ABT practice 1

Question 2

Question (with options)

Answer 2

Answer + Concept Refresher

Question 3

Which of the intracellular organelles is most involved with the autolytic removal of cellular debris?

Ribosomes

Golgi complex

Endoplasmic reticulum

Lysosomes

Mitochondria

Answer 3

D. Lysosomes — The cell’s degradative ‘lysosomal’ system contains acid hydrolases that digest worn-out organelles, pathogens, and debris (autophagy/autolysis).

Question 4

Which of the following defines the threshold limit value for a chemical?

The metabolic threshold in humans

The upper limit for the time-weighted average exposure for an 8-hour workshift

The concentration at which toxicity is seen in humans

The concentration at which a chemical can be smelled

The detection limit (analytically) of the chemical in the workplace

Answer 4

B. The upper limit for the time-weighted average exposure for an 8-hour workshift — ACGIH TLV-TWA is a guideline for average airborne concentrations considered safe for most workers over an 8‑hr day/40‑hr week.

Question 5

A chemical is administered daily by oral gavage to a test animal at a dose of 15 mg/kg/day. It takes 10 days to reach a steady state level in the body. Assuming first order elimination, if the dose were increased to 30 mg/kg/day, how long will it take to reach the new steady state level?

5 days

10 days

20 days

40 days

100 days

Answer 5

B. 10 days — Time to steady state depends on elimination half‑life (≈4–5 half‑lives), not the dose. Doubling dose raises the plateau level, not the time to reach it.

Question 6

The dose response curve is critical for which of the following?

Estimation of risk

Choice of species for study

Selection of an antidote

Determination of side effect frequency

Establishment of the frequency of dosing

Answer 6

A. Estimation of risk — Dose–response defines potency, slope, NOAEL/LOAEL and supports extrapolation to human exposure limits in risk assessment.

Question 7

The LD50 of a mixture containing 25 parts of A (LD50 = 250 mg/kg) and 75 parts of B (LD50 = 750 mg/kg) was determined to be 625 mg/kg. The dose-response curves for A and B, each given alone, are parallel. Which statement is correct?

The predicted LD50 of this mixture is 1000 mg/kg, this represents antagonism

The predicted LD50 equals the observed LD50, this represents summation

The predicted LD50 equals the observed LD50, this is synergism

The predicted LD50 is 1000 mg/kg, This is synergism

The predicted LD50 = 500 mg/kg, this is antagonism

Answer 7

B. The predicted LD50 equals the observed LD50, this represents summation — For parallel curves with similar action, effects add. Weighted harmonic mean predicts ≈625 mg/kg; matching observation = additivity.

Question 8

The effect seen when the administration of an agent with no appreciable effect on a biological system enhances the response to another agent is defined as:

Competition

Summation

Cumulative effect

Potentiation

Antagonism

Answer 8

D. Potentiation — A non‑toxic dose of one agent increases the toxicity of another (e.g., isopropanol potentiates CCl₄ hepatotoxicity).

Question 9

In doing a linear regression analysis on the dose of an agent you conduct a statistical test on the regression slope and find that it is significant. The interpretation of this result is that:

The intercept is large

The slope is large

The intercept is not zero

The slope is not zero

Both the intercept and slope are not zero

Answer 9

D. The slope is not zero — A significant slope indicates a real dose–response relationship (changes in response with dose) beyond random variation.

Question 10

High molybdenum content in the soil may lead to defective myelination in young ruminants by:

A direct destructive effect on myelin

Damaging the cells that produce and maintain myelin

Interfering with copper absorption to produce a copper deficiency which causes demyelination

Activation of a virus which produces demyelination

Stimulation of the immune system to produce antibodies against the basic myelin protein

Answer 10

C. Interfering with copper absorption to produce a copper deficiency — Excess Mo induces Cu deficiency (thiomolybdates), impairing enzymes (e.g., cytochrome c oxidase) crucial for myelination.

Question 11

Which of the following statements is not correct in regard to nitrite poisoning in wild and domestic ruminants?

Nitrates present in tissue and plants may be reduced to nitrites in the presence of moisture and bacteria

Methemoglobinemia is the principal toxic effect of nitrite poisoning in ruminants and in humans

Stomach cancer is the principal toxic effect of nitrites in ruminants but not in humans

Nitrites transform the iron in hemoglobin from the ferrous to the ferric state

Common clinical signs of nitrite poisoning in ruminants include cyanosis, dyspnea, tachycardia, weakness, coma and diarrhea

Answer 11

C. Stomach cancer is the principal toxic effect … — The key acute hazard is methemoglobinemia: nitrite oxidizes Fe²⁺→Fe³⁺, reducing O₂ delivery and causing hypoxic signs.

