Anchorage isn't notorious for bad air. But when it comes to one carcinogen, Anchorage residents might as well live in a Gulf Coast petrochemical corridor.
For decades, Anchorage has had some of the country's highest air concentrations of benzene.
Blame the chemistry of North Slope crude oil, which is naturally rich in benzene, and winter-weather conditions, like weather inversions and cold engine starts, for the unusually high outdoor concentrations. And blame the high indoor levels on the practice of storing solvents, gasoline containers and leaky vehicles in attached garages.
But some changes for the good are happening on the benzene front. Anchorage's main supplier of gasoline, the Tesoro refinery in Nikiski, has undertaken a series of multimillion-dollar projects to reduce the benzene in its refined product.
Benzene is a flammable, sweet-smelling hydrocarbon. It is trouble for people because high doses can cause cancer and respiratory problems like asthma. Even in low doses, benzene can impair the immune system by reducing white blood cell counts. Reports recently released by the city show that the amount of benzene detected in local outdoor air a few years ago didn't exceed federal health standards but the indoor air tested in dozens of homes did.
To keep legally selling gasoline, the Nikiski refinery is making roughly $140 million in upgrades to reduce the benzene content of the gas. Tesoro finished the first set of upgrades last year and will complete final upgrades before its July 2012 deadline, according to company officials. The federal Environmental Protection Agency mandated the benzene reductions at refineries across the country.
City public health officials recently predicted that the new benzene rule will reduce the amount of the carcinogen in local gasoline from about 5 percent to 1 percent. City health officials estimate that the amount of benzene in Anchorage air could drop by half.
According to federal air pollution data, an East Anchorage air monitoring site had one of the highest benzene concentrations of any such site in the country. Anchorage tested worse than a few Lower 48 cities that have high benzene levels due to industrial pollution. It tested slightly better than places like Port Arthur and Galena Park in Texas, both home to a number of refineries. That air data was collected in 2008 and it isn't comprehensive. Many U.S. cities do not have benzene monitoring.
Tesoro says local benzene levels should have declined already as a result of their first set of pollution reductions. The company built a new tower to separate chemical compounds in the crude oil that create benzene at the refinery. But so far no one has tested outdoor air this winter to see if benzene concentrations have dropped.
City public health officials say they hope to get federal money to pay for a local study to do more air monitoring and gauge the effectiveness of the EPA's rule.
Because the benzene content of Anchorage gasoline is several times higher than in most areas of the U.S., the city might see a fourfold reduction in benzene content after Tesoro's final upgrades. That's twice the decrease expected in other parts of the country, according to a city health department report published in December.
The report did not address benzene air concentrations in Mat-Su, on the Kenai Peninsula or in other Alaska locations that use North Slope crude. Federal air data for those places was not available.
NO HEALTH EMERGENCY
Even though outdoor air concentrations of benzene in Anchorage are much higher than at most of the country's other monitoring locations, local air typically doesn't exceed health guidelines.
On average, in 2008 and 2009, the outdoor air concentrations of benzene measured at the city's monitoring site near DeBarr Road and Lake Otis Parkway remained below the minimum health risk levels for chronic and short-term exposure to benzene. The testing happened 27 days during the winter.
Benzene in outdoor air is highest in winter. Over the testing period, the average benzene concentration was 1.7 parts per billion. A person would have to be exposed to a benzene concentration of 3 parts per billion for 365 days or longer to face health concerns, according to federal guidelines.
The benzene levels that seep into local homes from attached garages are much worse than those outdoors.
In a study published last June, University of Alaska Anchorage and city health department researchers disclosed that half of the 67 local homes they monitored in 2008 and 2009 exceeded the federal health guidelines -- 3 parts per billion -- to avoid harm from benzene exposures that last a year or longer. Roughly a quarter of the homes were just below and 10 percent of them exceeded the federal health guidelines -- 9 parts per billion -- to avoid harm from benzene exposures of 14 days or less. The risk guidelines were created by the federal Agency for Toxic Substances and Disease Registry.
City officials pointed out this week that they specifically targeted homes where, based on previous studies, they expected to find high benzene levels. They said testing the homes with the highest levels will make it simpler for them follow up with studies to determine whether the benzene reductions in gasoline are having a positive effect.
Researchers advised those residents on how to reduce their benzene exposure, said Anne Schlapia, an air quality specialist for the city health department.
Sometimes, it was as simple as putting a cap on a gasoline container or fixing a vehicle leaking gas vapors, she said.
"The interesting thing about indoor air that it is not regulated at all ... So it's up to people to take care of it," Schlapia said.
Ways to reduce benzene levels in your house:
• Do not store gasoline containers in attached garages.
• Weatherstrip the door between the house and garage.
• If you are doing a home improvement project that involves adding an exhaust-only ventilation fan, talk to an expert to make sure that you aren't drawing dirty air from the crawl space or garage into your living space. Perhaps the cheapest way to prevent that is to install fresh-air inlets inside the house.
By ELIZABETH BLUEMINK