You convert decimals to percents by multiplying the number by 100 or by simply moving the decimal point to the right 2 places. This would make the answer .001%.
The place value of .000001 is one millionth
one millionth
.000001
1 millionths
Micro
One in a million
000001
.000001 = one millionth
one millionth
.000001
.000001%
Multiply by 10,000: 0.5 x 10,000 = 5,000 ppm