QUESTION 1 1. Which of the following experiments/tests would prov...

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QUESTION 1 1. Which of the following experiments/tests would provide the most convincing data that a compound X is responsible for human pathogenesis (select one)? A. A dose-response experiment that determines the LD50 compound X in rats. B. A single individual exposed to a high dose of compound X dies. C. A cohort study in which individuals exposed and not exposed to Compound X are monitored over time for disease signs. D. The effect of compound X on a human cell line cytotoxicity assay is observed A. Reference Dose B. NOAEL C. Threshold Dose D. LOAEL E. Modifying Factor QUESTION 3 1. Risk assessment consists of four broad steps/activities. Match each of the following experiments with the risk assessment activity the experiment identifies. QUESTION 2 1. An estimate of a daily exposure to an agent that is assumed to be without adverse effects or health impact is called the _________? (Select one) The levels of toxicant in the air is quantified Animal experiment shows that exposure to chemical leads to lung damage in rats A. Exposure Assessment B. Hazard Identification C. Dose-Response Assessment Identification of NOAEL in rats of D. Risk Characterization the toxicant given to rats by inhalation It is estimated that 20% of individuals exposed to the toxicant at 1 mg/day will develop lung damage QUESTION 4 1. Which of the following are critical components of hazard identification (select all that apply)? A. Structure-Activity Analysis B. In vitro tests C. Animal studies D. Susceptibility E. Epidemiology QUESTION 5 1. The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal agency tasked with providing trusted health information to prevent harmful exposures and diseases related to toxic substances. Identify the Minimal Risk Level published by ATSDR for the following hazardous chemicals. Oral Acute Toxicity for Acrylamide mg/kg/day Oral Chronic Toxicity for Cadmium mg/kg/day Inhaled Acute Toxicity 1,2 Dichloropropane ppm Oral Acute Toxicity for Phenol mg/kg/day QUESTION 6 1. An common household chemical is tested in rats by giving single acute doses of 1, 3 and 10 mg/kg. Initial hazard identification studies indicate that this chemical inhibits the enzyme, acetylcholinesterase. Blood cholinesterase activity was monitored and complete inhibition was observed at all three dose levels. Using the standard uncertainty factors, what would be the acute RfD for this pesticide (select one)? A. 0.3 mg/kg B. 2.5 mg/kg C. 0.01 mg/kg D. 0.001 mg/kg E. 1 mg/kg QUESTION 8 QUESTION 7 1. Explain in 5-6 sentences how the choice of the effect used in calculating the NOAEL or LOAEL may influence the calculation of the Reference Dose and the use of the RfD to compare the risk of two different chemicals. 1. The dose response curves (avg of 12 animals) for Toxins A and B are depicted below. What can you conclude about the differences in the effects of these two compounds based on the curves (limit 4-5 sentences)? QUESTION 9 1. Explain how chemicals are evaluated differently for non-cancer and cancer risk assessment. Why are they evaluated differently (limit 6-7 sentences) QUESTION 10 1. You are asked to conduct a non-cancer risk assessment for toluene exposure for painters and office workers. Given the parameters below, quantify the risk of toluene for these two populations and whether their should be a level of concern. Justify your repsonse. RfC for toluene = 0.11 mg/kg/day Exposure Level for office workers = 0.08 mg/kg/day Exposure Level for painters = 73.6 mg/kg/day QUESTION 1 1. The ACME Chemical Company is discharging chemical X that is a byproduct of their manufacturing process into a local lake. After the company began discharging the chemical, large numbers of dead fish began appearing on the surface of the lake. Locals suspected that the chemical discharge was causing the fish kills and demanded that the EPA investigate the company. ACME denied responsibility and presented their own experiments that the chemical was not responsible for fish kills. In one of the experiments, the company maintained fish from the lake in an aquarium. They treated one aquarium with 10-fold greater concentration of Chemical X than is being discharged into lake. The number of dead fish in the treated aquarium was not statistically different from an untreated