Urea, not urine. Big difference. I handle and use pure urea in the gardens, it's fast acting, very water soluble, inexpensive, and scentless.
Humans (and other animals) produce it because it's a great, biochemically cheap way of jettisoning the extra nitrogen we get in our diets. The LD50 is incredibly high, and you can intake a huge amount of urea without any harm.
Commercially used urea--and the uses are legion--is cooked up wholesale in the factory, never saw a kidney, and is far more pure than anything you ever produce. The piddling, cheap fertilizer grade urea in my garage is 98.5% pure, with the other 1.5% mostly being biuret, two urea molecules bound together.
There's every reason to knock cigarettes, but that isn't one of them. It'd be like criticizing tobacco growers for spraying their plants with water...which is a component of urine, and therefore must be dangerous.