Hi, David,You are right about "worth". To deserve is to merit (similar to your Spanish word "merecer" - I think that �s right), and worth is value.
 
I deserve a raise.
Behavior like that deserves some punishment.
 
My house isn �t worth $150,000.
 
Pollute and contaminate are very similar, and can often be interchanged. I think of pollute as being bigger or more general in its results.
 
That factory is polluting/contaminating the environment.
The small difference I sense is that contaminating has the feel of contributing a single item (CO2, lead, etc.) into the environment, while polluting is a more general dirtying. It �s more a difference in how the words feel to me than in their actual definitions.
 
Be sure to wear gloves so you don �t contaminate the blood sample. (not pollute).
 
If you leave the potato salad out in the sun, it will become contaminated with salmonella. (not polluted).
 
I hope this helps,
Bruce