You should wash it (after you grate it) and squeeze out as much of the liquid as possible, that removes most of what is harmful, and cooking (heat) takes care of the rest.
Ema jaana ka mereo ya gago, le bontsi jwa ditoo tsa gago, e le dilo tse o sa leng o itapisa ka tsone le mo bokaung jwa gago; ya tla ya re gongwe wa bona thuso, e ka tla ya re gongwe wa fenya.