Crude oil prices suffered heavy losses Monday, the first full trading day of August, as Greek and Chinese economic ailments dragged down demand prospects.

Brent crude oil prices were down more than 4 percent at the opening bell on Wall Street to $50.08 per barrel. West Texas Intermediate, the U.S. benchmark for crude oil prices, fell nearly 2 percent to $46.27 per barrel. Both indices are flirting with the low points for the year, down more than 50 percent from one year ago

Crude oil prices had recovered to above $60 per barrel in June as short-term data showed recovery underway in the U.S. and European economies. The Organization of Petroleum Exporting Countries, meanwhile, said in the last year it was keeping production levels steady amid expectations of increasing demand from Asian economies.

Re-emerging concerns about the health of the Greek economy, which cast a shadow of the last fiscal crisis, pulled crude oil prices back toward the $50 mark starting last month. After a five-week closure, the main stock index in Greece, the Athex, dropped more than 20 percent Monday, with four of the nation's lenders taking the brunt of the crash.

Two major crashes on the Chinese exchange last month, meanwhile, sparked formal economic action from Beijing. The Shanghai Composite closed down 1.1 percent Monday after four accounts were suspended for abnormal transactions.

The low price of crude oil is leaving consumers with more to spend on other items besides fuel. In a U.S. economy where the labor market is improving, however, the U.S. Commerce Department said wages were off from May.

"Wages and salaries increased $18.3 billion in June, compared with an increase of $32 billion in May," the department said.