APES 8.12 and 8.13- Lethal Dose 50% (LD50) and Dose Response Curve WYRNTK

Which statement about dose-response studies is NOT true? a. Dose-response studies test chemicals across a range of concentrations. b. Dose-response studies only test for lethal effects. c. Dose-response studies can last for days or months d. LD50 values are divided by 10 to determine safe concentrations for wildlife e. LD50 values are divided by 1,000 to determine safe concentrations for humans

b. Dose-response studies only test for lethal effects.

The LD50 for arsenic in humans is 13 mg/kg. Which of the following approaches should be used to calculate the number of grams of arsenic it would take to reach the LD50 in a 140-pound person? (Note: 1-kg = 2.2 pounds).

140 lb x 1kg/2.2 lb x 14 mg x 1g/1,000 mg

A pesticide was applied to a population of roaches, and it was determined that the LD50 was 55-mg/kg. If the average mass of a roach was 0.02-kg, which of the following approaches will determine the dose in milligrams (mg) per roach?

55 mg x 0.02 kg

The graph below shows the LD50 for two different species of mice after being exposed to a mutagen for 30 days. Based on the data in the graph, which of the following should be used to calculate the difference in LD50 for the two different species of mice?

575 mg - 490 mg

An individual is exposed to the water in the stream from which the sample shown in the graph was taken. If the individual was exposed to the highest dose of bacteria, which bacteria would have the lowest probability of causing illness if ingested?

C. jejuni

How would including a control group be useful in this experiment?

It would provide a reference for the effects of random environmental factors.

The graph below depicts the dose response curves for three common bacteria and a newly discovered bacterium found in streams near certain agricultural properties.

Salmonella spp.

The LD50s of five chemicals are listed below. Which is the most toxic? a. 5 mg/kg body weight b. 500 mg/kg body weight c. 5 g/kg body weight d. 50 g/kg body weight e. 500 g/kg body weight

a. 5 mg/kg body weight

Which dose would most likely represent the LD50 for toxin A? a. Dose 1 b. Dose 2 c. Dose 3 d. Dose 4 e. Dose 5

a. Dose 1

The risk that many cancer-causing chemicals pose to humans can be estimated using laboratory tests on rats. A significant scientific limitation of such tests is that:

animal models may not reflect human responses

Based upon the data, what is the best description of this relationship? a. As the concentration of anastrozole increases, the percent induction of breast cancer also increases b. As the concentration of anastrozole increases, the percent induction of breast cancer decreases c. There is a direct relationship between the concentration of anastrozole and induction of breast cancer d. It is more advantageous to be exposed to low amounts of anastrozole e. Anastrozole has no effect on breast cancer induction

b. As the concentration of anastrozole increases, the percent induction of breast cancer decreases

Which statement about dose-response studies is NOT true? a. dose-response studies test chemicals across a range of concentrations b. dose-response studies only test for lethal effects c. dose-response studies can last for days or months d. LD50 values are divided by 10 to determine safe concentrations for wildlife e. LD50 values are divided by 1,000 to determine safe concentrations for humans

b. dose-response studies only test for lethal effects

Which of the following BEST describes an exposure threshold for a toxic chemical. a. the dose that is tolerable for all test subjects b. the dose at which the test subject begins to show harmful effects c. the dose at which 50% of a test population dies d. the dose that test subject can tolerate e. the dose at which infants die

b. the dose at which the test subject begins to show harmful effects

Where is the threshold level for toxin B?

between doses 1 and 2

The pH at which 50 percent of the Daphnia survive after 2 hours of exposure can be predicted from the data. This pH is closest to: a. 2.5 b. 3.5 c. 4.5 d. 7.5 e. 8.5

c. 4.5

On the basis of the data, the best prediction of the pH of the water in which Daphnia normally are found in the wild is: a. 1 b. 3 c. 5 d. 7 e. 9

d. 7

An experiment was carried out to determine the lethal dose of ammonium sulfate on mung bean germination. True statements about the experimental design include which of the following? I. The control group has neither the seeds nor the ammonium sulfate II. The independent variable is the concentration of the ammonium sulfate III. The dependent variable is the number of seeds that failed to germinate a. I only b. II only c. III only d. II and III only e. I, II, and III

d. II and III only

Toxicologists say, "the dose makes the poison," meaning that most substances are harmful in high enough concentrations. The data for anastrozole: a. supports this concept because as concentration increases, so does response b. supports this concept because as concentration increases, response decreases c. does not support this concept because as concentration increases, response increases d. does not support this concept because as concentration increases, response decreases e. does not support this concept because the experiment was not done in animals

d. does not support this concept because as concentration increases, response decreases

Some drinking water standards allow bacteria in water at dosages up to the 10% probability of illness. Which of the following statements is best supported by the data in the graph? a. if there are fewer than 102 colonies for all species in a drinking water sample, the water will be considered safe b. If C. jejuni is the only species of bacteria present in the drinking water sample, the water will be considered safe to drink at all doses c. E. coli and Salmonella spp. Would have the highest allowable dosage to meet the drinking water standards d. the newly discovered bacterium would have the lowest allowable dosage to meet the drinking water standards

d. the newly discovered bacterium would have the lowest allowable dosage to meet the drinking water standards

For a certain insecticide, the LD50 dosage level for rats is determined to be 250 milligrams per kilograms of body mass. On the basis of this information, which of the following is the best prediction regarding the consequences of receiving this dosage of the insecticide? a. fifty percent of any rat population would be sickened b. fifty percent of the population of any warm-blooded animal would die c. fifty percent of any population of mosquitoes would die d. five hundred out of every one thousand people would experience acute effects e. five hundred out of every one thousand rates would die

e. five hundred out of every one thousand rates would die

The concentration of chemical exposure does NOT depend on: a. the persistence of the chemical b. the solubility of the chemical c. the ability of the chemical to bioaccumulate d. the ability of the chemical to biomagnify e. the LD50 value of the chemical

e. the LD50 value of the chemical

The LD50 of a drug or compound:

is the dose that can kill 50% of the animals in a test population

A laboratory study using rats showed a steady increase in physical effects as concentration of a toxic substance in their food was increased. This suggests that:

the dose-response relationship is linear