I think the answer may be water pollution.
water pollution > Water pollution<span> is the contamination of </span>water<span> bodies (e.g. lakes, rivers, oceans, aquifers and groundwater). This form of environmental degradation occurs when </span>pollutants<span> are directly or indirectly discharged into </span>water<span> bodies without adequate treatment to remove harmful compounds.
source: Wikipedia </span>
The transition which could replace the word thus in this sentence is definitely consequently.
Workers bravely set dangerous explosives in the mountains by hand to make passes for railroads, and consequently hundreds lost their lives.
Can you please provide background information to your story? There can be no information created with the paragraph listed. Please let me know when you’ve done that and I’ll be happy to help!
If they're unlike things - it would be a metaphor.
When it comes to similes - you use words such as like or as when describing things. and since it emphasizes "unlike" things - metaphor would be the way to go.
It's quite hard sometimes when it comes for deciphering the two if you're familiar with the rule - so just remember: Simile: like or as.
Metaphor: extreme exaggeration, or a comparison without using like or as.
I hope all is well, and you pass! (: Good luck, rockstar! (:
