See:  https://www.airforcemedicine.af.mil/Resources/Missile-Community-Cancer-Study/

Quoting from the above link and magnified for an easier read - text in red added for emphasis:

ABOUT POLYCHLORINATED BIPHENYLS (PCBS)

• Q. WHERE EXACTLY WERE THE POSITIVE SAMPLES FOUND?
  
  Seven Launch Control Centers (LCC) at Malmstrom Air Force Base, Montana, had detectable levels of Polychlorinated biphenyls (PCB) above zero.
  
• The following items had detectable levels of PCBs: visual display screen, console keyboard, circuit breaker, LCDB panel, Oxygen Regeneration Unit, power supply, wall and floor below Electromagnetic Interface Filter, Receiver Digital Data, battery access charger, DC power switch, and LCC ceiling.
  
• This suggests PCBs were not transmitted within workspaces.
  
  
• Q. WHERE WERE THE MOST CONCERNING SAMPLES FOUND?
  
  Swipe samples from the underside of two LCC LCDB panels contained the concentrations of PCBs above the Code of Federal Regulations, Title 40, Part 761, Subpart G (40 CFR 761) standard for PCB cleanup following a previous spill.
  
  
• Q. HOW OFTEN ARE PEOPLE EXPOSED TO THESE AREAS?
  
  The equipment and surfaces that people commonly touched had detectable PCBs, but the levels fell below the 40 CFR 761 Subpart G standard for PCB cleanup. The two LCDB panels (underside) that tested above the standard is in an area people don’t commonly touch.
  
  
• Q. IS THERE A PLAN TO CONDUCT ANY FOLLOW-ON TESTING AT OR NEAR THE DETECTABLE AREAS?
  
  The areas detectable but not at zero are akin to levels one unknowingly encounters in the everyday environment. For those areas which tested above the 40 CFR 761 Subpart G, the U.S. Air Force will remediate and retest.
  
• While there is not a federal requirement for cleanup of detectable PCBs for areas below 40 CFR 761, the U.S. Air Force will work with the appropriate agencies to determine cleanup / remediation and follow-on actions. 
  
  
• Q: WHAT IS THE PLAN TO AVOID EXPOSURE TO AREAS THAT ARE CURRENTLY KNOWN TO BE CONTAMINATED?
  
  Immediate measures to limit exposure have been taken at the two facilities above the EPA cleanup standard. For all other areas subject matter experts recommend routine cleaning and general sanitation on/around workspaces. Additionally, personnel are recommended to use soap and water to wash hands prior to eating, drinking, or smoking. 
  
  
• Q: IS THERE A PLAN TO INCREASE TESTING IN THE AREA THAT PCBS WERE DETECTED?
  
  For those areas above the EPA 40 CFR 761 cleanup standard, remediation and retesting is being coordinated. While there is not a federal requirement for cleanup of detectable PCBs for areas below this standard, clean-up and remediation actions are being coordinated. 
  
  
• Q: WHAT IS THE EPA CLEAN UP STANDARD FOR PCBS?
  
  The EPA set the 10 microgram (µg) / 100 cm2 clean up standard considering human health impacts from inhalation and skin contact. This standard of 10 microgram / 100 cm2 assumes unprotected exposure 24 hours a day, 7 days a week for a high occupancy scenario on a nonporous surface. 
• • 10 micrograms: If you slice one regular sized paper clip into a million pieces, each slice would weigh one microgram.
  • 100 cm2: This is approx. a 4x4 inch square, about the size of the palm of your hand.
• 
  
• Q: HOW DO PCBS ENTER THE BODY?
  
  The CDC says the general population’s primary exposure to PCBs in through eating contaminated high-fat foods, mainly seafood and dairy. Occupational exposure to PCBs occurs mainly via breathing them in and when the skin is exposed to maintenance or repair of equipment manufactured before 1977, or as a result of accidents involving such equipment.
  
  
• Q: DO ALL THE LAUNCH CONTROL FACILITIES GET BIOENVIRONMENTAL REVIEWS EVERY YEAR FOR DIFFERENT POTENTIAL CONTAMINANTS, AIR QUALITY, WATER QUALITY?
  
  Missile Alert Facility and Launch Control Center water is tested quarterly by Bio-Environmental following EPA regulations, similar to water testing on any military installation. Missile Alert Facility Managers also test water weekly to ensure water filtration systems are operating. All Missile Alert Facility kitchens and food preparation areas are inspected by Public Health at least annually. Missile Alert Facility Managers do routine kitchen cleanliness inspections as well.
  
  
• Q. WOULD THE SENTINEL MODERNIZATION PROGRAM ADDRESS THIS RISK BY FULL REPLACEMENT OF THESE AREAS?
  
  PCBs were banned in the United States in 1977 and thus new construction materials and electrical components for the Sentinel modernization program will not contain PCBs.
  
  
• Q: WILL THERE BE A REGISTRY ASSOCIATED WITH THE MISSILE COMMUNITY CANCER STUDY?
  
  Data is currently being pulled from multiple databases to gather as much information as possible. In the event the study moves to a phase II, a registry may be created. Please reference the Missile Community Cancer Study webpage where information will be updated regularly.