How much benzene is too much in oil spills? 

Absence of clear federal guidelines and long-term studies make oil fume threats hard to determine. But Arkansas's safety level far exceeds one national measure.

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Since 2010, at least three ruptured pipelines have spilled oil and fouled the air in U.S. neighborhoods, forcing officials to decide quickly whether local residents would be harmed by breathing the fumes. But because there are no clear federal guidelines saying if or when the public should be evacuated during an oil spill, health officials had to use a patchwork of scientific and regulatory data designed for other situations.

As a result, residents of the three communities received different levels of protection.

No houses were evacuated in Salt Lake City, where a ruptured pipeline leaked 33,000 gallons of medium grade crude oil before it was discovered on the morning of June 12, 2010. The oil ran down Red Butte Creek, past neighborhoods where windows were left open in the summer heat. The fumes, which are known to cause drowsiness, left some people so lethargic that they didn't wake up until after noon.

In Marshall, Mich., officials called for a voluntary evacuation after more than a million gallons of heavy Canadian crude spilled into the Kalamazoo River on July 25, 2010. But they agonized over the decision for four days before making that recommendation.

In Mayflower, authorities quickly evacuated 22 families after a broken pipeline leaked what ExxonMobil said was 200,000 gallons of heavy crude on March 29, 2013. But people living in the same subdivision, just a few blocks away, were not asked to leave. Neither were the residents of the lakeside community where the oil eventually pooled and where the cleanup continues today.

After each of these spills, people complained of headaches, nausea and respiratory problems — short-term symptoms that health experts say are common after any chemical spill and usually disappear as the air clears.

What health experts don't know, however, is whether the fumes could also trigger long-term health problems that become evident only years or decades later. That gap will be increasingly important, because over the next few years the industry plans to build or expand more than 10,000 miles of oil pipelines — including the Keystone XL.

Many of these pipelines will go through or near populated areas. For instance, the Michigan pipeline that ruptured in 2010 — Enbridge Inc.'s line 6B — is being replaced with a larger line that will pass so close to some homes that one family is losing part of its back deck.

But despite the pipeline boom, there are no plans to conduct long-term health studies in Mayflower, Marshall or Salt Lake City. There also doesn't appear to be any momentum to set federal guidelines for chemical exposures at oil spills to better equip health officials for future emergencies. 

"The key question that people have — 'Will I be affected 20 years later given my two-week exposure' — is something no one can answer," said Judi Krzyzanowski, an environmental consultant in Ontario, Canada, who studies air pollution from oil and gas development. "If people in Mayflower develop cancer five years from now, it will be nearly impossible to point a finger at the oil spill." 

Crude oil typically contains more than 1,000 chemicals, many of them hazardous to humans. Of particular concern is benzene. Small amounts of benzene from car exhaust and cigarette smoke are commonly found in the air. But increased exposure is known to cause leukemia and neurological problems.

Despite decades of research, it's difficult to determine exactly how much benzene is too much. Although the federal government offers dozens of guidelines for benzene concentrations in air and water, each comes with different caveats and none is designed for oil spills in residential neighborhoods.

The federal Agency for Toxic Substances and Disease Registry (ATSDR), for instance, estimates that people can be exposed to air containing 9 parts per billion (ppb) of benzene for up to two weeks, or 6 ppb for up to a year, without a "likely" increase in harmful health effects. But those guidelines don't cover the risk of cancer, and they are "not intended to define clean up or action levels for ATSDR or other Agencies," according to ATSDR's website.

Speaking of Mayflower Oil Spill, ExxonMobil


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