OTSEGO, MI -- After dioxin was discovered in private wells in the area, the city of Otsego is conducting additional tests to check for the substance in wells that feed its municipal water system, City Manager Aaron Mitchell said.

While the city tested previously for dioxin and no issues were found, Mitchell said, he has been informed that the test the city did previously was not comprehensive and did not check for the type of dioxin discovered in private wells.

The city will request expedited testing for samples from the four wells that feed the municipal water supply, Mitchell said Tuesday, Sept. 4, just days after dioxin was discovered in nearby private wells.

Dioxins are a group of chemicals that can be formed during, among other things, chemical and paper manufacturing processes. They are highly toxic and can cause cancer, reproductive and developmental problems, damage to the immune system and can interfere with hormones, according to the Environmental Protection Agency.

Two types of dioxins -- 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8 tetrachlorodibenzofuran -- were found in Otsego-area private wells. The first of the two dioxins found is the most studied and most toxic of all dioxins, according to an EPA fact sheet.

Mary Zack, a former Otsego resident and cancer survivor, started asking questions in early 2018 about why several of her friends from high school had cancer and other serious diseases. Her questions caught the attention of the Centers for Disease Control and Prevention and other agencies, leading to environmental testing to search for chemicals used historically by industries in the area.

For months, residents did their own investigations. Zack collected hundreds of health surveys while others compiled a list of former industrial sites and investigated potential sources of contamination.

They obtained documents about contaminants disposed of in the area and pushed for officials to investigate.

Then, 56 local wells were tested for chemicals associated with former industrial practices. The tests searched for chemicals in waste from local paper mills that was applied to fields and roads in the area, the Allegan County Health Department said in a news release.

On Saturday, Sept. 1, the county health department announced preliminary results, saying dioxin was found in 14 private water wells in the Otsego area. Residents with impacted wells would be contacted, the department said.

The count of private wells where dioxin was found has now reached 19, Allegan County Health Department Medical Director Richard Tooker said after a multi-agency conference call Tuesday, Sept. 4.

A likely source of the environmental contaminants is sludge that was spread on farm fields in the area, the health department said in its initial news release.

The agencies are discussing the possibility of widening the sampling field, but have not made a decision, Tooker said on Tuesday.

"The question now is what additional wells would we consider testing?" he said.

He directed area residents to a form to fill out to request their well be tested.

Zack said when the announcement was made about dioxin, it felt like the group's hard work digging into the topic was finally bearing fruit.

"The ball's rolling and I'm excited to finally see this hard work coming together," she said. "Unfortunately it's only going to get worse."

Zack, who grew up in a home with Otsego city water, said it was concerning that the city wells were not tested alongside the 56 private wells.

Otsego's city manager said on Tuesday that the additional tests will search for the specific dioxins found in nearby private wells.

"We tested for dioxins in April, it turns out, the way we initially tested, we didn't do a comprehensive panel," Mitchell said. "We're going to test again to make sure."

The city is committed to working with the agencies and will do whatever test the DEQ recommends, he said.

"All the big hitters are working on this case," Mitchell said. "We're going to get to it, I just don't know how fast."

Otsego Township Supervisor Bryan Winn said he was under the impression the township tested for the full panel, but he is checking to see if that is true. If not, Winn said, the township will also complete additional testing with a full panel.

"We are going to do everything at the township level that we possibly can to make everything as safe as can be for our residents," he said.

Nearby, the city of Plainwell also tested for dioxins in the past and none were found, City Manager Erik Wilson said. Wilson said the city is ready to work with the DEQ if any additional testing is needed.

Zack and others are waiting to get more information on Sept. 7, she said. That is the date when Tooker said a full report will be complete on additional testing results and when the agencies involved plan to share more information with the public.

An initial press conference on dioxin being found in local wells was held over the Labor Day weekend on Saturday, Sept. 1, announced to members of the news media about 30 minutes before it occurred.

Zack called the preliminary results "horrific" and said she is concerned that more chemicals could be found.

"We don't know fully what they found, other than dioxin," she said.

She complained that communication could be improved, because people are concerned about the findings.

Residents with questions can call an Allegan County Health Department hotline at 269-686-4546 daily from 8 a.m. to 8 p.m. For more information on dioxins, contact Michigan Department of Health and Human Services at 1-800-648-6942 between 8 a.m. and 5 p.m Monday through Friday.