Pesticides are toxic. The health risk to people depends on the toxicity of the pesticide and the amount of exposure. Exposure to pesticides can produce a range of symptoms, depending on the method and length of exposure and type of pesticide. The method of pesticide application also influences the exposure. Applying chemicals in enclosed areas, such as grain bins, barns, and livestock facilities, may subject a person to higher levels of exposure than applying pesticides outdoors.
Pesticides may enter the human body through contact with the skin (dermal exposure) and through the mouth, lungs, and eyes. Different formulations of pesticides affect the body in different ways.
Dermatitis, inflammation of the skin, is generally accepted as the most commonly reported effect of pesticide exposure. Irritation caused by a single exposure to a pesticide is usually primary irritant dermatitis (PID). Symptoms range from a slight redness of the skin to blisters or ulcerated lesions. The severity of the irritation is influenced by the chemical properties of the substance, duration and method of exposure, condition of the skin, temperature and humidity, and location of the contact on the body.
A second type of dermatitis is called allergic contact dermatitis. The symptoms are similar to PID; however, allergic contact dermatitis occurs after repeated chronic exposure to a chemical, when the allergenic substance contacts previously sensitized skin. An applicator may be exposed to the chemical allergen for years before becoming sensitized and showing dermatitis symptoms.
Other acute symptoms of pesticide poisoning vary based on the class of pesticide. Symptoms of acute pesticide poisoning are described below for organophosphates, carbamates, pyretrhins and pyrethroids, arsenicals, fumigants, anti-coagulants, and bipyridilium.
Organophosphates (Examples: Thimet, Lorsban, Malathion, Di-Syston, Counter, Penncap-M, Guthion, Mocap, Dimethonate.) Symptoms of mild poisoning include fatigue, headache, dizziness, blurred vision, excessive sweating and salivation, nausea and vomiting, and stomach cramps or diarrhea. Symptoms of moderate poisoning include inability to walk, weakness, chest discomfort, muscle twitches, and constriction of the pupil of the eye. In addition, mild poisoning symptoms become more severe. Symptoms of severe poisoning include unconsciousness, severe constriction of the pupil of the eye, muscle twitches, secretions from mouth and nose, breathing difficulty, and if not treated, death. Illness may occur quickly or be delayed a few hours. However, if signs or symptoms start more than 12 hours after exposure to the pesticide, it is probably some other illness.
Carbamates (Examples: Temik, Lannate, Nudrin, Baygon, Sevin.) Carbamates act similarly to organophosphates, producing the same signs and symptoms. Carbamates also inhibit cholinesterase; however, their action is quickly reversed by the body. The illness caused by carbamates is usually not as severe or as long lasting as that caused by organophosphates.
Pyrethrins and pyrethroids (Examples: Ambush, Pounce, Pydrin, Warrior, Asana.) Pyrethrin is extracted from the flowers of certain chrysanthemum plants. Pyrethroids are chemically similar to pyrethrins and are manufactured in pesticide laboratories. Both are highly toxic to insects and fish but less toxic to humans than most insecticides. Pyrethrins and pyrethroids affect the central nervous system, and extremely high exposure results in convulsions and lack of coordination. However, because of their low level of toxicity, pyrethrins and pyrethroids usually cause respiratory concerns (for example, asthma) and irritation to the skin and eyes.
Arsenicals (Examples: CCA, Chemonite, Paris Green, DSMA.) Ingestion is the most common cause of most acute poisoning by the arsenicals. Stomach pain, vomiting, and diarrhea are the primary symptoms of acute poisoning. Symptoms are sometimes delayed for hours. A garlic odor to the breath and feces helps to identify the poisoning agent. Low-level exposure causes symptoms of poisoning, including chronic headache, stomach pain, and low-grade fever.
Fumigants (Examples: cyanide, methyl bromide, phostoxin.) Fumigants are among the fastest-acting poisons. Massive doses result in unconsciousness and death without warning. Smaller doses may result in the odor of bitter almonds on the breath, salivation, nausea, anxiety, confusion, and dizziness. Illness may last one or more hours, terminating with unconsciousness, convulsions, and death from respiratory failure.
Anticoagulants (Examples: Warfarin, Rodex.) The injurious effects of anticoagulants are due to bleeding, mainly into the body tissues. For example, the initial symptoms in chronic Warfarin poisoning are back pain and abdominal pain due to blood buildup in these tissues.
Bipyridilium (Example: Gramoxone.) Bipyridilium herbicides may be harmful if inhaled or absorbed through the skin, and may be fatal if swallowed. Severe irreversible lung damage can develop if they are swallowed or inhaled, and the symptoms of injury may be delayed. Prolonged skin contact generally causes severe irritation.
Unlike acute poisoning, symptoms of chronic poisoning may not become evident for weeks, months, or even years. When the symptoms finally develop, it may be difficult to prove a direct link between the symptoms and the earlier exposure. The symptoms of chronic toxicity may occur as a slowly progressive condition, such as increased breathing difficulty or skin sensitization (allergy) after repeated use of a pesticide. Sometimes, chronic toxicity may result in a disease such as cancer. The effects of chronic pesticide poisoning include oncogenicity, carcinogenicity, mutagenicity, neurotoxicity, and reproductive effects.
