What does “sub-lethal exposure” to pesticides mean?

The concept of "sub-lethal exposure" refers to situations where an organism is exposed to pesticides in a manner that does not result in immediate or severe illness. This means that while the exposure may not cause immediate adverse effects, it could still have potential long-term impacts on health or well-being. For example, an organism might experience subtle changes in behavior or physiological functions that are not apparent right away but could accumulate over time or affect its overall health or reproduction.

The other options refer to different conditions: immediate severe illness is associated with acute toxicity, harmless exposure implies no effects at all, and exposure only to non-toxic substances suggests an absence of pesticides or their effects altogether. Such distinctions highlight the importance of understanding pesticide exposure levels and their effects on organisms over different time frames and conditions.