EPA defines pesticide as any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest. Pests can be insects, rodents and other animals, weeds, fungi, bacteria and viruses. The term pesticide refers to not just insecticides but also to herbicides, fungicides, and any other substances used to control pests. Plant regulators, defoliants, or desiccants are also classified as pesticides.
Movement Of Pesticides In The Environment
The physical and chemical attributes of a pesticide such as solubility, adsorption, persistence, and volatilization influence its interaction with the environment. Solubility is a measure of the ability of pesticide to dissolve in a solvent. For pesticide mixing the most commonly used solvent is water. Adsorption is the process by which the pesticide binds to soil particles. A pesticide that adsorbs to soil particles is less likely to move away from the site of application than a pesticide that does not adsorb. Persistence is the ability of a pesticide to remain present and active in its original form for an extended period of time before breaking down. Pesticide persistence is described in terms of its half-life. The longer the half-life the more persistent that pesticide is. Volatility is the ability of a pesticide to turn into a gas or vapor. Volatility increase with an increase in air temperature and wind speed. Volatility is also high at low relative humidity levels.
Movement of pesticides from the site of application in the air to non-target areas is known as pesticide drift. Drift can be controlled by monitoring wind speed and increasing droplet size. Also, follow label information for wind speed related pesticide spray application. Pesticides can also move in the air as vapors. Some of the ways that pesticides can move offsite and enter water are through drift, leaching, or runoff. Runoff is the horizontal movement of water on the surface of the soil. Runoff can be caused by either an irrigation or a rainfall event in excess of the soils’ water holding capacity. Runoff aids in the non-point source pollution contamination of surface waters. Leaching is the vertical movement of the pesticide through the soil profile. Leaching can also be a source of non-point source of pollution of the ground water. Leaching is most influenced by the amount of organic matter in the soil. The more organic matter that is present in the soil, the more the soil is able to hold water and have pesticides bind to the particles which can then leach with heavy rainfall or flooding events. If rainfall is expected then a pesticide application should be avoided so as to not cause leaching.
Use Of Required Personal Protective Equipment
Pesticides can pose a hazard to humans, and the hazard level depends on the length of exposure to the pesticide and the level of toxicity of the pesticide. Wearing personal protective equipment (PPE) can greatly reduce the potential for exposure to the pesticides thus reducing the potential for pesticide poisoning. All pesticide handlers and early-entry agricultural workers are legally required to follow the PPE instructions outlined on the pesticide label. PPE includes coveralls, protective suits, footwear, gloves, aprons, respirators, eyewear, and headgear.
While some PPE may be water resistant, PPE made out of cotton, canvas, latex rubber, and leather are not chemical resistant. Chemical resistant materials include barrier laminate, butyl rubber, neoprene rubber, polyethylene, polyvinyl chloride (PVC), and viton. The selection of PPE should be based on the formulation of the pesticide. Human skin is more likely to absorb an oil based product over a water based one. Water based formulations include wetable powders, soluble powders, some solutions, dry flowables, microencapsulated materials. Non-water-based formulations include emulsifiable concentrates, ultra-low-volume concentrate solutions, low-concentrate solutions, flowables, aerosols, and invert emulsions. Some PPE may be the disposable type while others might be the reusable type. Disposable PPE are designed for brief use, they generally provide good flexibility, and are inexpensive. Reusable PPE should be cleaned daily prior to being taken off and checked regularly for tears and breaks. Store reusable PPE away from your regular everyday use clothing. Due to wear and tear, reusable PPE should still be discarded from time to time.
Skin gets the most exposure to pesticides, while hands and forearms are the most commonly exposed body parts to pesticides. To protect the skin during mixing, loading, or application, PPE choices may include: long sleeved shirt and long-legged pants, coveralls, chemical resistant suits, or chemical resistant aprons. Coveralls must fit loose. For highly or moderately toxic materials wear coveralls over another set of clothing. Spray starch or stain protector on lower pant legs provides a temporary barrier for low toxicity pesticides. Head, neck, and eye protection is also very important. For head and neck protection hard hats can be used, but a plastic safari hat works the best. Hats must not contain materials such as leather, cotton, straw, or foam because they absorb chemicals. Examples of PPE for eye protection include goggles, full-face shields, and shielded safety glasses. Mix pesticides below face level to reduce splashing injury. To avoid inhalation exposure to dust formulations use a respirator. Respirators are of two types, air-supplying and air-purifying. Air-supplying respirators supply air from a clean source, while air-purifying respirators remove contaminants. Chemical resistant footwear includes certain shoes, shoe covers, and boots. These materials should not be made from canvas, cotton, or leather as they absorb the pesticides.
Effects Of Exposure
Exposure to pesticides occurs when a pesticide is taken into the body. Pesticides enter the body through the skin (dermal), mouth (oral), eyes (ocular), or by inhaling through the nose. Oral exposure is most often seen in children. Make sure they do not have access to rodent or insect baits and other improperly stored pesticides in the house. Mark all measuring cups and containers used for mixing pesticides so that they are not used for measuring other food and drink materials. Inhalation exposure is seen due to poor ventilation, using improper respirators, and due to pesticide vapors. Ocular exposure is seen as a result of splashing pesticides, windy weather, rubbing eyes with contaminated hands or PPE, and when pouring dry materials. Ninety-seven percent of all pesticide exposure is through dermal exposure. Dermal exposure is most often seen when not using the right type or required PPE, not washing hands after working with the pesticides, due to drift, and due to splashing.
