(1) a. We stood up and left the house by [means of/using] the back door.
(1) b. He entered the house through the back door.
(2) a. All such grafts will die from lack of water.
(2) b. Farmers are losing crops for/because of lack of water.
(3) a. By conservative estimates, 2.5 million people [from] around the world die each year from smoking cigarettes.
b. The same thing that's happened in Ireland has happened all over the world.