Here is a sketch of each.
Pyrethrin:
Pyrethrin is based on an extract from the Chyrsanthemum flower.
* It has very low toxicity to mammals.
* Oral ingestion can cause vomiting.
* Dermalogical exposure might cause irritaion that does not, in
general last for more than 24 hours.
* Pyrethrins do not cause irreversible central nervous system damage.
Malathion:
Malathion is based on organic phosphates.
* it is extremely toxic if inhaled (including vapors) and
> can cause resperatory damage
> can disrupt pulmanary function
> can cause diareah and vomiting
* if it is either inhaled or absorbed dermally, it may
> induce severe headaches and nausea
> cause central nervous system disorders
> cause hypertension
> induce seizures
* There is a danger of reabsorbtion.
> For instance, if you applied the pesticide with
leather gloves and the chemical got inside the
gloves, then you can continue to absorb the Malathion
dermally.
* It is a hazard to fish/wildlife.
Chris