CES Environmental Health & Toxicology Flashcards
6 cards from real CES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CES Environmental Health & Toxicology flashcards as text
What is the significance of the LD50 value in toxicology?
Answer: The dose lethal to 50% of a test animal population in a specified time period
The LD50 (lethal dose 50%) is the dose of a substance that kills 50% of a test animal population under specific conditions, providing a standard measure of acute toxicity.
Which of the following is an example of a 'non-threshold' toxicant, meaning there is no exposure level considered entirely safe?
Answer: Ionizing radiation and genotoxic carcinogens
Genotoxic carcinogens and ionizing radiation are considered non-threshold agents because even a single molecular event could theoretically initiate cancer, so no dose is assumed completely risk-free.
What does 'bioavailability' refer to in the context of contaminated site risk assessment?
Answer: The fraction of a contaminant that is absorbed and available to cause a biological effect in a receptor organism
Bioavailability is the fraction of a contaminant that is actually absorbed into an organism's system and available to interact with biological targets, which may be less than the total measured environmental concentration.
Which type of study is considered the gold standard for establishing causal relationships between environmental exposures and human health outcomes?
Answer: Prospective cohort study
Prospective cohort studies follow unexposed individuals over time, allowing researchers to measure exposure before disease onset and establish temporal causality between environmental exposures and health effects.
Which pathway is of greatest concern for children's exposure to lead in older urban housing?
Answer: Ingestion of lead-based paint chips and dust
Ingestion of lead-based paint chips and household dust remains the primary exposure pathway for children in pre-1978 housing, where lead paint was legal and widely used.
What is the primary mechanism by which chronic arsenic exposure causes adverse health effects in humans?
Answer: Inorganic arsenic interferes with cellular energy production and causes oxidative stress, leading to skin lesions, cardiovascular disease, and cancer
Chronic inorganic arsenic exposure causes oxidative stress, DNA damage, and disruption of cellular signaling pathways, resulting in characteristic skin lesions (arsenicosis), cardiovascular disease, and increased cancer risk.