Inhalation toxicity ricin/abrin

Griffiths, G.D., Rice, P., Allenby, A.C., Bailey, S.C., Scawin, J.W., Rice, P., Upshall, D.G. (1995a). Inhalation toxicology and histo-pathology of ricin and abrin toxins. Inhal. Toxicol. 7 269-88. Griffiths, G.D., Rice, P., Allenby, A.C., Bailey, S.C., Scawin, J.W., Rice, P., Upshall, D.G. (1995b). Protection against inhalation toxicity of ricin and abrin by immunisation. Hum. Exp. Toxicol. 14 155-64. 

Griffiths GD, Lindsay CD, Allenby AC et al. (1995b). Protection against inhalation toxicity of ricin and abrin by immunisation. Human Exp Toxicol, 14, 155-164. 

Ricin is most toxic when inhaled and is therefore a potential aerosol threat. However, large quantities would he needed to cause toxicity. Ricin is much less lethal when ingested, suggesting poor absorption. The toxicity and lethality of parenteral exposure to ricin are well documented. Abrin which is closely related to ricin in structure is extremely toxic with an LD50 dose for humans of 2 pg/kg. 

Abrin, a potent toxin, is extracted from the seeds of the rosary pea (Abrus precatorius). Due to its easy availability and preparation, this toxin is an attractive option for weap-onizing in poor countries, and thus has also been included in the Sch ule 1 of the CWC. The mechanism of action of abrin is very similar to that of ricin however, in mice, abrin is 75 times more toxic than that of ricin (0.04 pg/ kg for abrin is equivalent to 3pg/kg of ricin). Similar to ricin, inhalation of abrin is found to be more toxic than ingestion. However, abrin ingestion has reported to be toxic to the liver, unlike ricin. At the cellular level, abrin is a potent toxalbumin known to cause cell death by inhibiting protein synthesis (namely, type 2 ribosomal inhibitory protein). Further, abrin is also known to induce endothelial cell damage leading to an increase in cell permeability, fluid and protein leakage, and tissue edema. 

The toxins ricin and abrin cause widespread damage to DNA in the body leading to multiple organ failure. Until recentiy, it was thought that they could only be introduced into the body by an injection, but there are indications that they could be active by inhalation of an aerosol. Ricin can be extracted from castor oil plants and there have been reported attempts to do this by terrorist cells. Ricin is highly toxic and was used in the assassination of the Bulgarian diplomat Georgi Markov in London in 1978. At present, there is no specific antidote for toxic trauma caused by ricin. 

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