Are there dangers to humans from PCB/Circuit Corrosion?
The green/blue substances are, as already noted by Andrew and Rev1.0, copper and or nickel compounds.

But to have them grow to such size there have to happen heavy corrosion processes which usually take place in presence of water and electrolytes.

The brown sediments usually are corrosion byproducts from different metals like iron. 

Also already mentioned is the fact that old PCBs contain roughly 30% lead in the solder points which is automagically released into similar crystalline products. So the green and brown stuff will be contamined by lead compounds. 

Anorganic heavy metal salts like those colourful crystals don't tend to evaporate. So you probably are safe if you only look at them. Incorporation could take place, if you touch those salts and either keep remnants on your skin for a prolonged period or by ingestion when you touch your face or food with dirty fingers. So take care to wear simple safety gloves when handling.

If you want to dispose of those parts ask for companies specialised in handling electronic waste.

If you want to salvage those things you may want to clean them to reduce the risk of possession and handling. Cleaning could take place with deionized water and an ultrasonic cleaner several times and washing with Propan-2-ol (aka isopropylic alcohol) afterwards. This probably has to repeated several times. The washing byproducts have to be disposed of by companies for handling chemical waste, as they pose an environmental risk. Heavy metal salts are of high aquatic toxicity, so you should not put it down the drain. 

After cleaning the circuits have to be stored dry and perhaps can be protected with a conformal coating from future corrosion.