aquarium. Therefore, ACME claimed that chemical X was clearly not responsible for fish kills. Given what you have learned about environmental toxicology in this learning unit, provide at least one explanation for how the logic in this experiment is flawed. How might you improve this experiment (limit 5-6 sentences)? QUESTION 2 1. The organophosphate pesticide chlorpyrifos (CPF) is shown below. The toxicity of CPF on cultured PC12 cells (derived from rat adrenal medulla) is measured by assaying the concentration of DNA in a sample after treatment with CPF with varying UV exposure.How would you explain the data in the figure below (limit 3-4 sentences)? QUESTION 3 1. Which of the following would enhance the bioaccumulation of a toxicant in a freshwater lake (select all that apply)? A. Chemical is very hydrophobic B. Chemical is highly susceptible to hydrolysis C. The chemical is highly polar D. Chemical is highly metabolized by organisms low in the food chain E. Chemical is well absorbed by organisms low in the food chain QUESTION 4 1. The concentrations (ng/g lipid weight) of the toxin PBDE were measured in various organisms in a polar ecosystem (Cop = Copepods, Kril = Krill,opl = Zooplankton, Amph = Amphipods). Explain why the levels of PDPE increase in the graph with each species? Speculate why there is a dip from seals to polar bears (limit 5-6 sentence). QUESTION 5 1. PCBs can significantly bioaccumulate in freshwater and marine environments and so methods for bioremediation of contaminated areas is of significant interest. The experiment below depicts the effects of adding activated carbon (essential charcoal) to a marine environment and then testing the PCB levels in two marine species: Leptocheirus (a crustacean) and Neanthes (a clam worm). Given the data below, explain the mechanism by which activated carbon inhibits PCB bioaccumulation (limit 3-4 sentences). QUESTION 6 1. There are three major characteristics of chemicals that confer a high risk of environmental hazard. Match the following examples with the characteristic that results in high environmental hazard. Chemical is taken up by trees and concentrated in acorns in a woodland ecosystem Chemical is highly resistant to hydrolysis and bacterial degradation Chemical accumulates on cellular membranes of fish and limits their ability to maintain salt balance Chemical only weakly associates with sediment in a freshwater lake A. Toxicity B. Environmental Persistance C. Bioaccumulation QUESTION 7 1. Which of the following cheimical transport processes are examples of advection (select all that apply)? A. Toxin accumulates on leaves and is then transported to soil when leaves fall B. Toxin is transported from water surface into the air C. Toxin is released by a single discharge into a pond upon which the toxin slowly accumulates at the same concentration throughout pond. D. Toxicant is transported by wind for 10 miles E. Toxin is transported downstream in a river to a lake QUESTION 8 1. The table below provides the octanol-water partition coefficients (Kow) for various Polychlorinated Biphenyl (PCB) cogeners. Which cogener is most likely to bioaccumulate in a fresh water ecosystem (select one)? Cogener PCB-9 PCB-56 PCB-100 PCB-183 Kow 8.7x10-6 7.8x10-7 5.9x10-7 6.1x10-8 A. PCB-9 B. PCB-56 C. PCB-100 D. PCB-183

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1.Ans: C. A cohort study in which individuals exposed and not exposed to Compound X are monitored over time for disease signs.

2. Ans: B. NOAEL or No-Observed-Adverse-Effect-Level

3. Ans:

The levels of toxicant in the air is quantified
D. Risk Characterization

Animal experiment shows that exposure to chemical leads to lung damage in rats B. Hazard Identification

Identification of NOAEL in rats of the toxicant given to rats by inhalation
C. Dose-Response Assessment

It is estimated that 20% of individuals exposed to the toxicant at 1 mg/day will develop lung damage
A. Exposure Assessment

4. ANS: ALL
A. Structure-Activity Analysis

B. In vitro tests
C. Animal studies
D. Susceptibility
E. Epidemiology
5. Ans:
Oral Acute Toxicity for Acrylamide    0.01                  mg/kg/day
Oral Chronic Toxicity for Cadmium          0.0001               mg/kg/day
Inhaled Acute Toxicity 1,2 Dichloropropane 0.05    ppm
Oral Acute Toxicity for Phenol      1         mg/kg/day...

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