Rice Production: Chapter 12 - Pesticide safety and agro-chemical use

Introduction

Tile se of chemical pesticides in developing countries is subject to considerable controversy. Pests destroy up to one third of the world's food crop every year. An even greater percentage is lost in developing countries, where safe and effective pesticide use is rare.

Fart of your Job as an agriculture extension agent will be to teach farmers and agrotechnicians how to control insect damage through a combination of preventive management practices and pesticide use This chapter provides a brief introduction to the basic safety measures which should always accompany the use of chemical pesticides.

I. Pesticide Toxicity

Pesticides are useful for keeping farm animals healthy and for killing insects, weeds, and plant diseases. When used improperly they car hurt or kill other things in the environment including you or the people you work with.

All pesticides are toxic, ranging from the most dangerous (Category I) to the least dangerous (Category IV).

The ID₅₀ rating (ID refers to lethal dose) indicates the amount of pesticide that will kill 50 % test animals (male rats) in terms of milligrams of pesticide per kilogram of body weight If the ID₅₀ of a rat poison is 148 then 149 mg of the poison will kill one of every two rats that weigh 1 kg each.

ID₅₀ values provide a fairly good measure of the relative toxicities of pesticides to humans Each type of pesticide is generally assigned two ID₅₀ values, for dermal contact through the skin) and for oral contact (ingestion through the moth).

The LD₅₀ rating gives no information on the cumulative effect of repeat exposure. Organophosphates such as Phosdrin ( mevinphos) and Parathion interfere with the transmission of nerve impulses by inhibiting the enzyme cholinesterase, and because the body cannot rid itself of these poisons, their effects can be cumulatuve. Several small nonlethal doses can add up to a lethal dose.

Even relatively "safe" pesticides such as Malathion or Sevin can cause severe poisoning if enough of the pesticide is ingested or spilled on the skin, particularly in concentrated form.

Toxicity of Common Pesticides

(ID₅₀ values in mg/kg)

Pesticide	Use*	Oral	Dermal
Category I- Most dangerous
Phosdrin ( Mevinphes )	I	6	4.7
Category II Dangerous Bidrin	I	21	43
Category III - Less Dangerous
BHC	I	600
Chlordane	I	335	690
2, 4 -D	H	650	-
Dithance D-14-	F	395	1000
Paranquat (Gramoxone)	K	120	480
Negamon	N	173	1423
Vapona (Dichlorvos)	I	90	107
Category IV - Least Dangerous
Captan	F	9000
Daconil (Bravo)	F	10000	10000
Malathion	I	1375	4444
Sevin (Carbarryl)	I	850	4000

*F = fungicide

I = insecticide

K = herbicide

N = nematocide

II. Safety Guidelines

1) Laws and Regulations

Make sure you are using, storing, and disposing of pesticides in accordance with the laws and regulations of the country in which you live and work.

2) Read and Understand the Label

All persons using pesticides should understand the directions and precautions on the label before opening the container. The label should state the name of the pesticide, amount of active ingredient, uses, suggested dosages, precautions and first aid instructions. If the label is vague or unclear try to obtain descriptive pamphlet.

Never buy or use pesticides that come in unmarked sacks or bottles. Any U.S. labels which lack the above listed information should be reported, with a copy of the label if possible to the Peace Corps Information Collection and Exchange (ICE), Washington D.C. 20525. All this information is required on the label by law, and any failures to comply will be brought to the attention of the S. Environmental Protection Agency.

3) Protect Yourself

The proper use of safety equipment and protective chloting is essential in handling and applying chemicals. Rubber gloves and boots, trousers (outside of boots) long-sleveed shirt, waterproof hat and coat, and proper measuring equipment are the minimum requirements when pesticides are applied. In many instances a respirator is necessary as well. Thoroughly wash all clothing before wearing it again. Avoid handling chemicals when wearing leather shoes, since chemicals are easily absorbed by leather arid are very difficult to remove.

4) Category I and Category II Pesticides

When working with Farmers, avoid using Category I and Category II pesticides, particularly Birdin, Phosdrin, Phosphamidon and Trithion. If you or other pesticide experts ever find i-t necessary to use pesticides in either Category I or Category II, be sure to wear the required protective clothing, regardless of how uncomfortable it many get Insist that farmers who use these pesticides (almost invariably they should not be) are trained to use protective clothing.

5 ) Exposure to Pesticides

In handling any pesticide, avoid repeated or prolonged contact with the skin or inhalation of dust or spray. Clothing should be changed and hands and face washed before eating, smoking, or going to the bathroom. Wash immediately with detergent and clean water when your hands, skin, or any port of the body become contaminated or exposed.

