Risks from Chemical Use on the Farm Frederick W Oehme DVM, PhD
Commodity producers undergo numerous risks in everyday farm activities. In the sophisticated operations of contemporary farms, dozens of chemical products are used, and like all chemical products, toxicity can result from improper use, accidents or even repeated exposures to sensitive workers. Insecticides, herbicides and rodenticides are intended to "kill" and their excessive application to targets other than those for which they are intended produces illness and even death. Petroleum products used for fuel and lubrication, as well as fertilizers such as anhydrous ammonia, can be toxic if mishandled. Chemicals used in specialized farm operations may produce gases that introduce risks in closed environments, and leeching of pesticides or wastes into water supplies provide opportunity for livestock and human drinking water becoming unfit.
Insecticides Organophosphates and the subsequently carbamates are extremely toxic to humans and other animals. Although they are less persistent in the environment and in food supplies, poisonings occur by inhalation, skin contact, and accidental ingestion. Working clothes saturated with spilled insecticide provide opportunity for skin absorption of these dangerous chemicals. Absorption of organophosphate/carbamate insecticides produces blurry vision, vomiting, muscle weakness, mental confusion, and muscle twitching and seizures that may lead to death from paralysis of the respiratory muscles.
While most organophosphate/carbamate insecticide poisonings occur within hours of excessive exposure, and intermediate syndrome beginning 1-4 days after exposure has been observed, and an even longer chronic neurological effect developing 2 or more weeks after exposure has been reported. Both conditions involve weakness and paralysis of the nervous system that produces chronic fatigue, difficulty walking and performing voluntary functions, difficulty breathing and eventual paralysis. While the acute organophosphate/carbamate poisoning has effective treatment, the intermediate and chronic nerve conditions are less responsive to therapy. Immediate attention to excessive exposure to this group of insecticides is therefore important, and health care providers should be given early opportunity to initiate decontamination and appropriate specific therapy. Fortunately a simple and readily available blood test may be performed to determine the presence and severity of organophosphate/carbamate poisoning. Delay in initiating treatment results in more severe and persistent effects from this common intoxication. To avoid the headache, diarrhea, fatigue and risk of respiratory poisoning associated with these commonly used insecticides, farm workers should use the least toxic pesticide available for the need, use only the recommended amounts of chemical, use protective clothing and exposure precautions, and when aerial spraying is involved "get out of the way", particularly by not using flaggers! Chlorinated hydrocarbon insecticides are restricted or banned in use in the United States, but in occasional disease control, their use is authorized. While less toxic on a dose per use basis, poisoning does result in effects upon the nervous system and of more potential consequence is the long persistence of the chlorinated hydrocarbon insecticides in body fat. Nursing mothers then risk passing the insecticide to their nursing children in breast milk. Long term exposure to this group of compounds has produced chronic illness affecting vision, persistent headaches, dizziness, behavioral problems, muscular weakness and decreased academic performance. Unfortunately there is no effective treatment to reverse these effects, so avoidance of exposure and prompt decontamination if clothes or skin are affected is important. Pyrethrins are a group of natural occurring substances that have insecticidal activity. These compounds are biodegradable in the environment and do not accumulate in body tissues. They are also of relatively lower toxicity than the other commonly used insecticide groups. Although poisoning can occur from exposure to extremely high doses, the effects are mildly neurotoxic (affecting the nervous system) with weakness, dizziness and occasional muscle twitches occurring. There are no known antidotes, but treatment of the symptoms by medical personnel usually results in recovery in a few days.
Herbicides Several types of herbicides in general use can pose health hazards for producers and applicators; however, as a general group herbicides are of low toxicity and are more of an environmental concern than a health risk. 2,4-D toxicity occurs from extremely large exposures (usually by swallowing or inhalation) that causes vomiting, diarrhea, changes in heart rhythm and muscle twitches. Studies of farmers using large quantities of 2,4-D has suggested an increased risk of non-Hodgkin’s lymphoma, but this observation is still controversial. Atrazine is a commonly used herbicide that has low acute toxicity, but is of concern because of its persistence in water supplies. The serious potential for cancer risk is still debatable, but atrazine’s wide use and continuing appearance in human drinking water supplies encourages responsible application rates and usage. 2,4,5-T and paraquat are formerly used herbicides that have demonstrated severe toxicity are therefore are banned from their use in the United States. 2,4,5-T was contaminated with a technical byproduct associated with cardiac and transient peripheral nerve pathology. Paraquat had potential for producing progressive lung fibrosis with a high death rate within 2 weeks. No effective treatment was available for both herbicides; thus alternative compounds were recommended.
