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An investigator wishes to perform a randomized clinical trial to evaluate a new B-blocker as a treatment for hypertension. To be eligible for the study, subjects must have a resting diastolic blood pressure of at least 90 mm Hg. One hundred patients seen at the screening clinic with this level of HPN are recruited for the study and make appointments with the study nurse. When the nurse obtains their BP 2wks later, only 65 of them have diastolic blood pressures of 90 mm Hg or more. The most likely explanation for this is
a. Spontaneous resolution
b. Regression toward the mean
c. Baseline drift
d. Measurement error
e. Hawthorne effect

b. Regression toward the mean

Although hypertension can resolve spontaneously, this is an unlikely explanation for resolution over a 2-wk period in 35% of the subjects. A much more likely explanation is regression toward the mean. Because of random fluctuations, any one measurement of blood pressure may be far from a persons normal BP. By referring patients for the study based on a single measurement, those in whom the measurement was high (which proved later not to reflect the actual BP) are much more likely to be referred than those in whom the measurement was too low. Thus, in any group selected based on a characteristic with substantial day-to-day variation, many will have values closer to the population mean when the measurement is repeated and the worst patients will improve.

Neither baseline drift (which occurs with measurements on certain machines that require frequent calibration) nor measurement error is as likely an explanation.

The Hawthorne effect refers to a tendency among study subjects to change simply because they are being studied. It is much more likely to affect studies of behavior or attitudes than a study of blood pressure.


Which of the following measures is used frequently as a denominator to calculate the incidence rate of a disease?
a. Number of cases observed
b. Number of new cases observed
c. Number of asymptomatic cases
d. Person-years of observation
e. Persons lost to follow-up

d. Person-years of observation

Person-years of observation are frequently used in the denominator of incidence rates and provide a method of dealing with variable follow-up periods. Person-years of observation simultaneously take into account the number of persons under observation and the duration of observation of each person. For example, if eight new cases of diabetes occurred among 1000 people followed for two years, the incidence would be 8 cases per 2000 person-years, or 4 per 1000 person-years of follow-up. The distinction between rates and proportions is not well maintained in standard epidemiologic terminology. Rates should have units of inverse time and will vary depending on the units of measurement of time; they can vary from 0 to infinity. However, such terms as case fatality rate, attack rate, and prevalence rate are in wide- spread usage even though technically they are all proportions; that is, they vary between 0 and 1 and are unitless.


Among women aged 18 to 34 in a community, weight is normally distributed with a mean of 52 kg and a standard deviation of 7.5 kg. What percentage of women will have a weight over 59.5 kg?
a. 2% b. 5%
c. 10% d. 16% e. 32%

d. 16%

For any normal distribution, 68% of the population values are contained within the interval of the mean 􏰀 +/-1 standard deviation (16% will be higher and 16% will be lower), 95% within the mean 􏰀 +/-2 standard deviations (2.5% will be higher and 2.5% will be lower), and 99% within the mean 􏰀 +/-3 standard deviations (0.5% will be higher and 0.5% will be lower). In this case, 59.5 kg is equal to the mean 􏰀 +/-1 standard deviation, which means 16% of women will be heavier.


A randomized clinical trial is undertaken to examine the effect of a new combination of antiretroviral drugs on HIV viral load compared to usual therapy. Randomization is used for allocation of subjects to either treatment or control (usual care) groups in experimental studies. Randomization ensures that
a. Assignment occurs by chance
b. Treatment and control (usual care) groups are alike in all respects
except treatment
c. Bias in observations is eliminated
d. Placebo effects are eliminated
e. An equal number of persons will be followed in the treatment and control group

a. Assignment occurs by chance

Randomization is the use of a predetermined plan of allocation or assignment of subjects to treatment groups such that assignment occurs solely by chance. It is used to eliminate bias on the part of the investigator and the subject in the choice of treatment group. The goal of randomization is to allow chance to distribute unknown sources of biologic variability equally to the treatment and control groups. However, because chance does determine assignment, significant differences between the groups may arise, especially if the number of subjects is small. Therefore, whenever randomization is used, the comparability of the treatment groups should be assessed to determine whether or not balance was achieved