Question 12

Facilitated diffusion and active transport share all but which of the following characteristics?

Substrate specificity

Transport at a rate greater than that by diffusion

Transport against a concentration gradient

Saturability of the transport system

All of the above

Answer 12

C. Transport against a concentration gradient — Both systems are carrier‑mediated (specific, saturable) and can exceed simple diffusion rates; only active transport moves uphill using energy.

Question 13

Which of the following is the most important first step in addressing an epidemiologic question?

Read extensively in the literature

Decide how you might carry out a study

Decide what you really want to know

Draft a study protocol and solicit comments on it

Check the regulations

Answer 13

C. Decide what you really want to know — A precise, well‑framed question (PICO) drives design, measures, and analysis.

Question 14

Which if the following is characteristic of ethylene glycol?

It uncouples oxidative phosphorylation

It is metabolized to formic acid

It is metabolized to oxalic acid

It inhibits aconitase

It inhibits the effect of vitamin K

Answer 14

C. It is metabolized to oxalic acid — EG → glycolic → glyoxylic → oxalic acid; calcium oxalate crystals deposit in renal tubules causing AKI and anion‑gap acidosis.

Question 15

In antagonizing methemoglobinemia, methylene blue

Serves as an artificial oxygen transporting system in blood

Is converted from its oxidized form to its reduced form by NADPH

Facilitates the reduction of iron in hemoglobin from FE+++ to FE++

Displaces the toxicant from hemoglobin

Is oxidized by methemoglobin reductase

Answer 15

B and C. NADPH reduces methylene blue to leucomethylene blue, which reduces Fe³⁺ (metHb) back to Fe²⁺, restoring O₂ carrying capacity (avoid in G6PD deficiency).

Question 16

Which of the following is the most reliable method of identifying a poisonous agent?

Locating a toxic agent near the victim

Observation of the symptoms

Pathologic changes observed grossly or microscopically

Chemical analysis of the blood or tissues

Effectiveness of a specific antidote

Answer 16

D. Chemical analysis of the blood or tissues — Direct analytical confirmation is definitive compared with circumstantial or clinical clues.

Question 17

Barium sulfate as used in radiology

Is nearly inert and is associated with few side effects

May cause barium intoxication if used more than once or twice

Has barium sulfate kidney stone formation as a hazard to use

Can be used orally or intravenously

Is used only occasionally because most people are sensitive to barium

Answer 17

A. Is nearly inert and is associated with few side effects — Insoluble BaSO₄ is safe for GI contrast (oral/rectal); IV use is contraindicated (soluble barium salts are toxic).

Question 18

Microsomes are defined as

Small liposomes

Isolated mitochondria

Fragments of nuclei

Small bodies present in living liver cells

Pieces of endoplasmic reticulum

Answer 18

E. Pieces of endoplasmic reticulum — ‘Microsomes’ are ER vesicles formed by cell homogenization/centrifugation; site of CYP450‑mediated biotransformation.

Question 19

A weak organic acid is 0% ionized at a pH of 3.9. What is the PKa of this acid?

About 1.95

3.9

7.8

Over 7.8

Insufficient information given to determine PKa

Answer 19

B. 3.9 — For a weak acid, when pH ≪ pKa the non‑ionized form predominates; the provided information implies pKa ≈ measured pH where ionization is minimal.

Question 20

An epidemiologist analyzed the last 100 evening rush hour automobile accidents and finds that23 of the involved drivers had potential occupational exposures to solvents. To conclude that solvent exposure may be an important factor in auto accidents, he needs to know

The number of automobile accidents in the morning rush hour

How many passengers in each car had consumed alcohol

How many pedestrians were involved and whether they had been exposed to solvents

How many evening rush hour drivers not involved in accidents had potential occupational exposure to solvents

All of the above

Answer 20

D. Exposure among non‑accident drivers — A control/comparison group is required to estimate relative risk/odds ratio and attribute risk to solvent exposure.

