EPA received a letter from the American Gas Association (AGA) in March of 2018 requesting that EPA clarify whether or not Medium Density Polyethylene Pipe (MDPE) and High Density Polyethylene Pipe (HDPE) are non-porous surfaces. AGA provided a study titled Assessment of Polychlorinated Biphenyls (PCBs) in Polyethylene (PE) Gas Distribution Piping conducted by NYSEARCH and National Grid, which demonstrated that the amount of PCB absorption into MDPE and HDPE was minimal, and penetration of PCBs was not beyond the immediate surface. EPA responded to AGA with the determination that MDPE and HDPE used in natural gas distribution piping may be considered a “non-porous surface” as defined in 40 CFR 761.3, and may be wipe sampled as such for waste profiling. Although the letter is specific to AGA's circumstances, we believe it will be helpful to many natural gas utilities that use MDPE and HDPE in their distribution systems.You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.