Lethal Dose- How Much Is Too Much?

<strong>Lethal</strong> <strong>Dose</strong>- <strong>How</strong> <strong>Much</strong> is too much?<br />

Purpose: In this activity you will compare the toxicity of various substances.<br />

ANSWER KEY<br />

I. Background information:<br />

1. a. What does <strong>Lethal</strong> <strong>Dose</strong> 50 (LD 50 ) mean? b. <strong>How</strong> is LD 50 determined?<br />

a. LD 50 is the amount required to kill 50% of the test population<br />

b. LD 50 is determined by testing substances on laboratory animals such as rats.<br />

2. In what units are <strong>Lethal</strong> <strong>Dose</strong>s (or LD 50 ) expressed?<br />

Mg/kg of body mass<br />

3. What are some of the ethical concerns regarding research for lethal doses?<br />

<strong>Is</strong>sues with animal testing<br />

II. Determining <strong>Lethal</strong> <strong>Dose</strong>s:<br />

To use LD 50 , you will need to convert measurements of body weight from pounds kilograms<br />

(1 kg = 2.2 lbs) do the following calculations:<br />

1. <strong>How</strong> many kg does a 132-lbs human weigh? 2. <strong>How</strong> many kg does a 22-lb child weigh?<br />

132 lbs x 1 kg/2.2 lbs = 60.0 kg 22 lbs x 1kg/2.2 lbs. = 10. kg<br />

1. <strong>How</strong> many mg of<br />

“medicine” would be<br />

lethal to a 132-lb adult?<br />

The LD 50 for acetaminophen (Tylenol)=<br />

2402 mg/kg (rat, oral).<br />

The LD 50 for aspirin =<br />

200mg/kg (rat, oral).<br />

60. kg x 2402 mg/1kg = 144, 120 mg 12, 000 mg<br />

2. <strong>How</strong> many 500mg tablets<br />

of “medicine” would be<br />

lethal for an adult?<br />

144, 120 mg x 1 tablet/500mg = 288<br />

tablets<br />

24 tablet<br />

3. <strong>How</strong> many mg of<br />

“medicine” would be<br />

lethal to a 22-lb child?<br />

10. kg x 2402 mg/1kg = 24, 020 mg 2, 000 mg<br />

4. <strong>How</strong> many 500mg tablets<br />

would be lethal for a<br />

child?<br />

24, 020 mg x 1 tablet/500mg = 48<br />

tablets<br />

4 tablets<br />

Acetaminophen versus aspirin:<br />

5. a. Which is more toxic, acetaminophen or aspirin? b. <strong>How</strong> great is the difference in their toxicities? Explain.<br />

Aspirin is about 12 times more toxic than Tylenol (the LD 50 for aspirin is about 1/12 th the LD 50 of Tylenol).

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Part II: Comparing <strong>Lethal</strong> <strong>Dose</strong>s (Use Table of <strong>Lethal</strong> <strong>Dose</strong>s).<br />

1. What substance in the table is the most toxic when ingested? Explain.<br />

Arsenic is the most toxic in the table with the lowest LD 50 (15mg/kg).<br />

2. Rank the substances as best you can based on their lethal doses for ingestion (1 = most toxic…etc).<br />

1= Arsenic (15mg/kg), Caffeine (140mg/kg), Aspirin & Lorchel mushroom (200mg/kg), Lead (450mg/kg), Vitamin<br />

A (2000mg/kg), Table salt (3g/1kg), Alcohol (7060mg/kg), Sugar (30g/kg)<br />

3. Are any substances in the table good for you? Explain.<br />

Vitamin A is good for you (and a necessary for normal body function).<br />

4. Are there any substances in the world that are non-toxic? Explain.<br />

Anything can be toxic if you consume too much of it.<br />

Part III: Summarizing<br />

1. <strong>How</strong> is dosage related to toxicity?<br />

Dosage determines how much should be taken at a time. The dosage should always be much lower than the<br />

toxicity level.<br />

2. Besides dosage, what other factors should be considered when determining the toxicity of a substance on a<br />

person?<br />

The overall health of an individual, if an individual’s organs are functioning normally, their metabolic rate and<br />

tolerance (for some substances).<br />

3. <strong>How</strong> many Flintstone vitamin tables would be a lethal dose of vitamin A for a 22 Lb child? Each Flintstone<br />

vitamin tablet contains 0.9 mg of vitamin A & Vitamin A- LD 50 2000 mg/ kg. (show work)<br />

10. kg x 2000 mg/1kg x 1 tablet/0.9 mg = 22, 222 tablets<br />

Part IV: At Home<br />

1. Find at least 3 products at home with labels that warn of toxicity. For each product give the following:<br />

Product Name<br />

Active Ingredient<br />

& % comp.<br />

<strong>How</strong> does the label advise<br />

you to avoid harmful<br />

exposure to the product?<br />

What does the label tell<br />

you to do if a dangerous<br />

exposure does occur?<br />

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2. Put this phone number in your home in a location everyone in your family can quickly & easily find (if it’s not<br />

already there). Poison Control phone number: 1-800-222-1222<br />

Parent Signature that this number is posted: