Exposure Levels for Evaluating Polychlorinated Biphenyls (PCBs) in Indoor School Air

EPA calculated exposure levels for evaluation that are intended to maintain overall PCB exposures below the oral reference dose (RfD) of 20 ng PCB/kg body weight per day. An RfD is an estimate of a daily exposure to the human population (i.e., sensitive subgroups) that is likely to be without an appreciable risk of harmful effects during a lifetime.

The Agency considered potential pathways of PCB exposure in school and non-school environments. Non-school exposure pathways include indoor and outdoor air, indoor dust, outside soils and diet. Although the concentrations of PCBs in environmental media are not well characterized, estimates of exposure could be determined using mean or median values from the scientific literature and average contact rates. For non-school exposures, inhalation of indoor air and dietary intake account for the largest portions of total PCB exposures in uncontaminated buildings. Together these non-school pathways generally result in PCB exposures that are significantly below the RfD.

School exposure pathways include school indoor and outdoor air, indoor dust, and nearby outside soils. To calculate the exposure levels for evaluating PCBs in indoor school air, the EPA made the following assumptions:

• PCB concentrations in dusts and soils in and around schools are the same as in average homes or other buildings without elevated PCBs.
• Adults and children less than three years old are in school for 8 hours per day; all other children are in school for six and a half hours per day
• Adults and children less than three years old are in school 185 days per year. All other children are in school for 180 days.

EPA calculated the school indoor air PCB concentrations that would result in an estimated total exposure equal to the RfD when all other school and non-school PCB exposure pathways were set to average background levels. These calculated indoor air concentrations are the exposure levels for evaluating PCBs in indoor school air provided in the table below. They were derived to serve as health protective values intended for evaluation purposes. They should not be interpreted nor applied as “bright line” or “not-to-exceed” criteria, but may be used to guide thoughtful evaluation of indoor air quality in schools.

*(Note: Exposure levels were rounded to the nearest hundred ng/m3)

EPA recommends that the concentrations of PCBs in indoor air be kept as low as reasonably achievable, and the total PCB exposure be kept below the RfD level. The concentrations provided in the table are based upon average situations. School-specific exposure levels can be calculated if sufficient data are available.

For example, if students spend more time in school than was assumed when calculating the values in the table, the levels of PCBs in the school’s indoor air may have to be lower to prevent overall exposure from exceeding the RfD. Similarly, PCB concentrations in a school’s outdoor soils or indoor dusts greater than those in non-school environments would indicate a potential for increased exposure from these pathways. Thus, school indoor air concentrations would need to be decreased to maintain overall exposure below the RfD. Building owners and school administrators who want to make calculations based on their own specific circumstances should contact their EPA regional PCB coordinator.