THE DALLES, Ore. – The Oregon Health Authority has determined that air near a railroad tie plant in The Dalles is safe for people to breathe, despite numerous residential complaints of health problems.

Several residents living near the Amerities plant in The Dalles have complained for years about health concerns stemming from the emissions released by the plant. Amerities uses a creosote mixture to treat wooden railroad ties, and then dries the pieces of treated wood in an open lot near downtown The Dalles, which is at the eastern end of the Columbia River Gorge.

The creosote emits several substances called polycyclic aromatic hydrocarbons (PAHs), which in high levels are known to cause cancer and other health problems.

One of those PAHs, naphthalene, is easily detectable in the air as a mothball-like odor. What residents haven’t known is whether the general level of naphthalene and other substances in the air they breathe is enough to harm them.

On Tuesday, the Oregon Health Authority released a report that found the air pollutants don’t pose chronic public health risks. The OHA said the odors, however, could still cause reactions in some people.

"Some health problems may be related to odors. We know that odors can cause immediate, strong physiological responses," said Susanna Wegner, public health toxicologist with the OHA.

The report was based on Oregon Department of Environmental Quality-led air monitoring that took place in the summer of 2016 and 2017. The monitoring found that naphthalene levels at the Wasco County building, which is near the plant, were on average 2.6 micrograms per cubic meter in 2016 and 1.2 micrograms per cubic meter in 2017.

OHA says cancer risk for naphthalene increases over a person’s lifetime if naphthalene levels are higher than 0.03 micrograms per cubic meter. The average naphthalene levels in a city center is usually around 1 microgram per cubic meter, due to asphalt, gas emissions and other sources.

OHA says acute health problems would happen immediately if people breathe air that has more than 200 micrograms per cubic meter of naphthalene. The federal Agency for Toxics Substances and Disease Registry has set the “minimal risk level” for naphthalene at 3.7 micrograms per cubic meter. Since the monitoring found air that was lower than the ATSDR risk level, OHA determined the air is safe for residents to breathe.

OHA hasn't historically had a benchmark for naphthalene between 0.03 and 200 micrograms per cubic meter, so by adopting the ATSDR minimal risk level they have set a middle-ground benchmark for naphthalene in the state.

Although the overall naphthalene levels in The Dalles were lower than the minimal risk level in the 2016 monitoring, several days had levels that were far higher, with several days recording levels between 4 and 5 1/2 micrograms per cubic meter.

The air samples were taken over 24-hour periods, which included times that Amerities was operating and times the plant was not treating ties.

KGW has reported on residents’ complaints of health problems, including migraines, nausea and vomiting. Officials have not directly linked any residents’ health concerns to Amerities emissions.

Some residents have filed a $20 million class action lawsuit against the tie plant, alleging the strong odors have interfered with their ability to fully use and enjoy living in their homes.

Amerities continues to operate with a valid DEQ air permit, which allows the plant to emit three times as many PAHs as it currently does and remain within the legal limit.

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