Royal Dutch Shell's net profits almost halved in the first quarter, hit by a vast impairment charge on downstream assets, the Anglo-Dutch oil giant said Wednesday. Earnings after taxation slumped 45 percent to $4.51 billion (3.27 billion euros) in the three months to March, compared with $8.18 billion a year earlier, it said in a statement. The group also took a huge impairment charge of $2.58 billion on its downstream earnings, including impairments of $2.284 billion related to refineries in Asia and Europe. Shell added that profit on a current cost of supplies (CCS) basis or current-cost accounting -- which strips out changes to the value of oil and gas inventories -- sank to $4.5 billion from $8.0 billion. "As we saw in 2013, we are in an industry where high volatility remains, both in the macro-environment and in our quarterly results," said chief executive Ben van Beurden. He added: "The impairments we have announced today in downstream reflect Shell's updated views on the outlook for refining margins. "There are substantial pressures on the industry from excess capacity, changing product demand, and new oil supplies from liquids-rich shales." The London-listed energy major also revealed it would sell its downstream refining and marketing businesses in Denmark, adding it was also considering the sale of its marketing assets in Norway.