Amnesty International believes that chemical weapons were used based on their own investigation [View all]
http://www.amnestyusa.org/news/news-item/syria-possible-international-armed-intervention-after-alleged-chemical-weapons-attack
Has Amnesty International found evidence of chemical weapons use in Syria?
Amnesty International has gathered information from survivors of the chemical weapons attack believed to have taken place in the Eastern Ghouta region, east of the capital Damascus, on 21 August, as well as doctors who examined those killed and treated those affected by the contamination. We have also shared this and other information about the alleged chemical release with specialists in chemical agents. Based on this research and the analysis by specialists, Amnesty International believes that it is highly likely that chemical agents contaminated several neighbourhoods in the adjacent towns of Zamalka and Ain Tarma in Eastern Ghouta.
According to the specialists consulted, symptoms exhibited by those affected by the alleged chemical release are consistent with exposure to organophosphorous nerve agents. These agents are part of compounds called cholinesterase inhibitors that prevent an enzyme responsible for nerve transmissions from transmitting messages effectively to the muscles, leading to reduced muscle activity. This prevents sufficient oxygen from reaching the lungs, leading to respiratory difficulties which, in severe cases, result in death. The reduced muscle activity caused by exposure to organophosphorous nerve agents also lead to involuntary muscle movements, including twitching and convulsions, and constricted pupils, all of which are symptoms that were exhibited by those present in Zamalka and Ain Tarma during the hours after the alleged attack.
More at link