-the burning of fossil fuel
-natural events
-waste in landfills
-agricultural activities
-mining operations
-etc
When you are scared and afraid?
A printable Snellen Chart, which you can download online.
Something to cover one eye at a time, like an eye patch or a paper cup.
Scissors.
Tape or tack to hang the chart on your wall.
Pencil or pen to record your results.