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QuickTake:
Regulators have known about dioxin contamination at Trainsong Park for five years, putting up fences to reduce exposure and keep health risks low. Cancer risks at Trainsong Park most likely could show up for older adults who played there decades ago, before the fences went up. But no clinical guidelines exist to tell doctors, or residents, how to address health concerns.
The polluted soil at Trainsong Park in west Eugene goes deep and wide, with the highest concentrations surrounding the playground.
In fenced-off areas lie dioxins — a group of chemicals that, at high levels, can increase the risk of cancer in people exposed to them, according to decades of research. This pollution pushes the limits of Oregon’s law that governs “acceptable risk level” of hazardous substances and public health, triggering cleanup at the park.
The city estimates estimates 6,600 people visit Trainsong Park each year.
The location of Trainsong Park in West Eugene
Low levels of dioxins can occur naturally, but government agencies believe those found at Trainsong Park were imported before the city of Eugene purchased the site in the 1980s.
The Oregon Department of Environmental Quality (DEQ) discovered the contamination in 2021 while sampling in shallow soil across west Eugene to understand the extent of pollution at J.H. Baxter & Co., a wood-treatment facility about a mile away that used chemicals linked to dioxins.
During a May public meeting, a parks employee announced that after more testing, the contamination is more extensive than first known, with so much toxic soil that it could fill 800 dump trucks.
Since then, Lookout Eugene-Springfield has sought to understand the health risks of the pollution through multiple rounds of questioning and interviews with DEQ, the city and Oregon Health Authority.
Nearly two months later, the most general answer is: People who stay out of the fenced-off areas of Trainsong Park do not face an increased risk of cancer. For those who came into contact with the soil before the fence went up, the picture is less clear.
Cancer risks from dioxins do not usually become apparent until decades after the period of exposure, according to Oregon Health Authority toxicologist David Farrer. In what he called “the unlikely event” of someone getting cancer from exposure to Trainsong Park’s dioxins, “it would most likely show up in an older adult who had played in the park as a young child.”
Below are the questions Lookout has asked regulators and health officials — what’s known and what isn’t, in plain language, along with some of the numbers that define risk.
Who is most at risk at Trainsong Park?
Environmental scientists and consultants for the city of Eugene found that dioxins at Trainsong Park stick to soil rather than dissolving into groundwater or becoming airborne. That means the risk is contained to the soil, and those in direct contact with it.
The population most at risk is children who play, or have played, in the soil, said Farrer and DEQ toxicologist Kaley Major, in an July 1 interview with Lookout Eugene-Springfield.
Compared with adults, kids are less likely to wash their hands — and as any parent knows, they tend to put their hands, and sometimes even dirt itself, in their mouths.
“That’s really the reason I think the fences are up, but basically anyone spending a lot of time in direct contact with that soil, ingesting it, inhaling it, dermal exposure (skin contact), and things like that. Those people are going to be at the greatest risk,” Major said. “The risks are mostly an increased incidence of cancer.”
“People who have been exposed in the past, before this (contamination) was really known about, before the fences were up, would have those risks,” Farrer said.
What are the cancers associated with dioxins?
According to Farrer, and an appendix he pointed to in a 2024 Oregon Health Authority health consultation report about J.H. Baxter, dioxin exposure has been linked to:
- Blood cancers like leukemia and lymphoma
- Thyroid cancer
- Liver cancer
- Oral cancers
- Prostate cancer
Research can’t identify whether dioxin makes any one type of cancer more likely than another. The clearest pattern in human studies is a general increase in cancer risk overall, not a link to a specific type, Farrer said.
Why does a J.H. Baxter report help explain Trainsong’s cancer risk?
There’s no proof linking J.H. Baxter to Trainsong Park — but no evidence ruling it out, either.
Erica Lindquist, Oregon Health Authority spokesperson, said health risks from dioxins are the same regardless of source.
“It is the amount of dioxin exposure – not the source – that determines health risks. Dioxins are the main chemical of concern for both J.H. Baxter and Trainsong Park,” she said in an email.
What is the guidance for those exposed?
There are no standard medical tests for dioxins in the human body, nor clinical guidelines for doctors whose patients may be concerned, according to Farrer and a senior investigator with the National Cancer Institute.
Rena Jones, a researcher in the institute’s division of cancer epidemiology and genetics, spoke with Lookout Eugene-Springfield generally about dioxin contamination and health.
She pointed to other environmental hazards, like lead and PFAS (a group of long-lasting chemicals), where studies connected a specific exposure level to harmful health effects. Those studies helped drive policy and recommendations, guided by the federal Centers for Disease Control and Prevention or groups like the American Academy of Pediatrics.
For dioxins, an exposure level connected to harmful health effects doesn’t exist.
Researchers who have measured dioxin levels in people across the United States have found that most people carry measurable, low levels of the chemicals in their bodies, because low levels of dioxins are common in the environment. Additionally, researchers face a logistical challenge of tracking people’s health outcomes over the many decades needed to understand long-term effects.
So while an individual can ask for tests to determine dioxin levels in blood samples, once results come back to them or their doctor, “there’s no sort of guidelines around what to do with that information,” Jones said.
“It’s perfectly understandable that people living in the community or who may have had contact with contaminated soil in that area would be concerned, because there are some dioxins that are known to cause cancer,” Jones said.
“Whether we would be able to make a direct connection for an individual potentially exposed to their specific cancer is not likely,” she said. “And I realize how unsatisfying that is to an individual.”
Defining an ‘acceptable risk level’
Oregon statute (ORS 465.315) sets an “acceptable risk level” as “a lifetime excess cancer risk of one per one million people exposed.”
“Excess” refers to additional cancer cases that someone may already develop in their lifetime from causes like age, genetics or lifestyle.
In assessing the risk at Trainsong Park, toxicologists at the Department of Environmental Quality and the Oregon Health Authority identified that the amount of dioxins corresponding to this risk level is 20 parts per trillion. (Parts per trillion is a unit for measuring extremely tiny amounts — about the equivalent of one drop of water in 20 Olympic-sized swimming pools.)
The most polluted pocket of the park is 360 parts per trillion, corresponding with a risk level of 20 cases in 1 million.
But these figures are a probability, not an actual count of real cases. Trainsong Park doesn’t see anywhere close to 1 million visitors, so the number isn’t describing an actual group of people who were measured or counted. Instead, it’s a rate regulators use to measure and compare risk.
Understanding the numbers for scale:
- 100,000 people is a little more than half of Eugene’s population.
- The highest dioxin reading in the park works out to nearly 2 additional cases for every 100,000 people who fit DEQ’s worst-case exposure scenario.
- DEQ’s worst-case exposure scenario is someone would have to ingest 200 milligrams of soil per day — the size of a large pinch, or what may collect under fingernails — for 84 days a year, over 26 years.
While these numbers and models exist to help direct environmental cleanup, they can’t determine whether any specific case of cancer was caused by exposure to dioxins from Trainsong Park.
What’s next?
Residents will have to wait at least another year before cleanup begins.
According to planners in the city’s Parks and Open Space Department, the contaminated soil won’t all be hauled out. Rather, they are weighing cleanup options that are a mix of excavation and containment, removing soil in some places and capping it in others to keep it buried.
Planners are finalizing cleanup designs and plan to return to the community later this year with more details. Construction is expected to begin in spring 2027 and take about 13 weeks to complete.
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