abominate
bacterium
biology
biomass
bottle
circle
clean
danger
dirt
dirty
disdain
ecology
engineering
environment
environmental
excremental
factory
garbage
global
industrial
industry
lake
nasty
natural
nature
ocean
plant
plastic
pollute
polluted
pollution
problem
processing
purity
recycle
reduce
resources
river
rivers
rot
rubbish
sewage
smell
toxic
trash
treatment
unhygienic
various
waste
water