Crop Science Sample Lesson

MAIN IDEA: How can the risk of pesticide use be minimized?

The equation RISK = TOXICITY X EXPOSURE demonstrates how risk is related to potential exposure during transporting, mixing, loading, applying and storing pesticides; in cleaning up pesticide spills, equipment and protective clothing; and in disposing of excess pesticides and containers.

TOXICITY is the capacity of a pesticide to injure or kill living things. Toxicity is determined by ACUTE (short term) and CHRONIC (long term) tests imposed on laboratory organisms. Acute tests involve oral (mouth) ingestion and dermal (skin) absorption studies.

An LD50 (Lethal Dose) value is assigned to all pesticides based on the results of acute exposure tests. Lethal Dose 50 or LD50 is the amount of pesticide, in milligrams of pesticide per kilogram of body weight, required to kill 50 percent of a test animal population.

Chronic toxicity is determined by administering various amounts of a test chemical in the daily diet of laboratory animals (rats and mice) for a life time (24 months). The potential of the chemical to produce cancer, birth defects, or reproduction effects in the test animals is evaluated.

Although the toxicity of an individual chemical product is constant, risk can be reduced by using the least toxic product suited for the job. Quicker reduction of risk results from minimizing the EXPOSURE of the user, other people, animals and the environment to the chemicals during and after pesticide use.

Exposure is pesticide entry into the body through the skin, mouth, eyes or nose resulting from inadequate protection during or after pesticide use. If pesticides are handled and used exactly as the label instructs, the potential exposure and risk of pesticide use remain quite low.

Pesticide entry into the body through the skin (dermal exposure) is the most common and subtle route of exposure for mixers, loaders and applicators. All exposure can be reduced by using protective clothing and safety devices.

Minimal protective clothing needed when handling even the safest pesticides includes a hat, long-sleeved shirt, long pants, shoes and socks, rubber gloves and goggles. In addition, for moderately or highly toxic materials, rubber boots, a rubber apron and often an approved respirator are needed as specified on the label.

Other simple safety measures for working with pesticides such as wearing rubber gloves and washing the gloves and hands after use help reduce exposure. Before handling any pesticide, become familiar with symptoms of pesticide poisoning and emergency first aid procedures. Information specific to each pesticide is listed on its label.

After handling or using pesticides, rinse or wash rubber gloves with water before removing them. And wash hands with soap and water, especially before smoking, chewing tobacco, eating, drinking, or using the toilet.

Water should always be available on equipment and at the loading site for washing and emergencies. If any part of the body is exposed to chemical, flush with plenty of water immediately. Keep children and animals away from spray equipment, pesticide mixing areas and recently sprayed fields. Change clothes and shower when necessary, especially if material is spilled on the body. Wash clothing daily, separate from other household laundry.

Transporting pesticides with any food product, feed or animal supplies is not recommended. Before transport, check cans or bags for leaks and tears. Tie down containers to avoid damage or spills. And remember wear rubber gloves when moving the pesticide materials.

The greatest danger of potential exposure occurs during pesticide mixing and loading, since these procedures involve handling pesticide concentrates. The operator, dressed in appropriate protective clothing or equipment, should mix and load the pesticide at the recommended rate, out-of-doors and in good light.

Other people and pets should not be present. Always stand upwind from the equipment being loaded. Never leave a spray tank unattended while filling. Use anti-backsiphon valves on pumping equipment to prevent backsiphoning from the spray tank into the water source.

Following a few simple guidelines in pesticide application increases the effectiveness of pest control and makes the job safer for the applicator, others, animals and the environment:

1. Read the label before application. If the pesticide label cites RESTRICTED USE, do not apply yourself, unless you are a certified applicator.
2. Properly maintain application equipment and check for leaky or worn parts before operation.
3. Calibrate equipment according to instructions on the label.
4. Apply pesticides at the specified dosage.
5. Apply chemicals when drift is not likely to occur to reduce pesticide exposure by inhalation, skin contact, or drift onto sensitive areas such as streams, playgrounds and sensitive crops.

To become a Certified Applicator you will have to attend a special training course sponsored by and approved in the state. You will learn about safe and approved uses of chemicals. You will have to take a written test and likely demonstrate your expertise at handling the equipment and the chemicals. After training and testing you will receive certification and a license to purchase and apply restricted use pesticides.

Cleaning equipment inside and out after use prevents a reaction of pesticide residue with the next chemical used and prevents corrosion of metal equipment. In the case of a pesticide spill, take immediate action. Confine the spill.

Pesticide labels provide spill cleanup instructions. Use personal protective measures. Being able to handle spills and leaks safely is as important as correct chemical use.

Store pesticides in a dry, cool, well-ventilated, separate room or building that is locked and posted as a pesticide storage area. Keep absorptive materials such as vermiculite and sawdust in the storage area to soak up spills or leaks.

The disposal of pesticides and containers is regulated by federal law. Charges can be brought against small users, homeowners and farmers if waste pesticides and containers are not discarded according to label directions. Avoiding surplus pesticides by careful prepurchase calculations is the best way to prevent pesticide disposal problems.

