On May 27, 2016, the California Office of Environmental Health Hazard Assessment published a Proposition 65 Safe Use Determination (SUD) for diisononyl phthalate (DINP) in Tandus Centiva ER3® Modular Vinyl Carpet Tiles. The SUD concludes that no Proposition 65 warnings are required for DINP exposures to residents with such carpet tiles installed in their homes, if DINP is present in the tiles only in the tiles’ secondary backing layer and at a concentration of no more than 9% by weight in that layer. The SUD also concludes that no Proposition 65 warnings are required for professional installers, if the DINP is present only in the secondary backing layer of the tiles at a concentration of no more than 8.7% by weight.
An SUD represents OEHHA’s formal interpretation of Proposition 65 as applied to a specific set of facts regarding an exposure to a listed chemical. The SUD applies only to the business that requested it, and only to the listed chemical and exposure scenario identified in the SUD. Although an SUD will not immunize a business from an enforcement action alleging the same exposures, as a practical matter enforcers are unlikely to pursue claims where OEHHA has weighed in with a conclusion that no warnings are required for those exposures.
SUDs also offer insights into assumptions that OEHHA uses in calculating exposures to listed chemicals. For example, for exposures to DINP via the dermal route, OEHHA assumes a low dermal absorption factor of 0.15%. For hand-to-mouth exposures, OEHHA assumes a transfer efficiency rate of 50%, i.e., OEHHA assumes that 50% of DINP on the skin is transferred to the mouth and perioral area. The 50% value is derived from prior studies involving certain pesticides. Most interesting for the calculation of residents’ exposures, OEHHA assumes that DINP migration to household dust can create a reservoir for DINP exposure. Even so, the calculated exposure for residents was 32.8 micrograms per day, well below the DINP warning level of 146 micrograms per day.
Businesses seeking to determine the levels of DINP exposure from their products should examine this SUD carefully and determine what assumptions are appropriately used in those determinations. Or, they may simply provide warnings, an option that still remains the best approach for avoiding enforcement actions.