Privet hedge death
My privet hedge, has virtually overnight, been affected by something that appears terminal; following a day of rain large sections have turned brown. Leaves initially retained moisture and were firmly attached, drying now but not falling. On a major road hedge is 60+ years old and is regularly subjected to road spray. In addition huge increase in delivery vans parking off road next to hedge. Is this natural die back - any remedies, or possibly chemical pollution. All advice welcome.