Harmful effects of pesticides are of three types: acute, delayed, and allergic. Injuries due to acute effects appear either immediately after exposure or within 24 hours of exposure. Delayed effects do not occur immediately after a pesticide exposure or within 24 hours. They may be due to either repeated or a single exposure to pesticides. Allergic effects vary from person to person, and are seen due to sensitization of the body to a chemical product after more than one exposure to the chemical. Signs of pesticide poisoning include nausea, vomiting, diarrhea, stomach cramps, headache, dizziness, confusion, excessive sweating, chills, thirst, chest pains, difficulty breathing, muscle/body cramps, and weakness. External irritants may cause redness, blisters, rash, burns, swelling, stinging, or burning sensation in eyes, nose, mouth, and throat. Some of the heat stress symptoms are similar to those of pesticide poisoning, therefore, sometimes it is difficult to differentiate between pesticide poisoning and heat stress. Heat stress is seen when the body is subjected to more heat than it can withstand. Heat stress symptoms include fatigue, headache, nausea, chills, dizziness and fainting, severe thirst and dry mouth, clammy skin or hot, dry skin, and heavy sweating or no sweating.
Safe Handling of Pesticides
Read the label thoroughly before using the pesticide or doing any pesticide handling activities. The label not only gives you the product use information, but it also gives you the information related to the required PPE to be used, and the precautions to be followed to avoid pesticide exposure. Make sure that the PPE is in working condition before using it, and be familiar with the proper use of the PPE as well. Make sure that the equipment that will be used for the pesticide application is in working condition, and also the person who will be operating the equipment is knowledgeable about its safe and correct use. Avoid accidental spread of the pesticides, and be prepared for emergencies. Keep personal decontamination supplies, such as clean water, soap, and paper towels, and spill cleanup equipment, such as cat litter, activated charcoal, sand, spill pillows, absorbent mats, and shovels at readily available distance. Have a first-aid kit on hand as well. Also, ensure that people and animals are out of the pesticide application area.
Management of Pesticide Spills
The accidental or unintentional release of a pesticide into the environment is known as a pesticide spill. Spills may occur at the pesticide storage site, at the mixing and loading site, or during transportation. Always have a spill kit in the vehicle when transporting pesticides. The spill can vary in magnitude, the spill be a minor one involving the tipping over of a container or could be a major accident for example the tipping over of a cargo container carry liquid pesticide inside it. In the event of a spill the three C’s that need to be followed are: Control the spill, Contain the spill, and Clean up the spill.
Control the spill: Before attempting to control a spill make sure that you have the required personal protective equipment as listed on the product label on. Having the right PPE on prevents your body from coming into contact with the spilt chemicals. Then, stop the source of the spill. Take immediate steps to control the release of the pesticide products being spilled. For example, if a pesticide container is damaged and leaking, put the damaged container into a larger container to prevent further release of the pesticide into the environment.
If the spill is large or dangerous, get help. But do not leave the spill site unattended. The first contact to make in case of a spill should be your county 911 emergency number. They will help coordinate the emergency response efforts. Therefore a cellphone should be standard equipment on every vehicle transporting pesticides. Cordon off the spill zone and warn other people to keep out of the spill zone. Make sure they are at least 30 feet or further away from the spill.
- Contain the spill: Prevent the spill from spreading and getting worse. As the leaking pesticides are being controlled, move quickly to keep the spilled material in as small an area as possible. If the spill is flowing toward a source of water, block it or redirect it.
- Clean up the spill: Dry pesticides can be swept up and reused if possible. For liquid spills items such as activated charcoal, absorptive clay, vermiculite, sawdust, or cat litter can be used to soak up the liquid. Do not hose down the site with water unless the spill is on a containment pad. Once the spill is contained, sweep up the pesticides and the spill control materials and place them in a steel or fiber glass drum lined with a heavy-duty plastic bag. The top 2-3 inches of soil saturated with the pesticides should also be removed and placed in the drum. Check the label for information on what is recommended for washing or further decontamination of the spill zone. If the materials are hazardous wastes they must be shipped to an incinerator or sanitary landfill approved for the disposal of hazardous wastes. Then decontaminate the equipment that was contaminated either because of the spill itself, or because of cleaning up the spill, or because of disposing the spilled pesticides. After cleaning up the equipment, decontaminate yourself by washing thoroughly with soap and water. Wash any part of your skin that may have been exposed to the pesticides, especially your hands, forearms, face and neck.
If a chemical spill occurs on a public road contact either the Florida Highway Patrol or local authorities. CHEMTREC, the Chemical Transportation Emergency Center can advise you on how to manage a chemical emergency 24 hours a day. Their contact number is 1-800-424-9300.
Credits: Fishel, F. 2010. “Applying Pesticides Correctly,” 7th Edition.