A research team wishes to investigate a possible association between smokeless tobacco and oral lesions among professional baseball players. At spring training camp, they ask each baseball player about current and past use of smokeless tobacco, cigarettes, and alcohol, and a dentist notes the type and extent of the lesions in the mouth. What type of study is this?
a. Case-control
b. Cross-sectional
c. Prospective cohort
d. Clinical trial
e. Retrospective cohort

b. Cross-sectional

Because the association between the risk factor (use of smokeless tobacco) and the disease (oral lesions) is measured at a single point in time in a whole group of subjects, this is a cross-sectional study. A case-control study might be performed over a similar time period, but the sampling would be different: one sample would be selected from among those baseball players found to have oral lesions (the cases) and a separate sample would be selected from among those players whose mouths were normal (the controls). In a cohort study, the habits of a group of players initially free of the disease would be measured, and these players would be followed over time to see how many develop the lesions. A clinical trial involves allocation of the subjects by the investigator (usually randomly) to one of two or more treatment groups.


A 6-y/o child is brought to the emergency room by her parents on a Friday night because they are concerned about rabies. A bat was present in the child s bedroom when they arrived at their country home that evening. It started flying around the head of the girl when she entered her room and it ruffled her hair. The parents heard her scream, ran up to her room, and shooed the bat out the window. Upon examination, there is no visible bite or scratch marks. Which is the most appropriate intervention at this time?
a. Reassure the parents that there is no risk of rabies given the history and examination
b. Consult public health authorities to determine the epidemiology of rabies in that area
c. Administer rabies vaccine and rabies immunoglobulin (RIG)
d. Administer rabies immunoglobulin (RIG) only
e. Administer rabies vaccine only

c. Administer rabies vaccine and rabies immunoglobulin (RIG)

Postexposure prophylaxis is recommended for any physical contact with bats. Bites or scratches may be too small to be visible to the naked eye. Both human rabies immunoglobulin (RIG) and vaccine should be administered to persons who have not been previously vaccinated. RIG is never recommended as only prophylaxis. It provides rapid passive protection with a half-life of 21 days. Active immunization induces response after 7 to 10 days and persists for at least 2 years. Only the vaccine is necessary if the person has a history of previous vaccination with documented antibody response. Consulting public health authorities before an intervention may be appropriate if the contact did not involve animals known to be a reservoir for rabies. Animals known to be reservoirs are the bat, skunk, raccoon, fox, coyote, and other wild carnivores, and prophylaxis is indicated regardless of the region.


Which of the following conditions has been associated with a false-positive Fluorescent Treponemal Antibody Absorption ( FTA- ABS) test?
a. Tuberculosis
b. Mononucleosis
c. Lyme disease
d. Viral pneumonia
e. HIV infection

c. Lyme disease

Lyme disease (caused by Borrelia burgdorferi, a spirochete) has been associated with false-positive treponemal FTA-ABS (Fluorescent Treponemal Antibody Absorption) tests which are designed for the diagnosis of Treponema pallidum infections (i.e., syphilis).

The nontreponemal test is often negative in this disease. Other conditions associated with false-positive treponemal tests include yaws, pinta, leptospirosis, and lupus.

Biological false-positive nontreponemal tests VDRL (Venereal Disease Research Laboratory), and RPR (Rapid Plasma Reagin) are classified as acute (reverting back to negative in six months) or chronic.

Acute reactions can occur with recent immunization, mononucleosis, viral pneumonia, tuberculosis, malaria, and a variety of viral diseases.

Chronic reactions can occur in users of intravenous drugs, with aging, and in autoimmune diseases, such as systemic lupus erythematosus.

A positive nontreponemal test must always be confirmed by a treponemal test: the TP-PA (Treponemal Particle Absorption test) or the FTA-ABS.

Nontreponemal and treponemal tests are reliable indicators of syphilis in HIV-infected persons. Although no false-positives are associated with the disease, some false-negatives may occur during end-stage disease because of severe immunosuppression.


