloride pesticides such as DDT started in use during the war II and continues even now though more rarely ( it is banned in most countries) to fight mosquitos that carry malaria.It can take 20+ years to break these types down as the body normally did not evolve with enzymes to break down chlorine products.. They are fat-soluble and accumulate in fish, humans etc. Older individuals still have traces in their bodies from exposure over 20-40 years ago.

3. After pesticide manufacturers were shown how persistant the organochlorides were they turned to organophosphate sprays. These do break down in a matter of days or a week.. however, since they breakdown so fast, they have to be more toxic in the first place. Many of these work on the nervous system.

4. More recently, manufacturers have moved to producing herbicides, which are meant to kill weeds. If the weeds die, then the farmer does not have to till/plow the ground. this is good to prevent erosion. this is bad as not all these herbicides just affect plants.
Some of these herbicides prevent the body from producing ATP.. what we use as our energy supply. Unfortunately since there are a lot of weeds, farmers spray a lot these herbicides.These sprays have now leached into the water supplies of these communites as in Long Island, Md etc.. and are taken in by farmers and close by residents. See the behavior section above to understand the concern of many about the use of these sprays.

The quetion then comes.. do Hungarians or any farmers out there need to use these sprays? Do we need to expose all school children to sprays in the schools? Do we need to spray our homes for ticks and other bugs, potentially affecting our children? Alterntives do exist.. we will cover some of them:

Alternatives to pesticides - what are they and are they really effective in agriculture and the home?

I. Biological controls: a. Use of larger natural predators includes the use of birds and other insects - we see here only an approximate 40% success rate. Why? Need to set up an appropriate home for the predator - nesting habitat etc. not to common in corn fields.Need to include tree and bush rows for nesting sites. If the the predator is too good, it consumes up all the pest and then migrates out- must be alternate prey for them to feed on... Need to have handy a good taxonomist who knows how to identify the pest and appropriate predator. In a number of cases, introduction of foreign predators has lead to problems as they move out into natural systems and take over the natural species.They themselves become pests eventually.

However, times are changing...... In a small town in Michigan, cockroaches became so plentiful that they were coming home in students' lunch boxes. Poisons had been used in the past but simply weren't killing the pests because the cockroaches had grown pesticide resistant. Additionally, Michigan state passed laws requiring schools to seek alternatives to chemical pesticides. The long-standing problem became so severe five or six years ago that the Allegan school district had nearly halted the school's lunch program when Praxis, a local company that sells biological pest controls, stepped in to, as Praxis co-owner Sam DeFazio puts it, "create an artificial ecosystem indoors." According to DeFazio, Allegan's school system became the first in the country to eliminate pesticides in favor of biological controls. Now the cockroaches in Allegan school district are dined on by tiny wasp parasitoids and attacked by nematodes, placed in strategic locations throughout the school. "When you start to talk about bringing in wasps, people start to panic," says Doug McCall, Allegan School Superintendent. "But these wasps are the size of a pinhead. And we've found that when we consistently apply and manage the biological controls, they work." The little predators may go hungry soon; the cockroaches have all but disappeared. And other methods have also replaced poisons for control of yellow jackets, ants, termites and mice. Results of the biological control have been entirely positive, says DeFazio: *The school is now pest free *Use of pesticides has been discontinued *The school system is spending up to 80 percent less on pest control than it did when it relied on conventional methods of control.

b. Bacterial predators; one of the most commonly used bacterial species is Bt or Bacillus thurigensis. At sporulation, the bacterium produces a spore and a protein crystal which releases powerful toxins when degraded by the gut fluids in larvae consuming it; death can occur in 30 minutes- to 3 days. Timing has to be right - larvae must be feeding on leaves treated with spores.Doesn't work with adults not feeding on leaves. The gene that produces this product is the one that has been bioengineered into some plants now!

h. Juvenile hormones anti-juvenile and juvenile hormones mess up the molting cycles of insects. Very species specific and timing is critical. For more information or background on insect cycles and juvenile hormones see here:http://www.ent.orst.edu/berryr/ENT311/LECTURE5/index.htm

from:http://www.ent.orst.edu/berryr/ENT311/LECTURE5/sld012.htm

II. Genetic controls a. Sterile male: Screw worm history: 62-71 a success; 72' strain ejected; 77' strain sexy 81' strain not sexy- consistency is a problem, though when it works can be a wonderful means of control. Still get damage by that years pest. b. Introduction of naturally resistant host strains; wild species are naturally resistant to insects via alkaloids and other chemical defense systems. These have been bred out over time due to taste or unintentionally. Aggies go back to find wild types and breed in naturally by crossing or insert gene directly to get plant to produce its own defenses. c. Bioengineered resistance: the alpha-endotoxin gene of Bt has been inserted into tobacco and other species so no longer need the bacterium itself. Problem if bug becomes resistant to this product. In plants they naturally evolve different forms of their chemicals via selection. Can this happen if the gene involved is not 'natural to the plant'?

