Human Risk Assessment for Nonylphenol

ABSTRACT

This article presents a risk assessment for human exposure to nonylphenol (NP). We critically reviewed and assessed all relevant full-text publications based on a variety of data quality attributes. Two categories of data, environmental monitoring and biomonitoring from exposed individuals, were used to estimate human exposure to NP. Environmental monitoring data included the measurement of NP in food, water, air, and dust. From these data and estimates of human intake rates for the sources, exposures were estimated from each source and source-specific Margins of Exposure (MOEs) calculated. However, the nature of the populations studied prevented the calculation of aggregate exposure calculations from these data. Rather, the most reliable estimates of aggregate exposure to NP were those derived from biomonitoring studies in exposed individuals. Using the daily absorbed dose estimates for NP, MOEs were calculated for these populations. The MOEs were based on the use of a No-Observed-Adverse-Effect-Level (NOAEL) for sensitive toxicological endpoints of interest, that is, systemic and reproductive toxicity from continuous-feeding more than 3.5 generations (13 mg/kg/day). The MOEs were all greater than 1000 (ranging from 2863 to 8.4 × 10⁷), clearly indicating reasonable certainty of no harm for source-specific and aggregate (based on biomonitoring) exposures to NP.

Key Words:

• nonylphenol (NP)
• biomonitoring
• environmental monitoring
• risk assessment
• Margin of Exposure (MOE)
• internal dose

ACKNOWLEDGMENTS

Thanks go to J. Klapacz and R. Sura from Dow Chemical Company for helpful discussions about selection of the Point of Departure for risk assessment calculations.

Notes

Consistent with water ingestion rate age cohort.

Statistical metric not specified, but assumed to be the 50th percentile.

Consistent with dust ingestion rate age cohort.