As we direct our senses globally we cannot help but see a changing and life-destroying society. There are so many factors including technology which contribute to the degradation of the environment. Coupled with this are varying degrees of risks to our health and the health of other species. The key questions we need to ask ourselves are whether the risks of damage from each hazard outweigh the short and long term benefits and how we can safely reduce the hazards and minimize the risks.
This curriculum unit is developed for seventh grade students over a period. It is designed to encourage critical thinking and for students to involved in the decision-making process resulting in success and good health for all life. This trend of thought will heighten their awareness of the risks and benefits involved in developing technology and therefore students must be guided to make informed decisions. Emphasis would be placed on the interdependence of all organisms and the many ways they can protect and improve the environment.
After studying this unit, it is my hope that teachers and students will become pro-active in identifying the risks and benefits involved in controversial issues having learned how things are interconnected and the relationship between the environment and human health. To adopt this approach and bring about a change in our attitudes and manner of thinking,
mankind
will survive the harmful effects of the environment.
Types of hazards:
Physical
noise, volcanic eruptions, or ionizing radiation
Chemical:
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a) harmful substances in the air, water, food, or sod.
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b) carcinogens refer to chemicals, ionizing radiation that can cause or promote the growth of a malignant tumor or cancer.
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c) mutagens are chemicals, ionizing radiation that can cause mutations.
Risk-analysis
involves identifying hazards, evaluating the nature and severity of risks, using that information to determine options and make decisions about reducing and eliminating risks.
Risk-benefit analysis
involves estimating the short and long term societal benefits and risks involved and then dividing the benefits by the risks to find a desirable quotient. In a risk-benefit analysis, the following factors can be considered:
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a) How important is the substance?
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b) How large is the segment of the population that would be expected to benefit?
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c) Is it possible that the benefits outweigh the risks?
Risk-benefit Factor
Objectives
Students will have opportunities to:
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1. Think critically on key issues and make informed decisions.
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2. Identify the risks and benefits involved in controversial issues.
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3. Describe and discuss alternate methods of controlling pests.
The following passage is read to the class. Students will be permitted to record important points mentioned in the passage to be discussed orally in small groups.
Living organisms interact with one another and their surroundings for survival. Their existence can deteriorate when lethal materials interfere and disrupt their efforts to survive. When the atmosphere and the oceans become polluted with toxic chemicals, the chain of reactions initiated can lead to death of these living organisms. The release of toxic chemicals in the atmosphere returns to the earth in the form of rain or wind and later enters the crops in farmlands. This crop is soon harvested and later enters into the bones of human beings leading to death. Conversely, these chemicals can seep through the soil, combine chemically with air and sunlight to form new chemicals which could kill the existing vegetation. The application of these chemicals is therefore non-selective and has the power to kill every insect—the “pest” and “non-pest”. Man’s total environment will become contaninated—the streams, insects, birds, plants, humans, and soil. So therefore it is not just the intended target that becomes affected. In the long run these deadly substances that penetrate the tissues of animals will soon harm the germ cells and alter the very material of heredity. Some chemicals can be mutagenic or may contain metabolic derivaties that are mutagenic. Because effects of induced mutations are generally detrimental, it is important to identify potential mutagens and to assess their possible impact on future human health.
Students will work cooperatively in small groups of four and discuss the following questions based on the above passage.
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1. What choice shall be made? Give reasons for your response.
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2. Should we risk our future lives over the choice of an insect spray? Why or Why not?
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3. Can we really control unwanted species by a method of “insect spray” without contaminating the environment and upsetting the delicate balance of the ecosystem? Explain.
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4. Imagine you are the owner of an apple orchard. Do you believe that the chemical pesticide you release into the environment should be assumed to be guilty of cansing harm until proven otherwise? Explain and give your opinion on this matter including any effects this principle would have on your life and lifestyle.
To assess the risk involved in spraying the crops with insecticide, one must regard the concept that the probability to harm from exposure to a toxic substance is a function of two variables: a) the exposure or potency b) the dose of the substance. It is very crucial to understand the degree or duration of exposure to certain chemicals in order to evaluate the canse of health problems. Exposure to a toxic chemical may be acute or chronic For example, taking one aspirin tablet every four hours for one day will be less toxic and harmful than taking fifty aspirin tablets at one time. Again, higher concentration of inhaled carbon monoxide from smoke can lead to higher concentration of carboxyhemoglobin versus inhaling just a sniff of smoke from a burning fire. Generally, higher levels of toxic exposure will therefore lead to greater response.
The dose-response model curve below shows that any dose of toxic chemical is harmful and the harm rises as the dose increases.
(figure available in print form)
Those engaged in spraying operations should be made aware of the effect of these chemicals on the soil, water, wildlife and
man
himself. As application of pesticides continue and residues continue to build up in the soil, it is almost certain that we are heading for double. Advance investigation as to the nature and effect of these chemicals and protective laws should in some way lower the risk of contamination to our natural world. We, the public, must assume these risks that the anthorities and condollers calculate. We
must
decide what action to take and we can only do so when we become informed and in full possession of the facts.
