One reason it was a health threat is it caused teeth to become ground down which would then lead to infections. The same was true with their eyes and lungs, sand would be blown into their eyes or inhaled into their lungs and then could cause infections.
Nationalism was a great cause of World War one because of countries being greedy and not negotiating. Nationalism shows you are proud of your country and want it to be the best. A lot of causes all linked back to countries all wanted to be better than each other.
The Natives have to use the trees for making houses and making pens for livestock. it is very bad for the rainforest and could disappear in a 5 million years to turn into grassland.
The difference is that one is fake material that didn't come from our environment and the other did.
HOPE THAT HELPED :)
