State health officials urged Ashland residents yesterday to consult a doctor about possible cancer risks if they swam or waded in polluted water and wetlands near a hazardous waste site before 1985.
The warning is based on a seven-year study released yesterday showing that people who grew up in Ashland 20 to 40 years ago and who came into contact with certain ponds and brooks contaminated by the former Nyanza Inc. chemical and dye factory had a risk of developing cancer that was two to three times greater than those who did not have contact with the water. The increased risk of cancer from contact with the water was even higher for those with a family history of cancer.
The state launched the study at the prodding of Ashland residents, concerned about rare cancers diagnosed in five young men in the 1980s and '90s. Two died of the disease. The study involved extensive interviews with 1,387 current and former Ashland residents who were children between 1965 and 1985, and 73 participants reported having been diagnosed with some type of cancer.
''We would strongly recommend individuals growing up in the area that had contact with the water should see their physician," said Paul J. Cote Jr., commissioner of the state Department of Public Health, which did the study. State officials were unable to say how many people in the western suburb of 14,674 residents would be affected by the alert, but said the last time such a broad health warning was issued in the state was in 1992.
The dye plant closed in 1978 but its sprawling grounds remained open to the public until about 1985, when a cleanup began under the federal Superfund program. When the 35-acre site was still accessible, students from the nearby middle and high schools would cut through the property to get to a bus stop. Occasionally after football games, some would take a celebratory dunk in wastewater lagoons, state health officials said.
Others who were children at the time reported in the study that they had waded and swum in polluted ponds and wetlands, dyed whatever color was being manufactured that day. Health officials say the waterways -- now largely cleaned -- were probably a cocktail of up to 100 different toxic chemicals and metals found on the site. One waterway was even named Chemical Brook.
''It was cool to kids," said Erin McGrath, 34, whose high school boyfriend David Keddy died at 20 from a rare soft-tissue cancer. ''The boys growing up used to play in the water" at 6 or 7 years old, she said. ''It was purple or blue."
McGrath, who took part in the study, was also friends with Keddy's childhood friend, Kevin Kane, who lobbied successfully for the health study before he succumbed to another rare cancer in 1998, at age 26. Both young men -- among the five who developed soft-tissue cancers of various types -- used to wade in the colored water as boys, McGrath said.
''It's good to hear about the study," she added, ''but it doesn't bring them back."
About 50 people at a meeting at Ashland High School last night heard state and federal public health officials explain the results of the study. Afterward, many walked to a microphone and peppered officials with questions. Some were weeping, others angry.
One man asked whether the drinking water is safe -- it is, he was assured. Another man asked whether the lining installed to hold in contaminants around the site is secure -- it is, he was told. A woman asked whether officials could test water seeping into her basement near the site. Federal officials said they would try.
Despite more than $46.5 million spent to scrub carcinogens and other contaminants from soil and ground water on and around the site, there is much more to do, according to Jim Murphy of the US Environmental Protection Agency. At least 20 miles of the Sudbury River downstream from the site is contaminated from Nyanza, mostly with mercury.
Nyanza closed in 1978 because of financial problems, and never fully paid for its pollution. Federal officials did win about $13 million from the estates of people who owned and operated the company, its successors, and other companies whose waste wound up there.
The state findings are unusual because discovering strong environmental links to cancer clusters is exceedingly rare, specialists say. While many people remember the Woburn case that sparked the book and movie ''A Civil Action," in which eight cases of childhood leukemia were linked to contaminated drinking water, even that association was never absolutely proven, critics say. Most of the state's investigations of suspected cancer clusters have yielded inconclusive results, or findings that the number or geographic distribution of the cases is normal.
Previous studies attempting to link cancer to the Nyanza site were inconclusive, or found no association. But health officials designed the latest study differently. Because they believed people who played at the site as children were particularly susceptible, they interviewed only residents who were between ages 10 and 18 during the 20-year span starting in 1965, when the plant began operating. While another dye manufacturer operated on the site prior to Nyanza, health officials did not believe they could contact enough people from that earlier time period.
The study's findings were particularly striking, state officials said, because two-thirds of the 73 people who reported having been diagnosed with cancer said they got the disease before age 35.
The study identified several areas on and around the site that put people most at risk of cancer. If people swam or waded in water on Megunko Hill, where the factory had two wastewater lagoons; in Chemical Brook; or along the Sudbury River near Myrtle Street, they had a statistically significant increased risk. The risk was highest for people with a family history of cancer -- up to nearly four times the risk for people who didn't have contact with the water.
For people with a family history of cancer, the risk was also elevated in an area known as the Eastern Wetlands, the Sudbury River near
State officials say they are pleased with their study, but they acknowledge they will probably never be able to answer important questions: How much contact with the water did someone need to have to get cancer? For what types of cancer are people most at risk? And exactly what in the water may be causing the cancer?
''We may never know. . . . There is no way to re-create the entire past," said Suzanne Condon, the assistant commissioner of public health, whose office, the Center for Environmental Health, conducted the study. Theresa Cassidy, a senior epidemiologist for the state, helped lead the study. Health officials said they didn't want to restrict the research to any specific type of cancer.
Condon said that while state officials often issue warnings to people to visit doctors because of a potential environmental link to illness, it is rare to issue such a broad warning. Health officials are unsure how many people the warning applies to, but it is likely to be at least hundreds. The last time such a health warning was issued was 1992, when Condon's office urged women to visit doctors because they could have been at a higher risk of developing cancer from a Superfund site in Holbrook called Baird & McGuire.
''One study never totally proves any association," said Richard Clapp, a professor at the Boston University School of Public Health. Rather, he said, it is taken into consideration with other studies to develop a consensus. Clapp, who studied the Nyanza case, has not yet seen the study.
Beth Daley can be reached at email@example.com. Michael Levenson of the Globe staff contributed to this report.