March . 29 ，According to the Reuters Report，Three companies that have purchased crude oil from the United States s now claim the oil contained unusually high levels of poisonous chemicals, according to Reuters.

　　Internal Energy Department emails obtained by Reuters show that Royal Dutch Shell, the Australian bank Macquarie Group, and PetroChina International America (the U.S. trading arm of a Chinese state-owned energy firm) have all been dissatisfied with the quality of oil purchased from the U.S. Strategic Petroleum Reserve (SPR). Shell oil trader Steve Sellers wrote that his multinational company was "unpleasantly surprised” to discover high levels of hydrogen sulfide (HS2) in oil purchased from the SPR, the world's largest government reserve.

　　High H2S incidents are rare in the crude world, but are typically caused by the blending of different crude grades. If one crude grade was placed in a barrel where a different crude grade has resided, contamination becomes a possibility. The Energy Department has declined to comment on the finding.

　　HS2 is a colorless, flammable, hazardous gas that naturally occurs in petroleum. It is detectable by its rotten egg smell. Decontamination before a sale is standard practice around the world, and not just because of the stink. HS2 can corrode pipelines and has a wide array of negative affects on people depending on levels exposure. According to OSHA, symptoms can range from nausea and loss of sleep to nearly instant death. ) 。

　　Initial tests run by Shell showed up fine, but further testing revealed H2S numbers running up to 600 parts per million (ppm), according to the Dutch-British company's emails to the department. OSHA says that levels that high could reduce a a grown adult to staggering and collapse within 5 minutes. 。

　　When a third party inspection group known as Inspectorate tested a sample from the SPR cargo purchased by the Australian Macquarie to be then sold to PetroChina, similar problems occurred. According to the Reuters-obtained documents, H2S levels of up to 9,000 parts per million (ppm) appeared. OSHA's warnings about H2S end at 2,000 ppm, where nearly instant death occurs. A terminal operator refused to allow workers to perform any additional tests out of concern about violating safety regulations.

　　Some crude grades can have H2S levels as high as 1000 ppm when produced, said Ramanan Krishnamoorti, chief energy officer and a professor of chemical and biomolecular engineering at the University of Houston. But producers remove most of that before transporting crude to customers.

　　Contamination could result from blending different crude grades, for example when one grade of crude is stored in a tank that previously contained a different grade.