III. Integrated Pest Mangement (IPM) includes the use of cultural, biological (see above) and chemicals (pesticides at low doses). They use any technique at the appropriate time. Idea is not to completely kill off the pest but to control at an economically sustainable injury level.

Boll Weevil, common name for a destructive beetle that infests cotton plants. The adult insect has a long snout, is grayish in color, and is usually less than 6 mm (less than 0.24 in) long. Feeding only on the cotton plant, it begins in early spring to puncture the buds and bolls and lay its eggs in them. The eggs hatch into larvae in three to five days. The life cycle of the boll weevil from egg to egg-laying adult is about three weeks. Four or five generations may breed in one season. The larva, a fat, white maggot, does the most damage. It lives on the internal tissues of the buds and bolls. An infested bud usually drops, but most of the damaged bolls remain on the plant and become stunted or dwarfed. Adult weevils that emerge in the autumn hibernate in grass, old bolls, or other vegetation or in the seeds around the cotton gins. They reappear in spring. The insect was first known in Central America, Mexico, and Cuba. In 1863 its ravages stopped the cultivation of cotton in Mexico. About 1892 it spread across the Río Grande to Brownsville, Texas. From this focal point it moved outward at a rate of about 113 km (about 70 mi) a year, eventually infiltrating into every cotton-growing district in the United States east of the Rocky Mountains. The boll weevil has been the target of intensive pesticide spray programs. Today, however, it is increasingly treated using nonchemical means of pest control, including pheromone-baited traps and so-called clean culture, the careful removal of old cotton stalks to deprive the beetle of its overwintering refuge.

a. Cultural methods:these are techiniques used before the use of pesticide spraying. Many worked well and are being used by organic farmers...do they work.. yes.

• Rotating crops to decrease weeds and insects while also increasing soil nitrogen and decreasing soil loss.
• Burning infested crop residues to kill off eggs instead of tilling back into earth
• Planting crops at times that conflict with pest emergence
• Mixed crops- plant crops with horizontal vs vertical leaves so pests can move readily or mixed crops which appeal to limited insect tastes so not one species can grow quickly.

These techniques require more knowledge, more labor ( some difficult to use large equipment)

The American Farmland Trust found about three fourths of the 150 farms participating in its sustainable agriculture demonstration project maintained or increased crop yields while reducing their chemical use.

Slow support and too many restrictions by the government:

Myth versus Reality: Views of Various Forms of Farming
Studies indicate that although yield drops in some but not all cases, profitabilty increases with reduction of use of expensive pesticides and less cropland is used. However there is more labor involved. Much of the conlfict comes from lack of information, support by the government, and lack of consumer demand.
Could it all revert to organic? it would take a while, but most likely with the new techniques discussed above, it could be done.

conventional farmers	vs. low-input farmers ( what they actually found)
Yields: 70.9% think yields will fail if they cut chemicals	vs. 35.3% say yields fell: 17.6% say they rose.
Profits: 63.8% say fear of lost profits is 1 of 3 barriers to low-input farming.	vs 76% say lower costs increased profits. * Campbell Soup Company reduced pesticide application by more than 50 percent in four years without sacrificing yields or quality. Campbell farmers in Ohio lowered the number of pesticide applications by 80 percent and saved $26 per acre * Illinois soybean producers saved an estimated $23 million in 1992 by using innovative crop rotations and planting pest-resistant crops * a collaborative effort between governments, academic institutions, growers and processors reduced pesticide spraying on potato fields in Wisconsin and saved almost $6 million on pesticides and irrigation.
38% Worry that increases in pests will decrease yield	xvs. 43.4% say pests were a problem at first ; just 33.3% say they remained a problem after a few years of farming with fewer chemicals
Labor needs 28.3% expect low-input farming to increase their labor needs	vs 63.6% say labors needs increased.
Information on 18.2% say lack of good information would keep them from trying new methods.	vs. 71% said finding good information was a problem in the beginning only
Crop base 13. 1% expect cutbacks in crop base acres if they use fewer chemicals	vs. 25.6% say base acres fell when they cut back on chemicals. That is they did not need to as many acres to get the same amount of crops.. used less land

If consumers were to consider the cost of health effects, orgnanic farming would really be much more profitable. How the farmer can not include savings for prevention of disease, unless the governement would support subsidies to include these savings. Can you image any government doing this?