6) Safe Working Area

Prepare pesticide solutions in a well-lit, well-ventilated place, preferably outside. Keep livestock, pets, and people out of the mixing area. Wear proper protective clothing and read the label before opening the container. ix the solution carefully to avoid accidental splashing. If a spill occurs, soak up the spill with sawdust or soil and bury the contaminated material in a hole at least 50 cm deep in an isolated place where water supplies will not be affected. Cover the material with dirt.

7) Windy Days

Never spray or dust on windy days. Do not spray pesticide if people or animals are nearby. Avoid treating crops while bees or other pollinators are active in the field. Do not apply pesticides if apiaries (beehives) are near enough to be affected adversely; notify the beekeeper so he can move the hives if necessary.

8) Protecting Passersby

Do rot permit unprotected passersby to enter treated fields until the spray has dried or the dust has settled.

9) Pesticide Storage

Store pesticide in a dry, well-ventilated place out of the reach of children and away from food and animals, pesticides in the original, labelled containers, tightly sealed to prevent the release of harmful vapors.

10) Pesticide Containers

Make sure that pesticide containers are never put to any other use. Burn all empty bags, as well as cardboard and plastic containers Do this in an isolated place, when the wind will not cause contaminated smoke to drift among homes, people, livestock, or crops. Keep well out of the smoke Bury the ashes 50 cm deep in an isolated place where water supplies will not be contaminated. Break all class containers, crash or punch holes in metal cans, and burn and bury as above.

11) Water Source

Do not contaminate streams, swamps, or other water sources either during application or when cleaning equipment. Rinse water and leftover spray mixture should be poured into a hole in the ground, never into a stream or swamp.

III. Symptoms of Poisoning

Symptoms of pesticide poisoning vary depending on the chemical group of the pesticide and the severity of the exposure. Repeated exposure to small amounts of some pesticides, can cause sadden severe illness. Poisoning caused by synthetic organic pesticides (organophosphates, chlorinated hydrocarbons, crarbamates) may cause one or more of the following symptoms:

Wild poisoning:

- irritation of the skin, eyes, nose, throat

- weakness, dizziness

- nausea, stomach cramps or diarrhea

- excessive sweating and salivation

- chest discomfort

- blurred vision

- numbness of hands and feet

Moderate poisoning:

- difficulty talking and breathing

- poor muscle coordination

- rapid pulse, flushed skin constriction of pupils

- miscle twitching

- increased severity of earlier symptoms

Severe poisoning:

- inconsciossness

- severe constriction of pupils

- convulsions

- inability to breathe

- secretion from the mouth and nose

- death

Symptoms may be delayed several hours following exposure. Appearance of come of the symptoms does not necessarily indicate poisoning - other kinds of sickness may cause similar symptoms. Always consult a physician to be certain.

IV. First Aid Measures

1) If breathing has stopped, give artificial respiration immediately.

2) Get the victim to a doctor or hospital as soon as possible. Take the pesticide label along for the doctor's information. Do not carry the pesticide container in the passenger space of a car or truck.

3) If the pesticide has been swallowed, check the label to see if the victim should be made to vomit. Vomiting can be induced by giving the victim one tablespoon salt dissolved in half a glass of warm water. To avoid dehydration, however, the preferred method is to stick a finger or spoon down the victim's throat. Position the victim face down or kneeling forward to avoid choking and/or strangulation. After vomiting has been induced, make the victim lie down and keep warm. Never induce vomiting in a person who is unconscious or having convulsions.

4) If a pesticide gets on the skin, immediately remove all contaminated clotting and wash the affected skin with detergent and water. Don't forget hair and fingernails.

5) If a pesticide gets in the eyes, wash immediately and for at least five continuous minutes with generous amounts of water. Have them checked by a doctor.

6) If a pesticide has been inhaled, get the victim to fresh air immediately and have them lie down Lossen clothing and keep the victim warm and quiet If breathing stops, begin artificial respiration. Summon medical assistance immediately

ARTIFICIAL RESPIRATION

1) Place the victim face up.

2) Remove all foreign matter from the victim's mouth with your fingers.

3) lift up under the neck and tilt the head as far back as possible, until the chin points up. This position is important to keep the air passage open.

4) For an adult victim, pinch the nostrils shut and place your mouth tightly over the victim's mouth. For a child victim, place your mouth over the mouth and nose. A handkerchief should be placed between your lips and the victim's to prevent your coming into contact with the pesticide.

5) Take a breath and exhale into the victim until you see the victim's chest rise se shallower breaths for children.

6) Remove your mouth and release the victim's nostrils. Listen for the sound of air coming out.

7) Repeat

- every 5 seconds for adults

- every 3 seconds for children

8) Bulging of the stomach may make breathing more difficult. Turn the head of the victim to one side and press gently on the stomach. This will force air out of the stomach but may cause vomiting.

9) If vomiting occurs, quickly turn the victim on their side, wipe out the mouth and then re-position them.

10) Continue artificial respiration until the victim begins to breathe unassisted, or until a doctor pronounces the victim dead, or until the joints stiffen.