ABT Environmental Toxicology 2

Question 1

The EPA's Reference Dose (RfD) is defined as an estimate of daily exposure that:

Accepted Answer

Is likely to be without appreciable risk of deleterious effects over a lifetime

Answer

The RfD is an EPA estimate of daily oral exposure to a chemical that is likely to be without appreciable deleterious effects over a lifetime, used for non-carcinogens.

Question 2

Methylmercury exposure in humans primarily occurs through:

Accepted Answer

Consumption of contaminated fish and seafood

Answer

Methylmercury bioaccumulates in fish and seafood, making dietary consumption of large predatory fish (tuna, swordfish) the primary human exposure route.

Question 3

Which class of pesticides inhibits acetylcholinesterase and was originally developed as nerve agents?

Accepted Answer

Organophosphates

Answer

Organophosphate pesticides are structurally related to nerve agents and inhibit acetylcholinesterase, causing accumulation of acetylcholine at synapses.

Question 4

Lead exposure in children is most commonly associated with which source in older US homes?

Accepted Answer

Lead-based paint chips and dust

Answer

Lead-based paint used in homes built before 1978 is the most common source of lead exposure in US children through ingestion of paint chips and inhalation of dust.

Question 5

Dioxins (PCDDs) exert their toxic effects primarily through which molecular mechanism?

Accepted Answer

Activation of the aryl hydrocarbon receptor (AhR)

Answer

Dioxins bind with high affinity to the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that alters gene expression leading to diverse toxic effects.

ABT - American Board of Toxicology Practice Test

ABT - American Board of Toxicology Practice Test

ABT Environmental Toxicology 2