Read the label to rule out PCBs. Some ballasts specifically say they contain no PCBs. This is the only way to determine that your ballast does not contain PCBs. Because many ballasts do contain the hazardous compounds, assume they are present if the label does not specifically say "no PCBs."
See if your ballast is electronic or magnetic by checking the label and observing the type of light fixture it was in. Electronic ballasts are newer technology and found in T5 and T8 fluorescent light fixtures and in retrofitted T12 fixtures. Electronic ballasts do not contain PCBs or any other hazardous materials. Magnetic ballasts, on the other hand, are outdated technology and commonly contain PCBs.
Check the ballast's manufacturing date. If you know the ballast was installed or manufactured before 1978, it most likely contains PCBs. Ballasts were commonly produced containing PCBs before their ban in 1978.