Sources please. Last I've learned in school, apple and especially Apricot seeds contain cyanogenic glycosides, which are hazardous to your health.

Be very careful. The Government and FDA are not to be trusted. They've spread lies about the seeds and actually banned them as being cancer treatment. Why? Money. They make loads of money when people by a life time supply of their pills that only treat cancer, not cure it. They lose all of this money if people cured their cancer by eating these seeds.
Now, how the seeds can do it? Apricot seeds has a lot of Vitamin B-17 which attacks Cancer Cells and kills them. Eating enough seeds per day will eventually lead to all of your Cancer Cells getting killed thus curing yourself. You will go into a comma afterwards due to lack of cells but you wont die. Your body will heal itself during this time and once you wake up, you will be healthy once again.
Actually, this guy cured his cancer. He did research on the seeds then begin eating a lot of them. After awhile, he was in a comma for 2 days and when he awoke, he went to the doctor and figured out his cancer was gone. He actually begun selling the seeds as a "cure" and had over 40,000 happy customers. But sadly, the FDA arrested him for some stupid crap they made up because they don't want to lose money. I think he was sent to jail for 20 years. (Off-topic, ik but this will be my last since I have no more to say)
~Edit~
Oh and yes. Apricot seeds does contain that stuff you've said but it is in a form that shows min risk of harming your cells. In other words, it rarely kills people.