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University of Michigan Dioxin Exposure Study |
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Definitions |
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BMI: Body Mass Index is a measure of weight that adjusts for differences in height. People with a higher BMI tend to be overweight. People with a lower BMI tend to be underweight. |
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Congener: One type of chemical in a group of other similar chemicals. One type of dioxin. |
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Mean: The arithmetic average, which is the sum of the values on a list divided by the number of values on the list. |
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Median: The middle value of a list. The number for which half the numbers on a list are below and half of the numbers on the list are above. This is also known as the 50th percentile. |
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Parts per trillion: Parts per trillion (ppt) is a unit of how much of one substance is mixed in another substance, or its concentration. One part per trillion is about the same as mixing one drop of ink into an Olympic-sized swimming pool. A part
per trillion in soil means that there is one ounce of dioxins in one trillion ounces (31,250,000 tons) of soil. |
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TEF: Dioxins vary in their effects on people. Some have more toxic effects than others. The Toxic Equivalency Factor, or TEF, is a measure of the toxicity of each of the specific dioxins compared to the most toxic dioxin, 2,3,7,8-TCDD. |
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TEQ: The combined toxicity of all 29 dioxins is called the “TEQ” (for Toxic EQuivalency). The TEQ is a summary measure of the toxicity of the 29 dioxins in a sample, giving them different weights (the TEFs) depending on how toxic they are. Another way of saying it is that the TEQ is a measure of total 2,3,7,8-TCDD-like activity in a sample. The TEQ is the sum over all 29 dioxins of the TEF multiplied by the congener concentration in that sample. |
