Sarin
Sarin is very dangerous, whether someone touches it or breathes it in. The LD50 of sarin is 172 μg/kg. This means that a group of people were injected with 172μg of sarin per kilogram of body weight, 50% of the people in that group would die. This was determined when scientists injected mice with sarin. They then did calculations to determine the ratio of sarin per kilogram and get the LD50.