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acid
carbon
chemicals
close
closeup
contamination
cyanide
danger
dangerous
dioxide
disaster
disposal
earth
ecological
ecology
environment
environmental
fuel
global
hazard
hazardous
hydrogen
impact
industrial
insecticide
mask
mercury
metals
pesticide
petroleum
plastic
poison
poisonous
pollute
pollution
problems
protective
recycle
research
responsible
scientist
sign
skull
suit
symbol
toxic
toxicology
up
waste