There was scarcely time to process the fatal Boston Marathon bombings on Monday when the news broke late yesterday afternoon that a letter mailed to Republican Senator Roger Wicker had tested positive for ricin, one of the most potentially toxic and easily-synthesized poison substances in the world, which is extracted from beans of the commonly available castor plant. Recent reports indicate that other letters mailed to other government officials, including President Obama himself, may have tested positive for ricin as well.

"You can make it in your kitchen from a plant you grow in your garden."

People can be exposed to ricin through a variety of ways: inhaling the powder, ingesting powder or castor beans, or having it injected straight into the bloodstream. Absorption through the skin is rare. The symptoms and health effects vary depending on the route ricin was administered, including everything from coughing, nausea, diarrhea, vomiting, accumulation of fluid in the brain, low blood pressure, and potentially, death.

No injuries have been reported yet due to the letters reported this week, but the close timing of both the bombings and the ricin mailings to one another this week recalled the tense months after the September 11th, 2001 terror attacks, when letters containing anthrax, a separate bioterror agent, were mailed to several Congressmen and national media figures. But anthrax is much harder to make into a biological weapon, requiring a specific knowledge of biology and medicine. "The reason we keep seeing ricin used in bioterror is that you can make it in your kitchen from a plant you grow in your garden," Dr. Eric Toner, a senior research associate at the University of Pittsburgh Medical Center's (UMPC) Center for Biosecurity.

"Most ricin used in bioterror and biocrimes has not been effective."

Indeed, ricin has a much lengthier public history as a bioweapon, going back the 1978 murder of Bulgarian journalist Georgi Markov, who was killed after having a pellet thought to contain ricin injected into his leg. Since then, there have been dozens of incidents of attempted ricin poisonings against various victims, but few recorded fatalities, or even illnesses. That's because although ricin is lethal in its most potent forms, very few amateurs are able to extract and concentrate it to the point that it could cause death, or even severe illness.

"Most ricin used in bioterror and biocrimes has not been effective," Toner said. Although we still don't know all the details about the ricin mailing incidents this week, Toner cautions against overhyping the threat. "The fact that they [authorities] have been able to detect ricin does not mean there was a toxic amount present," Toner told The Verge.

"The stuff you make in your kitchen is not very potent or pure."

So despite the fact the instructions for making ricin are readily available to amateurs on the internet, and the poison has been featured as a recurring weapon in the hit drama Breaking Bad, making the poison itself in any significant dose to seriously harm or kill someone would require a chemistry lab, Toner said. "The stuff you make in your kitchen is not very potent or pure," he explained.

That goes doubly true for ricin being used as a type of letter attack: even as a powder, the individual ricin particles don't stay suspended in the air nearly as long as anthrax spores. "The notion that someone would get a toxic dose of ricin through a letter that they opened, via inhalation or absorption, is doubtful," Toner asserted. "Ricin isn't in the same category as other biological agents. We're much more concerned about anthrax, smallpox and ebola."

That's a good thing, all the more so because as of now, there is no US-government approved antidote for ricin, nor vaccine, although a vaccine is in development. Toner cautions against findings by other researchers that natural properties of milk and black tea may be effective defenses. "I'm sure none of that is based on strong science," he said. Instead, treatment for ricin poisonings includes general "supportive therapy" such as intravenous fluids and medicines to maintain blood pressure.

"The intent may simply be to cause havoc."

Without further details on who is behind the latest ricin attacks, and the precise method that was used to extract the ricin, it's tough to evaluate the physiological danger they may have posed. But the psychological effects of the attacks on society are fairly clear: panic and terror.

"Because ricin is very unlikely to kill anybody, that may not be the intent," Toner said. "The intent may simply be to cause havoc. People know they can do this and it will set off all sorts of alarms in the media, like we are seeing today."