B. Sources of Exposure
Pesticide exposure can occur through ingestion, dermal absorption, inhalation, and absorption through the eyes. Exposure through ingestion is usually due to carelessness. If pesticides were always stored and disposed of correctly, children would never have access to them. The most frequent cases of accidental ingestion occur when pesticides are taken from the original labeled container and put into an unlabeled bottle or food container. At least one-half of the accidental pesticide deaths in this country involve children under 10. Inhalation, dermal absorption, and absorption through the eyes usually result when pesticide applicators fail to wear the proper protective equipment.
C. Population at Risk
Workers involved in the manufacture of chemicals, and applicators exposed to high levels of pesticides over many years, run the greatest risk of developing any chronic effects. Applicators who do not follow label directions and fail to wear protective equipment increase their risk of developing chronic effects. Children are at the highest risk of accidental ingestion.
D. Diagnosis, Treatment, and Prognosis
Supervisors, applicators, and co-workers should receive training to help them recognize symptoms of pesticide poisoning. With quick recognition, a pesticide applicator or co-worker can act to decrease exposure and facilitate treatment sooner. A pesticide applicator should seed medical advice immediately if unusual or unexplained symptoms appear at work or later the same day. A person who may have been poisoned should not be left alone. There should be no delay in calling a physician or taking a pesticide-exposed person to a hospital. It is better to be too cautious than too late. A clean container (or the label) of the pesticide should be taken to the physician. Under the Worker Protection Standard, it is the responsibility of the agricultural employer to provide emergency assistance if there is a reason to believe that an employee has been poisoned or injured by a pesticide. Different classes of pesticides have distinct poisoning symptoms. Applicators should always be aware of the class of pesticide being used and of the symptoms that may result from exposure.
Treatment of dermatitis involves removing contaminated clothing, washing the skin, and avoiding contact with the offending allergen. For treatment of other exposures, read the directions in the “Statement of Practical Treatment” in the “Precautionary Statements” on each pesticide label. These instructions can save the life of someone who has been exposed to a pesticide.
If a pesticide contacts the skin, quick action should be taken to remove all contaminated clothing, wash contaminated skin with water, wash hair and fingernails, and remove solutions of pesticides in petroleum oil or other solvents with soap or detergent.
If a pesticide gets in the eyes, eyelids should be held open and eyes washed immediately with a large amount clean, warm water. Medical personnel should be called for advice on further treatments.
If a pesticide is inhaled, the affected person should be moved to fresh air right away and tight clothing loosened. Medical treatment should be sought immediately, and artificial respiration used if breathing has stopped or if the victim’s skin is blue. However, people should never attempt to rescue a victim from an enclosed area without proper protective equipment. If equipment is unavailable, emergency personnel should be called.
If a pesticide is swallowed, the mouth should be rinsed with plenty of water and medical assistance sought immediately. Label directions should be followed, and patients should not be allowed to lie on their backs if they are vomiting because the vomitus could enter the lungs and do additional damage.
Organophosphate pesticides cause more cases of occupational poisoning and death than any other single group of pesticides. Therefore, pesticide applicators using carbamate and organophosphate pesticides on a regular basis should consider having their blood tested to find their normal or base levels of cholinesterase. Applicators should have their normal or base levels of cholinesterase established during the “off season” before applying or handling organophosphate or carbamate insecticides.
People have wide differences in blood cholinesterase levels. Once a pesticide applicator’s base cholinesterase level has been determined by a doctor, a blood test after pesticide handling or application determines whether there has been overexposure to either an organophosphate or carbamate pesticide. If so, further contact with these pesticides should be avoided until the cholinesterase level has returned to normal. In severe cases, antidotes must be given. In the absence of additional exposure, blood cholinesterase enzyme regenerates in about 120 days from very low to normal levels for organophosphate poisoning and more rapidly for carbamate poisoning. Cholinesterase testing must be done immediately after exposure to carbamate insecticides to be of value.
By law, highly toxic pesticides must have instructions for the physician on the label in case of a pesticide poisoning. Instructions include information on medical antidotes, if available. Remember that medical antidotes can be very dangerous if misused. They should never be used as a preventive treatment and should be prescribed and given only by a qualified physician. If instructions for a physician are not on the label, contact the Iowa State Poison Center at 800-222-1222.
The prognosis varies based on the toxicity of the chemical and the amount, duration, and method of exposure.
E. Prevention of Exposure
Accidental poisonings can be prevented by:
- Always storing a pesticide in its original labeled container.
- Never use the mouth to clear a spray line or nozzle, or to begin siphoning a pesticide.
- Never eating, drinking, or smoking until after leaving the work area and washing thoroughly.
- Always keeping pesticides in a locked storage area.
Approximately one percent of the population has abnormally low levels of cholinesterase. People with this abnormality are at extreme risk when applying certain pesticides. For safety’s sake, applicators should have their base cholinesterase level determined before applying any organophosphate or carbamate insecticides.
Applicators and workers involved in the manufacture of chemicals should follow label directions and wear protective equipment