Question 21

It has been estimated that, if the average 60 kilogram person consumes one diet drink per day (about 150 mg of saccharin), the lifetime risk of bladder cancer is

Greater than 24%

10% to 24%

Between 1% and 10%

Equal to 1%

Less than 1%

Answer 21

E. Less than 1% — Human risk estimates for saccharin are very low; early rodent bladder findings did not translate to substantial human risk at dietary exposures.

Question 22

Which of the following is/are standard study designs in epidemiology?

Cohortcross-sectional

Case-control

All of the above

None of the above

Answer 22

C. All of the above — Core designs include cohort, case‑control, and cross‑sectional; each answers different causal/association questions.

Question 23

Differential susceptibility of males and females to toxicants is likely to result from sex differences In

Rate of absorption

Urinary excretion

Nutritional requirements

Hormones affecting biotransformation

Body weight and surface area

Answer 23

D. Hormones affecting biotransformation — Sex steroids regulate expression of drug‑metabolizing enzymes (e.g., CYPs, UGTs), altering kinetics/toxicity.

Question 24

Which of the following substances prevents the release of acetylcholine from the axon terminal?

Curare

Parathion

Carbaryl

Botulinum toxin

DDT

Answer 24

D. Botulinum toxin — Cleaves SNARE proteins at cholinergic terminals, blocking ACh vesicle release and causing flaccid paralysis.

Question 25

Which of the following is the single greatest contributor to degradation of surface water quality? Contaminated industrial waste discharged directly into waterways Burial of solid waste Burial of liquid waste Soil erosion Acid rain

Answer 25

D. Soil erosion — Sediment loading from erosion is the dominant pollutant by mass, degrading clarity, habitat, and transporting attached contaminants.

Question 26

Which one of the following governmental bodies does not have guidelines for conducting toxicology studies? Environmental protection agency Department of transportation Food and drug administration Consumer product safety commission National institute of occupational safety and health

Answer 26

B. Department of transportation — DOT focuses on hazardous materials transport; EPA/FDA/CPSC/NIOSH issue testing/study guidance.

Question 27

Extrapolation of toxicity data from animal to man can best be done by Structure-activity relationships Physiological, anatomical and kinetic models Genetic studies of animals and man Comparisons based on organ weight to body weight ratio Computer models of biochemical schemes

Answer 27

B. Physiological, anatomical and kinetic models — PBPK and mechanistic models capture cross‑species differences in ADME and target tissue doses.

Question 28

A wide spectrum of lung changes varying from a clinically insignificant focal pigmentation to crippling fibrosis is most likely to be encountered among which of the following? Distillery workers Coal miners Farmers Histologists City traffic directors

Answer 28

B. Coal miners — Coal workers’ pneumoconiosis ranges from anthracosis (pigment) to progressive massive fibrosis from chronic dust exposure.

Question 29

Which of the following metals has been associated with an increased incidence of cardiomyopathy in heavy beer drinkers? Chromium Cobalt Nickel Cadmium Copper

Answer 29

B. Cobalt — Cobalt salts used historically as foam stabilizers in beer led to dilated cardiomyopathy outbreaks in heavy drinkers.

Question 30

Pseudocholinesterase activity in the serum is a useful indicator of occupational exposure to Organophosphate insecticides Nitrites vinyl chloride DDT Chlordane

Answer 30

A. Organophosphate insecticides — OPs inhibit cholinesterases; depressed pseudocholinesterase is a biomarker of exposure/effect.

Question 31

Opisthotonus, which may occur following a toxic dose of strychnine, refers to Paralysis of involuntary muscles Labored breathing Back arched in hyperextension with only the head and feet touching the ground Muscles of the face and neck relaxed All of the above

Answer 31

C. Back arched in hyperextension — Strychnine blocks spinal glycine receptors, producing severe extensor convulsions/opisthotonus.

Question 32

The toxic substances control act delineated the concept of unreasonable risk in greater detail than any previous regulatory enabling legislation. However, several real constraints are factored into decision making. These include Technical feasibility Cost of control Availability of chemical A and B are correct All of the above

Answer 32

E. All of the above — TSCA risk management balances health/environmental risk against feasibility, costs, and market/availability considerations.

Question 33

Which of the following soil properties affect the persistence of organic insecticides in soils? Organic carbon content Moisture content pH temperature all of the above

Answer 33

E. all of the above — Sorption (organic C), hydrolysis (pH), microbial activity (moisture/temp) all drive persistence/attenuation.

