Formaldehyde is a highly reactive molecule that can be directly irritating to tissues with which it comes into contact. Human and animal studies indicate that formaldehyde, at certain exposure levels, can be irritating to the upper respiratory tract and eyes with inhalation exposure, to the skin with dermal exposure, and to the gastrointestinal tract with oral exposure. Formaldehyde-induced noncancer and cancer effects appear to occur only at portals-of-entry (i.e., upper respiratory tract, gastrointestinal tract, and skin).
Maritime trade is when you trade by sea and boat. They had ports that people sailed in and out of. The other civilizations used these ports as well, in the Afro Eurasian zone. The concept of having ports has carried into the modern age as well.
The final major factor that contributed to the Renaissance was the rise of city-states in Italy. At a time when most of Europe was rural, agricultural, and manorial, Italy was much more urban and commercial.
