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Prop 65: Amendment to Safe Harbor Level of Butyl Benzyl Phthalate (June 2013)

The Office of Health Hazard Assessment (OEHHA) has adopted a Maximum Allowable Dose Level (MADL) for oral exposures to butyl benzyl phthalate (BBP) of 1,200 micrograms per day. The proposed oral MADL was derived using scientific methods, including the review of research material using human and laboratory animal studies. The MADL calculations were performed as follows:

Calculation of NOEL dose for a 58 kg woman:


    - 20 mg/kg-day x 58 kg  =  1160 mg/day


    - Or 1,200 mg/day after rounding


Derivation of the MADL by dividing the NOEL expressed in mg/day by one thousand (section 25801(b)(1)):
   

    - MADL oral   =  1,200 mg/day / 1000  =  1,200 micrograms/day

    This MADL applies to exposure to BBP by the oral route.

The listing of BBP under Proposition 65 is based solely on developmental toxicity, therefore studies of prenatal exposure and developmental outcomes were selected as the possible basis for MADL development. The data from human studies did not provide a sufficient basis for developing the MADL for BBP. Consequently, three sensitive studies in animals on the developmental effects resulting from prenatal exposure to BBP were chosen for review. The study by Nagao et al. (2000), “Effect of butyl benzyl phthalate in Sprague-Dawley rats after gavage administration: a two-generation reproductive study,” was chosen as the most sensitive study to provide the basis for the proposed oral MADL. A full analysis on the BBP MADL can be found
here.

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