I see it like antibiotics - local usage probably pales in comparison to agricultural/industrial usage (e.g. sheep dip [1] and neonicotinoid usage [2] )
Yeah, I don't think dousing yourself with insecticide is all that dangerous unless you're doing it constantly like the agricultural examples above.
One can guess that the primary source of release of the chemical is not by rubbing yourself on things, but from washing your clothes. Thus, it would end up in the oceans.
When the alternative is Lyme Disease? I'm not giving it up. My cousin is severely affected by it right now, in her brain, affecting everything. It's awful.