Alternative Methods of Controlling Pests
Can we fertilize our crops primarily with organic fertilizer and/or control pests by a combination of cultivation and biological methods?
The following alternative methods can be safer, more effective and ultimately discourage and inhibit pests.
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1.
Crop rotation
in which the types of crops planted in fields are changed from year to year so that populations of pests that attack a particular crop do not have time to multiply to uncontrollable sizes.
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- adjusting planting times to ensure that most major insect pests either starve to death before the crop is available or are consumed by their natural predators.
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- planting rows of hedges or dees in and around drop fields to act as barriers to invasions by insect pests.
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2.
Artificial Selection, Cross Breeding and Genetic Engineering
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Varieties of plants that are genetically resistant to certain pest insects, fungi, and diseases can be developed. Insect pests and plant diseases can develop new strains that attack the once healthy resistant varieties. The use of genetic engineering can somewhat reduce pest damage.
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3.
Biological Control
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Various natural predators, parasites and pathogens can be introduced or imported to regulate the populations of specific pests. (In the United States natural enemies have been used to control about seventy per cent of insect pests).
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4.
Integrated Pest Management Program
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In this approach, each crop and its pests are evaluated as an ecological system. Pest control is basically an ecological problem and not a chemical problem. That is why using large quantities of broad-spectrum chemical poisons to kill and control pest populations eventually fails and ends up costing more than it is worth. The aim of this method is to keep pest populations just below the size at which they canse economical loss. Thus crop fields should be carefully monitored to check whether pests have reached an economically danaging level.
Occupational Hygiene in Agriculture
Even though pesticide use patterns have changed significantly during the past ten to fifteen years, developing countries still use mainly insecticides, many of which are acutely toxic.
Insecticides kill aphids, weevils, and other insect pests and are use on growing crops. As well as killing pests, they often also kill the insect predators which feed on them. Becanse insecticides do not degrade rapidly, they can be passed on in foods and can canse liver failure.
In considering the evaluation and control of agricultural pesticide exposures, it is useful to distinguish between workers who directly handle pesticides during application and those who are exposed primarily to residues following application.
Suggested Activities
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1. Have students debate the topic: “Should DDT continue to be banned or should it be made legal again?”
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2. Have students create a one-act play or dialogue between students who see a threat and those who do not see a threat or/and health risk in using
pesticides.
(This play can be performed in class at the end of the unit during Earth Day week.)
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3. Students may visit the Agricultural Center or the Department of Environmental Protection Agency in Hartford and lean how bugs and weeds are controlled in gardens, parks, and in private yards.
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4. Have students develop rules regulating pesticide use in their neighborhood. Letters restricting the use of toxic chemicals could be mailed to the Environmental Protection Agency.
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5. Invite a speaker, for example a Greenpeace representative, to give a presentation on altemative methods of
insect control
and the
threats to human health from pesticide.
Mutagenesis
Mutation refers to any change in the genetic material of the cell that is transmitted to descendent cells. A mutation may affect a single nucleotide of the DNA, several nucleotides in a gene, several genes, large segments of one or more chromosomes or the entire chromosome.
Genetically engineered organisms might mutate and change their form and behavior. The altered genes transmit these traits from the parent to the offspring. Environmental factors are also capable of causing mutations and the evolution of new combinations.
New varieties of plants can be bred by mutations, crossing and grafting.
Permit students to respond to the following questions:
Do you think that a
mutation
is always for the worse?
Consider an intricate molecule of DNA strand replicating itself and getting a wrong building block into position, is it likely to do a better job because of the mistake? A mutated cell within one’s liver or bone will tend to perform so poorly and very likely unable to multiply. The normal cells surrounding this mutated cell will continue to multiply when necessary and soon crowd it out of existence. So the tissue as a whole stays normal despite the mutations.
On the other hand, what if the mutation just happen to affect the process of growth?
The normal cells in a tissue will continue to grow and multiply as needed to repair damaged cells, but a mutated cell may lack the mechanism to stop the growth at the right time. This rapid, continuous growth can lead to cancer. Thus, most mutations are for the worse, leading to the death of the offspring.
Suggested Activities
Divide the class into teams of four to discuss one of the assigned topics and then present their findings to the rest of the class.
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1. Assume yon have been appointed to a technology risk-benefit assessment board. Explain why yon approve or disapprove of the widespread use of:
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a) drugs that would retard the
aging
process
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b) genetic engineering that would produce people with superior strength.
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2. Students will debate the following issues:
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a) Do benefits of genetic engineering outweigh the risks?
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b) All smoking should be banned in public buildings, buses, subways and trains.
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3. Have students list daily activities that help contribute to
pollution.
Then create a poster depicting this activity.
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4. Have students discuss the pros and cons for the implementation of genetic engineering to improve the growth and appearance of tomato plants.
