White House spokesman Jay Carney revealed that a letter addressed to President Obama tested positive for ricin. It’s a nasty substance:
USA Today — The U.S. Secret Service is investigating a letter containing a “suspicious substance” that was addressed to President Obama, the agency confirmed on Wednesday, and at least three U.S. senators also reported receiving suspicious mail. FBI spokesman Paul Bresson said the letter to Obama tested positive for the substance ricin. The letter was sent to Obama on Tuesday, and was intercepted at the White House mail screening facility, according to Secret Service spokesman Brian Leary.
Ricin is toxic at the microgram level because it disrupts the ability of RNA to maintain and repair cells. It acts like a low abundance protein, actually it is a low abundance protein, just a deadly one rather than a helpful version. Other letters have also tested postive, one sent to Sen Shelby (R-AL). If those results are confirmed, this is not a partisan effort. It remains to be seen if these letters have anything to do with the Boston bombing.