If a facility only knows the upper bound concentration of a TRI chemical in a mixture, the upper bound must be used for threshold determinations. If a facility knows both the lower and upper bound concentrations of the TRI chemical, EPA recommends that the midpoint of the two concentrations be used for threshold determinations. If a covered facility receives a material safety data sheet (MSDS) from its supplier that states that the concentration of the TRI substance in the mixture ranges between zero and 10 percent, can the facility estimate the concentration of the TRI chemical in the mixture by using zero as the lower bound?
No, a facility cannot estimate the concentration of a TRI chemical in a mixture by using zero as a “lower bound” concentration, even if the facility receives an MSDS from a supplier stating that the concentration of a TRI substance is between zero and a stated upper bound. If an MSDS shows zero as the “lower bound” of the concentration range, then the lower bound concentration is unknown, and the facility must use the provided upper bound for threshold determinations (40 CFR §372.30(b)(3)(ii)). Therefore, in the scenario above, since the facility only knows that the upper bound is 10 percent, it must calculate the amount of TRI chemical in the mixture based on the 10 percent concentration.