Full Text
The Full Text of this article is available as a PDF (661.9 KB).
. 2004 Jan;112(1):A26. doi: 10.1289/ehp.112-a26b
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.