Well, this would be one reason for a quick rinse with boiling water and throwing out the water. I don't use a full steeping, I personally just flash rinse to a level above the tops of the tea leaves in gaiwan or pot, and throw that out.
We all know that produce of any kind is going to be involved with pesticide use, unless specified when you buy it at a market of any kind. How do you clean fruits and vegetables before you prepare or eat them?
In another post on a similar subject, betta (whose research gives her expertise in these sorts of questions) says - if I understood correctly, betta may wish to correct me - that if the pesticide is organic substance then it may convert to other substance in a plant. Old-style pesticides like DDT may have done this. But most of modern pesticides decompose in the plant or upon long contact time with air.
That's my understanding of what betta has written elsewhere... betta can speak for herself much "betta" than I can!