SAN DIEGO - As we celebrate Tony Gwynn's life, there is a continuing scientific debate about the cause of his cancer.
Gwynn started using dip – or smokeless tobacco – in minor league ball in the early 1980s, always putting in in his right cheek. He used chew throughout his career and after retirement.
In 2010, he was diagnosed with cancer of the salivary glands. Two lymph nodes were taken out.
After a tumor was removed from his cheek in 2012, he talked to 10News.
"Think about the decisions you're making," said Gwynn. "Realize that when you make a wrong one, when you make a bad one, there's things you'll have to deal with later on."
A few years prior, the American Council on Science and Health had sent out a press release about his cancer, saying, "There is no evidence at all linking salivary gland cancer with smokeless tobacco."
Gwynn's response was he repeatedly said it was the cause, pointing out the cancer was in his right cheek.
"It's not proven so scientists will say it's unproven," said Georgia Robins-Sadler, the associate director of community outreach at UCSD Moores Cancer Center.
Robins-Sadler, the former president of the California division of the American Cancer Society, says there is no evidence of a link because the salivary glands cancer is rare and has not been studied enough.
"In the absence of evidence, you know that if you are putting something you know is cancer-causing in a warm place day after day, and someone has developed cancer there, then there is probably a causal relationship," said Robins-Sadler.
When Gwynn was first diagnosed, Major League Baseball banned players from putting tins in back pockets and using during interviews, but usage during games is still allowed.
Critics say usage by major league athletes is a main reason why 20 percent of high school boys use chew, according to a federal study.
Ronnie Trentham dipped for 12 years and then developed mouth cancer, leading to nine surgeries.
"I hope his legacy is to encourage his fans, young and old, to stop using tobacco or never start using it," said Trentham.
In 2011, Gwynn protégé and star pitcher Steven Strasburg quit tobacco after Gwynn's diagnosis but reportedly has since started using again.
About a third of major leaguers use chew. Chewing tobacco is banned in minor league and college ball.
The issue will come up for discussion again in the major leagues in 2016 when a new labor agreement will be hammered out.