What is poisoning?

Quick Answer
Exposure to any substance in sufficient quantity to cause adverse health effects, from severe to fatal
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Causes and Symptoms

Probably the most accurate statement that can be made about the occurrence of poisoning in the United States is that the numbers vary widely depending on the information source and definition of poisoning. Incidents can be grouped into intentional poisonings, accidental poisonings, occupational and environmental poisonings, social poisonings, and iatrogenic poisonings. There is no single organization that collects and analyzes data from hospitals, physicians’ offices, police and court records, and industrial accident and exposure records. One source has reported that as many as eight million people are accidentally or intentionally poisoned each year. It has been stated further that 10 percent of all ambulance calls and 10 to 20 percent of all admissions to medical facilities involve poisonings.

Many incidents of poisoning go unreported because a poison control center is not consulted or the effects are not severe enough to require extensive medical treatment. In other cases where exposure to the toxic agent involves constant contact to low but toxic levels of industrial chemicals, such as occupational or environmental exposures, symptoms may be subtle or confused with diseases that are associated with the normal aging process. The degree of illness and/or the number of premature deaths resulting from environmental exposure to naturally occurring or artificial toxic substances—radiation, chemical waste, and other toxins in the air, water, and food supply—is simply not known.

The most consistent and reliable sources of information on accidental poisoning in the United States are the annual statistics compiled by the American Association of Poison Control Centers. While poison control centers receive some calls related to intentional poisonings, 88 percent of the calls are considered accidental exposures. Combining all the poisoning types together, poison control centers are called concerning about 2.2 million human cases each year. It is important to note, however, that extrapolations from the number of reported poisonings to the number of actual poisonings occurring annually in the United States cannot be made from these data alone.

About 93 percent of exposures occur in the home, more than half involve children under six, and three-fourths involve ingestion. The great predominance of young children in the accidental poisoning category reflects the inquisitive behavior of that age group. For children under the age of one year, inappropriate administration of medications by the parents is the dominant cause of poisonings. For children over the age of five, exposure to toxic substances often represents the simple misreading of a medication label or the manifestation of family stress or even suicidal intent. These children have increased incidence of depressive symptoms and family problems compared to their nonpoisoned peer group.

Intentional poisoning of children also occurs—usually as a well-planned act of a psychologically disturbed parent. Although many of these incidents are clearly homicidal and abusive by design, some have received medical notoriety as cases of Münchausen syndrome by proxy. Münchausen syndrome itself is a psychiatric disorder in which the patient achieves psychological comfort from the attention and treatment received under the pretense of being afflicted with a serious or painful illness. In a variation of this condition, the psychiatric needs of an adult are fulfilled through an induced medical disorder in the child. For example, a parent might surreptitiously administer syrup of ipecac to his or her child, inducing unexplained vomiting and gastrointestinal disorders that requires extended hospital care. The phenomenon is rare but well documented in the medical literature and is classified as a form of child abuse.

Intentional poisonings are mostly suicide-related. The Centers for Disease Control and Prevention (CDC) reported that more than 38,000 Americans killed themselves in 2010. Of all suicides from 2005 to 2009, poisoning was the method chosen by almost 40 percent of women and about 12 percent of men. Although carbon monoxide (as in motor vehicle exhaust) is one of the most common agents used, intentional dosing with large quantities of drugs is also very frequently involved. Of the many thousands of drugs that could be used for overdose incidents, 90 percent of actual cases involve only about twenty products in nine drug groups. Most of these are addictive or abused drugs, including stimulants, antidepressants, tranquilizers, narcotics, sedatives or hypnotics, and antipsychotics. Alcohol alone is seldom lethal but is often consumed along with the more deadly drugs and may make the lethal effects possible.

Social poisoning is related to drug use or abuse, which can have significant societal consequences. There are hundreds of thousands of hospital and emergency room admissions each year for overdose treatment as well as for the indirect consequences of recreational drug use, such as violent crime, trauma, and vehicular accidents. Almost 400,000 drug-abuse-related emergency room visits were projected to have occurred in 1990 by the Drug Abuse Warning Network (DAWN), a federal government-sponsored data collection system. These figures do not include alcohol, however, unless it is mentioned as having been involved in a mixed drug exposure event.

The abuse of alcohol, the most widely available chemical intoxicant legally allowed for recreational use, is a major social problem in the United States. While a majority of the alcohol-consuming public demonstrates a lifelong pattern of little or moderate drinking without the development of addiction-related problems, it has been reported that a small percentage of the population (5 percent to 10 percent) drinks between one-third and one-half of all alcohol consumed. The causes of alcoholism involve a complex interaction of social, physiological, and genetic risk factors. In the United States, there are approximately 9 million people classified as chronic alcohol abusers, and according to the CDC, about 80,000 deaths per year are attributable to alcohol-related causes.

