419. Xylene mixed isomers are present in two of a facility’s refined products. For EPCRA section 313 reporting, may the isomers be reported separately? For a mixture of the isomers, how are thresholds and de minimis to be determined? Reported separately, the facility exceeds thresholds but is below de minimis concentrations.
All of the xylene isomers are individually listed under EPCRA section 313. In addition, there is a listing for xylene (mixed isomers) that covers any combination of xylene isomers. When the threshold and de minimis concentration for each isomer in the mixture are exceeded independently, the facility may report under the individual isomer listings or under the mixed isomers listing. When the threshold and/or de minimis for each isomer in the mixture are not exceeded independently, but are exceeded collectively, the facility should report under the CAS number for xylene (mixed isomers). Therefore, if a covered facility otherwise uses a mixture containing 8,000 pounds of ortho-xylene, 4,000 pounds of meta-xylene, and 2,000 pounds of para-xylene, the facility would report as xylene (mixed isomers) because it exceeded the 10,000-pound otherwise use threshold for xylenes (mixed isomers).