Properly rinsed containers may be discarded in an approved sanitary landfill. Although there are several approved rinsing techniques, the triple rinse method is simple and adequate:

1. Empty container and drain for 30 seconds
2. Fill container 1/4 full with water
3. Swirl, pour into spray tank, and drain for 30 seconds
4. Complete steps 1 through 3 three times, then puncture container to prevent reuse.

Pesticides are common and important tools in modern agricultural production. However prevalent they are they must always be handled responsibly and safely.

EXERCISES:

1. List safety measures that are needed when mixing and loading pesticides. List the hazards that could occur if these safety measures are ignored.

2. Using a pesticide label, prepare an outline of procedures to safely mix, load and apply the pesticide and store the excess.

3. Choose one phase of the pesticide use process, from transporting to container disposal, and develop a detailed plan, including illustrations, for safe use during that phase. Or, make a pesticide poisoning symptom chart and a general plan for emergency first aid. Combine individual research projects to make a safe pesticide use wall chart or bulletin board.

4. Contact local pesticide dealers and Extension agents to find out what instructional programs on safe pesticide handling are available.

INTERNET RESOURCES:

** California Environmental Protection Agency - Pesticide Product/Label Database
http://www.cdpr.ca.gov/docs/label/labelque.htm

** Environmental Protection Agency - Pesticides
http://www.epa.gov/ebtpages/pesticides.html

** University of Nebraska-Lincoln - Pesticide Education Resources
http://pested.unl.edu/pesticide/pages/index.jsp

TEST:

1. How can the risk involved in pesticide use be reduced?

2. What is the most common route of pesticide entry into the body?

3. List five ways to reduce exposure to pesticides.

4. Why do mixing and loading pose the greatest chance of pesticide poisoning?

5. Where should pesticides be stored and what are the most satisfactory storage conditions?

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Copyright © 1997 Stewart-Peterson, Inc. All Rights Reserved.
END STUDENT SECTION

TEACHER'S GUIDE

OBJECTIVE: Students will be able to reduce dermal (skin), oral and respiratory exposure when working with or around pesticides, thus minimizing the risk involved with pesticide use.

PREPARATION: Have students complete lesson CS210 Reading Chemical Container Labels, the second in a series on safe use of pesticides. For extended study, obtain pesticide applicator study guides from your local Cooperative Extension Service. This lesson is based upon information provided by the National Agricultural Chemicals Association.

IMPORTANT TERMS: risk, toxicity, acute toxicity, chronic toxicity, exposure, LD50, lethal dose.

EXTENSION: Have students participate in a Cooperative Extension Service safe pesticide use seminar or training session. Encourage students especially interested in pesticide use and safety to participate in applicator training sessions and become certified. Less interested students can contact and encourage local farmers to participate in training and certification programs.

INTERNET RESOURCES:

** California Environmental Protection Agency - Pesticide Product/Label Database
http://www.cdpr.ca.gov/docs/label/labelque.htm

** Environmental Protection Agency - Pesticides
http://www.epa.gov/ebtpages/pesticides.html

** University of Nebraska-Lincoln - Pesticide Education Resources
http://pested.unl.edu/pesticide/pages/index.jsp

EXERCISE ANSWERS:

1. Wear protective clothing to avoid dermal exposure; use an approved respirator to avoid respiratory exposure; become familiar with symptoms of pesticide poisoning to recognize early signs of exposure; and learn emergency first aid procedures to avoid incorrect treatment of a pesticide poisoned victim. Other responses are possible.

2. Answers will vary depending on pesticide label

3. Answers will vary depending on choice of topic

4. Answers will vary in different communities

TEST KEY:

1. How can the risk involved in pesticide use be reduced?

By using the least toxic product suited for the job and by reducing exposure, since risk = toxicity X exposure

2. What is the most common route of pesticide entry into the body?

Through the skin

3. List five ways to reduce exposure to pesticides.

Wear protective clothing; use an approved respirator; after handling or using pesticides, wash rubber gloves before removing them; wash hands with soap and water, especially before smoking, chewing tobacco, eating,drinking, or using the toilet; have soap and water at all pesticide handling, use and storage areas. Other answers are possible.

4. Why do mixing and loading pose the greatest chance of pesticide poisoning?

Mixing and loading pose the greatest chance of pesticide poisoning because pesticide concentrates are being handled.

5. Where should pesticides be stored and what are the most satisfactory storage conditions?

In a dry, cool, well-ventilated, separate room or building that is locked and posted as a pesticide storage area.

CROSSWORD PUZZLE ANSWERS:

Across: 2. gloves, 4. chronic, 5. sawdust, 6. children, 7. daily, 13. oral, 14. vermiculite, 15. label.
Down: 1. toxicity, 3. upwind, 8. lethal, 9. goggles, 10. dermal, 11. boots, 12. acute.
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Copyright © 1997 Stewart-Peterson, Inc. All Rights Reserved.
STEWART-PETERSON and AGEDNET.COM are registered trademarks of Stewart-Peterson, Inc.
Photo credit: USDA photo by Tim McCabe

END TEACHER'S GUIDE

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