Crumb rubber is made from shredded tires and is used in soccer fields all over the country. The turf is especially popular in Seattle because the tires get recycled and the reliable surface can stand up to soggy weather.
But one local coach sees a troubling connection between the turf and cancer among soccer players.
Soccer runs in the blood of University of Washington assistant coach Amy Griffin. She started playing goalie as a child, and now helps UW goalies stay fit and improve their skills.
Griffin's always searching for new talent and keeps a list of top players. But one list of names isn't about recruiting. On it are 13 players from Washington who have all been diagnosed with rare types of cancer.
Of those 13, 11 come from an even smaller pool of players: Goal keepers.
"Everyone says it's just a coincidence and kind of walks away, but the ratio of goal keepers to field players is 15 to 1, 16 to 2, and I know plenty of goal keepers that have cancers and I don't know many field players," Griffin said.
Griffin said she can't walk away from what she's discovered, and she's not alone. Former professional goalie and reality TV star Ethan Zohn, who has twice beaten non-Hodgkins lymphoma, had been keeping his own list, which he has now handed over to Griffin.
Combined, the lists name 27 players with cancer, and 22 of them are goal keepers.
Griffin can't say why goalies are getting cancer, but she wonders if it's the field turf and the crumb rubber used to make it. She said goalies spend a lot of time on the ground diving for balls, blocking shots and sometimes ingesting the small rubber pellets.
"I lived in the stuff," former UW goal keeper Jorden Alerding said of the turf. "Four to five times a week I was on it for hours -- bleeding sweating, everything. Looking back now I wonder could that have been the cause."
Griffin's first brush with the unproven connection between cancer and the pellets came when she visited Alerding, who was being treated for cancer.
"She said, 'I just think it's something with the field turf. I don't know what it is, but I think there's something in those black dots,'" Griffin said.
The former Husky was diagnosed with non-Hodgkins lymphoma during her freshman year of college when doctors discovered a large, deadly tumor.
"It was about the size, a little bigger than a softball, right in the center of my chest," Alerding said.
Alerding is now cancer free, but she still questions the health effects of crumb rubber and the lack of further research.
"If this can be prevented, I don't know why there isn't more effort being made to do the research and find out," she said.
The pain is still fresh for June Leahy. Her daughter, Austen Everett, a star goalie for Seattle's Blanchet High School and later the University of Miami, died a year and a half ago.
By the time Everett lost her second battle with non-Hodgkins lymphoma, Leahy was raising questions about the use of crumb rubber on soccer fields.
"I feel like there is a strong correlation with the turf," she said.
This isn't the first time people have raised concerns about the turf, either. In 2008, a goal keeper at Tacoma's Stadium High School battled Hodgkins lymphoma. Back then, Luke Beardemphl and his family wondered if crumb rubber had played a part in his cancer.
"I'll catch it. It'll stop the ball but not the pellets. They'll go into my face, go into my eyes, my mouth," Beardemphl said in 2008.
Earlier that year, the US Consumer Product Safety Commission tested some blades of grass used in synthetic turf for lead. The commission found they did not contain enough of it to put children at risk.
The agency later stated that its "exposure assessment did not include chemical or other toxic metals, beyond lead."
Tires do contain metals and chemicals that have been ruled too toxic to burn in Washington state. The average athletic field uses 27,000 of them.
So, can prolonged exposure to the fields make people sick? The Synthetic Turf Council says no.
The president of the trade organization was unavailable to talk about this story, but the group directed us to a statement on its website.
"For 40 years, under EPA oversight and OSHA- regulated manufacturing, not one person has ever reported ill effects related to any materials associated with synthetic turf," the statement reads.
Those statements and tests cannot shake loose the feeling Griffin gets every time she learns the name of another goal keeper with cancer.
She also knows that feelings and suspicion do not equal evidence.
The team's head physician, Dr. John O'Kane, says the concern is valid and has talked with Griffin about the need for scientific and medical research on the effects of crumb rubber.
He said Griffin's list is only a starting point.
"The question you would need to ask is over that same time period, how many goalies are there that haven't gotten cancer?" O'Kane said. "And until you understand that number, you really can't interpret that there's anything particularly dangerous about being a goalie when it comes to cancer."
O'Kane said that kind of research could take years. Griffin hopes someone is willing to take on the work to provide her with an answer. She said any answer will do.
"I would love for it to be disproven or for someone to grab me by the throat and say,'These are the facts. This is why it could never be this. This is just happenstance.' That would be great," she said.
One one former Husky -- Alerding -- is on Griffin's list.