Actually wooden cutting boards are safer than plastic ones because the plastic ones not only result in lots of plastic particles being dislodged while cutting but also the cuts into the board are harder to clean and result in a higher likelihood of contamination.

Wooden boards need to be maintained, however, which with frequent use means occasionally sanding them down a bit in addition to the usual cleaning and oiling. The problem with wooden boards is mostly that they're not dishwasher-safe and people are too lazy to clean them properly by hand. A plastic cutting board you regularly put in the dishwasher is probably safer than a wooden one you only half-heartedly rinse, at least in terms of contamination.