Question # 529

529. A covered facility processes two of the three xylene isomers in separate streams, along with an additional stream containing a mixture of xylene isomers of unknown concentrations. How would the facility determine if an activity threshold has been exceeded? How would the facility report the xylene on the Form R?
The toxic chemical list at 40 CFR Section 372.65, contains four xylene listings (mixed isomers, ortho-, meta-, and para-xylene) that appear with their own CAS number. The CAS number specified for xylene (mixed isomers), 1330-20-7, applies to any combination of xylene isomers. The facility must make separate threshold determinations for each individual chemical listed at Section 372.65. If the thresholds are not exceeded for any of the individual xylene listings of Section 372.65, then the facility would not have to report on any releases of xylene at the facility. For example, if the facility processes, in separate streams, 10,000 pounds of ortho-xylene (CAS number 95-47-6), 10,000 pounds of para-xylene (CAS number 106-42-3), and 10,000 pounds of xylene in which the isomers are mixed in unknown concentrations (CAS number 1330-20-7), a threshold is not exceeded for any of the xylene listings. Therefore, no reports for xylene would be required. The quantities of the individual xylene listings processed by the facility should not be aggregated for the purposes of making threshold determinations. If the thresholds are exceeded for two or more of the individual isomer xylene listings, the facility has two choices when filling out the Form R. The facility may file separate Form Rs for each isomer or unique isomer mixture listed in Section 372.65, or the facility may file one combined report. For example, the facility processes, in separate streams, 30,000 pounds of ortho-xylene, 30,000 pounds of para-xylene, and 30,000 pounds of xylene where the isomers are mixed in unknown concentrations. Because the activity threshold for each of the three xylene listings is exceeded independently, the facility can report releases and other waste management activities from each of three listings separately on three different Form Rs (one for ortho-xylene, one for para-xylene, and one for the mixed isomers) or the facility can report all xylene releases and other waste management estimates on one Form R as xylene (mixed isomers).