One of your patients, a 30y/o developer, tells you he is planning a trip to the Dominican Republic the following month. He will need to travel in rural areas. Which is the most appropriate intervention for malaria prophylaxis for this patient?
a. No prophylaxis
b. Chloroquine
c. Mefloquine
d. Doxycycline
e. Primaquine

b. Chloroquine

The Dominican Republic is one area of high risk for malaria where no chloroquine-resistant strains of Plasmodium falciparum have been identified. Other areas include Central America west of the Panama Canal Zone, Haiti, Egypt, and most of the Middle East. Almost all other countries with a high risk for malaria have resistant strains.

The drug of choice for prophylaxis in these areas is mefloquine or doxycycline. Primaquine is given to prevent relapses due to P. vivax or P. ovale. Current information on the foci of drug-resistant P. falciparum is available through the Centers for Disease Control (CDC) travel Web site or the annual publication of the World Health Organization (WHO).


A 20 mo old child presents to your office with a mild viral infection. The results of examination are normal except for a temperature of 37.2°C (99°F) and clear nasal discharge. Review of her vaccination records reveals that she received only two doses of polio vaccine and diphtheria-tetanus-pertussis (DTaP) vaccine, and that she did not receive the measles-mumps-rubella (MMR) vaccine. The mother is 20 weeks pregnant. Her brother is undergoing chemotherapy for leukemia. Which of the following is the most appropriate intervention?
a. Schedule a visit in two weeks for DTaP
b. Administer inactivated polio vaccine (IPV) and DTaP
c. Administer DTaP, oral polio vaccine (OPV), and MMR
d. Administer DTaP, IPV, and MMR
e. Administer DTaP and OPV and schedule a visit in three months for

e. Administer DTaP and OPV and schedule a visit in three months for

Children who are late in their immunization schedule should be vaccinated when the opportunity arises. Mild acute illness or antibiotic use is not a contraindication to immuniza- tion. MMR is not contraindicated in children of pregnant women. OPV, but not MMR, is contraindicated in any household contact of a severely immunocompromised person. In fact, in an effort to reduce vaccine-associated paralytic polio (VAPP), OPV is no longer recommended for the first two doses of polio immunizations in infants since 1997, and effective January 2000, the CDC recommendations are to give 4 doses of IPV at 2 months, 4 months, 618 months, and then at 68 years. OPV can be considered only under a few specific circumstances. If the parents refuse the schedule, OPV could be given only for the third or fourth dose and parents should be counseled about the possible occurrence of VAPP. In this case scenario, however, OPV would not be acceptable given the sibling situation. Live and inactivated vaccines can be given at the same time.


Prevention of human brucellosis depends primarily on
a. Pasteurization of dairy products derived from goats, sheep, or cows
b. Treatment of human cases
c. Control of the insect vector
d. Immunization of farmers and slaughterhouse workers
e. Destruction of infected animals

a. Pasteurization of dairy products derived from goats, sheep, or cows

Prevention of human brucellosis depends on pasteurization of dairy products from cows, goats, and sheep; education of farmers and workers in the live-stock industry as to the dangers of infected animals; and care in handling products from aborted animals. There is no insect vector. No vaccine for human use is available. Since person-to-person transmission does not occur, treatment of individual cases will not control spread of brucellosis. Destruction of infected animals will prevent transmission to other animals and is a method to control an outbreak in animals. Vaccine is available for livestock, for prevention but not control of outbreak. Vaccines have been used for workers in the meat and dairy industries in the former Soviet Union and Europe, but it is not used in the United States. Immunity from the vaccine lasts only two years.


