You didn't say, but I think you meant to, that it affects people (and animals) exactly the same way as it does insects, only less so because people are bigger. Organophosphate pesticides can cause permanent nervous system damage with very little exposure and in my mind are not worth the health risk. In fact, they are more acutely toxic than the organochlorines (like DDT) that they replaced, but DDT was banned first because it builds up in the environment and damages ecosystems to a greater extent.
Absolutely. The effects on humans and other animals is
exactly the same as the effect on insects and other arthropods. The only difference is that it takes more to poison larger animals than it does to poison insects.
When they first came out, organophosphates were considered "safer" than the organochlorines because they're much less persistent in the environment and much less accumulative in the body. But their
effects in the body are accumulative: Continued sub-acute exposure to organophosphate insecticides before AChE levels have recovered can cause an acute poisoning event. We handled a lot of them back when I was with EMS in the 1980s when I lived in Central NY, mainly farmers who applied "moderately" toxic OPs like chlorpyrifos and malathion day after day, suffering no apparent effects, and therefore getting lax about exposure protection; and then one day -- BAM -- OP poisoning hit them like a bullet.
In addition, many chronic effects of organophosphates have been uncovered in the intervening decades (reproductive toxicity and probable carcinogenicity and teratogenicity, among others), mainly by looking at the health histories of pesticide applicators and their families. I'm glad the organophosphates as a group are being phased out for all but a very few uses.
All that being said, if someone who lives in an area where it's legal wants to
properly apply Dursban or Orthene around the exterior perimeter of their house to keep arthropod pests out, I don't lose any sleep about that. Applied and handled properly, there will be no actual exposure and little or no risk. Also, none of the alternative residual insecticides are risk-free, either, other than boric acid if you can get the insects to eat it; or maybe microencapsulated pyrethrum as a spray, depending on the formulation. Sometimes the "inactive" ingredients are more toxic than the "active" ones.
As for alternatives, the neonicotinoids are pretty low-risk to humans and mammals in general, but come with huge risks to non-target invertebrates, fish, and birds, in that order. They're also slower-acting against insects; but they do tend to eliminate entire nests of social insects like ants. Unfortunately, they also wipe out entire bee colonies if the foragers are exposed
The cyano-pyrethroids seem pretty low-risk as long as there's no drift or run-off, but most of them are also very repellent and scare off more insects than they kill (which may or may not be a bad thing). Deltamethrin seems to be an exception in this regard. It's not very repellent at all. I sometimes use deltamethrin dust up inside hornets' nests when they build them too close to the house for comfort. The returning foragers walk right over it like it wasn't even there. The nest is usually dead within an hour or two.
Back to safety, what it all comes down to is that there's really no such thing as a "safe" insecticide: but almost any of them can be used "safely." When applied correctly observing all safety precautions, there usually is no exposure, and therefore little or no health risk. The problem is that too many people either don't read labels or try to "improve" upon the label instructions, especially with OTC products, which they tend not to respect as "real" pesticides.
Personally, I usually treat the exterior of my home twice- or thrice-yearly, once in the early spring, and then again (if needed) in June and August. If there's no activity, I defer the subsequent treatments until there is. I use one or the other of the neonicotinoids as a crack-and-crevice treatment up under the siding around the foundation; a boric acid bait like Niban sprinkled around the perimeter; and a cyanopyrethroid (usually deltamethrin) behind the shutters and under the deck for the wasps. Anything else exterior, like hornets' nests, are only as-needed, and my thresholds are high.
I almost never apply anything at all
inside the house. It's almost never necessary if the exterior is thoughtfully treated.
Rich
