Cholinesterase-inhibiting pesticides (i.e., organic phosphates and carbamates), widely used in agriculture, can cause illness if they contaminate food or drinking water. Aldicarb, a regulated carbamate pesticide, is highly toxic, and the U.S. Environmental Protection Agency (EPA) requires applicators to be trained and certified. This report describes a foodborne outbreak of aldicarb poisoning that occurred when improperly stored and labeled aldicarb was used mistakenly in food preparation.
On July 19, 1998, 20 employees attended a company lunch prepared from homemade foods. Shortly after eating, several persons developed neurologic and gastrointestinal symptoms. Ten visited a hospital emergency department, and two were hospitalized. On July 20, a hospital infection-control nurse reported the incident to the Louisiana Office of Public Health, which then investigated the outbreak.
Investigators interviewed all 20 lunch participants about illness and foods eaten during the meal; 14 (70%) reported gastrointestinal or neurologic symptoms. The most common gastrointestinal symptoms were abdominal cramps (13 [93%]), nausea (13 [93%]), and diarrhea (12 [86%]). Neurologic symptoms included dizziness (13 [93%]), sweating (12 [86%]), muscle fasciculations (12 [86%]), eye twitching (eight [57%]), and blurred vision (six [43%]). Illness lasted a median of 4 hours (range: 1-8 hours). Median time between ingestion of food and onset of symptoms was 45 minutes (range: 40 minutes-3 hours). The heart rate of one of the two persons hospitalized was 20 beats per minute on arrival at the emergency department, but his heart rate increased after treatment with atropine. The second person was hospitalized for an increased and irregular heart beat that responded to treatment with digitalis.
The lunch consisted of pork roast, boiled rice, cabbage salad, biscuits, and soft drinks. Only the cabbage salad was associated with illness. Of the 16 persons who ate the cabbage salad, 14 became ill (attack rate: 88%); the four persons who had not eaten the cabbage salad did not develop symptoms (attack rate: 0%, p=0.003, Fisher's exact test).
The employee who prepared the cabbage salad reported mixing two 1-lb bags of precut, prepackaged cabbage in a bowl with vinegar and ground black pepper. The black pepper came from a can labeled "black pepper" that he had found 6 weeks before the lunch in the truck of a deceased relative. This black pepper had not been used by the employee for food preparation before the company lunch. The cabbage salad was prepared the night before the lunch and stored in the refrigerator until it was brought to work and served at approximately 11 AM.
The contents of the black pepper container were tested for organophosphate and carbamate pesticides. High-performance liquid chromatography identified the granules in the container as 13.7% aldicarb, the pesticide TEMIK® 15G.* A 6-g portion of cabbage salad contained 272.6 parts per million (ppm) of aldicarb.
The deceased owner of the pepper can had been a crawfish farmer. After its investigation, the Louisiana Department of Agriculture and Forestry believed the crawfish farmer had used aldicarb on bait to prevent destruction of his crawfish nets, ponds, and levees by wild dogs and raccoons. The source of the TEMIK® 15G could not be determined despite the department's extensive traceback effort.
TA Farley, MD, L McFarland, DrPH, State Epidemiologist, Infectious Disease Epidemiology Section, Louisiana Dept of Health and Hospitals; J McClelland, Louisiana Dept of Agriculture. Health Studies Br, Div of Environmental Hazards and Health Effects, National Center for Environmental Health; Div of Applied Public Health Training, Epidemiology Program Office; and an EIS Officer, CDC.
Aldicarb (2-methyl-2-[methylthio] propionaldehyde O-[methylcarbamoyl] oxime) is one of the most potent pesticides used in the United States. It is absorbed rapidly through the gut and, in liquid form, through intact skin.1 As a cholinesterase inhibitor, it increases parasympathetic nervous system activity. Common symptoms of poisoning include malaise, dizziness, sweating, nausea, diarrhea, and muscle weakness; blurred vision and muscle spasms also can occur. EPA has placed aldicarb in its highest acute toxicity category.
Aldicarb is classified as a restricted-use pesticide and can be sold to and applied by trained certified applicators only. Applicators are required to wear personal protective equipment (i.e., coveralls, waterproof gloves, chemical-resistant footwear and headgear, and protective eyewear). In cases of aldicarb poisoning, atropine sulfate is the antidote of choice and can be supplemented by treatment of symptoms and rapid removal of the toxin (e.g., by induced vomiting).2
The 272.6 ppm of aldicarb found in a 6-g cabbage salad sample was enough to be toxic to humans. Each person who had eaten the salad would have consumed approximately 17 mg of aldicarb if equal amounts of salad had been eaten. A 150-lb (70-kg) adult would have ingested 0.2 mg of aldicarb per kg of body weight, nearly 10 times the lowest observed effect level for subclinical blood cholinesterase depression (0.025 mg per kg body weight). Blood levels as low as 0.0011 mg per kg body weight have been associated with poisoning in humans.3 In addition, cabbage and vinegar, both acidic substances, are less effective than alkaline substances at breaking down aldicarb to less toxic chemical compounds.
In addition to occupational exposures,4 aldicarb poisoning has resulted from unintentional or suicidal ingestion of aldicarb illegally used as a rodenticide5 and from eating contaminated watermelons6,7 and cucumbers.7 The largest pesticide-related foodborne outbreak in the United States occurred in 1985 when 1373 persons reported becoming ill after eating watermelons grown in soil treated with aldicarb; 78% of these persons had probable or possible pesticide-related illnesses.6 The median amount of aldicarb sulfoxide eaten per person in that outbreak was approximately 0.027 mg per kg body weight.8 Aldicarb residues have been detected in ground water and drinking water wells,9 but studies of the clinical implications of these exposures have been inconclusive.10 EPA has developed tolerance levels for aldicarb residues on food or animal feed and a maximum contaminant level for aldicarb in drinking water (0.003 mg/L).
Nonprofessional pesticide users and certified applicators should be alert to the adverse effects of pesticides on human health and to the risks involved in distributing pesticides to noncertified persons. In addition, the public should be reminded to store pesticides and other hazardous chemicals exclusively in containers that are clearly and correctly labeled and secured by safety caps. Finally, health-care providers and public health officials should keep in mind that food poisoning might result from pesticide or other chemical contamination as well as from infectious organisms.
Aldicarb as a Cause of Food Poisoning—Louisiana, 1998. JAMA. 1999;281(21):1979-1980. doi:10.1001/jama.281.21.1979