Which of the following vaccines is CONTRAINDICATED during pregnancy?
a. Hepatitis B vaccine
b. Varicella vaccine
c. Influenza vaccine
d. Tetanus toxoid
e. Rabies vaccine

b. Varicella vaccine

Varicella-zoster vaccine is a live attenuated vac- cine. In general, live attenuated vaccines, such as the MMR, should be avoided during pregnancy because of the potential of infecting the fetus, which may result in congenital malformation. If a susceptible pregnant woman comes in contact with varicella, the administration of varicella- zoster immunoglobulin (VZIG) should be strongly considered because the disease can be very severe for women during pregnancy. However, there is no assurance that VZIG may prevent congenital infection and malformation, a relatively rare event (risk 0.7% if acquired early in pregnancy and 2% if acquired between 12 and 20 weeks of gestation). Because neonates are at risk of developing severe generalized varicella, VZIG is also indicated for newborns of mothers who develop chicken pox 5 days prior to or within 48 hours after delivery. Hepatitis B and influenza vaccines are inactivated and should be administered to women at risk of infection. Both vaccines available for the prophylaxis of rabies are inactivated and should be given to pregnant women when indicated. Tetanus toxoid and diphtheria toxoid are the only immunobiological agents routinely indicated for susceptible pregnant women. Previously vaccinated pregnant women who have not received a Td vaccination within the last 10 years should receive a booster dose.


A 32y/o farmer presents to the emergency room with a crushing injury of the index finger and thumb that occurred while he was working with machinery in his barn. Records show that he received three doses of Td in the past, and that his last dose was given when he was 25 years old. In addition to proper wound cleaning and management, which of the following is the most appropriate prevention intervention?
a. No additional prophylaxis
b. Administration of tetanus toxoid
c. Administration of tetanus immunoglobulin only
d. Administration of tetanus toxoid and immunoglobulin
e. Administration of tetanus and diphtheria toxoid

e. Administration of tetanus and diphtheria toxoid

If a person has received three doses or more of the Td, and the last dose was given more than five years before an injury, a tetanus and diphtheria booster should be given if the wound is contaminated, such as the one described. It is prefer- able to administer the combined diphtheria and tetanus booster (Td). You are then also using the opportunity to provide primary prevention for diphtheria. If the last dose of Td was given in the preceding five years, then no further action would be necessary. Td and tetanus immunoglobulin (TIG) are recommended for prophylaxis of contaminated wounds when the history of tetanus toxoid is unknown or the person received less than three doses. TIG is never recommended as sole prophylaxis as prolonged immunity is desired.


Epidemics of typhus fever have been associated with war and famine for several centuries. What factor was most important in the control of such epidemics following the end of World War II?
a. Eradication of Anopheles mosquitoes
b. Improved sanitation practices
c. Improved methods for handling
food supplies
d. Disinfestation by use of DDT
e. Mass therapy with antibiotics

d. Disinfestation by use of DDT

The infectious agent for epidemic forms of typhus fever is Rickettsia prowazekii, which is transmitted from person to person by the human body louse, Pediculus humanus corporis. Disruptions of social and economic institutions by war, famine, or natural catastrophes are associated with declining standards of personal hygiene and spread of lice. Even before social and economic recovery after World War II, epidemic typhus was controlled by mass application of DDT powder. This insecticide killed the body lice; thus, the transmission cycle was interrupted. Widespread resistance to DDT and lindane now exists, and other products such as permethrin should be used. Effective antibiotic therapy with chloramphenicol and tetracycline was not available until the early 1950s. Anopheles mosquitoes are vectors in the transmission of malaria, not typhus.


Immunization of preschool children with diphtheria toxoid results in
a. Protection against the diphtheria carrier state
b. Lifelong immunity against diphtheria
c. Detectable antitoxin or immunologic memory for about 10 years
d. Frequent adverse reactions
e. Protection against infection of the respiratory tract by Corynebacterium diphtheria

c. Detectable antitoxin or immunologic memory for about 10 years

Diphtheria toxoid, alone or in combination with pertussis vaccine and tetanus toxoid (DTaP), induces protective levels of antitoxin that persist for about 10 years. Boost- ers are required every 10 years after completion of primary immunization in order to maintain protective concentration of antibody. Antitoxin antibodies do not prevent infection of the respiratory tract with C. diphtheriae and do not prevent the development of the carrier state. The antibodies are directed against the exotoxin produced by the bacteria, not against the bac- teria themselves. Adverse reactions from the toxoid are very infrequent in infants and young children but are more common in adults; therefore, the administration of a reduced dose of toxoid is recommended for children after their seventh birthday and for adults. The reduced dose is symbolized by a lowercase d. It is usually combined with tetanus toxoid as a Td.


