Should very similar combinations of hazardous chemicals be aggregated?

How should a person determine whether very similar combinations of hazardous chemicals (e.g., different colors of paint or different blends of gasoline) that have separate MSDSs (Material Safety Data Sheet) should be aggregated for Tier II reporting?

The owner or operator of a facility may make the EPCRA §§311 and 312 threshold determination for a hazardous chemical that is a mixture of non-EHS hazardous chemicals based on either the total quantity of each component of the mixture or the total quantity of the mixture itself.  If the owner or operator chooses to make the threshold determination based on the mixture as a whole, he or she is required to aggregate all amounts of the same mixture present throughout the facility.  This aggregation obligation requires owners/operators to determine if hazardous chemical combinations present at their facility are the "same" mixture or are "different" mixtures.

In general, "different" mixtures are represented by different MSDSs.  However, the fact that a facility has two or more MSDSs for its chemical combinations does not necessarily mean that these combinations are considered "different" mixtures.  For example, if a facility receives multiple MSDSs for essentially the same material simply because the mixture is provided by different suppliers, all quantities of the mixture present at the facility must be aggregated for mixture threshold determinations.  Conversely, if two or more chemical combinations are represented by different MSDSs and present different physical or health hazards, they would not be aggregated for §§311/312 purposes.  Beyond this, the facility owner/operator must determine, based on professional judgment, if the two materials present the same physical/health hazards and are sufficiently similar to warrant aggregation as the "same" mixture.  

Once a facility owner/operator has made a compliance determination and identified which hazardous chemicals must be reported, questions about whether similar mixtures may be reported together on a Tier II report should be directed to the appropriate State Tier II contact.