On one of the episodes in the 2nd season of House of Cards there is a white powder incident at the US Capital, causing a lockdown. In the episode, the lockdown lasts for hours while the powder is tested and ultimately revealed to be a mixture containing flour (wheat) and talcum powder. It was stated that pesticide on the wheat caused a false positive on initial tests, requiring the longer lock down of the area while confirmatory tests were performed.. There were several references to anthrax, which was actually released from an envelope in the Capital in 2001, in the dialogue.
White powder incidents abounded after the events of 2001 and still continue to this day--witness the Super Bowl's corn starch incident. What is often overlooked is the amount of law enforcement, public health, and clinical resources that are absorbed--and diverted from other functions--in the response to these incidents. Much like a bomb threat, a white powder incident can't be ignored as both anthrax and ricin have been sent in the mail.