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Significant Figures

Certain digits in a measurement plus one uncertain digit

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How Much is in There?

How Much is in There?

Credit: Abhijit Tembhekar
Source: http://www.flickr.com/photos/24340456@N03/3345977842
License: CC BY-NC 3.0

Apples and other fruits are undeniably healthy. They provide protein, fiber, vitamins, carbohydrates, and are lower in fat than many other foods. But they also have had some negative publicity in years past. Contamination of apple juice with arsenic has created concerns for many people.

News You Can Use

  • Arsenic is a small component of natural systems. This metal, either free or in combination with oxygen, can be found in the atmosphere, in water, and in soils. For some animals, arsenic serves as a trace element.
  • Arsenic is extremely toxic. Symptoms of arsenic poisoning include irritation of the stomach and intestines, decrease in lung function, and nerve and brain damage.
  • Exposure to arsenic can comefrom many sources. Many plants will absorb arsenic and pass it on to animals that consume the plants. Water contaminated with arsenic will produce high levels in fish.
  • Calculations determined that a possible safe dose of arsenic for humans is \begin{align*}15-25 \mu g\end{align*}. For inorganic arsenic compounds, lethal doses may range from 70-200 µg or so, depending upon the specific arsenic compound.
  • 50% of the arsenic produced in the world comes from China. The arsenic is recovered mainly as a side product from the purification of copper. 
  • Credit: Wikimedia
    Source: http://en.wikipedia.org/wiki/File:World_Arsenic_Production_2006.svg
    License: CC BY-NC 3.0

    Map of worldwide arsenic production. Arsenic is mainly produced in China and South America [Figure2]

  • The Food and Drug Administration (FDA) tests apple juice for arsenic. Upper limits for acceptable arsenic content have been set at 10 ppb for inorganic arsenic. Amounts above that level will result in administrative action by the agency. The same upper limits for arsenic content have been set for bottled water. In addition to apple juice, other fruits juices are currently been studied.
  •  Watch a video dealing with arsenic contamination of juice:


Show What you Know

Use the links below to answer the following questions.

  1. What type of arsenic was the focus of the new FDA limits on arsenic in apple juice?
  2. What is the EPA standard for inorganic arsenic in drinking water?
  3. When does acute arsenic poisoning occur in humans?
  4. What were arsenic compounds widely used for in the nineteenth century?
  5. How did Mithridates deal with his fear that someone would poison him with arsenic?

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Image Attributions

  1. [1]^ Credit: Abhijit Tembhekar; Source: http://www.flickr.com/photos/24340456@N03/3345977842; License: CC BY-NC 3.0
  2. [2]^ Credit: Wikimedia; Source: http://en.wikipedia.org/wiki/File:World_Arsenic_Production_2006.svg; License: CC BY-NC 3.0

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