There are 42 so-called disease clusters in 13 U.S. states, showing incidence of numerous types of cancer, birth defects and other chronic illnesses, the Natural Resources Defense Council reported on Monday.
A study by NRDC and the National Disease Clusters Alliance, drawn from research by federal, state and local officials and peer-reviewed academic studies, urges federal coordination and support to help confirm these clusters and determine their causes.
"The faster we can identify such clusters, and the sooner we can figure out the causes, the better we can protect residents living in the affected communities," NRDC's Dr. Gina Solomon, co-author of the study, said in a statement.
The study looked at clusters that have occurred since 1976 when Congress passed the Toxic Substance Control Act, which was meant to regulate the use of toxic chemicals in industrial, commercial and consumer products.
The U.S. Center for Disease Control defines a cluster investigation as "a review of an unusual number, real or perceived, of health events (such as reports of cancer) grouped together in a time and location."
Monday's study is the first of several that are planned. It examined clusters in Texas, California, Michigan, North Carolina, Pennsylvania, Florida, Ohio, Delaware, Louisiana, Montana, Tennessee, Missouri and Arkansas.
Only one of the 42 clusters -- in Libby, Montana -- showed a specific source for chemical contamination: asbestos. In the other clusters, NRDC saw signs that documented exposure to toxic chemicals hurt the people who lived nearby.
The Senate Environment and Public Works Committee has scheduled a hearing for Tuesday on disease clusters and environmental health.