 Some reported that the chemical used was adamsite, a yellow-green arsenical chemical weapon that can cause respiratory distress, nausea and vomiting.In April 2014, Amnesty International worried about "the use of chemical toxins in high concentrations” by government forces and recommended better training for them.A study by Mónica Kräuter, a chemist and professor, involved the collection of thousands of tear gas canisters fired by Venezuelan authorities in 2014.