After discovering that four people living on her street have battled thyroid cancer, one of whom is her teenage daughter, Susan Wind raised over $100,000 for a cancer cluster investigation on her neighborhood.

About 1,000 suspected cancer clusters are reported to state health departments each year, according to the American Cancer Society. They are geographic locations where the cancer rate is higher than average. Nevertheless, cancer clusters are hard to prove, and a low number of reports actually confirm an environmental influence.

The Center of Disease Control and Prevention (CDC) plans on updating its cancer cluster investigation by 2021. The organization sought public comment and feedback on its research policies.

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In a North Carolinian town, a teen’s cancer diagnosis led her mother to discover a potentially cancer-prone neighborhood, reports NBC News.

Susan Wind’s 16-year-old daughter Taylor was diagnosed with papillary thyroid cancer in 2017 – she later learned that three people living on her street also battled with the same form of cancer, and another two had thyroid tumors.

“If she had been the only one to have been diagnosed with thyroid cancer, I would have accepted this as a card we had been dealt,” Wind wrote in a USA TODAY post. “However, that was not the case.”

Wind noticed an alarming pattern and turned to experts for advice. After confirming that the thyroid cancer rates in her neighborhood are much higher than they should be, she set out to raise $110,000 to fund a study on her town’s groundwater, soil, and air. The mother is still waiting for the test results.

North Carolina is not the only state with this problem

Wind’s home in Mooresville, North Carolina, may be on its way as one of the 1,000 suspected cancer clusters reported to state health departments each year, according to the American Cancer Society. The Center of Disease Control and Prevention (CDC) defines a cancer cluster as a geographic region in which cancer cases are more concentrated within a group of people.

A similar case of the north Houston neighborhoods in Texas identified a cancer cluster near a rail yard site with creosote, a potential cancer-causing chemical, reported the Houston Chronicle. Though the state department assessment found plausible evidence of the contamination in August, residents weren’t notified until December. Some other ongoing cluster investigations are located in Washington County, Pennsylvania, and Waycross, Georgia.

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The CDC is updating its investigation guidelines

Substantial research suggests that certain jobs like firefighting and rubber manufacturing come with more health risks. The CDC provides resources on cancer rates by state – giving breakdowns of the illness by sex, age group, and cancer types. Nevertheless, researchers still struggle to find a direct link between cancer and the environment.

Of the 567 state and federal cluster investigations conducted between 1990 and 2011, only 72 of those cases were confirmed, according to a 2012 Emory University study. In other words, cancer clusters are hard to prove.

Last May, the CDC made a public announcement and sought comment on how to better approach cancer cluster investigations. It plans to update guidelines by 2021.

NBC News reports that the open docket prompted residents impacted by cancer clusters to voice their opinions – including an Indiana woman who shared that four children living within a one-block radius were diagnosed with brain tumors and other commenters who regret moving to a cancer hotspot without federal warning.

How the environment may share the blame

Certain cases of cancer are out of our control, Business Insider reported. They are determined by genetic defects that are passed down from one generation to the next. Some external factors or lifestyle factors, like tobacco-smoking or a high sugar intake, can also increase our chances for a diagnosis.

However, environmental factors are harder to avoid. The air we breathe, the water we drink, or our job demands are often underrated contributions to our health.

In Susan Wind’s case, the presence of two power plants and coal ash, a potential chemical contaminant, may have contributed to the unusual cases of thyroid cancer in Mooresville, but researchers aren’t certain of its direct correlation. There’s simply not enough evidence (yet) to link environmental pollution with cancer diagnoses. Wind is still waiting for her fundraised research results.