BOSTON -- Boston-area researchers believe that floor finish applied to homes in the 1950s and 1960s may continue to expose occupants to cancer-causing polychlorinated biphenyls (PCBs).

A study published Thursday in the Journal of Environmental Health suggests that old wood floor finishes in some homes may be an overlooked source of exposure to the now banned chemical.

The floor finish, Fabulon, was used in Cape Cod homes where researchers from the Silent Spring Institute found high concentrations of PCBs.

“The use of a commercially-available PCB-containing wood floor finish in residences in the 1950s and 1960s is an overlooked but potentially important source of PCB exposure,” researchers Ruthann Rudel, Julia Brody and Liesel Seryak wrote in the journal.

The homes tested still had very high indoor air levels of PCBs almost 50 years later.

"Our findings suggest that the exposure potential posed by historic use of PCBs in building materials may be significantly underestimated," the researchers said.

PCBs have been identified as human blood and breast milk contaminants which have been associated with adverse effects on immune, reproductive, and nervous systems, as well as cancer, according to the researchers.

Fabulon, which was first manufactured in the 1930s as a finish for bowling alleys, is still marketed. However, its products were reformulated in the 1970s, when PCBs were banned.