From what I remember of this when it first hit the news the aim of the study was to assess the exposure of children to household pesticides - NOT to deliberately expose them to such. If you want the data it has to be collected - low income families are more likely to live in infested premises which are more likely to have household pesticides used in them - they give a worst case group to assess exposure against.
If I've got it wrong excuse me but I'm dragging this out from an old memory!
Pete
God is our guide! from field, from wave, From plough, from anvil, and from loom; We come, our country's rights to save, And speak a tyrant faction's doom: We raise the watch-word liberty; We will, we will,we will be free!