With each down almost 3% Wednesday, the Market Vectors Oil Service ETF (NYSEArca: OIH) and the iShares U.S. Oil Equipment & Services ETF (NYSEArca: IEZ) are among a long list of exchange traded funds hitting 52-week lows.

Increased concerns that Halliburton (NYSE: HAL) will not be able to complete its acquisition of rival Baker Hughes (NYSE: BHI) is pressuring the oil services space. Halliburton announced a buyout deal of Baker Hughes for $34.6 billion back in mid-November 2014. The two companies are the second and third largest in the oil services space, and the merger would have helped the new firm better compete against the much larger Schlumberger (NYSE: SLB).

Shares of Halliburton are off 3.5% at this writing while Baker Hughes is lower by 8.3% on volume that is already more than quadruple the daily average after Bloomberg reported the proposed deal has met significant regulatory hurdles.

“Justice Department lawyers reviewing the proposed $34.6 billion transaction are worried that the oilfield services industry would become too concentrated after a combination of its No. 2 and No. 3 firms, said the person, who asked not to be identified because the review is confidential. Though Halliburton has proposed selling some assets to other companies, government officials aren’t convinced its plan would restore sufficient competition, the person said,” reports David McLaughlin for Bloomberg.

The $995.9 million OIH allocates a combined 22.1% of its weight to Halliburton and Baker Hughes. Baker Hughes, OIH’s third-largest holding, commands a weight of 8.71% in the ETF, more than 320 basis points ahead of Cameron International (NYSE: CAM), OIH’s fourth-largest holding. [A Look at the Merger Arbitrage ETF]

The $307.3 million IEZ has a combined Halliburton/Baker Hughes wait of 19%. Baker Hughes, also IEZ’s third-largest holding, is 8.53% of the ETF, well ahead of the 6.14% IEZ allocates to National Oilwell Varco (NYSE: NOV).