Fungicides A variety of chemicals are used to prevent fungal growth on perishable crops, seeds and wood materials used in agriculture. All the various groups of fungicides have potential for causing allergic reactions: asthma, contact dermatitis (skin irritation), hives and anaphylaxis have all been reported. Organic metal fungicides are highly irritating and produce variable general toxicity. Copper-containing organic fungicides are irritants; organic mercury fungicides produce injury to the nervous system with permanent nerve damage possible; tin-containing fungicides cause both irritation of skin, eyes and respiratory tract as well as headaches, seizures and coma with severe exposures and resulting poisonings. Organochlorine fungicides are also irritants, but may be absorbed and cause general toxicity with chronic high exposures. Thiram, one of the thiocarbamate fungicides, also irritates and has a unique interaction with alcohol producing headache, skin rash and mental confusion. Other thiocarbamte fungicides are also contact irritants and may cause toxicity to the nervous system and red blood cells upon repeated exposures. The thiazoles (TCMTB) produce severe itching and peeling skin, nose bleeds, and other effects of direct irritation. The phenol fungicides (PCP, creosote) have particularly severe skin irritating properties, and are also systematically absorbed following skin exposure. Their affinity for fat results in considerable fat accumulation in exposed workers. In closed environments, the vapors from the phenolic fungicides may cause eye and respiratory tract irritation, often to the point of making the facility unworkable.
Rodenticides A number of toxic rodenticides are used on the farm. In general, toxicity only arises from accidental or intentional ingestion, but children may contaminate their hands by handling baits and become at risk from ingestion. A variety of effects may occur from bleeding due to super-warfarins to cardiac toxicity and liver and kidney damage from other rodent-control agents. Because effects are variable and rodenticides have significant toxicity associated with human exposures, prompt medical attention should be sought upon recognition of such rodenticide ingestions.
Fertilizers Fertilizers used in agriculture are composed of nitrogen, phosphates, lime and potash, all of which are irritating when applied to skin, eyes or mucus membranes of the body. Some fertilizers, such as anhydrous ammonia, are gases that form extremely alkaline solutions when in contact with the membranes of the body. Eye burns and irritation to the nose and throat, as well as the upper respiratory passages develop rapidly and can produce sudden lethal affects when pulmonary fluid or adult respiratory distress syndromes occur. Immediate first aid is important for these irritant exposures. Flushing contaminated areas with large amounts of water is of initial urgency prior to seeking medical care.
Chemical Hazards of Equipment and Facilities Solvents used on farm machinery are often flammable and explosive. Exposure may also occur to these solvents through skin contact, accidental ingestion, or inhalation of vapors. Vapor inhalation will produce mucus membrane and respiratory tract irritation with coughing, sneezing, dizziness and mental confusion and occasional death in severe cases. Siphoning gas is a "no-no" to avoid ingestion or even more severe pulmonary aspiration. Saughtering or welding broken equipment produces metal fumes and gases that are hazardous. Appropriate protective clothing and safety goggles are essential when working with these irritating chemicals. Children on farms present a special problem in assuring that agricultural liquids are in sealed containers and children are warned of the hazard. Chemicals in animal confinement areas are largely wastes and the gases generated by these organic waste materials. Methane, and carbon-dioxide asphyxiate when ventilation is insufficient by displacing oxygen from the needed respiratory environment. Hydrogen sulfide is a highly toxic poison that initially has a "rotten egg" odor but becomes nondetectable by smell as the sensory apparatus is paralyzed. Death may then result quickly by continued presence in the toxic atmosphere. Other animal confinement aerosols, including dust and fecal material, will produce bronchitis, asthma, chronic obstructive pulmonary disease and hypersensitivity upon repeated exposure by continuing occupational contact. Silos generate fermented animal feed that results in decreased oxygen levels in the breathing atmosphere. Toxic levels of nitrogen oxides may also occur. Mechanical asphyxia may occur in grain silos or bins from becoming trapped and "drowned" in the fluid-like grain content. High concentrations of nitrogen oxides present upon entering a silo can produce immediate loss of consciousness. Farmer’s lung is a hypersensitivity of pulmonary tissue related to inhalation of fungi present in the feed storage atmosphere. Sudden onset of fever, chills, muscle aches, coughs and shortness of breath occur within 4-8 hours after breathing the decomposing feed material from the top layer of silage. Silo unloader’s syndrome is a form of the organic dust toxic syndrome associated with excessive exposure to the molds at the top of a silo. When the moldy silage is handled, the toxins produced from the organisms in the silage trigger a flu-like effect with fever, muscle aches, headache, cough, wheezing, and nose and throat irritation. Prompt removal from the environment producing these toxic effects is vital. A few days of rest with appropriate medication will allow most workers to return to their chores in a few days.
