You can even buy it for a dollar per gallon at your local grocery store!
And there are few regulations against just dumping it on the ground or in our rivers and streams. In fact, chemical plants dump the chemical into our waterways every day!!
When indiscriminately dumped on the ground, it has a high likelihood of being absorbed into the local ground water.
DHMO is a common contaminant in the exhaust stacks of power plants yet is completely unregulated. Industrial plants vent it and leak it on the ground as a matter of normal operation. (don't even get me started on cooling towers)
In larger volumes, it can support microbes and bacteria that are harmful to public health.
It often mixes with salts and can lead to corrosion of metals.