What is the recommended interval in months between the administration of whole blood transfusion and the measles-mumps-rubella (MMR) vaccine?
a. 0
b. 1
c. 3
d. 6
e. 10

d. 6

Whats important here is to remember the concept that passively acquired measles antibody can interfere with the immune response of the measles vaccine. The intervals suggested by CDC are extrapolated from an estimated half-life of 30 days for passively acquired antibody and an observed interference with the immune response to measles vaccine for five months after a dose of 80 mg IgG/kg. The intervals vary according to the amount of plasma (containing the anti- bodies) or immunoglobulins present in the preparations. The recommended interval is 0 months for washed red cell transfusion; 3 months for adenine- saline RBC transfusion; 6 months for packed RBCs or whole blood; and 7 months for plasma/platelet transfusion. An interval of 3 months is recom- mended between the administration of tetanus immunoglobulin (TIG), hepatitis A prophylaxis with serum immunoglobulin (IG), and hepatitis B immunoglobulin (HBIG), and the MMR vaccine; 4 months between human rabies immunoglobulin (HRIG) and the MMR vaccine; and 5 months between varicella zoster immunoglobulin (VZIG) and MMR.


Professional organizations recommend that all pregnant women be routinely counseled about HIV infection and be encouraged to be tested. What is the most important reason for early identification of HIV infection in pregnant women?
a. A cesarean section can be planned to reduce HIV transmission to the newborn
b. Breast feeding can be discouraged to reduce transmission to the newborn
c. Early identification of a newborn at risk of HIV infection will improve survival
d. Counseling on pregnancy options, such as termination, can be offered
e. Antiretroviral therapy can be offered to reduce the chance of transmission of HIV to the newborn

e. Antiretroviral therapy can be offered to reduce the chance of transmission of HIV to the newborn

The landmark randomized placebo controlled trial ACTG 076 demonstrated that zidovudine (ZDV) given at the beginning of the second trimester, during labor and delivery, and to the newborn for 6 weeks, significantly reduced the transmission of HIV to the newborn from 25.5% in the control group to 8.3% in the treatment group. Thus, ZDV can be highly effective for primary prevention in the newborn. Other promising treatment schedules with ZDV and other antiretrovirals are under study. Recent data demonstrates that a cesarean section can reduce vertical transmission, but it should not supersede antiretroviral therapy.

Currently, it appears that it is not a routinely recommended procedure for HIV-infected pregnant women, but this may change in the future. HIV can be transmit- ted by breast feeding, and in some studies, the risk is increased by 14%. However, breast feeding has no impact on the highest risk of transmission, which occurs during gestation, labor, and delivery. Early identification of newborns at risk of HIV infection will guide the medical management and improve outcomes. It has no impact on the primary prevention of the infection to the newborn. Finally, all HIV-infected women should be made aware of the benefit of ZDV so they can make informed choices.


A 35y/o patient comes to your office in early April for a routine examination. In the course of the history, he tells you that he plans to go turkey hunting in Nantucket, Massachusetts, for one week in May. He is concerned about Lyme disease. Which is the most appropriate intervention for preventing Lyme disease?
a. Vaccination
b. Avoidance of bushy areas
c. Tick check at the end of each day
d. Protective clothing and DEET
e. Antibiotic prophylaxis for one week

d. Protective clothing and DEET

Nantucket Island (off the coast of Massachusetts) has one of the highest rates of Lyme disease in the United States. Lyme disease is a tick-borne zoonosis from the spirochete Borelia burgdorferi. Avoidance of bushy areas is the first line of prevention recommendation for patients traveling in endemic areas. Risk is higher in summer and spring. However, it is unrealistic to expect this patient to keep away from bushy areas. His best protection would be wearing appropriate clothing and applying DEET to avoid tick bites. Next, since infection rarely occurs if the tick has been attached for less than 36 hours, daily checks for ticks may be helpful. Antibiotics are used for treatment but not prophylaxis. Optimal protection for the vaccine is obtained after three doses at 0, 1, and 12 months. Vaccine is currently primarily recommended for persons 15 to 70 who engage in activities that result in prolonged exposure to tick-infested habitat in areas of high to moderate risk. Benefit of the vaccine for short exposure beyond that provided by personal protection is uncertain. Furthermore, there would not be enough time to complete the series in this case.