Animal Drugs and Chemicals Numerous chemicals, including antibiotics and trace minerals, are added to animal feeds as growth promoters and disease preventive agents. Contact dermatitis may occur from handling such medicated animal feeds. Allergic reactions have also been reported for antibiotics such as tylosin and nitrofurazone. Disinfectants (iodine, phenols and hypochlorite) may cause irritating contact dermatitis. Allergic reactions can develop on skin when rubberized clothing is worn. The medication of animals with antibiotics and biologicals presents the potential for farm animal movement resulting in workers accidentally injecting with the animal medication. Such injections may be painful and in rare instances produce localized antiphyllatic reactions. Individuals allergic to specific antibiotics may develop life-threatening antiphyllactoid responses. Since needles used for animal injection may not be sterile, the potential for infections to develop at the site of accidental injection of animal drugs is high. Inflammation occurring within hours of such self-administration should be rapidly called to the attention of a physician.
Mycotoxins and Crops Mycotoxins are by-products of fungal metabolism which produce toxic effects when inhaled or ingested. They contaminate most animal feeds, such as corn, cottonseed, wheat, nuts, soy beans, sorghum, barley and sweet potatoes. Drought, high temperatures, insect infestation and crop harvesting during periods of high moisture all favor the growth of fungi and the production of mycotoxins in the field or in the storage area. While most affects occur in animals consuming the contaminated feedstuff, farm workers may inhale these toxic products in dust or contaminate hands leading to ingestion when eating occurs without appropriate hand washing. Liver and kidney problems, usually of a chronic nature, may develop from various types of these fungal products. A green tobacco syndrome is caused by adsorption of nicotine from skin contact in workers handling wet tobacco plants. Headache, dizziness, and vomiting are characteristic effects. Up to 50% of tobacco handlers have reported such symptoms; fortunately they usually resolve within a few hours of removal from tobacco plant contact and washing of the contaminated skin, arms and other exposed areas.
Drinking Water Although most ground water from wells or springs is safe to drink, pollution from agricultural chemicals or wastes may result in unsafe drinking water. The chemicals leeching from soils sprayed with pesticides and the organic wastes from animal holding facilities may produce low levels of chemical contamination or nitrates unacceptable for human consumption. Newborn babies are particularly susceptible to nitrate concentrations when ground water is used to prepare formulas. Animal wastes may carry bacteria into water supplies and transfer intestinal organisms, such as E coli, to susceptible children or adults. Testing of the waters are important to assure the absence of these contaminants. If pollution is present, it is nearly impossible to remove it. Water must often be secured from another source (another well or pipeline) or through the utilization of bottled drinking water. Community Health Departments may be able to assist in dealing with such drinking water concerns.
Conclusions A number of chemicals are used on modern farms, many of which are dangerous to the health of farm workers. Potentially toxic are pesticides designed to kill plants and animal pests. Fertilizers can be caustic to skin and eyes, and anhydrous ammonia spills may produce severe burns. Animal confinement facilities often lead to a complex indoor air environment which may produce toxic gases and byproducts. Decayed vegetation and wastes on farms can liberate toxic respiratory gases or contaminate human drinking water supplies. Farm workers must recognize the dangers of farm chemicals, because with understanding these dangers and routine practices that provide such exposure, the risk from chemical hazards in farming can be minimized through the use of appropriate protective clothing and prompt decontamination in the unhoped for event of chemical exposure.
|