Question 34

Which of the following statements is/are true about a 60-day toxicity study of a proposed new food additive to be conducted in ferrets using GLP guidelines? The balances used to weigh out the amount of test compound must be calibrated at prescribed intervals The study cannot be conducted according to GLP because only dogs, rats, mice, hamsters and monkeys may be used in toxicity studies The stability of the test compound in the dosing solution needs to be determined and the concentration of the test compound monitored in the dosing solution The study cannot be conducted in accordance with GLP because the guideline specify that subchronic studies must be at least 90 days long. A and C

Answer 34

E. A and C — GLP requires calibrated equipment and verified concentration/stability of dosing solutions; GLP does not restrict species nor forbid 60‑day (study type dictates duration).

Question 35

Occupational exposure to asbestos may lead to Pulmonary fibrosis An increased risk of bronchogenic carcinoma which may be potentiated by cigarette smoke Pleural mesothelioma Peritoneal mesothelioma All of the above

Answer 35

E. All of the above — Asbestos causes asbestosis (fibrosis), lung cancer (risk amplified by smoking), and mesotheliomas of pleura/peritoneum.

Question 36

If the rate of excretion of A chemical is 0.3 g/hr, which of the following is true? Its biological half-life is 2.31 hours It follows first order kinetics It follows zero order kinetics 30% of the chemical is excreted in an hour None of the above

Answer 36

C. It follows zero order kinetics — A constant amount per unit time indicates capacity‑limited (zero‑order) elimination.

Question 37

Under the current FDA regulations, the sponsor of an IND trial is required to notify FDA and all participating investigators of any adverse experience associated with use of a drug. Such notification shall be made within ____ after the sponsor’s initial recipe of the information? 1 working day 10 working days 1 month 6 months 1 year

Answer 37

A. 1 working day — Serious and unexpected adverse experiences require rapid safety reporting to FDA and investigators under IND rules.

Question 38

Which of the following correctly describes the “Delaney Clause”? Prohibits marketing of a new human prescription drug that has been shown to cause cancer in rats Allows the marketing of a new food-animal feed additive that increased the number of tumors (over control) in a 2-year rat carcinogenicity/toxicity study, but the mechanism of the occurrence of increased tumors was shown to be non-genotoxic but rather hormonal Allows the marketing of a new food-animal drug that has been shown to cause cancer in mice but produces residues of the drug in meat, milk or eggs below the NOAEL Applies to herbicides applied to human food crops None of the above

Answer 38

E. None of the above — The Delaney Clause prohibits approval of any food additive found to induce cancer in humans or animals, regardless of dose/mechanism.

Question 39

Licensing, distribution and tolerance limits of pesticides are regulated by which governmental body? Department of agriculture National institute of occupational safety and health (NIOSH) Environmental protection agency (EPA) Department of transportation None of the above

Answer 39

C. Environmental protection agency (EPA) — EPA registers pesticides and sets tolerances for residues in foods under FIFRA/FFDCA.

Question 40

In the extrapolation of animal data to man it has been suggested that mg/surface area/day provides an equivalent dose between species. To a close approximation, the surface area is proportional to the: 2/3 power of the weight Square of the body weight expressed in grams Square root of the weight expressed in kilograms Reciprocal of the square root of the weight in kilograms ¾ power of the weight expressed in grams

Answer 40

A. 2/3 power of the weight — Body surface area scales as W^(2/3), which underlies common interspecies dose scaling.

Question 41

Circle all correct answers Which of the following chemical pair interactions are appropriate? Propanol-carbon tetrachloride: potentiation Morphine-naloxone: synergism Mercury-BAL: chemical antagonism Propoxyphene-amytal: dispositional antagonism

Answer 41

A, C, and D — Isopropanol potentiates CCl₄; BAL (dimercaprol) chelates mercury (chemical antagonism); propoxyphene induces metabolism reducing amytal effect (dispositional). Naloxone is a pharmacologic antagonist of morphine, not synergist.

Question 42

Emesis is contraindicated in which of the following cases? Child who just swallowed an estimated number of 100 mg/kg salicylate tablets Young adult in deep coma following narcotic ingestion Child who ingested two mothballs 20 minutes before Child who ingested a strong acid 20 minutes before

Answer 42

B and D — Do not induce vomiting in comatose patients (aspiration risk) or after caustic ingestion (risk of further esophageal injury).