An 18y/o sexually active college student presents with complaints of lower abdominal pain and irregular bleeding for five days. She has no fever. She uses oral contraceptives as method of birth control. Upon examination, the cervix is friable, there is cervical motion tenderness and adnexal tenderness. The pregnancy test is negative. Which is the most likely etiologic agent responsible for these findings?
a. Neisseria gonorrhoeae
b. Chlamydia trachomatis
c. Treponema pallidum
d. Herpes simplex virus type 2
e. Mycoplasma hominis

b. Chlamydia trachomatis

Chlamydia trachomatis is the most frequently reported bacterial sexually transmitted disease (STD) in the United States. Infections of the cervix may present as a friable cervix, but are most often without signs or symptoms.


An 18y/o sexually active college student presents with complaints of lower abdominal pain and irregular bleeding for five days. She has no fever. She uses oral contraceptives as method of birth control. Upon examination, the cervix is friable, there is cervical motion tenderness and adnexal tenderness. The pregnancy test is negative. She tells you that she had a similar episode two years ago. What is her risk of infertility following this second clinical episode of pelvic inflammatory disease?
a. <1% b. 5% c. 10%
d. 20% e. 40%

d. 20%

Pelvic inflammatory disease (PID) caused by chlamydia often presents with milder symptoms than when it is caused by gonorrhea. Prompt treatment reduces the occurrence of long-term sequelae such as infertility, ectopic pregnancy, and chronic pelvic pain. The risk of infertility appears to be higher for chlamydial infections compared to any other STD. Screening women is important to reduce the risk of PID and its sequelae.


In the course of investigating a 24y/o HIV-infected male, the HBsAg is positive. He is currently asymptomatic, his physical examination is essentially normal, and his CD4 cell count is 800. Which of the following tests is most helpful in determining whether the patient is in the acute phase of viral hepatitis?
a. ALT levels
b. HBeAg
c. HBsAg
d. IgG anti-HBcAg
e. IgM anti-HBcAg

d. IgG anti-HBcAg

Currently available laboratory tests for hepatitis B include HBsAg (hepatitis B surface antigen), anti-HBs (antibody to hepatitis B sur- face antigen), IgM anti-HBc, IgG anti-HBc (antibodies to the core antigen), HBeAg, and anti-HBe. Because HBcAg is sequestered within an HBsAg coat, HBcAg is not routinely detected in patients with hepatitis B. IgM anti- HBc appears soon after the onset of infection and the detection of HBsAg, and precedes by many weeks detectable levels of anti-HBsAg. It generally disappears after 6 to 8 months. The presence of IgM is a marker for acute (less than 6 months) hepatitis B. IgG anti-HBc appears somewhat later than the IgM and may persist for years. Elevated ALT may be present both in the early and chronic phases of the disease. HBeAg may persist for years in patients with chronic disease and is associated with high infectivity. HBsAg remains detectable beyond 6 months in chronic hepatitis B.


Which of the following complications has been associated with the recall of rotavirus vaccine?
a. Guillain-Barr syndr ome
b. Hemolytic anemia
c. Febrile seizures
d. Intussusception
e. Neutropenia

d. Intussusception

The rotavirus vaccine was rapidly removed from the market (a few months after the CDC had recommended its use) because of reports of intussusception ocurring in infants within three weeks of vaccination.


Which etiological agent was responsible for most cases of illness due to waterborne-disease outbreaks in the US in the 1990s?
a. Salmonella enteritidis (serotype typhimurium)
b. Giardia lamblia
c. Campylobacter jejuni
d. Cryptosporidium parvum
e. Shigella sonnei

d. Cryptosporidium parvum

Cryptosporidium parvum was responsible for illness in 403,271 persons, the greatest number of cases of illness due to outbreaks of waterborne disease in the US in the 1990s. During an outbreak in Milwaukee in 1993, an estimated 403,000 persons became ill and 4,400 were hospitalized.

