Additional Resources
Teacher Notes
Scenario: What’s in the Countertops?
Teacher Notes
Student Handout
Discuss with your class the “granite scare” in which people were
Student Solution
concerned that their granite countertops were “radioactive.” This idea has
been in the news off and on over the years, for example the 2008 article
NYTimes Article
“What’s Lurking in Your Countertop?” that appeared in the New York
Times 1. Either print the article for your students and discuss student responses to the
questions in the worksheet included, or project/read the following description and discuss it as
a class without using the worksheet.
A granite shop owner is concerned over the recent “granite scare” that competing countertop companies
have promoted. People are afraid that granite contains dangerous levels of radioactivity; however they
still admire the beauty and durability of granite. To try to ease his customers concerns the owner of the
store posts a 24 June 2008 New York Times article about the situation, and decides to purchase a device
to measure the level of radioactivity (or activity) so that he can provide on-the-spot evidence to his
customers that the granite is safe. However he needs to figure out what measuring device to use, what
the device is measuring, how it works, and what these measurements mean to his customers.
How could the owner make his customers feel confident that the countertop they are purchasing is not
radioactive?
During the class discussion on this scenario the first thing that may come up is how to detect if
there is ionizing radiation present and how much of it is there. This leads to the technology or
tools used to determine if ionizing radiation is being emitted. Ask students if they know of any
measuring devices. The cloud chamber might be mentioned. If so, point out that it is probably
not sensitive enough and it is hard to quantitatively define the level of radiation with a cloud
chamber. Emphasize that a measuring device that can give a numerical “answer” would be
useful.
Discuss how to determine how much ionizing radiation is too much? Who decides how much is
too much?
The person in the story mentions that she was having her house tested for radon levels. She
assumed that her house may have had radioactive materials in it even before she knew about the
possible problem with the countertop. Ask students where they think this radiation is coming
from. Students should have a sense that there is background radiation almost everywhere
coming from the materials inside the earth itself and from the cosmos, but they may not grasp
this idea until later in the lesson. This background radiation is always present, but the amount of
background radiation depends upon the geology of your local environment as well as the manmade environment. Thus before being able to determine if a material you introduce into an area
is producing radiation at a dangerous level, it is also important to determine the background
radiation level. Students will measure the background radiation later in the lesson.
Let students know that the experts called upon to help address these questions are often health
physicists, environmental scientists, or engineers with expertise in nuclear science. They also are
aware of the state and national regulations and standards associated with exposure to ionizing
1
(http://www.nytimes.com/2008/07/24/garden/24granite.html
radiation. They are aware of the typical levels of background radiation as well as the levels of
radiation that are considered “safe.”
The student handout What’s in Countertops? can be given as a homework assignment if desired.
Note: The safety issues associated with ionizing radiation being emitted by granite countertops
has hit the national news several times in the past. When searching the internet to find out more
information about the issue, a large number of the sources found will indicate that all
homeowners with granite countertops should be very concerned while an even larger number of
sources indicate that granite countertops are typically quite safe. Typically, when a “breaking”
print or broadcast news story on the dangers associated with granite countertops is published, a
steady stream of follow-up stories are published showing that the “science” behind the original
story is often faulty. The story behind the granite countertop story is as interesting as the science
and can serve as a teaching moment on both good research (just because you find it on the web
doesn’t mean it is accurate) and good science (just because a scientist is interviewed for a story
doesn’t mean the story is accurate). We’ve chosen to focus on the NYT article because it is
reasonably balanced.