Squiggle, I'm not surprised by that plant cover being blown off as it's very windy here.
I didn't know that mustard gas was used in chemo but knew that chemicals which are poisonous can also be used for medical treatment, a well know one being warfarin used for vermin control and for preventing blood clots in people. The key difference being that in warfare the gas was/is used indiscriminately but the compound as used for your chemo would have been very carefully administered, monitored, and much smaller in quantity,