The DEP first became aware of the potential contamination problems in 1998 when researchers at the University of Illinois notified DEP that several sites in Connecticut were used for radium dial clock manufacturing in the past. Using hand-held portable radiation detection instruments and interviewing former employees, the DEP identified locations in Bristol, New Haven, Thomaston, and Waterbury where radium contamination was present. Since identifying the contamination, the DEP has been working with local municipal officials and community groups to best determine the methods for remediation. Once the radium abatement is completed the sites will be free for unrestricted use and redevelopment. Radium is a naturally occurring radioactive material that was used from the 1900s to the 1940s to paint dials on clocks, watches, and aircraft navigation equipment due to its luminescent qualities, i.e., glows in the dark.
Radium is known to have caused health problems for persons who ingested it for long periods of time.
In the past, workers in these clock factories would dip paint brushes in their mouths to form a fine point then dip the brushes in the radium paint. The use of radium was not completely discontinued in the 1940s but the manner in which it was applied changed, minimizing direct exposure. Eventually, materials that possessed similar qualities but were less hazardous, such as phosphors, replaced radium.