Toxicology Enrichment Materials
Topics in Toxicology Independent Assignments
Teacher's Notes
These questions will require students to perform independent research. Information can be gathered from encyclopedias, other reference books and periodicals. Increasingly, information on these and other toxicology topics can be found at various internet Web sites. The questions range from factual to interpretive to evaluative. The goal is for students to gain enough information on a particular topic to be able to form an opinion about it. What follows is a brief description of each of the topics and suggestions for use.
Students could be assigned a short report, using the questions as a guide.
Students could work on these research projects individually or in groups.
The topics could be covered individually in class, emphasizing different aspects of the topic as they are covered in the course curriculum.
Gulf War Syndrome This assignment may be useful as a current event or "in the news" topic. It also illustrates complex problem solving. The syndrome symptoms would fit into a study of the nervous system.
This has been a 'hot' topic in the news and continues to receive attention. Complaints from Gulf War veterans include memory problems, sleep problems, confusion, dizziness, muscle pains and fatigue. Causes under investigation include chemical exposure, stress and infectious disease. Chemicals under consideration include insecticides, anti-nerve gas agents and chemical weapons. Some combination of these or other causes are also possible factors.
Thalidomide This assignment would fit into the study of reproduction, birth or development. Also, it exemplifies issues related to epidemiology and animal testing. The drug is lipophillic and crosses the placenta by simple diffusion, thus would fit into the study of membranes.
Thalidomide is a sedative and hypnotic commonly prescribed in Europe in the late 1950's to pregnant women to decrease vomiting and nausea and as a sleeping aid. In 1960, an epidemic of newborns with rare limb deformities was identified in West Germany and other parts of the world. Thalidomide is a teratogen which, when exposed during fetal development, causes missing and malformed limbs, as well as other malformations and even death. In 1961, thalidomide was identified as the causative agent of the epidemic and it was withdrawn from the market. By 1962, the epidemic had subsided. Approximately 7000-8000 children were affected. The drug was tested in the mouse and rat, both of which are resistant to the effects of the drug.
Dichlorodiphenyltrichloroethane (DDT) This topic would fit into the study of enzymes, ecology, populations and the food chain.
DDT was discovered over 100 years ago, and its use as an insecticide began in 1939 by a Swiss chemist. In World War II it was used to dust soldiers for prevention of insect bites and diseases passed on by insects. This chemical was considered ideal because it was persistent, highly toxic to invertebrates and had low toxicity toward vertebrates. However, when it was used in agriculture, problems quickly developed. Both a spatial and temporal correlation were made between its use and to the decline in populations of several bird species. DDT bioaccumulates, thus its effects were primarily seen at the top of the food chain. Fish-eating birds affected included bald eagles, pelicans, osprey, heron and gulls. Bird-eating birds included falcons and hawks. DDT caused a decrease in egg shell thickness and an increase in egg breaking in the falcons. Subsequent research revealed that DDT inhibits an enzyme (Ca ATPase) that transports calcium from the blood to the oviduct where the egg shell is formed. Once DDT was banned, the falcon population and others bounced back.
Aflatoxin This assignment should illustrate the point that not all dangerous chemicals are human-made. It also demonstrates differences in susceptibility between animal species. Aflatoxins and other toxicants that interfere with DNA can be incorporated into the study of molecular genetics. The biotransformation of aflatoxin should be interesting to chemistry students in their study of functional groups.
Aflatoxin is a natural toxin produced by the fungus Aspergillus flavus that contaminates corn, peanuts and other grains. Because it is produced by a fungus, aflatoxin is a "mycotoxin." This compound is very potent as a hepatotoxin and hepatocarcinogen, meaning it is toxic and causes cancer of the liver. Aflatoxin will cause 50% lethality due to liver toxicity at 0.5 mg/kg in ducklings to 60 mg/kg in mice. The compound is biotransformed and subsequently causes cancer by binding to DNA.
Lead The study of lead is appropriate within the context of the nervous system, development and behavior. It is also frequently in the news, most recently regarding laws regulating the removal and disposal of lead-based paint.
Humans are exposed to this heavy metal in food, in lead-based paint in older dwellings, in air from combustion of lead-containing auto exhausts or industrial emissions and lead-glazed earthenware. The major risk is toxicity to the nervous system, though other forms of toxicity have been reported, especially in adults with high occupational exposure. The most susceptible populations are children, particularly toddlers and infants in the neonatal period, and the unborn fetus. Neurological, neurobehavioral and developmental effects have been described in children. A variety of tests are used to evaluate the effects of lead in children including impact on behavior, intelligence (IQ) and other psychological skills. Testing is also done in laboratory animals. Clinically overt signs of lead toxicity can be seen in children with blood levels of 80 µg/dl. Children with levels between 50-70 µg/dl may have decreased cognitive function as measured by IQ.
Domoic Acid Outbreaks of domoic acid poisoning occur periodically. The study of domoic acid is appropriate within the context of the nervous system, especially in terms of neuron structure and nerve impulses. A discussion of domoic acid would also be appropriate in the context of the food chain, protozoa and/or invertebrate animals. Finally, domoic acid is an amino acid (an unusual one) and could be discussed in relation to protein chemistry.
Domoic acid is an "excitotoxin." It is a neurotoxin that causes overstimulation of a particular type of nerve cell receptor (glutamate receptors). Upon initial exposure, people exhibit gastrointestinal distress. Within 48 hours, these symptoms are followed by neurological symptoms including convulsions, agitation, memory impairment and/or coma. The toxin has proved to be fatal in some cases. The toxin is produced by a species of plankton that serves as a food source for shellfish, including mussels. In 1987, an outbreak of domoic acid poisoning occurred in Canada. The cause was traced to blue mussels and over 100 cases were documented. The most severe cases occurred in those aged 60 or over and lead to studies to correlate glutamate receptors with the aging of the nervous system.
[Author's Note] [Toxicology Terms] [Toxicology Careers] [Toxicology and Biological Organization] [Some Basic Principles of Toxicology] [Find the Toxic Dose] [Topics in Toxicology] [Toxicology on the World Wide Web] [Table of Contents]
