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Due to the lapse in government funding, only websites supporting excepted functions will be updated unless otherwise funded. As a result, the information on this website may not be up to date and the agency will not be able to respond to inquiries until appropriations are enacted.

Updates regarding government operating status and resumption of normal operations can be found at

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Now that you’ve read through the information in this section, test yourself! See how much you’ve learned about the environment and how it affects your health.


Content last reviewed July 20, 2010
Page last updated October 31, 2013