Although the actual number of outbreaks as opposed to number of cases is about the same for C. parvum and G. lamblia, outbreaks of G. lamblia caused illness in an estimated 385 persons.


The most important risk factor for heat-related illness is
a. Age over 65
b. Age under 1
c. History of prior heat stroke
d. Low socioeconomic status
e. Obesity

a. Age over 65

Older adults over the age of 65 are particularly at risk of death due to heat-related illness because of decreased response of the cardiovascular system during hot weather.

Very young children under the age of 1 are also at risk, but less than older persons.

Heat-related illness is seen more frequently in lower-socioeconomic areas, presumably because of no access to air conditioning and good ventilation and because of higher temperatures in urban areas (heat islands).

Obesity and prior history of heat stroke also increase the risk, but to a much lesser degree than older age. Drugs that inhibit sweat production, cause dehydration, and reduce cutaneous blood flow (atropine, antidepressants, diuretics, etc.) also increase susceptibility to heat.


Following an accident in a nuclear laboratory, some workers were exposed to 300 rem (3 Sievert) of radiation. They are immediately sent to your emergency department. Which of the following effects will most likely occur among the majority of these workers?
a. Bone marrow depression
b. Neurovascular syndrome
c. Gastrointestinal syndrome
d. Cardiovascular syndrome
e. No detectable physiological effect

a. Bone marrow depression

Disturbances begin to occur at exposures above 100 rem. Following an acute exposure to 100 to 200 rem of ionizing radiation, mild hematopoietic disturbances may occur (5% at 100 rem and 50% at 200 rem) after a few wks, which only warrant surveillance. Some patients may have vomiting 3hrs after the exposure. Between 200 and 600 rem, more severe hematopoietic disturbances will occur, with a peak at 4 to 6 wks, requiring transfusions, antibiotics, & hematopoietic GF. Patients will vomit within 2hrs. Extreme disturbances will occur after an acute exposure of 600-1000 rem, with a high case fatality rate (80 - 100% within 2 mos). Vomiting will occur within 1hr. All patients with exposures above 1000 rem will die, with early onset (1-14 days depending on exposure) of GI syndrome (diarrhea, fever, and electrolyte disturbances) and CNS problems dominating the clinical picture.


The Haddon matrix is used for assessing interventions for the prevention of
a. Water pollution
b. Air pollution
c. Radiation exposure
d. Injury
e. Toxic substance exposure

d. Injury

This is a systematic approach to injury prevention developed by William Haddon Jr. of the New York State Department. The matrix categorizes interventions as modifying the host, agent, and environment either before, at the time of, or after the event.


The most effective means of preventing trichinosis in humans is
a. Cooking pork to reach a internal temperature of at least 40°C (104°F)
b. Proper disposal of hog feces
c. Prohibiting feeding garbage to hogs
d. Testing hogs with Trichinella antigen prior to slaughter
e. Freezing pork at 10°F

c. Prohibiting feeding garbage to hogs

Infection of hogs with nematodes of the genus Trichinella can be prevented by ensuring that all garbage and offal fed to the hogs are heat-treated to destroy the cysts or, preferably, by using feed devoid of animal meat, such as grain. Prohibition of marketing of garbage-fed hogs is easier to enforce than inspection to ensure that all garbage is properly cooked. The disease is transmitted by ingestion of larvae in hog skeletal muscle, not by hog feces. Thorough cooking of pork and pork products so that all the meat reaches at least 71°C (160°F) destroys the encysted larvae. Freezing pork also destroys the larvae if adequate time-temperature schedules are followed. In order to be effective, freezing must be done at −15°C (−5°F) for 30 days if the piece of meat is 15cm in thickness or less.


Which engineered water purification system is the most effective for the elimination of Cryptosporidium parvum?
a. Flocculation
b. Sedimentation
c. Disinfection
d. Boiling
e. Filtration

e. Filtration

Slow sand, rapid granular, or membrane filtration is the most effective water treatment method to remove Cryptosporidium cysts, as they are not destroyed by disinfection.