Question 43

Hyacin droplet nephropathy induced by unleaded gasoline (trimethylphentane) or D-limonene is characterized by which of the following? Activation of these agents by proximal tubular (P-2 segment) cytochrome P450 A male specific response in the rat Binding of activated metabolites to basement proteins in the glomerulus Binding of the agents to alpha-2-microglobulin and subsequent accumulation in P-2 segment proximal tubular cells

Answer 43

B and D — Classic male‑rat α2‑microglobulin nephropathy: hydrocarbons bind α2u‑globulin, accumulate in P2 proximal tubules → hyaline droplets; not relevant to humans.

Question 44

Which of the following are factors that may influence the rate of excretion of a chemical by the kidneys? Renal blood flow Protein binding of the chemical Urine production pKA of the chemical

Answer 44

All of the above — They determine filtration (blood flow/protein binding), secretion, and reabsorption (urine flow, ionization via pKa and urine pH).

Question 45

Which of the following is/are true of salicylate poisoning? Causes disturbance in acid base balance Causes metabolic acidosis Is treated by administration of sodium bicarbonate Is treated by administration of sodium lactate

Answer 45

A, B, and C — Early respiratory alkalosis progresses to metabolic acidosis; therapy alkalinizes serum/urine with sodium bicarbonate to enhance salicylate elimination.

Question 46

Which of the following are characteristic of first-order kinetics? The toxicant is eliminated at a fixed amount per day A constant fraction of the toxicant present is eliminated per unit time It can occur when the toxicant elimination process is saturated and a fixed number of mg or rams are excreted per unit time When toxicant concentration is high such as occurs after acute exposure a large amount initially eliminated per unit time

Answer 46

B and D — First‑order processes eliminate a constant fraction; at high levels the absolute amount per time is larger even though the fraction is constant.

Question 47

A conservative estimate of carcinogenic risk may involve which of the following? Extrapolation into a region below the lowest observed adverse effect level (LOAEL) The use of a linearized, non-threshold multistage model The use of animal data from the most sensitive species Assumption of a threshold in the dose-response

Answer 47

A, B, and C — Protectiveness often uses linear no‑threshold extrapolation, low‑dose modeling below LOAEL, and data from the most sensitive species/sex/site.

Question 48

The reason that the epidemiological approach for discovering the relationship between chemicals and human disease is not more successful lies in the Complexity of human genetic make-up Long latent periods required to detect changes Diversity of human social and economic conditions Difficulty of accurate exposure assessments

Answer 48

B, C, and D — Long latency, heterogeneous populations, and imprecise historical exposure data reduce power and can bias associations.

Question 49

Induction of vomiting is recommended for poisonings involving which of the following? Ingested anticonvulsants Inhaled poisons with systemic action Ingested anticoagulants Sodium hydroxide ingestion

Answer 49

A and C — For select recent oral ingestions, decontamination may be considered; never with caustics (NaOH) or inhaled poisons (aspiration risk). Follow modern guidelines favoring activated charcoal when appropriate.

Question 50

The principles of “selective toxicity” implies The selection of the drug with the least toxicity The toxicity of drugs dictates the drug that must be selected The selection of one toxic effect of a drug that can be monitored to determine the risk to benefit ratio of therapy He exploitation of differences between the biochemistry of the infecting organism and the host

Answer 50

D. Exploitation of biochemical differences — Antimicrobials target pathogen‑specific pathways (cell wall, ribosomes, folate) minimizing host toxicity.

Question 51

For a toxic effect to occur, it is necessary that the toxic agent or its metabolites Reach an appropriate receptor Be present at sufficiently high concentrations Be present for enough time to produce an effect Exhibit bioaccumulation

Answer 51

A, B, and C — Toxicodynamics requires target site exposure of sufficient magnitude and duration; bioaccumulation is not required for acute effects.

Question 52

If saturation of a sulfate conjugation pathway occurred with increased dosage of a compound and if urinary excretion of the sulfate conjugate was a major means of elimination, at higher dose levels one would expect: Decreased blood levels of the sulfate conjugate Increased blood levels of the parent compound Increased percentages of the does being eliminated in the urine Decreased percentage of the dose being eliminated in the urine

Answer 52

B and D — When a conjugation pathway saturates, parent compound accumulates and the fraction excreted as the conjugate falls; overall clearance decreases (nonlinear kinetics).