You need to be careful when preparing root vegetables such as carrots, parsnips, potatoes and  leeks. This is because they often have small amounts of soil on them.  Even when they are shop bought vegetables will have traces of soil on that can contain harmful bacteria.  This could cause food poisoning if consumed.  You need to wash them thoroughly especially if they will be eaten raw.  Don't keep vegetables stored for too long and if they start to rot throw them away and do not eat them.