2002 BMW 525 excessive exhaust fumes

I have a 525d which recently has staretd producing excessive white / blue exhaust fumes when it has been idling for a long while (say in trafiic jam) - these do nto seem to smell any different to normal exhaust fumes. It runs OK and had all new injectors and fuel pump in the last 2 years. Have checked coolant and does not seem to be contaminated. Does not seem to be using oil and ecomony is OK. Any ideas on possible problems?