Tobacco use, although not as closely associated with criminal behavior and vehicular accidents as drugs and alcohol, has been connected with increased incidence of cancer, respiratory illnesses, and cardiovascular diseases. According to the World Health Organization, more than 5 million deaths worldwide per year are attributable to tobacco use. Both smoking and excessive alcohol consumption are becoming increasingly less socially accepted, but the continued wide acceptance of both alcohol and tobacco use obscures their potential to poison.

Treatment and Therapy

Emergency medical treatment of the poisoned patient is most often based on the relief of symptoms and the provision of life support. If the patient is awake and alert, a medical history is taken and a clinical examination is performed, both of which can help determine substance exposure. The medical staff must never assume that the patient is providing truthful information, especially if clinical impressions conflict with the patient account. If the patient is comatose, then stabilization and life support take immediate priority over determination of the specific toxic substance involved. The attending physician will want to prevent airway blockage and to maintain respiration and circulation, which may require mechanical aids for breathing assistance. Treatment of cardiac and blood pressure problems can be accomplished with drugs, fluid, or oxygen administration. If the patient is unconscious, the depth of central nervous system depression can be evaluated using a standard test of reactivity to light, sound, pain, and the presence or absence of normal body processes. If the patient is suffering from seizures, drugs that counteract these symptoms can be administered.

Although many hospitals offer in-house toxicology testing in a clinical laboratory, treatment usually must begin before results are available. For this and several other reasons, a comprehensive toxicology testing laboratory is not as useful an asset in the emergency treatment of poisoning as might be assumed. It would be impossible for any analytical laboratory to provide timely or cost-effective emergency identification of all potentially toxic substances. Instead, a more efficient strategy concentrates on analyzing those substances for which a specific antidote exists or for which specific medical procedures are required in a critical period of time. A very high percentage of drug overdose cases involve one of a group of six or eight drugs that will vary depending on locality. Pesticide poisoning, for example, is a more prevalent medical problem for rural than urban hospitals. Drug abuse is a problem in all localities, but the frequency and type of drugs abused vary. Regional preferences exist for PCP, cocaine, amphetamines, and opiates. Even prescription drug abuse depends on locality and the patient population.

Common pain relievers found in virtually every home medicine cabinet constitute a large number of both adult and pediatric poisoning incidents. Preparations containing aspirin, as well as nonaspirin analgesics containing acetaminophen (such as Tylenol), are possibly life-threatening when consumed in excess. Acetaminophen poisoning is particularly insidious since death from total and irreversible destruction of the liver will occur unless the antidote, a chemical called acetylcysteine, is administered within six hours of ingestion of a lethal dose. Since a specific antidote exists, most hospitals with emergency service will offer around-the-clock testing for acetaminophen levels in the blood. Aspirin, although not as lethal as acetaminophen, can be fatal if a sufficient amount is consumed. Its universal availability and common usage make aspirin a significant poisoning agent encountered in all localities. The symptoms of toxicity are related to aspirin’s effects on temperature regulation, rate of breathing, and the body’s ability to influence the acidity of the blood. Treatment involves monitoring the patient’s vital signs and calculating the severity of the dose taken. Vomiting may be induced with syrup of ipecac, or charcoal (a very active adsorption agent) may be given orally to limit gastric absorption. Intravenous fluids may also be given to counteract the blood acidity changes.

Prescription drugs that are commonly overused or abused (antiepileptic medication, sedatives and tranquilizers, and antipsychotic or antidepressant drugs) are often routinely assayed in the hospital laboratory as part of the treatment process for patients receiving these medications. The levels in the blood can be monitored to determine the toxicity status of the patient. Usually, supportive care is sufficient for treatment until the drug clears the system. For certain tranquilizers and antidepressants, an antidote called flumazenil can be administered, but it must be used with caution.

Poisoning from an overdose of opiates or morphinelike drugs is a special treatment case. A specific antidote called naloxone can be administered if the patient is treated before irreversible respiratory depression occurs. Recovery is virtually instantaneous and dramatic, with a comatose patient becoming alert within seconds of naloxone administration. For this reason, the routine treatment of comatose patients includes the administration of opiate antidote even when the cause of the unconscious state is unknown.