Flocculation is used to help form large floc particles from particulate matter including bacteria which can then can be more easily removed.

Sedimentation, through gravity, makes particulates including bacteria settle to the bottom of a tank.

Flocculation and sedimentation do not effectively remove cysts. It is important to note that high water turbidity may affect the ability of filtration to remove the parasite, and that filtration may not always afford absolute protection.

Boiling is not an engineered water sanitation process, but it is the simplest effective method to prevent Cryptosporidium parvum infections if drinking water is contaminated or has not been treated adequately. The water intended for drinking should be boiled for 1 min. Immunosuppressed persons, such as those with HIV, are particularly at risk of severe infections.


The major environmental source of lead absorbed in the human blood stream in adults is
a. Air
b. Water
c. Lead-based paint
d. Food
e. Soil

a. Air

Although most lead intake in humans is from ingestion of lead-contaminated food (about 0.1 mg of lead is ingested daily per person), the amount of lead that is absorbed after inhalation of lead-contaminated air is of greater significance because up to 50% of inhaled lead, compared with only as much as 10% of ingested lead, is absorbed and circulated through the blood.

Because modern building codes require the replacement of lead domestic water-supply pipes with those made of copper or galvanized iron, drinking water has become a decreasing source of lead poisoning.

The intake of lead through ingestion of lead-based paint is mainly a problem with children.

GI absorption of lead appears to be more efficient in children, while pulmonary absorption is more efficient in adults.


You are asked to evaluate the working environment in a manufacturing plant processing metal parts. In one area of the mill, where such parts are flattened, the sound level is measured at 85dB. The workers responsible for this process are exposed to this sound for the entire 8-hr shift. The most appropriate intervention for this level of sound is
a. None. This level of sound is below the level at which OSHA regulations apply
b. A hearing conservation program
c. A shutdown of the manufacture until the level of sound is reduced
d. A shutdown only of the process area where the sound is 85dB or higher
e. Enforcement of hearing protective devices for all exposed workers

b. A hearing conservation program

Exposures of 85 dB or more for 8 hrs/day or more require the implementation of a hearing conservation program (HCP) under OSHA (Occupational Safety and Health Administration) regulation. This program includes noise monitoring, engineering controls, administrative control, worker education, selection and use of hearing protection devices (HPD), and periodic audiometric evaluations.

Engineering controls where possible are always the preferred method of controlling sound levels.

Administrative controls include reducing the amount of time the worker is exposed to high levels of sound. This is often difficult to achieve and requires constant oversight to ensure implementation.

Hearing devices must be able to bring the level of sound to 90 dB or less, the permissable exposure level for sound. However, workers may not always wear these devices. At levels of sound below 90 dB, OSHA requires that HPD be made available to workers. At level 90 or above, HPD must be provided and proper use must be enforced by the employer.


A 42y/o welder is brought in the emergency room complaining of a sore throat, headache, and myalgias. He also started feeling a tightness in the chest and shortness of breath. He works in an electroplating operation brazing and cutting metals. Pulmonary function tests reveal a reduced FEV. The CXR is normal. Which of the following exposures is the most likely cause of the workers symptoms?
a. Lead
b. Mercury
c. Chromium
d. Copper
e. Cadmium

e. Cadmium

Acute exposure to mercury results in cough, inflammation of the oral cavity, and GI symptoms. Renal injury is of particular concern. Neurological symptoms can later occur. Mercury is often used in the manufacturing of control instruments (such as thermometers). Dimercaprol is used for treatment.

Copper toxicity (in the US) is primarily due to accidental ingestion or suicide attempts and leads to intravascular hemolysis and methemoglobinemia. No specific treatment exists. The initial symptoms associated with acute exposure (ingestion or inhalation) of lead are primarily gastrointestinal (abdominal cramps). Encephalopathy can follow.

Lead is used intensively in the production of storage batteries.

Chromium is used in plating. Acute exposure results in irritation of eyes, nose, and throat with epistaxis.