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The insecticide DDT has a half-life in the human body of approximately 7 years. [In 7 years its concentration decreases to half its initial concentration). Although DDT is no longer used in the United States, 25 years ago that average farmer had a body DDT concentration of 22ppm [parts per million by weight). Estimate what the farm workers present concentration is?

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Answer:

explanation below

Explanation:

Dichlorodiphenyltrichloroethane, also known as DDT is a chemical compound that is found in insecticides. In 1972, the United States Environmental Protection Agency issued an order for the cancellation of requests for the chemical compound because it affects wildlife and pose risks to humans as well.  

From the question here, it was noted that the initial concentration was 22ppm 25years ago and so if it takes 7years to decay by half, the actual concentration in present day farmers could be calculated as follows;

25years ago  - 22ppm

18years ago  - 11ppm

11years ago – 5.5 ppm

4 years ago -  2.75ppm

Since 7yrs = 0.5

Then 4yrs will be [ [4/7] x 0.5] = 0.2857

Then if 0.5 = 2,

Then 0.2857 = [ [ 0.2857/0.5] x 2] = 1.1428

So present year concentration would then be [2.75ppm/1.1428] = 2.406ppm

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