Safety is relative; nothing is absolutely safe. Malathion is a level III which carrys the caution label.As a comaparison Rotenone is a level I (DANGER label) in liquid concentrates, but level three in dusts. Toxity to humans is higher than Malathion ( LD 50 of 300 mg per kilogram of body weight. Malathion takes in excess of 1000 mg per kilogram of body weight. For comparisons use the link

Here is a link that might be useful: Extoxnet

If you google "Malathion," you'll find the answers you're looking for. Below is a consolidation of medical research from various independent researchers (as opposed to the Chemical-industry's own research, which may be biased in favor of the substance being scutinized). You'll find these chapters:

Wildlife Photos - Photos of animals killed, organs damaged & mutations from malathion
ÂHuman Deaths from Malathion - 5 die and 2,800 poisoned after spraying in Pakistan
ÂIntestinal Disorders in Children - Take Note! this research does show significant public health problems after aerial spraying
ÂIntestinal Disorders in Test Animals - more evidence supporting intestinal defects in children from malathion
ÂLeukemia - Child leukemias develop after homes sprayed
ÂKidney Damage- Physician finds kidney damage after patient sprays home
ÂHuman Birth Defect - suspected from exposure to malathion lice shampoo
ÂBrain Damage - for unknown reasons malathion causes far more damage in older brains
ÂChromosome Defects - found in human blood cells
ÂGene Loss - malathion is able to literally "knock-off" genes from our DNA molecule
ÂReview of Malathion Genetic Studies - technically oriented - recommended for health professionals
ÂHealth Disorders found in Second Generation Offspring - evidence for harmful effects appearing in future generations
ÂLung Damage - unusual effect from malathion ingredient - not found in other pesticides
ÂBirth Defects - occurs in hens after malathion feeding
ÂImpurities in Malathion - highly toxic compounds increase during storage due to time and heat
ÂImmune System Weakening - thereby increasing risk of bacteria or viral infections (2 studies)
ÂSunlight Makes Toxic - malathion reacts with ultraviolet light to become more toxic
ÂImpurities Weaken Detoxification - impurities found to weaken ability of liver to detoxify
ÂBreakdown of Malathion - time periods for malathion breakdown in soil - forming of malaoxon
ÂFish Heart Defects - heart defects appear in exposed fish
ÂFish Gill Damage - low levels of malathion cause deterioration of Blue Fish gills
ÂTurtle Birth Defects - turtles unusually sensitive to birth defects
ÂFrog/Tadpole Mutations - evidence of genetic damage
ÂShrimp Effects - malathion at low levels affects a shrimp's ability to locate food
ÂLizard Organ Damage - small lizards suffer internal organ damage
ÂUnknown Risks of Malathion - Surprising information about what we do not know
ÂAlternatives to Malathion for Medfly Control - The best alternative to malathion to date (for Medfly control only) is called "SUREDYE." This highly researched product is a food grade red dye which kills the medfly after ingestion and reacting with sunlight. The advantages are it does its job without poisoning beneficial insects, wildlife, the environment or people!
ÂAlternatives to Malathion for Mosquito Control - Research shows that the natural pesticide "pyrethrum" has characteristics which make it especially effective for eliminating biting mosquitoes without harming the environment or public health. Visit this company's web site which is producing a viable alternative..

"A horticulturist told me some time back that malathion is the safest insectide on the market. Has anyone else heard this or have any information about it?"

Obrionusa, did you find the information you were seeking, and did you come to any conclusions?

Just wondered.....