Question from Lisa
Dear Debra,
I live in an area where people do not want dandelions or other common weeds in their yards, and spray chemical pesticides and herbicides to kill them.
I see the chemical lawn application signs everywhere, warning to stay off the grass for 24 to 48 hours.
The signs themselves have the poison sign right on them, and warn particularly that children and pets should avoid the area.
I’m just wondering, how long would it take for this area to be safe? I try to avoid the sidewalks where they spray, but then I find I can’t get outside to enjoy the outdoors or go for walks.
Also, I wonder if any of these chemicals become airborne as the water they are mixed with evaporates.
Debra’s Answer
Well, if the sign says stay off the lawn 24 to 48 hours, then it probably takes 24 to 48 hours for the area to be safe.
There is a difference between how long it might take for the lawn to be safe and how long it takes for the surrounding air to be safe. The pesticide will sit on the lawn until it breaks down or is washed away. Pesticides in the air immediately after application will blow away from an area much faster, depending on the rate of air movement. Even if the air seems still, a particle in the air will still move (note that bubbles move even when the air is still). How soon after application the air will be safe to breathe depends on the rate of air movement at any given time–obviously if a hurricane is blowing through, the pesticide would be gone in seconds.
I would keep windows closed while the spraying is occuring. Do they spray on a schedule? Is it possible to find out that schedule? Could you be away from home when they are spraying? Could you go for a walk elsewhere while they are spraying?
Yes, the chemicals probably become airborne as the water they are mixed with evaporates, but whether they are a problem or not depends on the ambient air flows, as I already mentioned above.
