Spanish paralysis

Another strange idea:

When I had my mandatory Aztec course, they taught us that at that
time, Spanish x = sh and j = zh. Now of course they are both = kh.

Later, I was interested in what caused the Spaniards to behave the
way they did in the colonies. I dicovered that each year several tons
of mercury was carried in clay jars as return cargo in Spanish
galeons (both Atlantic and Pacific) to be used in gold mining
(amalgamation, roasting). One dropped jar, improper cleaning up (the
whole galeon should have been scrapped), and anybody on the ship,
sailing in the tropics for months, would be sure to be seriously
brain-damaged.
In addition to what this did to their spongy brains and minds, some
of the first signs of mercury poisoning is a slight paralysis
(clumsiness) of finger tips and tip of the tongue. This would attack
also the leading layers of Spnish society (since they used the ships
too).

Therefore sh, zh -> kh?

BTW, is this also why people are worried about those who
speak "guttural" languages (German, Klingon, etc)?

Torsten