Pre-course Knowledge Check
CE Original Date: 08/05/2022
CE Expiration Date: 08/05/2024
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This case study will help you assess your pre-course knowledge about trichloroethylene toxicity. Read the case presentation and answer the questions that follow.
Your practice is in a suburban community with a number of high-technology industries. A couple for whom you have been the family physician asks for an appointment to discuss their daughter’s illnesses and a matter of concern to them.
During the initial consultation, the mother reports that they are living in an area supplied by municipal well water. They have recently received a notice from the municipal water district stating that their drinking water contains 100 parts per billion (ppb) trichloroethylene (TCE). As a precaution, they are being supplied with bottled drinking water until an alternative well can be put into service. The notice indicates that the well water is suitable for bathing and laundering. The father says he is familiar with TCE; it is used in the electronics plant where he works.
The daughter, aged 4 years, had several ear infections during her first 2 years, culminating in a myringotomy at age 3 years. Follow-up by an ear, nose, and throat specialist has shown normal hearing. Although there have been no further infections, the mother stresses that her daughter seems to have a greater number of colds than her classmates and “has not seemed as healthy as she should be.” However, the daughter’s chart does not reflect an unusual number of office visits or calls. The mother also notes that the child’s day-care center is next to “some kind of machine shop” where a chemical odor has been noticed recently. Several of the children and one of the teachers have complained of eye and throat irritation in association with the odor.
The mother, aged 33 years, then reveals that she might be pregnant, and she has had mild nausea for 1 week. It has been 8 weeks since her last menstrual period. Both parents are concerned about the possibility that the TCE in the drinking water might have affected the fetus. Although this pregnancy was planned, they might consider terminating the pregnancy if the fetus was likely to be “damaged.” They are also concerned that the entire family might suffer from cancer or other diseases in the future.
Before receiving bottled water, the family drank tap water when thirsty and made coffee with tap water. Tap water also was used for cooking and brushing teeth and is still used for bathing. They have never noticed discoloration or an off-taste to the tap water. They encourage their child to drink water instead of sodas during the summer and estimate the amount of water each of them drinks is two to three glasses a day.
You schedule each parent and the child for an individual office visit.
Answer: The mother has a focused concern about the effects of exposure; the child has frequent otitis media (status post myringotomy and tympanostomy tube placement) and frequent upper respiratory infections (Pre-Course Knowledge check).
Answer: You will need information on TCE toxicity, including reproductive and developmental effects, information on TCE contamination of the family’s drinking water, including duration and level of contamination; and copies of information provided to the family by the municipal water company and responses, if any, from local and state health agencies. When appropriate, consult a specialist in occupational and environmental medicine (Chapter 1 Section 1.3 and Chapter 2 Section 2.2).
Answer: None of the symptoms described in the case indicate serious illness. However, you should reassure the family that you will perform a complete physical examination with appropriate testing at the next visit. In response to concern about the child’s infections, you should indicate that you will collect information about possible TCE effects on the immune system. Explain to the parents that tests of immune function are often difficult to interpret and might not be appropriate. You might indicate that you will consult sources of information on TCE’s effects on pregnancy. It is important to maintain a balance between reassurance and concern for the possible risk to the fetus. Reassurance should not, however, appear to trivialize the family’s fears. It would also be appropriate to discuss that no evaluation, however thorough, can totally exclude the possibility that a person might develop an illness, including cancer. (Chapter 2 Section 2.2)
Answer: Possible sources of the family’s TCE exposure include home drinking water (ingestion and dermal and inhalation exposure during bathing), the father’s workplace (inhalation and possibly dermal), and the daughter’s day-care center (inhalation). Exposure also might occur from washing dishes, laundry, cooking, or any other use of hot water in the home, or use of TCE-containing consumer products such as correction fluid or spot removers (Chapter 1 Section 2.1).
Answer: The most convenient biologic indicators of TCE exposure are the urinary metabolites, trichloroethanol and trichloroacetic acid. However, these metabolites are not specific to TCE because they are also metabolites of tetrachloroethylene (perchloroethylene), 1,1,1-trichloroethane (methyl chloroform), and certain medications. TCE itself can be measured directly in blood or exhaled air, but because of the difficulty of obtaining samples, such measurements are not indicated here (Chapter 3 Section 3.1).
Answer: To properly interpret any of the tests mentioned in answer 6, knowledge of the time lapse between exposure and collection is needed. To prevent contamination or sample loss (evaporation or adsorption), proper collection, handling, storage, and transportation procedures must be followed. Members of this family likely would have elevated levels of TCE or its metabolites above background levels for a few hours after exposure, for instance, after they shower. However, there are no appropriate reference values currently available for a health risk assessment (Chapter 3 Section 3.1).
Answer: Evidence from animal and epidemiologic studies suggests that several reproductive and developmental toxicity end points might be associated with TCE exposure, including infertility in males and females, impaired fetal growth, and cardiac teratogenesis. Additional evaluation with fetal echocardiogram is therefore justified in this case. Depending on findings, it may be helpful to consult a maternal fetal medicine specialist for additional recommendations (Chapter 2 Section 2.2).
Answer: No. A survey of infections in children younger than 3 years over a September-to-March period found an average of 2.5 total infections and more than one episode of otitis media per child (1.4 episodes per child for those in day care). More than 3% of the children in day care were hospitalized for tympanostomies (Bell et al., 1989). The child described in the case study appears to have an above-average rate of infections, but they are not frequent enough to suggest immunologic impairment (Chapter 2 Section 2.2 and Chapter 3 Section 3.1).
Answer: No. Immunocompetence tests are not appropriate because no evidence of immune function abnormalities has been found in this case. Primary immunodeficiency is suspected in an infant who has repeated upper respiratory tract or other infections. It is also suspected if repeated infection occurs in a child who has had little exposure to infectious agents, or any child with unusual infections, incomplete clearing of infections, growth failure, hepatosplenomegaly, or features associated with specific immunodeficiency disorders, such as ataxia or telangiectasia. The child described in the case study has none of these indications (Chapter 3 Section 3.1).
Answer: The EPA has identified TCE as one of 33 hazardous air pollutants that present the greatest threat to public health in urban areas. Per EPA’s National Ambient Air Quality Standards in the Clean Air Act, TCE is controlled as a volatile organic compound under state regulations implementing the standards for ozone. Assuming discussions with the owner or operator of the shop adjacent to the day-care center have not been effective in reducing the level of ambient TCE, the state agency responsible for enforcement of air standards should be contacted to investigate possible release of TCE onto the day-care center property (Chapter 3 Section 3.3).