Although heavy, long-term ethyl alcohol use invariably leads to liver dysfunction and a number of other organ disorders, alcohol is not usually life-threatening unless it is consumed in quantities sufficient to cause a coma. Death most commonly results from respiratory depression and related complications. Other types of alcohols, as well as antifreeze, can be involved in both accidental and intentional poisonings. Methanol or wood alcohol is a common industrial solvent found in materials around the home or work site; consumption can cause blindness and death. Isopropyl alcohol (or rubbing alcohol), although not as toxic as methanol, can also cause severe illness and death when consumed in sufficient quantities. Ethylene glycol, a common ingredient in antifreeze, is highly toxic and is especially attractive to small children and pets because of its sweet taste. It may also be consumed by alcoholics as an ethanol substitute. When not treated, its consumption can result in kidney failure. It is not the alcohols themselves that are the primary toxins but the degradation products called metabolites that form in the body in an attempt to eliminate the foreign substance. Ironically, the treatment for both methanol and ethylene glycol poisoning is administration of high doses of ethanol, which prevents the formation of toxic metabolites by the liver.

In the United States, lead poisoning is a major medical problem for children living in older, substandard housing; they can become exposed to large amounts of lead from the consumption of lead-based paint. (Even though such paints are no longer used in residential housing, many older buildings remain contaminated.) Another major source of exposure is inhalation of leaded gas fumes and exhaust. Other less common sources of lead poisoning include the consumption of food stored in leaded crystal or pottery or moonshine whiskey distilled in automobile radiators. Intentional gasoline sniffing by adolescents can also be a problem. Lead exposure is extremely hazardous because its effects are both severe and cumulative. Children are especially susceptible to lead poisoning because they absorb and retain more of this substance and have less capacity for excretion than adults.

The nervous system is a major site for lead toxicity, causing both psychological and neurologic impairment. The blood cell production can also be affected, with resulting anemia and decreased oxygen-carrying capacity. Because lead toxicity can result in behavioral and learning disorders that may already afflict children living in substandard conditions, sometimes poisoning cannot be detected by clinical symptoms alone and must be diagnosed through blood testing. Test data indicate that the level of lead associated with nervous system disorders is probably lower than previously believed. In the United States, a major screening effort has been financed by the federal government to detect high lead body deposits in children. The goal is to find affected children and to treat them before permanent damage occurs.

Perspective and Prospects

Poisoning has been a medical problem since the earliest times of human history. A tremendous variety of poisonous substances can be encountered in the natural world alone. It has been estimated that 200,000 plants and animals are known to be toxic to humans, some organisms producing as many as fifty or sixty toxins. The potential of almost any substance to be poisonous was recognized during the Renaissance by Paracelsus, a founder of modern toxicology, who stated, “All substances are poison; only the dose makes something not a poison.” Many folk remedies and tribal medicine practices were derived from centuries of trial-and-error experiences with toxic plant and animal species in the environment. Historically, the development of the sciences of pharmacology and toxicology is closely related to the study of poisons.

As societies become more urban and technology-based, poisoning problems shift away from natural toxin exposures to those related to drugs and industrial chemicals. For many of these types of poisonings, sustaining the vital life processes until the toxin is cleared from the body is the only method of treatment. Specific antidotes are not available for many drugs or even for many natural poisons. Since a large number of toxins critically affect the nervous system, a diagnostic and treatment system has been developed based on the “toxidrome” concept. If a specific area of the nervous system can be shown to be affected, treatment can begin to counteract those effects even if the identity of the toxin is not known.

The symptoms of acute poisoning or overexposure to a toxic agent are likely to be treated as individual medical problems by physicians in an emergency medicine environment. Meanwhile, social poisons, which often do not create immediate medical emergencies, continue to exact enormous economic and medical costs to society over the long term; these poisoning problems have not been dealt with successfully by social, medical, or governmental agencies. In the case of environmental toxins, little if any well-established information on the long-term toxicity of these substances is available. The science of toxicology, particularly with regard to establishing the risk of exposure of a population to environmental toxins, often becomes a guessing game played by a governmental regulatory agency. Until societal and environmental poisonings can be better evaluated and controlled, they will continue to constitute serious economic and quality-of-life problems.

Bibliography

Baselt, Randall C. Disposition of Toxic Drugs and Chemicals in Man. 9th ed. Foster City, Calif.: Biomedical, 2011.

Dart, Richard C., ed. Medical Toxicology. 3d ed. Philadelphia: Lippincott Williams & Wilkins, 2004.

Garriott, James C., ed. Medicolegal Aspects of Alcohol Determination in Biological Specimens. Littleton, Mass.: PSG, 1988.

Klaassen, Curtis D., ed. Casarett and Doull’s Toxicology: The Basic Science of Poisons. 8th ed. New York: McGraw-Hill, 2013.

Morgan, Monroe T. Environmental Health. 3d ed. Belmont, Calif.: Thomson/Wadsworth, 2003.

"Poisoning." MedlinePlus, August 30, 2013.

Timbrell, John. Introduction to Toxicology. 3d ed. Washington, D.C.: Taylor & Francis, 2003.

Warren, Christian. Brush with Death: A Social History of Lead Poisoning. Baltimore: Johns Hopkins University Press, 2001.

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