Death By Frack Oil?

Wall Street Journal:

The deaths of Trent Vigus and at least nine other oil-field workers over the past five years had haunting similarities. Each worker was doing a job that involved climbing on top of a catwalk strung between rows of storage tanks and opening a hatch.
There were no known witnesses to any of the men’s deaths. Their bodies were all found lying on top of or near the tanks. Medical examiners generally attributed the workers’ deaths primarily or entirely to natural causes, often heart failure.
But in the past few months, there has been a shift. Though still unsure of the exact cause of the deaths, government agencies and some industry-safety executives are now acknowledging a pattern and are focusing on the possible role played in the deaths by hydrocarbon chemicals, which can lead to quick asphyxiation or heart failure when inhaled in large quantities....
According to some industry-safety and government officials. The industry has been ignoring warning signs for years and has been resistant to implementing some steps that would reduce or eliminate the risk to workers.
“I was trying to get workers into respirators and all kinds of things and running an uphill battle,” said a former industrial hygienist for a large oil company who said he had noticed dangerously high hydrocarbon levels in some of his testing as far back as 2009. “They say, ‘Everyone does it this way.’ But that doesn’t make it any less right or wrong.”
The documented deaths date back to 2010, with six last year. Three were in North Dakota, three in Colorado, one in Texas, one in Oklahoma and one in Montana, according to the Centers for Disease Control, which first highlighted the pattern in May 2014. This year there was at least one death, in North Dakota. It’s still under investigation and may fit the pattern, federal officials said....
It’s unclear why these types of deaths were noticed only recently, and the cause is still under study. Unlike many previous oilfield deaths involving toxic fumes, the culprit doesn’t appear to be hydrogen sulfide, which has long been well-known in the industry as a hazard. Some experts have focused on the unusually high levels of certain hydrocarbons, including benzene, in the type of crude that is now common in the U.S....
Some industry and government experts say they believe the danger may be exacerbated in part by a recent environmental rule designed to protect public health.
In 2012 the Environmental Protection Agency enacted a rule that new oil-field tanks would have to capture hydrocarbons coming out of well sites rather than vent them into the atmosphere. As a result of the requirement, the same dangerous chemicals that had been emitted regularly were now more likely to build up pressure inside the newer tanks, industry and government scientists say....
Some industry experts say the industry knew the plumes could unleash potentially dangerous vapors and should have been monitoring the chemical levels all along. And, they say, companies could implement safety fixes that would reduce or remove hazards. One option is to use automated or remote methods to read tank levels. That is done regularly elsewhere, including in Canada.
“There’s no question in my mind it was absolutely known” that there were dangerously noxious fumes coming from the tanks, said Dennis Schmitz, a safety consultant for oil companies in North Dakota. “You are absolutely required to evaluate that hazard before you put that employee up there.”

I would wager that the main issue is that a lot of the fracked oil is actually condensate and natural gas liquids, which are much more volatile than traditional crude oil.  That is the reason why many refineries in the U.S. are not set up to handle the fracked crude, and it is also the reason why so many train derailments have led to massive explosions.  I bet it's why these workers have been dying.